Acquired Foot Deformities: Clinical Guidelines

List of Abbreviations

EFA – external fixation apparatus

DPN – deep peroneal nerve

PT – posterior tibial muscle

BMI – body mass index

SSI – surgical site infection

CT – computed tomography

PT – physical therapy

MRI – magnetic resonance imaging

NSAIDs – nonsteroidal anti-inflammatory and antirheumatic drugs

CPN – common peroneal nerve

SPN – superficial peroneal nerve

TPT – tibialis posterior tendon

FDLT – flexor digitorum longus tendon

US – ultrasound examination

ENMG – electroneuromyography

Terms and Definitions

Hallux valgus – a forefoot deformity comprising varus deviation of the first metatarsal bone, its pronation, and valgus positioning of the first toe.

Forefoot deformities – a supra-nosological concept encompassing a complex of disorders of the anatomical shape and function of the toes and forefoot, which may present in various forms, the most common being hallux valgus and hammer toe deformity of the lesser toes.

Hammer toe deformity of the lesser toes – a pathological condition characterized by the flexion or extension malalignment of one or more lesser toes, caused by extension contracture of the metatarsophalangeal joint, flexion contracture of the proximal interphalangeal joint, and hyperextension at the distal interphalangeal joint.

Hohmann procedure – resection of the head of the proximal phalanx of a toe, aimed at correcting its hammer toe deformity.

Lapidus procedure – arthrodesis of the first tarsometatarsal (cuneometatarsal) joint, aimed at correcting the deviation of the first metatarsal bone.

Akin osteotomy – a wedge osteotomy of the proximal phalanx of the first toe, with the apex pointing medially in most cases.

Dwyer osteotomy – a closing wedge resection of the lateral part of the calcaneus with the wedge base directed laterally, allowing medialization of the hindfoot, correcting varus heel alignment and restoring a neutral position of the hindfoot.

Evans osteotomy – a surgical procedure in which a linear osteotomy of the anterolateral calcaneus is performed, followed by the insertion of a bone graft to lengthen the lateral column of the foot.

Scarf osteotomy – a diaphyseal osteotomy of the first metatarsal bone consisting of three bone cuts arranged in a "Z" shape, allowing correction of distal fragment displacement in three planes.

Lisfranc joint – a composite joint formed by the bases of the five metatarsal bones on one side and the cuboid and three cuneiform bones on the other side.

Chopart joint – a composite joint formed by the talonavicular and calcaneocuboid joints.

Silfverskiöld test – a clinical maneuver used to differentiate gastrocnemius contracture from a broader contracture of the entire triceps surae muscle or Achilles tendon. It is particularly important when assessing limited dorsiflexion of the foot.

Coleman block test – a diagnostic test used to assess hindfoot rigidity in cavovarus foot, valgus foot, varus foot, or planovalgus deformity. It helps determine whether varus or valgus heel positioning is primary or secondary relative to the forefoot.

Jack test – a clinical diagnostic test used to assess the function of the medial longitudinal arch of the foot and determine flexibility in planovalgus foot deformity. During the test, the patient is asked to stand barefoot, and the clinician passively elevates (dorsiflexes) the great toe. The response of the medial arch is observed: normally, or in flexible (functional) flatfoot, the arch forms or accentuates, whereas in the rigid form, the arch does not elevate. This test is particularly useful for differentiating between flexible and rigid flatfoot: a positive result (elevation of the arch) indicates preserved function of the musculotendinous apparatus, whereas a negative result indicates structural changes in the foot.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Acquired foot deformities – a supra-nosological concept encompassing a complex of disorders of the anatomical shape and function of various foot segments, including the toes, which may present in various forms and develop during the patient's lifetime

To facilitate the description of conditions and deformity components, the foot is conventionally divided into hindfoot, midfoot, and forefoot segments. The boundary between the hindfoot and midfoot runs along the Chopart joint (including the talonavicular and calcaneocuboid joints), and the boundary between the midfoot and forefoot runs along the Lisfranc joint (including the joints between the bases of the metatarsal bones on one side and the cuboid and cuneiform bones on the other).

Among forefoot deformities, the most common are hallux valgus and hammer toe deformity of the lesser toes.

Hallux valgus – a forefoot deformity comprising varus deviation of the first metatarsal bone, its pronation, and valgus positioning of the first toe.

Rigid great toe (hallux rigidus) is a limitation of the range of motion of the proximal phalanx of the first toe at the first metatarsophalangeal joint in the sagittal plane due to the development of arthritic changes within it. Normally, dorsiflexion in this joint is approximately 55°–65°. In this disease, the range of motion decreases to 25°–30°. With the ongoing loss of dorsiflexion, degenerative changes in the first metatarsophalangeal joint also progress, manifesting as restricted movement, increased pain, and ultimately leading to complete immobility. Subsequently, pain occurs with any attempt at flexion.

Lesser toe deformities are a group of pathological changes in the shape, position, and function of the second, third, fourth, and/or fifth toes, arising as a result of disruption of the normal anatomical axis and biomechanics of the joints and tissues of the forefoot. The most common are hammer toe, claw toe, mallet toe, as well as varus or valgus deviations.

Hammer toe of the lesser toes is a pathological condition characterized by the curvature of one or more lesser toes, caused by extension contracture of the metatarsophalangeal joint, flexion contracture of the proximal interphalangeal joint, and hyperextension in the distal interphalangeal joint.

Claw toe of the lesser toes is a pathological condition characterized by the curvature of one or more lesser toes, caused by flexion contracture of the interphalangeal joint and simultaneous hyperextension at the metatarsophalangeal joint.

Mallet toe is a pathological condition characterized by the curvature of one or more lesser toes, caused by flexion contracture of the distal interphalangeal joint.

In the midfoot and hindfoot, the main acquired deformities are flat-valgus deformity, acquired clubfoot, and drop foot (equinus foot).

Flat-valgus foot deformity is a static, multi-component, and multi-planar foot deformity manifested by a decrease in the height of the longitudinal arches with a reduction in the calcaneal inclination angle and its pronation, abduction of the midfoot, and supination of the forefoot. In modern Russian-language literature, this pathology has several names: flatfoot, longitudinal flatfoot, flat-valgus foot, splayfoot, abducted foot. In English-language literature: pes planus, pes planovalgus, flexible planus foot.

Acquired clubfoot (pes cavovarus) is a pathological condition characterized by adduction and supination of the forefoot, varus heel position, and equinus foot setup, developing outside of a congenital form as a result of neurological, traumatic, orthopedic, or systemic diseases [1]. This pathology is complex in nature, can affect any part of the foot, and covers a wide spectrum of deformities ranging from mobile forms up to pronounced rigid equinovarus foot [2]. It is often associated with neurological diseases and muscle imbalance [3].

Drop foot syndrome is a complex of neurological, muscular, skeletal, and articular symptoms that leads to the inability to lift the front part of the foot due to weakness of the dorsiflexors of the foot, namely the tibialis anterior, extensor digitorum longus, and extensor hallucis longus, and/or increased tone in the gastrocnemius and soleus muscles [4]. In the long term, incorrect gait leads to abnormal loading of the entire skeletal axis. As a result of muscle imbalance causing constant tension of the plantar flexors and shortening of the Achilles tendon, an equinus position of the foot may develop. Gait asymmetry in drop foot syndrome leads to increased stress on the hip and knee joints, which can subsequently cause degenerative changes in them.

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

If one attempts to summarize the causes of virtually any acquired foot deformities in adults, the following list can be obtained:

1. Traumatic causes

2. Neurological causes

3. Causes related to metabolic disorders, including bone tissue

4. Connective tissue dysplasias

5. Overweight

6. Impaired local circulation

7. Autoimmune and rheumatological diseases

8. Combined and mixed causes

However, it should be noted that each deformity has its own specific etiology and pathogenesis features, which will be discussed in more detail in subsequent sections.

Thus, for instance, the development of valgus deviation of the first toe has a complex polyetiological and polypathogenetic character [5], [6], which in turn complicates its treatment.

The deformity typically develops in individuals wearing fashion footwear, predominantly women. Many authors consider wearing uncomfortable shoes, in particular, narrow-toe and high-heeled shoes, as the primary etiological factor contributing to the development of hallux valgus [7], [8]. The combination of a pointed toe and high heel causes an increased load on the 2nd, 3rd, and 4th metatarsals, intensifying metatarsalgia caused by hallux valgus and first ray insufficiency [9].

In addition, the development of the pathology is associated with changes in the tendoligamentous apparatus of the foot against the background of prolonged static and dynamic loads [7], [10]. M. Libotte et al. (1985) assigned the primary role in the deviation of the first metatarsal bone to the loss of function of m. adductor hallucis, which, displacing along with the sesamoid hammock, becomes a plantar tendon, losing its "antivalgus" function. M. abductor hallucis and m. flexor hallucis brevis transform from plantar to lateral muscles, worsening the deformity, while m. flexor hallucis longus and m. extensor hallucis longus acquire excessive tension and pull the toe laterally with every movement [11].

It is also necessary to draw attention to the first cuneometatarsal joint. Unlike the other four joints, where rotational movements are limited to a range of 3–5 degrees, excessive rotation is observed here, associated with the obliquity of the articular surfaces [5], [12].

Many authors, investigating the causes of hallux valgus, designate the weakness of the ligamentous and muscular apparatus of the foot as the main pathogenetic factor [12], [13]. Speaking about hallux valgus, one should not forget the hereditary factor, which is recognized by many scientists as fundamental [5], [12], [14]. According to Astapenko M.G. et al. (1986) and Leonova N.M. (1989), dysplasia is observed in 30–60% of patients. L.S. Barouk et al. (1991) and J. Pontius et al. (1994) state in their studies that in 20% of cases one can speak of the presence of a congenital predisposition in patients, in which the deviation of the first metatarsal bone is merely a consequence rather than the cause of the deformity [15]. In more than 50% of cases among those who actually have the deformity, it was noticed before the age of 20, usually during puberty (Piggott H., 1960). J.F. Hicks (1965) concluded that if a woman at age 20 has a valgus toe alignment of less than 10° on radiographs, it is unlikely she will ever develop the deformity.

Foot pronation and non-functioning arches, both longitudinal and transverse, have been cited by many authors as the main factors in the development of the deformity [16], [17]. J.E. McNerney and W.B. Johnston (1979), as well as A. Carl et al. (1988), demonstrated greater ligamentous laxity in those who had the deformity compared to those who did not.

Thus, summarizing the above, we can propose a scheme including the causes of hallux valgus development, developed by M.J. Coughlin (2007) [18]:

1. External causes:

• Wearing uncomfortable, narrow shoes – 32%.

2. Internal causes:

• Heredity;

• Joint hypermobility;

• Flat-valgus deformity, tarsal coalitions, secondary hallux valgus (rheumatoid arthritis, neurogenic disorders);

• Metatarsus primus varus (32%);

• Gastrocnemius and Achilles tendon contractures (11%).

Ever since Davies-Colley first used the term hallux limitus (rigidus) in 1887 to describe a stiff big toe, various theories regarding the formation of this condition have been proposed. In 1930, Nilsonne suggested that this disorder is a consequence of an excessively long first metatarsal bone, which exerts pressure on the base of the proximal phalanx. It is caused by the inability of the base of the proximal phalanx to achieve adequate dorsiflexion over the head of the first metatarsal bone. This anatomical feature of the first metatarsal bone is termed Metatarsus primus elevatus. Kessel and Bonney also found that in a small percentage of cases, osteochondritis dissecans of the first metatarsal head leads to degenerative changes in the joint with subsequent restriction of dorsiflexion.

The assertion that osteochondritis dissecans of the first metatarsal head is involved in the development of hallux rigidus was confirmed by Goodfellow in 1966, who discovered that trauma to the hallux can disrupt the integrity of the cartilage on the head of the first metatarsal bone. In 1978, McMaster more precisely localized this lesion, noting that it most frequently occurs at the level of the dorsal margin of the base of the proximal phalanx of the first toe.

Root et al. characterized hallux rigidus as a multifactorial condition, with causes including hypermobility, potential joint immobilization, relative lengthening of the first metatarsal bone, Metatarsus primus elevatus, osteoarthritis, traumatic injury, osteochondritis dissecans, gout, and rheumatoid arthritis. Neuromuscular disorders cause hypermobility or hyperactivity of the tibialis anterior muscle or weakness of the peroneal muscles, which may lead to hallux rigidus by causing instability of the first ray.

During excessive pronation in the subtalar joint, the tendon of the peroneus longus muscle loses its fulcrum on the cuboid bone and is therefore unable to stabilize the first ray. As a result, hypermobility of the first ray occurs, followed by its dorsiflexion, which contributes to the base of the proximal phalanx of the hallux abutting against the head of the first metatarsal bone. With repetitive microtrauma in this area, an osteochondral defect develops. The body attempts to repair the damaged area by forming new bone tissue. This new bone formation manifests as a dorsal osteophyte on the head of the first metatarsal bone, which leads to further impingement and restriction of dorsiflexion of the first toe.

Hallux rigidus may also occur as a postoperative complication following surgery on the first metatarsophalangeal joint.

Lesser toe deformities result from the interplay of anatomical features, external influences, and systemic disorders, making their etiology complex and multifaceted [19], [20].

Among the biomechanical factors contributing to lesser ray deformities, particular attention is paid to hallux valgus. The deviation of the first toe toward the second is accompanied by a relative shortening of the first ray and a decrease in plantar fascia tension. This, in turn, leads to splayfoot, the development of instability in the metatarsophalangeal joints, and increased stress on the lesser toes. The resulting muscle imbalance between the flexors and extensors of the toes contributes to the progression of the deformity [21]. The relationship between hallux valgus and lesser ray deformity has been repeatedly emphasized in the literature [22].

The literature also mentions the impact of metatarsal length anomalies on load distribution in the foot. For example, D. J. Morton believed that an elongated second metatarsal bone (compared to the first) or its plantarflexion increases pressure on the second toe, predisposing it to deformities [23], [24].

External factors, particularly those related to footwear and trauma, are significant causes of lesser toe deformities. Tight shoes with a narrow toe box or high heels compress the toes, fixing them in an abnormal position and causing joint flexion. This is especially relevant for women, where the incidence of deformities is higher due to footwear features [25].

Mechanical injuries, such as phalangeal fractures, dislocations in the metatarsophalangeal joints, or plantar plate tears, disrupt foot anatomy and contribute to deformities. Trauma can act either as an acute cause or as a factor accelerating a chronic process.

Systemic and local diseases significantly increase the risk of deformities by affecting the muscles, nerves, and joints of the foot. Rheumatoid arthritis and other inflammatory processes destroy joint capsules and ligaments, causing subluxations and lesser toe deformities [26].

Conditions such as cerebral palsy, Charcot-Marie-Tooth disease, poliomyelitis, or lumbar disc herniation disrupt the innervation of the foot muscles, leading to spastic contraction of the flexors and weakness of the extensors.

Genetic predisposition and age-related changes also play a role in the etiology [27].

Functional insufficiency of the muscular-ligamentous apparatus of the foot plays an important role in the development of lesser ray deformities. With prolonged static or dynamic load, the muscles stabilizing the forefoot become fatigued and lose the ability to effectively maintain its arches. This leads to a redistribution of load to passive stabilizers—the capsular-ligamentous structures—which over time become overstretched, contributing to instability of the metatarsophalangeal joints and the formation of deformities [28].

The pathogenesis of flatfoot (valgus flatfoot deformity) is based on the insufficiency of the musculotendinous and ligamentous complex that maintains stability in the transverse tarsal (Chopart) joint. This complex, multi-component process of foot shape alteration occurs gradually, progressing through specific stages:

Stage 1 – internal rotation in the subtalar joint, which forms the axis of rotation. Here, the calcaneus gradually transitions into a pronated position. Normally, the pronation angle of the calcaneus is 5–7 degrees. During rotation, this angle increases to 10–12 degrees, after which the progression of displacement ceases. From this point on, the main load shifts to the talonavicular joint, marking the onset of Stage 2.

Comment: as is customary in traumatology and orthopedics, in this case we consider the dislocation of the peripheral segment relative to the central segment. Special attention should be focused on this, because in routine practice and even in scientific publications, authors mistakenly use the term "dislocation of the talus" when describing this process.

Stage 2 – alteration of angular relationships in the talonavicular joint due to degenerative changes in the musculotendinous and ligamentous complex of this joint. The calcaneonavicular (spring) ligament holds the navicular bone in a position where the tibialis posterior muscle can act upon it; the tendon of this muscle supports and depresses the navicular bone during toe-raising, thereby participating in the stabilization of the foot arch.

With a complete rupture of the calcaneonavicular ligament, Stage 3 ensues. Due to the insufficiency of the musculotendinous complex of the talonavicular joint, gradual extension and abduction occur in the Chopart joint. This is accompanied by stretching of the plantar aponeurosis followed by tilting of the calcaneus. Crucially for understanding the mechanism of pathogenesis, the pronation angle of the calcaneus remains unchanged.

Stage 4 is characterized by the entire body of the calcaneus (including the neck) resting against the support plane (the floor). The main load falls on the sustentaculum tali, and maximal pronation of the calcaneus occurs (up to 30–35°), terminating when the talar head abuts the floor. The inclination angle of the calcaneus becomes negative, forming a rocker-bottom foot.

The development of acquired clubfoot can be triggered by various pathological processes, which can be divided into the following main groups:

• Neurological disorders: Charcot-Marie-Tooth disease, cerebral palsy, spinal pathologies (spinal dysraphism, syringomyelia, spinal cord tumors), poliomyelitis [29], [30], [31], [32].

• Idiopathic form – in some cases, the cause of acquired clubfoot cannot be determined: a family history is identified in 25% of patients without neurological disorders [33]. A latent neurological component that is not diagnosed in the early stages is possible [34]. Congenital anatomical variations, such as hypertonus of the peroneus longus muscle, may also occur.

• Traumatic causes: spinal cord injuries (following traumatic brain injury or compression fractures of the spine), peripheral nerve injuries (peroneal or sciatic nerves) [35], [36], [37]. Fractures of the leg and foot can lead to malunion and subsequent foot deformity.

• Congenital orthopedic pathologies, such as connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome), can cause foot ligament instability, leading to deformity [38].

• Metabolic disorders: Vitamin D and calcium deficiency can lead to rickets, which is one of the possible causes of acquired clubfoot [39].

The pathogenesis of acquired clubfoot is complex and associated with muscle imbalance, neuromuscular disorders, and structural changes in the foot. The main mechanism of development is related to an imbalance between the flexors and extensors of the foot, which leads to characteristic anatomical and functional changes that form an equinovarus deformity.

Foot drop (equinus foot) can be of peripheral or central origin, and based on this circumstance, various causes of this condition must be considered.

Foot drop of peripheral origin:

• Compressive neuropathy.

  External compression is the most frequent cause of peroneal neuropathy and can occur due to several reasons, such as prolonged external compression from an incorrect posture in daily life: the habit of crossing legs while sitting, prolonged squatting or kneeling, which may be related to occupation. Casts and orthoses with a hard upper edge that can compress the nerve as it crosses the fibular neck, as well as tight bandages around the knee, are frequent causes of peroneal nerve neuropathy [40].

• Inflammatory or neoplastic lesions on the lateral surface of the lower leg.

  The peroneal nerve can be affected by an inflammatory or neoplastic process on the lateral surface of the lower leg (compression-ischemic neuropathy of the common peroneal nerve of Guillain-Sèze-Babin-Vulpian; tulip diggers' paralysis). A neuroma or a Baker's cyst of the knee joint is another rare cause of damage to this nerve [41].

• Traumatic injury of the peroneal nerve.

  A frequent cause of peroneal nerve injury is acute trauma, including the consequences of direct blows and lacerations, knee joint trauma and dislocations, fractures of the fibular head or neck, as well as gunshot wounds. The common peroneal nerve can also be accidentally injured during surgery, such as total knee arthroplasty or internal fixation [42].

• Intervertebral disc herniation (L5 radiculopathy).

• Compartment syndrome (anterior tibial artery syndrome).

  The name of the syndrome implies ischemic damage to the muscles of the long extensors of the foot and toes (tibialis anterior and extensor digitorum longus). They lie in a narrow canal formed dorsally by the anterior surface of the tibia and ventrally by the stretched fascia. Overload of these muscles can lead to their edematous swelling. Since the fascia limits the space, the swelling leads to capillary compression and ischemic muscle necrosis along with ischemic damage to the deep peroneal nerve. A similar mechanism (edema and muscle tissue ischemia) is observed with excessive muscle strain, for example, during soccer playing or prolonged walking [43].

• Iatrogenic paralysis due to incorrect intramuscular injection.

  Another example of iatrogenic injury is an incorrect intramuscular injection into the gluteal region. The division of the sciatic nerve into its main branches, the peroneal and tibial nerves, sometimes occurs quite high, so that only the peroneal nerve is affected. About 10% of patients do not experience paresthesia and pain during or immediately after the injection, and the onset of weakness may be delayed [44].

  Foot drop of central origin:

• Ischemic stroke and brain tumor.

• Post-ictal paresis.

• Traumatic brain injuries.

Foot drop syndrome can be divided into 2 main types: flaccid and spastic. The development of foot drop syndrome is based on insufficient dorsiflexion of the ankle joint during the swing phase, which can lead to a reduced toe clearance, averaging 1.6 cm during normal gait. Compensatory strategies for these changes include step shortening and a decrease in walking speed. The combination of excessive activity of the gastrocnemius muscle and tibialis posterior muscle leads to a change in ankle kinematics in the frontal plane, forming an equinovarus foot position. Conversely, an equinovalgus foot position can occur with excessive activation of the peroneus brevis muscle or insufficient activity of the soleus muscle in flaccid paresis [45]. Spasticity of the ankle extensor muscles (gastrocnemius and soleus) contributes to pathological gait alterations in both phases of the gait cycle. The combination of insufficient knee flexion and ankle dorsiflexion can lead to the stroke-specific stiff knee gait, resulting in functional lengthening of the paretic leg during the swing phase. Options for compensating for the relative lengthening of the transferred limb are very diverse and depend on the cause that triggers it [46].

Compensation mechanisms used include: circumduction of the paretic leg, toe-standing on the healthy leg during the stance phase, and pelvic tilt toward the healthy leg. Authors disagree regarding the compensatory or adaptive nature of such movements in patients. Some researchers argue that, for example, circumduction has no compensatory significance from a biomechanical point of view and is, conversely, a more energy-consuming movement to reduce stiff knee gait, but occurs primarily due to impaired activation connections of the gluteus maximus and rectus femoris muscles [47], [48], [49]. At the same time, pelvic tilt, on the contrary, is one of the main compensatory strategies for reducing knee flexion [47]. Classically, impaired kinematics of ankle movements manifests as its insufficient dorsiflexion during the swing phase. Impaired ankle kinematics, according to many authors, is one of the most significant factors leading to reduced speed, walking quality, and altered kinematics of movements in both the paretic and healthy legs.

It is also worth considering that almost any type of forefoot, midfoot, and hindfoot deformity can result from trauma. In severe injuries, the deformity can be multiplanar and combine a combination of components from different nosological forms.

1.3 Epidemiology of the Disease or Condition

Due to the specifics of the formation of various variants of foot deformations, data on their epidemiology are also presented by section.

Hallux valgus is the most frequent orthopedic disorder, accounting for, according to various authors, from 72% to 80% of all foot orthopedic pathologies [50]. According to a meta-analysis by S. Nix conducted in 2013, hallux valgus occurs in 23% of the general population aged 18 to 65 years, and already in 35.7% of those older than 65 years. This disease refers to static foot deformities, which affect at least 50% of the adult European population, with about 30% having deformities of the first ray of the foot [51]. In the USA, static foot deformities are observed in 40% of the adult population [52]. In Russia, this figure ranges from 15% to 58% [50]. Hallux valgus occurs predominantly in women, who make up the overwhelming majority of patients: from 97% to 99.1% [15]. The social significance of this pathology lies in the fact that it usually affects individuals of working age who have high demands on their physical activity [53].

Hallux rigidus is the second most common condition of the first metatarsophalangeal joint after hallux valgus. It occurs in approximately 1 in 40 people over the age of 50. There is a clear correlation with hereditary factors. Coughlin and Shurnas in 2003, based on a meta-analysis, showed that 80% of patients suffering from this disease have the problem in both feet, 98% noted the presence of the disease in their direct relatives, and 62% of patients were women.

According to studies, hammer toe deformity of the lesser toes occurs in 20–30% of the adult population, with women being 2 to 4 times more prone to this deformity than men. One of the main contributing factors is wearing uncomfortable and narrow shoes, including high heels. The prevalence of hammer toe increases with age. Approximately 25% of people over 65 years old have varying degrees of this deformity. Aging factors, such as decreased ligament elasticity and weakened muscle tone, contribute to the development of deformities [54].

An analysis of scientific studies shows that the incidence of flatfoot (pes planovalgus) in adults varies depending on the geographic region, diagnostic methodology, and risk factors, ranging from 3 to 25% [55]. A study conducted in Riyadh (Saudi Arabia) revealed that flatfoot is more common in individuals with a high body mass index (BMI), and there is a significant correlation between overweight and the development of this pathology [56].

Acquired clubfoot is a common foot deformity that can range from mild, barely noticeable changes to severe, rigid forms requiring surgical correction. Despite its clinical significance, its prevalence and epidemiological data remain insufficiently studied due to the variability of the deformity's severity and its multifactorial nature [57].

Data on the incidence and prevalence of drop foot (equinus foot) are currently very scarce in the literature. Several authors note that this syndrome is quite common and affects patients across a wide age range [58]. It is worth noting that there are no clearly defined criteria for patient susceptibility to this condition. However, according to scientific literature, an increased risk of its development is observed in young patients actively involved in sports, individuals whose occupational activity involves prolonged static loads (especially in a squatting position with flexed knees and hips), as well as in patients with central nervous system diseases and spinal pathology [59].

1.4 Features of Coding the Disease or Condition

M20.1 Hallux valgus (acquired)

M20.2 Hallux rigidus

M20.3 Other deformities of hallux (acquired)

M20.4 Other hammer toe(s) (acquired)

M20.5 Other deformity(ies) of toe(s) (acquired)

M20.6 Acquired deformity of toe(s), unspecified

M21.3 Drop foot or hand (acquired)

M21.4 Flat foot [pes planus] (acquired)

M21.5 Acquired clawhand, clubhand, pes cavus, and clubfoot

M21.6 Other acquired deformities of ankle and foot

M21.9 Acquired deformity of limb, unspecified

1.5 Classification of the disease or condition

Considering the foot as a whole, all deformities can be divided into forefoot, midfoot, and hindfoot deformities. However, in practice, isolated deformities are rare because all parts of the foot function within an interconnected kinematic system. Therefore, classifying pathologies by individual nosological forms appears more appropriate.

For hallux valgus, the descriptive classification by M.J. Coughlin and R.A. Mann best meets modern requirements. The authors distinguish mild, moderate, and severe deformities [11].

In mild deformity, the hallux valgus angle is radiographically no more than 20°, and the deformity is often aggravated by the valgus deviation of the hallux itself. The first metatarsophalangeal joint is usually congruent, and the first intermetatarsal angle does not exceed 11–12°. Typically, patients with such a deformity complain of discomfort in wearing shoes due to skin friction in the medial region of the first metatarsophalangeal joint. The osteophyte of the first metatarsal head is small, localized dorsomedially. Radiography reveals a minor subluxation of the lateral sesamoid bone, maximally up to 50% of its size.

Moderate deformity is usually accompanied by subluxation in the first metatarsophalangeal joint, unless there is a pathological inclination angle of the first metatarsal articular surface. The hallux valgus angle ranges from 20° to 40°, with the first toe exerting pressure on the second toe and displacing it. The hallux itself is most often pronated. The first intermetatarsal angle ranges from 12° to 16°, with lateral sesamoid bone displacement from 75% to 100%.

Severe hallux valgus exceeds 40° of lateral deviation, causing the second toe to shift over or under the first toe. The hallux is moderately or significantly pronated. Due to the medial displacement of the first metatarsal head, body weight bearing during standing and walking falls on the second metatarsal head, which is usually accompanied by pain. The first intermetatarsal angle exceeds 16%. Lateral sesamoid bone displacement reaches 100%, with subluxation or dislocation in the metatarsophalangeal joint.

In the case of hallux rigidus, the radiological classification by Hattrup and Johnson, created in 1988, best meets modern requirements. The authors distinguish 3 stages of the disease:

Stage I – slight joint space narrowing, absence of osteophytes.

Stage II – severe changes, joint space narrowing, osteophytes on the first metatarsal head and proximal phalanx, subchondral cysts and sclerosis zones.

Stage III – fibrous ankylosis of the joint, pronounced osteophytes, absence of joint space.

However, other scoring systems for arthritic changes (such as Kosinskaya, Kellgren-Lawrence, etc.) can also be used for the radiological classification and assessment of Hallux Rigidus.

Three main deformities of the lesser toes can be distinguished [60]:

• Hammer toe – accompanied by extension contracture of the metatarsophalangeal joint, flexion contracture of the proximal interphalangeal joint, and hyperextension of the distal interphalangeal joint.

• Claw toe – accompanied by extension contracture of the metatarsophalangeal joint, and flexion contracture of the proximal and distal interphalangeal joints.

• Mallet toe – accompanied by extension contracture in the metatarsophalangeal and proximal interphalangeal joints, and flexion contracture in the distal interphalangeal joint.

Hammer toe is the most common; to assess its severity, the Hamilton-Thompson classification can be used, which is based on the stability of the metatarsophalangeal joint [61]:

• G0 – joint is stable

• G1-G2 – subluxation is present in the metatarsophalangeal joint (violation of the axes of the toe and metatarsal)

• G3 – metatarsophalangeal joint is easily "displaceable", there is a full reducible or non-rigid dislocation of the proximal phalanx of the toe

• G4 – metatarsophalangeal joint is displaced, there is a full irreducible or rigid dislocation of the proximal phalanx of the toe

A classification has also been developed that divides hammer toe deformities into the following categories:

1. By degree of fixation:

o Fixed:

■ Characterized by the presence of contracture in the joints.

o Non-fixed:

■ Contracture in the joints is absent.

2. By type of deformity:

o Flexion:

■ Deformity is limited to the proximal interphalangeal joint.

o Flexion-extension:

■ Deformity involves both the proximal interphalangeal joint and the metatarsophalangeal joint.

3. By stability of the metatarsophalangeal joint:

o Without instability:

■ MTP joint remains stable, without toe displacement.

o With instability:

■ MTP joint is unstable, accompanied by:

▪ Abduction (lateral displacement of the toe).

▪ Adduction (medial displacement of the toe).

The C. Nery classification of second metatarsophalangeal joint instability [27] is known, according to which five degrees of deformity in the metatarsophalangeal joint are distinguished based on joint congruity and corresponding clinical manifestations: pain, edema, weight-bearing capacity of the toe, drawer test, subluxation, and dislocation in the joint.

Dhukaram et al. described three types of hammertoes [62]:

Type 1 — correctable metatarsophalangeal joint and proximal interphalangeal joint;

Type 2 — correctable metatarsophalangeal joint, but fixed interphalangeal joint;

Type 3 — fixed or subluxated metatarsophalangeal and fixed interphalangeal joints.

Acquired flatfoot (pes planovalgus) is a heterogeneous group of deformities with various causes and clinical manifestations. Because of this, several classifications are presented in the medical literature, but the classification developed by V.G. Protsko appears to be the most optimal.

Valgus foot deformity is divided into:

1) hindfoot deformity,

2) midfoot deformity,

3) ankle joint deformity.

The following classification is adopted for the hindfoot:

• Grade I is characterized by moderate heel pronation (up to 10º) and internal tibial rotation. With the knee extended, the foot is brought to an angle of up to 90º relative to the tibia (the Achilles tendon is not affected). Plantography shows narrowing of the support in the lateral division or a complete break in the footprint. Tests for posterior tibial tendon dysfunction are negative. On radiographs: calcaneal-first metatarsal angle (Bogdanov's angle) < 131º. The talonavicular-first metatarsal angle (lateral view) is 5–10º. The talonavicular-first metatarsal angle (plantar view) is 3–8º. The calcaneocuboid angle (CCA) is within 0–1º. The calcaneal pitch angle (CPA) is equal to or exceeds 18º. The talocalcaneal angle (TCA) in the lateral view may exceed 30º; in the plantar view – 15–20º. Sye's line (SL) is tortuous in the lateral view and smooth in the plantar view. Medial longitudinal arch height > 35 mm. Talonavicular joint angle (TNJA) = 0–4º. All tests for talonavicular joint stability are positive (Jack's test, tip-toe test, etc.).

• Grade II features stage 1 posterior tibial tendon dysfunction (PTTD). With the knee extended, the foot is brought to 95–100 degrees relative to the tibia. On radiographs, the calcaneal-first metatarsal angle (Bogdanov's angle) is 131–140º. The talonavicular-first metatarsal angle (lateral view) is 5–8º. The talonavicular-first metatarsal angle (plantar view) is 3–8º. CCA is 2–4º. CPA is 17–14º. TCA in the lateral view is 30–35º, in the plantar view – 20–25º. SL is tortuous in the plantar view and sharply tortuous in the lateral view. TNJA is 1–4º. Tests for the competence of the talonavicular musculotendinous complex are positive. The height of the medial longitudinal arch is 35–25 mm. Plantography reveals a flattened footprint type. The main difference between grade II and grade I deformity is a lower CPA and tortuosity of the SL in the plantar view.

• Grade III is characterized by stage 2–3 PTTD. With the knee extended, the foot cannot be brought to an angle less than 100º relative to the tibia. There is pronounced forefoot supination. Plantography reveals a flatfoot-valgus footprint type.

  o Grade III-a features moderate mobility of the talonavicular joint and naviculocuneiform joint; stage 2 posterior tibial tendon dysfunction – with a negative Jack's test, the tip-toe test is weakly positive (the heel is in a coaxial position with the tibia or slightly supinated). On radiographs, the calcaneal-first metatarsal angle (Bogdanov's angle) is 141–155º. The talonavicular-first metatarsal angle (plantar view) – 9–20º, CCA 5–10º, CPA 13–11º. TCA in the lateral view is 35–45º, in the plantar view – 25–30º. SL is sharply tortuous. Medial longitudinal arch height is 25–17 mm. TNJA is within 5–14º. The main tests determining the stability of the talonavicular musculotendinous complex in patients with grade III-a deformity: negative podometric dynamics - Jack's test, weakly positive "tip-toe standing" test, i.e., the heel axis runs parallel to the tibial axis or in slight supination relative to it. Negative podometric dynamics of Jack's test is explained by the fact that in case of failure of the tendon-ligament complex, the talar head is internally rotated and lies on the calcaneonavicular ligament. At the same time, the articular part of the navicular bone adjoins the antererosuperior part of the articular surface of the talus. The articular part of the talar head mostly lies below the articular part of the navicular bone and acts as a strut during Jack's test, since the navicular bone rests against the head rather than sliding down along it, preventing greater concavity formation along the medial border of the foot.

  o Grade III-b is characterized by pronounced hypermobility of the talonavicular joint or naviculocuneiform joint and stage 3 PTTD – the tip-toe test is negative. On radiographs, the calcaneal-first metatarsal angle (Bogdanov's angle) is > 155º. The talonavicular-first metatarsal angle in lateral and plantar views is greater than 20º, CCA > 10º, CPA > 11º. TCA in the lateral view is > 45º; in the plantar view – > 30º. SL is sharply tortuous. Medial longitudinal arch height is less than 17 mm. Talonavicular relationship angle (TNRA) exceeds 15º. Plantography reveals a flatfoot-valgus footprint type.

• In grade IV deformity, the talus touches the support plane. On the radiograph, the calcaneal pitch angle is close to 0° (grade IV-a) or negative (grade IV-b), and the navicular bone slides upward over the talar head. On anteroposterior radiographs, the navicular bone barely covers the talar head, forming pronounced abduction in the midtarsal (Chopart's) joint, with a large calcaneal-talar angle exceeding 40º. Pronounced heel pronation is characteristic: up to 15° in grade IV-a deformity and more than 15° in grade IV-b. The talus touches the support plane in grade IV-a, and there is full weight-bearing on it in grade IV-b. The tip-toe test is negative (the heel remains pronated), with extension and abduction of the foot in Chopart's joint (positive too-many-toes sign).

Acquired clubfoot (pes cavovarus) is a heterogeneous group of deformities with various causes and clinical manifestations. Because of this, several classifications are presented in the medical literature based on etiology, anatomical distribution, rigidity grade, and radiological parameters, each used depending on diagnostic and treatment goals:

• Etiological (neurological, idiopathic, traumatic, etc.) [29].

• Anatomical (anterior, middle, posterior pes cavus, cavovarus deformity, equinocavovarus deformity, etc. – depending on the deformity components) [31].

• By rigidity grade (correctable, semi-rigid, rigid) [32].

• Radiological (Meary's angle, calcaneal pitch, etc.).

There are several classifications of foot drop based on various criteria:

• By lesion location: central, peripheral

• By etiology: traumatic, neurodegenerative, vascular, muscular

• By clinical characteristics: acute, chronic, reversible, and irreversible

• By severity of impairment: partial (paresis), complete (paralysis)

• By deformity features: supple, rigid

1.6 Clinical presentation of the disease or condition

All foot deformities are characterized by both general and specific complaints, which are best considered in relation to a specific nosology.

The main complaints in hallux valgus are pain and a feeling of stiffness in the forefoot during walking or after functional load, inability to find normal and sometimes even special orthopedic footwear, as well as a noticeable cosmetic defect [63]. The formation of hyperkeratoses is characteristic, both on the plantar surface of the foot and on the dorsal and lateral surfaces of the toes. Bursitis may develop in the area of the first metatarsophalangeal joint. Some patients complain of nail plate deformation, which can lead to ingrown toenails. Skin irritation, ulceration, and long-term non-healing wounds may form at sites of greatest contact with footwear [64].

Patients with hallux rigidus typically present with a primary complaint of pain in the first metatarsophalangeal joint. The pain is most often associated with weight-bearing and is also frequently combined with swelling of the first metatarsophalangeal joint. There may be redness around the joint, although this usually occurs after heavy exertion and causes an exacerbation of the disease.

The main clinical manifestations of hammer toe deformity of the lesser toes include a change in the shape of one or more toes, leading to their shortening and alteration of their normal alignment. In addition to a cosmetic defect, patients often complain of pain in the area of the deformed toes, which intensifies when wearing shoes or during weight-bearing. In general, lesser toe deformities are characterized by friction and pressure symptoms leading to the formation of abrasions, hyperkeratosis, superficial skin damage, and maceration, which not only worsen discomfort but may also be complicated by secondary infection. Lesser ray deformities, including hammer toe, limit toe mobility, which can lead to gait changes and increased load on other parts of the foot.

The most characteristic sign of flatfoot (pes planovalgus) is the lowering of the medial longitudinal arch of the foot, up to its complete absence. This is often accompanied by gait changes, pain, and muscle fatigue. The clinical presentation can vary significantly depending on the severity of the deformity. In mild cases, symptoms may be minimal, whereas in severe cases, there is persistent pain in the feet, lower legs, and knees, limited mobility, rapid fatigue when walking, and the development of secondary deformities of the forefoot and lower limb [65]. With pronounced longitudinal flatfoot, there is a noticeable decrease in the distance from the navicular tuberosity to the support plane. Long-standing deformity can lead to secondary degenerative joint changes.

Clinical manifestations and complaints in acquired clubfoot depend on the severity of the deformity, its rigidity, and the presence of concomitant neurological disorders. Acquired clubfoot may be asymptomatic.

Pain is the main symptom, and it can be localized in different parts of the foot: in the forefoot due to the development of metatarsalgia and claw toe deformity, along the dorsal aspect of the midfoot due to shoe pressure and the development of arthritic changes with osteophyte formation, along the plantar aspect due to plantar aponeurosis contracture with the potential development of plantar fasciitis, etc. [31], [32], [38].

Patients with acquired clubfoot often experience instability when walking, associated with a hindfoot varus alignment that increases the risk of rolling the ankle and damaging the lateral ankle ligaments, and a shift of the center of gravity to the forefoot, which impairs balance and can cause an unsteady gait and weakness in the foot muscles, making it difficult to maintain stability while walking [3], [29], [66].

In addition, fixation of the foot in inversion (hindfoot varus) and forefoot pronation reduces shock absorption and increases the risk of joint damage [66]. Meanwhile, shifting the load to the forefoot increases the risk of calluses and trophic disorders [57].

As acquired clubfoot progresses, the following complications may develop:

⮚ Stress fractures of the fifth metatarsal – due to the shift of the load to the lateral edge of the foot [67].

⮚ Chronic ligamentous sprains and tears – as a result of foot instability [66].

⮚ Osteoarthritis – due to constant overload of the foot joints [2].

⮚ Iliotibial band syndrome – a compensatory walking posture abnormality leading to knee and hip pain [31].

The main complaint of patients with foot drop syndrome is weakness in the foot and its dropping when walking, resulting in an unsteady gait and an increased risk of stumbling and falls. Weakness of the ankle and toe extensors of the right leg may interfere with the patient's ability to drive (transferring the foot from one pedal to the other is difficult, as is operating the clutch in a manual transmission car). If a person fails to fully appreciate the problem, this creates conditions for road accidents. Functional impairments associated with weak foot and toe extension may include the inability to accelerate the pace and/or run, or engage in sports. Persistent numbness in the innervation zone of the peroneal nerve creates unpleasant sensations, but patients focus more on painful paresthesias and pain syndrome [68].

Clinical symptoms of compression of the common peroneal (CPN), deep peroneal (DPN), and superficial peroneal (SPN) nerves differ. CPN neuropathy manifests as weakness of the peroneal muscle group and sensory impairment on the anterolateral surface of the lower leg and the dorsum of the foot. In the early stages, clinical symptoms of SPN neuropathy may occur only during physical exertion. In SPN neuropathy, the strength of the big toe and foot extensors is not altered, although there may be weakness in the foot during pronation. Most commonly, there is a reduction or alteration of sensation on the dorsum of the foot and the lateral surface of the lower leg, the first web space, as well as pain along the anterolateral surface of the lower leg and the dorsum of the foot [69]. The clinical picture of DPN neuropathy is mainly represented by weakness of the foot extensors, extensor digitorum longus and hallucis longus, and extensor digitorum brevis. Pain in the anterior ankle joint may also occur, which worsens with physical activity and tight footwear.

2. Diagnostics, medical indications and contraindications for diagnostic methods

Criteria for establishing the diagnosis/condition

The diagnosis of any acquired foot deformity is established based on:

1) complaints (pain, deformity, limited movement in the joints of the foot and ankle joint);

2) anamnestic data (indication of neurological disorders, family history, injuries);

3) physical examination (clinical inspection data);

4) instrumental examination (radiography, MRI, CT, ENMG, etc.).

2.1 Complaints and Anamnesis

• To establish a diagnosis when assessing patient complaints, it is recommended to pay attention to: pain and its localization, deformity of various parts of the foot, limitation of the range of motion in the joints of the foot and ankle, impaired weight-bearing capacity, presence of hyperkeratosis, toenail deformity, difficulty in choosing shoes, and the presence of a family or traumatic history [63].

Strength of recommendation 2 (level of evidence – A).

2.2 Physical Examination

Comments: given the rather complex anatomy and biomechanics of the foot, the physical examination of relevant patients is a multicomponent complex of inspection, questioning, and special diagnostic tests. To facilitate comprehension and highlight the most important aspects, the information below is divided into separate blocks.

Direct assessment of the first ray of the foot. The first metatarsophalangeal joint is inspected, noting the presence of bursitis and palpating the exact localization and extent of tenderness.

When determining the valgus deviation of the big toe, it is necessary to assess whether the valgus alignment of the toe is a consequence of the varus deviation of the first metatarsal or if it is a deformity at the level of the proximal phalanx, which may have its own deformity [71].

Movements in the first metatarsophalangeal joint are examined (normally they are 70-90º of dorsiflexion and 30º of plantarflexion). Any movement limitations are assessed to determine the cause of the limitations – whether it was related to the presence of osteophytes, joint arthrosis, or is merely a consequence of deformity and lack of congruence in the joint. Lateral stability in the first metatarsophalangeal joint, which normally has no movement in the horizontal plane, is also assessed at this stage.

The study of foot elasticity is carried out by attempting to bring the heads of the first and second metatarsals together manually. With the first type of elasticity, compression of the foot allows the metatarsal heads to be brought together and easily forms the transverse arch of the foot. With the second type, a certain amount of effort was required to bring the metatarsal heads together, and with the third type, this was impossible. According to A.A. Kardanov et al. (2008), the first type of elasticity is the most unfavorable for the long-term results of surgical treatment [53].

Direct assessment of the lesser rays of the foot. When assessing forefoot deformity, inspection of the feet in a standing position may be recommended, which allows for the assessment of the contact of the lesser toes with the surface. Further examination can be performed in a sitting or lying position.

Motions in the interphalangeal joints are assessed with the ankle joint set at a 90-degree angle, while the patient should actively perform dorsiflexion and plantarflexion in the metatarsophalangeal and interphalangeal joints. Passive movements can also be assessed simultaneously. It should be noted that there is a high degree of individual variability in the range of motion of the small toe joints: total dorsiflexion ranges from 45 to 90 degrees, and plantarflexion ranges from 10 to 40 degrees, depending on the mobility of individual joints [72]. Assessment of metatarsophalangeal joint stability (vertical and horizontal) may also be useful to determine the treatment strategy.

Assessment of the ankle joint and Achilles tendon. Attention is paid to the symmetry of the malleoli, the presence of edema, and the presence of deformities. It is important to assess the axis of the entire lower limb rather than focusing solely on the ankle joint and foot. The shape and symmetry of the Achilles tendons can be assessed visually. Palpation begins with the medial and lateral malleoli, then proceeds to the anterior capsule of the ankle joint. The areas of the medial and lateral ligamentous complexes, as well as the syndesmosis, are checked. The Achilles tendon is palpated along its entire length from its insertion at the calcaneal tuberosity to its transition into the gastrocnemius muscle—the presence of induration, tenderness, or crepitus is assessed. The range of motion in the ankle joint is evaluated: dorsiflexion — normal up to 20°, plantarflexion — normal up to 45°; it is recommended to compare the results with the contralateral limb. Assessing ankle stability (anterior drawer test) can be useful to rule out concomitant ligamentous injuries. Both acquired flat-valgus deformity and acquired clubfoot may be characterized by Achilles tendon contracture. To assess it, the Silfverskiöld test is recommended. Test name spellings and translations may vary across different sources.

Silfverskiöld test is a clinical maneuver used to differentiate gastrocnemius contracture from a deeper contracture of the entire triceps surae muscle or Achilles tendon. It is particularly important when evaluating limited ankle dorsiflexion.

Performing the test:

• The patient is in a supine or sitting position.

• The physician first flexes the patient's knee (to eliminate tension in the gastrocnemius muscle) and checks the range of ankle dorsiflexion.

• The physician then extends the knee and reassesses dorsiflexion.

Interpretation:

• If dorsiflexion increases with the knee flexed but is limited when extended, this indicates an isolated gastrocnemius contracture.

• If dorsiflexion is limited in both positions, an Achilles tendon contracture or triceps surae contracture is likely.

Assessment of the hindfoot. It is recommended to examine the patient in standing and supine positions. From the rear, the position of the calcaneus relative to the axis of the lower leg is evaluated: in valgus alignment, the heel is tilted outward (characteristic of flatfoot), and in varus alignment, inward. In the toe-standing position, the ability of the heel to invert is checked—this is called the single heel-rise test: if inversion is absent, it may indicate posterior tibial tendon dysfunction or a rigid deformity. The range of motion in the subtalar joint is evaluated: normally there should be approximately 20–30° of inversion and 5–10° of eversion. The symmetry of the Achilles tendon and the presence of calcaneal deformity in its insertion area are also assessed. The subtalar joint, posterior margin of the calcaneus, Achilles tendon, and the insertion areas of the posterior tibial and long peroneal tendons (as well as the tendons themselves) are palpated. Tenderness in the subtalar joint may indicate osteoarthritis, coalition, or overload, especially in flat feet. It is also important to identify possible inflammation in the Achilles tendon insertion area.

Assessment of the midfoot. The foot is examined at rest and under weight-bearing: attention is drawn to a prominence in the area of the talonavicular joint (often in flatfoot), arch flattening, asymmetry, adduction or abduction, pronation or supination. Palpation is performed along the medial border — tenderness may indicate inflammation, instability, or stress injuries. Joint stability of the Lisfranc joint can be assessed manually. The medial longitudinal arch is also assessed using the Jack test.

Jack test is a clinical diagnostic test used to evaluate the function of the medial longitudinal arch of the foot and determine flexibility in flat-valgus foot deformity. During the test, the patient is asked to stand barefoot, and the physician then passively raises (dorsiflexes) the big toe. The reaction of the medial arch is observed: normally, or in flexible (functional) flatfoot, the arch forms or increases, whereas in the rigid form, the arch does not rise.

Coleman block test is a diagnostic test used to assess hindfoot rigidity in cavovarus foot, valgus foot, varus foot, or flat-valgus foot deformity. It helps determine whether heel varus or valgus alignment is primary or secondary relative to the forefoot [73].

Coleman block test procedure: the patient stands with the foot placed on a 2–3 cm thick block that supports only the lateral or medial border of the foot and heel, leaving the first ray free, which eliminates its influence on the hindfoot. If the heel position improves, the deformity is considered secondary, associated with plantarflexion of the first ray. If the heel remains in position, the deformity is considered fixed, indicating a rigid deformity[16].

Gait analysis. This is an important part of the physical examination and can begin even before the formal examination—from the moment the patient enters the office. The physician evaluates rhythm, symmetry, stride cycle, use of assistive devices, and the three phases of gait: heel strike, midstance, and toe-off. Abnormalities may manifest as shortened stride, altered foot position, asymmetric weight-bearing, or lack of a normal roll-off.

Vascular examination of the feet. Vascular status in patients with foot disorders is of great significance; therefore, the examination includes checking pulses in the lower limbs in general and in the feet in particular, such as: dorsalis pedis artery, posterior tibial artery, popliteal artery. Neurological examination. Tactile sensitivity is compared in both feet and lower legs, and muscle tone is compared between both lower limbs.

Dermatological examination. Both legs are examined for skin lesions or ulcerations. Skin elasticity and turgor are compared between both lower limbs. The plantar surfaces of both feet are examined for hyperkeratosis, after which their size, location, firmness, and tenderness are assessed.

It should be noted that the physical examination algorithm may be modified depending on each specific pathology and patient characteristics. Furthermore, new functional tests regularly emerge for various pathologies, and their selection and use remain at the physician's discretion.

2.3 Laboratory Diagnostics

Laboratory tests play a supportive role in the diagnosis of acquired foot deformities, but they can be useful when infectious, rheumatological, or metabolic diseases are suspected, such as diabetes mellitus, rheumatoid arthritis, gout, and osteomyelitis.

Key laboratory tests for relevant patients include: complete blood count (CBC) to assess inflammatory processes, serum C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to assess inflammation activity, as well as blood rheumatoid factor (RF) and anti-citrullinated vimentin antibodies (anti-CCP) when rheumatoid arthritis is suspected. Blood glucose and glycated hemoglobin tests are necessary to detect or monitor diabetes, especially in the presence of neuropathic deformities (e.g., Charcot foot). Elevated blood uric acid levels may indicate gout. In addition, cultures and swabs may be indicated if an infectious process is suspected. Although primary diagnosis of deformities relies on clinical examination and imaging (X-ray, CT, MRI), laboratory tests can provide valuable additional information and aid in diagnosis [18, 74].

2.4 Instrumental Diagnostics

Instrumental diagnostics of acquired foot deformations is based on the sequential use of various imaging modalities for pathological changes, starting with radiography and, if necessary, supplementing it with other methods: CT, MRI, ultrasound, etc.

If the patient has a forefoot deformity only, weight-bearing (load-bearing) foot radiographs in anteroposterior (AP) and lateral projections should be performed. If necessary, they can be supplemented with an oblique projection.

• In the presence of a midfoot or hindfoot deformity, as well as combined deformities, it is recommended to supplement the AP foot radiograph with AP and lateral radiographs of the ankle joint (with the lateral projection capturing the foot), and if necessary, an axial projection of the hindfoot. These radiographs are also recommended to be performed under load [75].

GPP CLOE 4Grade of Recommendation C (Level of Evidence – 4).

Comments: if technical capabilities are lacking, non-weight-bearing radiographs are permitted, but in such cases, it should be taken into account that they will be less informative.

Proper execution of these radiographs allows for the measurement of a number of parameters and angles that can help evaluate deformations affecting the midfoot, hindfoot, and ankle joint, for example [76]:

• Meary's angle:

  o Normal: 0–5°.

  o Pes cavus: angle greater than 5°, open plantarly; pes planus: angle greater than 5°, open dorsally.

  o Technique: measured as the angle between the longitudinal axis of the talus and the axis of the first metatarsal bone in the lateral projection [13], [50].

• Hibbs' angle:

  o Normal: 150°.

  o Pes cavus: if the angle is >150°.

  o Technique: measured as the angle between the axis of the calcaneus and the axis of the first metatarsal bone in the lateral projection [14], [50].

• Calcaneal pitch:

  o Normal: 17–25°.

  o Technique: measured as the angle between a line drawn along the inferior border of the calcaneus and a horizontal line (the floor surface) in the lateral projection [15], [50].

• Talo-calcaneal angle:

  o Normal: 15–30°.

  o Technique: measured as the angle between the axial lines of the talus and calcaneus in the lateral projection [50], [51].

• Metatarsal declination angle:

  o Normal: 15–25°.

  o Technique: measured as the angle between the long axis of the first metatarsal bone and a horizontal line in the lateral projection [10], [52].

• Metatarsal declination angle:

  o Normal: 15–25°.

  o Technique: measured as the angle between the long axis of the first metatarsal bone and a horizontal line in the lateral projection [10], [52].

• Calcaneocuboid angle (CCA): formed by a line running along the lateral surface of the calcaneal region and a line running along the lateral surface of the cuboid bone. Normally, these lines are almost parallel or form a small angle. In planovalgus deformity, the angle is greater than 8°. An increase in this angle is a sign of forefoot abduction.

• Talonavicular coverage angle (TNCA): measured in the plantar projection. Formed by the intersection of a line connecting the extreme points of the articular surface arc of the navicular bone and a line connecting the extreme points of the articular surface of the talar head. Normally 2–7°. An angle greater than 7° is a sign of longitudinal flatfoot and foot abduction at the Chopart joint.

• First cuneiform – first metatarsal angle (1C-1MT): evaluated on AP radiographs. Formed by the intersection of the axes of the medial cuneiform and the first metatarsal bone. Normally, the angle is 162–168°. An increase in the angle indicates the degree of foot abduction at the Lisfranc joint. In this case, the angle approaches 180° and, with further deformity, can exceed 200°. Foot abduction is also accompanied by an increase in the calcaneocuboid angle.

• Tibio-talar angle (TT) evaluated in the AP projection. The angle is formed between the axis of the tibia and the perpendicular to a line drawn parallel to the line of the articular surface of the talus, which is formed by connecting the extreme points of the talar articular surface. Normally, the lines merge with each other (angle is 0°). With angular displacements of the talus, the angle increases.

• Tibio-calcaneal angle (TC): formed between the axis of the tibia and the axis of the calcaneal tuberosity determined in the AP projection. Normally, the angle is from 3° to 7°. In hindfoot valgus deviation, the angle may increase up to 15°. When the calcaneal pitch is 0 and especially when it becomes negative, the value of the TC angle can increase sharply, reaching 45°. In case of valgus deviation in the ankle joint, the magnitude of the TC angle is directly proportional to the increase in the TT angle.

• Medial anatomical angle of the Chopart joint: determined in the AP projection between the Chopart joint line and the anatomical axis of the 2nd metatarsal bone. In the absence of midfoot deformity, the anatomical axis of the 2nd metatarsal bone intersects the Chopart joint line at its center at an angle of 90.3 (+3.9°), opening medially.

• Lateral mechanical angle of the midfoot: determined from lateral radiographs. In the absence of midfoot deformity, the mechanical axis of the 1st metatarsal bone intersects the line of the talar dome at its posterior point at an angle of 23.4 (+3.02°).

• Lateral anatomical angle of the midfoot: determined from lateral radiographs. In the absence of midfoot deformity, the anatomical axis of the 1st metatarsal bone intersects the line of the talar dome at a point determined by the formula: (length of the talar dome line) x (coefficient 0.49) at an angle of 26.1 (+3.5°).

• Lateral hindfoot angle: determined from lateral radiographs. In the absence of hindfoot deformity, the anatomical axis of the calcaneus intersects the anteriorly extended line of the talar dome at a point determined by the formula: (length of the talar dome line) x (coefficient 1.87) at an angle of 17.7 (+5.1°).

• Posterior (axial) tibio-calcaneal angle: determined from axial radiographs. In the absence of hindfoot deformity, the anatomical axis of the calcaneus is located lateral to the anatomical axis of the tibia by up to 10 mm and has a valgus deviation of up to 10°.

Comments: other radiological parameters may also be used; the choice is determined individually depending on the deformity components in a particular patient. Also, slight differences in measurement techniques and normal angle values can be found in various literature sources.

Radiological parameters for planovalgus deformity are described in detail in the Classification section.

• To diagnose forefoot deformity, it is recommended that all patients undergo foot radiography in two projections. All radiographs are recommended to be performed under load, since the difference between the angle values on weight-bearing radiographs compared to non-weight-bearing ones can reach 20% [53].

Level CLevel 5Level of recommendation evidence C (reliability level of evidence – 5).

Comments: in the absence of technical capabilities, non-weight-bearing radiography and specific projections are permitted, but in such cases, it should be taken into account that they will be less informative.

The AP projection is performed as follows: the distance from the X-ray tube to the examined foot should be 1 meter, which allows for accurate determination of the dimensions of the metatarsal bones, and it is taken at an angle of 15 degrees relative to the vertical plane, which ultimately provides a strictly perpendicular projection to the metatarsal bones, whose angle of attack averages 15 degrees relative to the horizontal plane.

After obtaining the radiographs, measurements of values used for preoperative planning must be performed on them. The following parameters are noted as the most informative for planning surgical treatment of the forefoot:

1. First intermetatarsal angle – the angle between the reference line of the first metatarsal bone and the reference line of the second metatarsal bone (Fig. 1). Normally, it ranges from 0° to 14°. An increase in this value is referred to as metatarsus primus adductus [77].

2. Hallux abductus angle – the angle formed by the reference lines of the first metatarsal bone and the proximal phalanx of the hallux (Fig. 1). Normally, it is less than 16°. The deformity is characterized as mild at an angle of 16° to 25°, moderate at 25° to 35°, and severe with a present subluxation in the first metatarsophalangeal joint at an angle greater than 35° [78].

3. The proximal articular set angle (PASA) is formed by a line drawn parallel to the effective articular surface and a perpendicular line to the reference line of the first metatarsal bone [79]. Normally, this angle should not exceed 8°.

In the early stages of hallux rigidus (hallux rigidus), the radiographic presentation includes osteophyte formation along the dorsal aspect of the first metatarsal head. There may also be asymmetric joint space narrowing of the first metatarsophalangeal joint. In late stages of the disease, osteophytes are present on all surfaces of the first metatarsal head as well as the proximal phalanx, and the joint space is often obscured.

Most patients with foot drop require weight-bearing radiographs of the feet and ankles in two projections (if possible), as well as axial calcaneal views. Radiography is necessary to assess the condition of the foot and ankle joints, because long-standing foot drop leads to joint damage due to abnormal load redistribution.

Computed tomography (CT) provides excellent visualization of bone structures and allows for the assessment of complex anatomical relationships in three planes, which is important when occult bone anomalies or small joint pathology of the foot are suspected [80].

Magnetic resonance imaging (MRI) plays an important yet adjunctive role in the diagnosis of acquired foot deformities in adults, especially in complex clinical cases and when planning surgical treatment. For example, in acquired flatfoot, MRI can be used to assess the condition of the tibialis posterior tendon and the spring ligament complex [80]. MRI allows for fairly accurate visualization of soft tissue abnormalities, including tendinopathy, ligamentous changes, and even articular cartilage lesions [81].

Ultrasound (US) also plays an adjunctive role, but has a number of advantages: it is a non-invasive, rapid, and cost-effective method that allows for dynamic evaluation of soft tissue structures, including stress and active movement tests [80].

When diagnosing peripheral nerve lesions, neuroimaging methods provide information on the exact location of the lesion and its morphology. In addition to magnetic resonance imaging (MRI) and MR neurography, ultrasound of the nerves is actively used as a non-invasive and cost-effective method. Ultrasound and MR neurography are prescribed to more accurately identify the nerve compression zone, assess the surrounding tissues (presence of osteophytes, hygromas, etc.), and in neurosurgical preoperative planning [82].

Comments: the decision to prescribe any instrumental diagnostic method rests with the attending physician based on each specific clinical case.

2.5 Other Procedures

May include evaluation of the patient's standing and gait, stabilography, dynamometry, podography, plantography, and electroneuromyography. It should be noted that none of these diagnostic tests are mandatory, and their necessity should be fully assessed by the attending physician.

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

Treatment of patients with acquired foot deformities (AFD) should ideally begin in the early stages of disease progression and continue until recovery.

The goals of treatment are: complete elimination or possible correction of acquired foot deformities, prevention of disease progression, stabilization or improvement of the function of affected foot joints and other vital anatomical structures, relief or reduction of pain severity, improvement of health-related quality of life in affected patients. It should be noted that patients with AFD require ongoing dynamic monitoring during the treatment process.

Treatment options include conservative (non-pharmacological and pharmacological) methods, injection therapies, and surgical interventions, the choice of which depends on the severity of deformities, the stage of disease progression, and the nature of clinical manifestations [83, 84].

• Conservative (non-surgical) treatment is recommended at all stages of AFD development, while surgical treatment is primarily indicated for late stages and when conservative treatment fails [85].

Level CLevel 5Level of recommendation evidence C (reliability level of evidence – 5).

Comments. In some cases, the treatment option and scope for a specific patient may be determined not only by the stage of disease progression, the severity of acquired deformities and pathological changes in the anatomical structures and tissues of the affected feet, but also by the patient's age, comorbidities, prevalence (unilateral or bilateral) of the lesion, biomechanical relationships of the affected foot joint elements, and deformities or other pathological changes located in more proximal segments of the lower extremity [86, 87].

3.1 Conservative Treatment

Conservative treatment for patients with acquired foot deformities includes non-pharmacological methods and pharmacological therapy.

The main goals of conservative treatment in patients with AFD are: preventing the progression of deformities and pathological changes in foot structures and tissues, effective control of disease symptoms—primarily pain in the affected joints and other anatomical structures, preservation and improvement of their function, and relief or reduction of inflammatory and other pathological processes [88].

Conservative treatment for AFD may be indicated for moderate foot deformities that do not require surgery, or if the patient declines surgery, or when there are contraindications to surgery. At the same time, the patient should be warned that currently there is no conservative treatment method for AFD that achieves a reliable and significant positive clinical effect. All conservative treatment methods presented below are aimed solely at relieving or alleviating symptoms and preventing disease progression, but do not eliminate its pathogenetic causes or existing deformities.

3.1.1 Non-pharmacological therapy

• Modification of sports/physical activities and unloading of the affected feet are recommended for all patients: avoiding dynamic and static load factors (running, prolonged walking, jumping, heavy lifting, prolonged static working postures, etc.); wearing shoes with well-cushioned soles; using an auxiliary walking device such as a cane or crutch in the hand contralateral to the affected limb [89, 191].

Level CLevel 5Level of recommendation evidence C (reliability level of evidence – 5).

Comments: in patients with AFD, a frequent cause of pain is the presence of osteoarthritic changes in the foot joints, primarily the first metatarsophalangeal joint. These changes typically develop due to non-physiological functional loads on these joints caused by pathological alterations in joint and periarticular tissues and corresponding disturbances in biomechanical parameters. The use of a cane and properly fitted footwear can reduce the functional load on the affected foot joints and improve biomechanical parameters of their function, which in turn leads to a reduction in pain severity and functional insufficiency of the affected feet.

• Physical exercises may be recommended for all patients with AFD to reduce pain in the affected feet, strengthen lower extremity muscles, facilitate walking, and improve self-care capabilities and overall quality of life [90, 91].

Level of Evidence BLevel of Confidence 2Level of recommendation B (level of evidence – 2).

• In patients with AFD, it is recommended to perform therapeutic exercise sessions for joint diseases and injuries, as well as post-isometric muscle relaxation, hydrokinetotherapy for joint diseases and injuries, and manual therapy techniques for the skeletal and joint systems, which are indicated primarily in the early stages of acquired foot deformity progression to improve mobility in the affected and adjacent joints [92, 93, 94, 95, 96].

GCR BLOE 2Grade of Recommendation B (Level of Evidence – 2).

Comments: physical therapy (PT) techniques help strengthen the tibialis posterior muscle and increase the stability of the first metatarsophalangeal joint, which can have a positive effect on reducing pathological symptoms in patients with AFD [96].

Comments: the main goal of educational programs is to increase the effectiveness of conservative treatment by actively involving the patient in the therapeutic process. Educational programs have a positive effect on disease symptoms, improve joint function, quality of life of specialized patients, and their treatment adherence.

Comments: the choice of a specific physiotherapeutic treatment method depends on the stage and severity of clinical symptoms of the pathology in question, as well as on the presence of concomitant diseases (comorbidities).

• For AFD patients, it is recommended as prescribed by the attending physician to use custom and prefabricated orthoses and insoles, as well as specialized footwear, to redistribute the load in certain areas of the affected feet in order to reduce the severity of pain and improve impaired biomechanical parameters [105, 106, 107, 108].

GPP CLOE 4Grade of Recommendation C (Level of Evidence – 4).

Comments: orthopedic insoles (ready-made or custom) can help achieve a number of therapeutic goals by providing: support for the first metatarsal head; support for the longitudinal arch of the foot; correction of valgus or varus positioning of the midfoot and hindfoot (in soft deformity); increased shock absorption of the affected feet (especially important for rigid deformities); offloading of specific foot areas to avoid the formation of hyperkeratosis and stress bone fractures. The choice of a specific orthosis, orthopedic footwear, or insoles is highly individual and varies depending on the specific nosological form and the progression stage of AFD. They can also be used as temporary devices when the patient is unable or unwilling to use other methods of conservative treatment.

The combination of conservative treatment methods and the duration of their application may be adjusted by the attending physician depending on the dynamics of symptoms of the pathology in question and the characteristics of the individual patient.

3.1.2 Drug therapy

Medical treatment for patients with acquired foot deformities, like all conservative treatment in general, should be aimed at relieving suffering and, above all, reducing the severity of pain, preventing the progression of pathological changes, preserving vital anatomical structures and tissues, and improving quality of life by stopping or reducing the severity of inflammatory and other pathological reactions and processes in the affected foot area.

When prescribing drug therapy to AFD patients, it should be taken into account that currently the number of scientific publications reflecting the results of studies on various pharmacological agents in patients with this pathology is quite limited, and for a number of areas or certain highly effective drugs, scientific papers are entirely absent. Therefore, given that pain and the pathophysiological reactions and tissue pathological changes of the affected feet causing it are generally determined by arthritic changes in the foot joints, primarily in the first metatarsophalangeal joint, it is entirely justified when prescribing pharmacotherapy to AFD patients to be guided by current national clinical guidelines for osteoarthritis of other joints, specifically 'Coxarthrosis' and 'Gonarthrosis' [109, 110].

Comments: in the presence of arthritic changes in the foot joints of specialized patients, the prescription of symptomatic slow-acting drugs for osteoarthritis (SYSADOA), which according to the Anatomical Therapeutic Chemical (ATC) classification belong to group M01AX ('Other non-steroidal anti-inflammatory and antirheumatic products'), can be considered justified. Drugs of this group are considered the basis of pharmacotherapy for osteoarthritis of various localizations, as they have proven anti-inflammatory and chondroprotective effects on articular cartilage. At the same time, it should be taken into account that the most convincing evidence base for efficacy in osteoarthritis belongs to chondroitin sulfate and glucosamine sulfate molecules, as noted in the current national clinical guidelines 'Coxarthrosis' and 'Gonarthrosis' [109, 110].

• For AFD patients with moderate to severe pain, it is recommended to prescribe non-steroidal anti-inflammatory and antirheumatic drugs (NSAIDs) for rapid and effective reduction of pain in the affected joints and tendon-muscle structures, taking into account patient comorbidity [86, 105, 106].

GCR CLOE 5Grade of Recommendation C (Level of Evidence – 5).

Comments: there is no clear data confirming the advisability of long-term NSAID use in AFD. These drugs should be used only for pain control, and upon achieving significant improvement, they should be discontinued. Depending on the clinical situation, NSAIDs can be used in long or short courses, as well as on an 'on-demand' regimen to relieve disease exacerbations. The choice of a drug from this group for therapy in specialized patients should be made individually, taking into account the pharmacological characteristics of each drug and the comorbidities (concomitant diseases) of the specific patient.

3.1.3 Perioperative medical management of surgery.

Perioperative antibiotic prophylaxis

• Due to the lack of a clear evidence base for or against perioperative antibiotic prophylaxis (PAP) of surgical site infection (SSI) in the surgical treatment of patients with acquired forefoot deformities in an outpatient setting without the need for subsequent hospitalization, the decision to perform PAP is recommended to be made individually based on the presence of SSI risk factors in the patient, the scope of the planned surgery, and the local protocol of the medical organization [111, 112].

GPP BLOE 3Grade of Recommendation B (Level of Evidence – 3).

• For patients with risk factors for SSI development (diabetes mellitus, arterial hypertension, hindfoot bone fractures, smoking, etc.) undergoing surgical treatment for foot bone deformities in an outpatient setting without the need for subsequent hospitalization, it is recommended to administer perioperative antibiotic prophylaxis (PAP) with a single dose [113, 114].

GPP CLOE 4Grade of Recommendation C (Level of Evidence – 4).

Comments: a recent meta-analysis of SSI prevalence in patients undergoing foot and ankle surgery found that the incidence of infectious complications significantly increased in the presence of hindfoot fractures, diabetes mellitus, arterial hypertension, and smoking [114]. Meanwhile, a randomized clinical trial showed that extending PAP into the postoperative period in the outpatient management of specialized patients does not affect the incidence of SSI [113]. In general, existing differences in the prevalence of SSI after foot surgery in various studies are justified by the presence of various patient-related risk factors; therefore, the final decision on prescribing PAP when performing osteosynthesis of foot bone fractures in patients not requiring hospitalization is made by the operating surgeon.

• All patients with foot bone deformities scheduled for inpatient surgery are recommended to receive PAP for surgical site infection (SSI) lasting no more than 24 hours [115].

GRL CLEL 4Recommendation Grade C (Level of Evidence – 4).

• Patients with foot bone deformities undergoing surgery using a tourniquet are recommended to be administered a systemic antibacterial agent for PAP after its application [115, 116].

Level of Evidence BLevel of Confidence 2Level of recommendation B (level of evidence – 2).

Comments: in accordance with the regulatory documentation in force in the Russian Federation (SanPiN 3.3686-21) and clinical guidelines [117], the main drugs for perioperative antibiotic prophylaxis (PAP) in orthopedic surgery are cefazolin** (average preoperative dose – 2.0 g, single dose – 1.0 g) or cefuroxime** (average preoperative dose – 1.5 g, single dose – 0.75 g); in case of hypersensitivity to 1st and 2nd generation cephalosporins – #clindamycin** (starting dose – 0.9 g) or #vancomycin** (starting dose – 1.0 g for body weight up to 80 kg, 1.5 g for body weight > 80 kg) [186]. The latter is also the drug of choice when there is a risk of infection caused by MRSA. To achieve an effective tissue and serum concentration of the systemic antibacterial drug at the time of the skin incision, systemic antibacterial drugs for the prevention of surgical site infections (SSIs) should be administered intravenously within 30 to 60 minutes before the skin incision, or within 2 hours before the incision when using #vancomycin**. A prospective randomized clinical trial showed that administration of a systemic antibacterial drug for PAP 1 minute after the application of a tourniquet demonstrated a statistically significant advantage in terms of reducing the incidence of SSI, wound healing time, and overall patient satisfaction compared with administration of the systemic antibacterial drug before tourniquet application [116]. The maximum duration of prophylactic systemic antibacterial drug administration should not exceed 24 hours after the end of the surgery. In most cases, a single dose of the systemic antibacterial drug is sufficient for effective prophylaxis. In some cases, PAP may not be performed [118, 119, 199]. Additional doses may be justified in prolonged procedures (lasting more than 3 hours). Large cohort studies also show no need to extend PAP beyond 24 hours after forefoot bone surgery [113].

Prophylaxis of venous thromboembolic events (VTE)

• Due to the lack of a clear evidence base for or against pharmacological prophylaxis of venous thromboembolic events (VTE) in the surgical treatment of patients with forefoot deformities, the decision on pharmacological prophylaxis is recommended to be made individually based on the patient's VTE risk factors, the scope of the planned surgery, and the local protocol of the medical organization [119, 120].

GPP BLOE 3Grade of Recommendation B (Level of Evidence – 3).

• Patients with forefoot deformity and a history of VTE are recommended to receive pharmacological thromboprophylaxis before surgery and until the recovery of motor activity [120].

GPP BLOE 3Grade of Recommendation B (Level of Evidence – 3).

Comments: the risk of venous thrombosis after surgical treatment in patients with forefoot bone deformities is low and, in the absence of risk factors, ranges from 0 to 0.3. The risk of VTE after elective foot and ankle surgery (excluding joint replacement and Achilles tendon surgery) increases by more than 4% in the presence of a history of VTE and 2 or more of the following risk factors: obesity with BMI >30 kg/m², age >40 years, comorbid conditions, systemic hormonal contraceptives, bed rest, and recent travel within 2 weeks after any surgery [120]. However, a prospective study including patients undergoing correction of hallux valgus showed that age was the only significant risk factor for venous thrombosis according to phlebography. The authors believe that regular pharmacological prophylaxis of venous thrombosis may be justified for patients over 60 years of age [119].

Injection therapy

• Patients with acquired foot deformities presenting with pain syndrome caused by degenerative-dystrophic joint changes may be recommended intra-articular administration of synovial fluid substitutes*** based on hyaluronic acid [121, 122, 123, 124, 125, 126].

GOM ALOE 1Grade of Recommendation A (Level of Evidence – 1).

Comments. Intra-articular administration of synovial fluid substitutes*** based on hyaluronic acid derivatives can lead to a positive clinical effect of varying severity, the average duration of which ranges from 4 to 6 months or more, varying greatly depending on the physicochemical characteristics of a specific medical device and the patient's clinical features. When using these drugs in small joints, the risks must be fully assessed by the attending physician.

Regarding intra-articular administration of glucocorticoids, it is known that such surgical procedures exert a pronounced anti-inflammatory effect in arthritic joint changes (in osteoarthritis), but are associated with a high risk of accelerated articular cartilage degradation and the development of osteonecrosis in the epiphyseal regions of the bones forming the joints. Therefore, in the management of patients with acquired foot deformities, it is advisable to adhere to the recommendations in the relevant sections of injection therapy from the current clinical guidelines for "Coxarthrosis" and "Gonarthrosis", according to which intra-articular glucocorticoid injections should be performed no more than once every three months, and their course-based intra-articular administration is prohibited [109, 110].

• Administration of platelet-rich plasma to the pain area in patients with acquired foot deformities may be recommended in the event of tendinitis and arthritis of the foot and ankle joints, provided there is patient initiative [127, 128, 129].

GPP CLOE 4Grade of Recommendation C (Level of Evidence – 4).

• Administration of an autologous stromal vascular fraction to the pain area in patients with acquired foot deformities and/or autologous red bone marrow cells may be recommended provided there is patient initiative [130, 131, 132].

GPP CLOE 4Grade of Recommendation C (Level of Evidence – 4).

Comments: currently, there is no convincing evidence of the efficacy of injection of platelet-rich plasma, autologous stromal vascular fraction, and/or autologous red bone marrow cells in patients with acquired foot deformities, and the exact precise indications for such surgical procedures are currently under development.

3.2 Surgical Treatment

In general terms, surgical intervention is advisable under the following conditions:

• pronounced pain syndrome resistant to comprehensive conservative therapy;

• progressive formation or worsening of foot deformity leading to functional failure;

• marked cosmetic changes limiting footwear selection and significantly reducing the patient's quality of life;

• development of complications, including chronic ulcer defects, secondary inflammatory processes, and joint instability;

• inefficacy or impossibility of orthopedic correction methods, including when there is no effect from comprehensive non-pharmacological and pharmacological treatment of the pain syndrome.

Level CLevel 5Level of recommendation evidence C (reliability level of evidence – 5).

Any surgery for hallux valgus must achieve several objectives [135]:

1. Improvement of the first metatarsal bone axis;

2. Improvement of relationships in the first metatarsophalangeal joint. A number of interventions (but not all) aim to increase the range of motion in the first metatarsophalangeal joint.

3. Restoration of the weight-bearing capacity of the first ray of the foot.

4. Creation of stability in the first metatarsophalangeal joint.

Comments: there are a number of surgical interventions performed in patients with hallux valgus. The choice depends on the severity of the deformity, functional demands, anatomical features, presence of comorbidities (e.g., rheumatoid arthritis), and arthritic changes in the first metatarsophalangeal joint. Given the variety of existing surgical techniques and the need to account for patient factors, there is no single algorithm for choosing a surgery. The optimal treatment method should be selected individually. None of the treatment methods can fully prevent the recurrence of deformity or the development of arthritic changes in the first metatarsophalangeal joint.

All corrective surgeries on the first ray of the foot can be conditionally divided into two broad groups taking into account the affected foot tissues: soft tissue procedures and bone structure procedures.

Soft tissue procedures. Soft tissue procedures began to develop earlier than bone surgeries because they do not require specialized instruments and equipment that did not exist at the dawn of operative orthopedics. The isolated use of any soft tissue surgical technique is possible based strictly on individual indications. In cases of severe deformity, when it is necessary to restore the axis of the bones of the first ray, they are used in combination with osteotomies [53].

Bone procedures. Procedures on the bone structures of the first ray of the foot are classified according to the localization of the surgical site into: resection arthroplasties of the first metatarsophalangeal joint; distal, diaphyseal, and proximal osteotomies of the first metatarsal bone; arthrodesis of the medial cuneiform-metatarsal joint; arthrodesis of the first metatarsophalangeal joint; and osteotomies of the proximal phalanx of the great toe. However, this classification does not exclude other surgical sites, which are described less frequently than the above-mentioned techniques, as well as certain other proprietary operations.

Resection arthroplasty of the first metatarsophalangeal joint. Various types of resection arthroplasties involve the removal of a portion of the proximal phalanx or the 1st metatarsal bone. For example, the Schanz procedure involves the removal of up to 1/3 of the base of the proximal phalanx of the great toe, while the Keller-Brandes procedure involves up to 2/3 of the proximal phalanx. In our country, Ya. M. Voloshin (1936) was the first to use resection arthroplasty in the area of the first metatarsophalangeal joint. To prevent ankylosis in the metatarsophalangeal joint, J. D. Singley (1872) proposed wrapping a flap from the joint capsule into the joint; in our country, it was proposed to use traction on the nail phalanx for 3 weeks in the postoperative period to create a neoarthrosis, in which the space between the metatarsal head and the proximal phalanx fragment is filled with scar tissue.

Despite the active introduction of resection arthroplasty procedures in our country and the achievement of relatively good results, there are data indicating a loss of weight-bearing capacity of the first metatarsal head and subluxation of the great toe, joint stiffness, and the development of deforming arthrosis in the first metatarsophalangeal joint [53]. Variants of resection arthroplasty in the area of the 1st metatarsophalangeal joint are applicable, but require an individual determination of indications.

Distal osteotomies of the first metatarsal bone. Currently, a large number of distal osteotomy variants have been proposed, each of which is applicable in patients with hallux valgus. One of the widely used distal osteotomies of the first metatarsal bone is the chevron osteotomy. Performing cuts at various angles allows, in addition to lateralization of the first metatarsal head, for its plantarization and rotation. S. Sarrafian et al. (1985) indicated in their study that the average width of the first metatarsal bone in the distal metaepiphysis is 15 mm, which is recommended to be taken into account when planning distal osteotomies. As with other methods, the determination of indications must be strictly individual, taking into account the age of the patients to prevent the progression of arthrosis or avascular necrosis of the metatarsal head under conditions of reduced blood supply.

Diaphyseal osteotomies of the first metatarsal bone. The greatest number of surgical interventions for hallux valgus has been proposed specifically at the level of the diaphysis of the first metatarsal bone. The most frequently performed diaphyseal osteotomy is the Scarf osteotomy, which, unlike the chevron osteotomy, has three osteotomy arms and, accordingly, requires a larger incision and soft tissue mobilization [136, 137]. Manipulating fragments with three contact planes between them is more difficult, but, as in the case of the chevron osteotomy, it provides the ability to displace the fragments of this bone in three planes. According to S. Smith (2012), the Scarf osteotomy allows for the correction of a larger intermetatarsal angle than the chevron osteotomy due to greater contact of the bone fragments and, consequently, greater possible lateral displacement, which can be utilized during preoperative planning [138].

Interventions on the proximal first metatarsal bone. Interventions on the proximal part of the first metatarsal bone provide an opportunity to correct the position of the first ray of the foot in severe deformity and an angle between the first and second metatarsal bones exceeding 30 degrees [53]. Some researchers consider this criterion key to justifying a proximal osteotomy [73]. Correctly performed interventions on the proximal part of the first metatarsal bone can be applied and demonstrate good results at any angle of deviation, but often require extensive surgical experience and technical equipment, and therefore have not become widespread for mild and moderate Hallux valgus.

Proximal osteotomy with the removal of a bone wedge from the lateral side was first described by M. Loison (1901). The removal of the bone wedge made it possible to shorten the first metatarsal bone simultaneously with the correction of the deformity. In 1992, G.W. Patton and J.E. Zelichowski proposed not cutting through the medial bone cortex, which increased the stability of the osteotomy and increased the contact area of the bone fragments, minimizing the likelihood of nonunion [139].

Proximal osteotomy involving the opening of a medial wedge was first described by J. Trethowan in 1923; the author proposed placing a graft harvested from the removed exostosis of the first metatarsal head into the resulting defect [139].

To prevent potential complications of proximal osteotomies, such as nonunion, bone fragment migration, and overcorrection, careful planning must be performed, stable fixation of bone fragments must be achieved, and external immobilization should be used if necessary [140].

One of the options for correcting hallux valgus that demonstrates good results in the presence of first ray hypermobility is arthrodesis of the medial cuneiform-metatarsal joint, proposed by P.W. Lapidus in 1934. The Lapidus procedure, unlike distal and diaphyseal osteotomies of the first metatarsal bone, requires avoidance of weight-bearing on the operated limb in the postoperative period, which may be viewed by patients as a drawback of the technique [141, 142].

Arthrodesis of the first metatarsophalangeal joint. Arthrodesis of the first metatarsophalangeal joint can be used to correct hallux valgus with a good long-term outcome and a low risk of deformity recurrence. The limitation of its use is the functional feature associated with the absence of motion in the metatarsophalangeal joint. The technique can be used in all patients based on individual indications (the patient's functional demands and mandatory notification regarding the subsequent lack of motion in the first metatarsophalangeal joint). The use of first metatarsophalangeal joint arthrodesis is optimally suited for older patients, those with severe deformities, comorbidities that increase the risk of recurrence (e.g., rheumatoid arthritis), and osteoarthritic changes in the joint.

Osteotomies of the proximal phalanx of the great toe. The most common such intervention is the Akin wedge osteotomy of the proximal phalanx, which allows for the correction of the deformity of the phalanx itself, corrects valgus deformity at the level of the interphalangeal joint, or serves as an adjunct to the main surgery on the first metatarsal bone to achieve a better cosmetic effect.

All surgeries on the first ray of the foot in the treatment of hallux rigidus can be divided into two large groups based on the preservation of the first metatarsophalangeal joint: joint-preserving surgeries and joint-sacrificing surgeries.

Joint-preserving surgeries of the first metatarsophalangeal joint. Such surgical interventions are used only in stages I-II of arthrosis development and can be performed on either the proximal phalanx or the first metatarsal bone:

1. The Kessel-Bonney procedure was described in 1958 and consists of a closing wedge osteotomy of the proximal phalanx with the base of the wedge directed dorsally. It is used in the early stages of the disease when there is no severe cartilage damage yet, and the main complaint is painful dorsiflexion in the first metatarsophalangeal joint. Performing this osteotomy alters the plane of motion in the first metatarsophalangeal joint and consequently increases dorsiflexion during walking [143].

2. Waterman's procedure (1927) [143]. A closing wedge osteotomy is performed with the wedge facing dorsally (similar to the Kessel-Bonney procedure) at the level of the distal metaepiphysis of the first metatarsal bone. Changing the plane of motion also helps increase the range of motion. This procedure is contraindicated in Metatarsus primus elevatus.

3. If patients with osteoarthritis of the first metatarsophalangeal joint exhibit hypermobility in the medial cuneometatarsal joint, it is necessary to perform an arthrodesis of the first cuneometatarsal joint, as proposed by P.W. Lapidus in 1934, placing the first metatarsal in a plantargrade position. Creating greater plantarflexion of the first metatarsophalangeal joint increases the phalanx's capacity for dorsiflexion during the propulsive phase of gait [144].

4. If the patient has a relatively long first metatarsal bone, the optimal approach is a shortening osteotomy of the first metatarsal bone using any established technique.

5. Cheilectomy was described by DuVries in 1965. The excision of partial osteophytes is sometimes referred to as a "joint toilet". The intervention involves removing the medial, dorsal, and lateral osteophytes of the first metatarsal head, which impede the dorsiflexion of the proximal phalanx of the hallux [145].

Following cheilectomy, early mobilization of the joint is required (usually within 7 to 10 days), which is an advantage of this procedure.

Non-joint-sparing procedures for the first metatarsophalangeal joint. These surgical interventions are used for stages II-III of osteoarthritis:

1. Resection arthroplasty – the Keller-Brandes procedure, where up to 2/3 of the proximal phalanx is resected. In our country, Ya.M. Voloshin (1936) was the first to use this operation [139, 146].

2. First metatarsophalangeal joint arthroplasty. This procedure may be used if technically feasible and the patient is fully informed of potential complications and outcomes.

3. First metatarsophalangeal joint arthrodesis. Although arthrodesis deprives the first metatarsophalangeal joint of motion, it stabilizes the medial column of the foot and allows for efficient weight transfer across the forefoot during gait.

Procedures for lesser toe deformities can also be divided into soft tissue interventions and bone procedures.

Soft tissue interventions are predominantly aimed at restoring the disrupted tendon-muscle balance and joint stability; these include manipulations of the toe flexor and extensor tendons as well as the plantar plate of the metatarsophalangeal joint. These types of procedures are more frequently used in an isolated form for lesser toes than for the hallux, but they are also often adjuncts to comprehensive forefoot reconstructive surgery.

Complete tendon transection at various levels, lengthening and shortening tenotomies, tenodeses, and transpositions are permitted. These can be performed either open or using percutaneous and minimally invasive techniques. In some cases, suture anchors made of various materials may be required.

Tenotomy and tenodesis. Transection or lengthening of the flexor tendons (usually the flexor digitorum longus or brevis) followed by redirection or fixation to the extensor apparatus to correct flexion contracture. Tenotomy and tenodesis of the flexor digitorum longus and brevis to the extensor capsule were first described by Taylor in 1951 [147]. Variations of this procedure are now widely used to treat hammer toes. Barbari and Brevig performed this procedure on 39 flexible claw toes and achieved an 84% patient satisfaction rate [148].

Tendon transposition. Transposition of the flexor digitorum longus tendon was introduced by G.R. Girdlestone and R.G. Taylor [54] and involved transferring the split tendon from the medial and lateral sides of the proximal phalanx to the dorsum and securing them with interrupted sutures beneath the extensor tendons, thereby achieving toe depression. Losa et al. conducted a meta-analysis of 515 flexor-to-extensor tendon transfers for lesser toe deformities and found an 87% patient satisfaction rate [149]. W. Bavarian's technique [20] also involves transferring the flexor digitorum longus tendon to the dorsum of the toe [150]. Extensor tendon transposition techniques for correcting lesser toe deformities are also known [151].

Repair or reinforcement of the plantar plate. Given the significance of plantar plate capsule injury in the pathogenesis of hammer toe deformity, its repair is advisable. Surgical methods for plantar plate reconstruction exist that allow the correction of dislocations in the metatarsophalangeal joints, but they require specialized devices and expensive equipment. Furthermore, in cases of severe plate destruction, these methods become inapplicable [152].

Bone interventions. Various metatarsal osteotomy techniques continue to be used today in the treatment of hammer toe deformities to shorten the metatarsal, correct the Lelièvre parabola, unload the metatarsal head, and correct the dorsal deviation of the toe at the metatarsophalangeal joint [27]. Similar to the first metatarsal, these can be categorized as distal (subcapital) [153], [154], diaphyseal, and proximal. In cases where the patient has osteoarthritic changes in the cuneometatarsal joints or pronounced metatarsal deviation, arthrodesis at the Lisfranc joint level is recommended. For severe, rigid hammer toe deformities (especially in patients with systemic reactive arthritis), resective procedures at the metatarsophalangeal joint level (resection of the metatarsal head, the base of the proximal phalanx, or a combination of both) may be recommended.

To correct hammer toe deformity, interventions on the proximal phalanx or the proximal interphalangeal joint are very frequently required. These are primarily aimed at correcting flexion contracture. Interventions on the proximal interphalangeal joint itself include resection arthroplasty (e.g., the Hohmann procedure – resection of the head of the proximal phalanx), arthrodesis, and arthroplasty. Interventions on the phalanx include various types of osteotomies, which are most commonly aimed at shortening it.

An adjunct to any toe procedure may be the excision of hyperkeratoses, which not only yields a more aesthetic outcome but also improves the clinical and functional result.

Comments: the combination of techniques may vary depending on each specific clinical case; the primary goal is to achieve the objectives of surgical treatment. Many of the procedures described above require fixation, which can be internal and/or external. External fixation may be used in combination with internal fixation, or one may be transitioned to the other. The choice of fixation method is at the discretion of the surgeon. Most of the surgical techniques discussed can be performed openly or percutaneously using minimally invasive techniques [153], or in combination. The surgical approach is determined individually based on the severity of the deformity, as well as the surgeon's preference and experience. Performing corrective procedures on both feet simultaneously is permitted.

For flatfoot (pes planovalgus) deformity, the range of surgical techniques, their combination, and the scope of intervention are determined by the severity of the deformity.

For grade I, the most common type of surgery is subtalar arthroereisis. This is a minimally invasive procedure based on the exogenous restriction of motion in the subtalar joint. It is performed using an implant placed in the sinus tarsi. The subtalar implant acts as a mechanical blocking device that eliminates the pathological range of motion in the subtalar joint, which in turn reduces excessive motion in the talonavicular joint and corrects the rotation of the talus relative to the calcaneus, as well as the eversion of the latter. The presence of a contracture in the joint is an indication for Achilles tendon lengthening.

For grade II deformity, subtalar arthroereisis is most often combined with tenoplasty of the tibialis posterior tendon.

To correct grade III-a deformity, the following interventions are usually performed:

– subtalar arthroereisis (for patients under 40) or medializing calcaneal osteotomy (for patients over 40);

– lengthening of the Achilles tendon via complete or partial transection of the gastrocnemius muscle tendon and reinforcement of the posterior tibial tendon by transferring the flexor digitorum longus tendon to the navicular bone and suturing it to the posterior tibial tendon.

– proximal osteotomy of the first metatarsal with plantar displacement.

In grade III-b deformity, medializing calcaneal osteotomy, Achilles tendon lengthening via complete or partial gastrocnemius muscle recession, and talonavicular arthrodesis are generally performed. To correct forefoot supination, a proximal osteotomy of the first metatarsal bone or the medial cuneiform with plantarflexion of the metatarsal bone (Cotton procedure) can be performed.

In grade IV deformity, the following surgical procedures may be performed:

– double arthrodesis: subtalar joint, talonavicular arthrodesis with correction of valgus deformity (in case of navicular excision – talocuneiform arthrodesis);

– triple arthrodesis: procedures performed in double arthrodesis, supplemented by opening-wedge arthrodesis of the calcaneocuboid joint;

– forefoot supination correction: medial cuneiform osteotomy – Cotton procedure (in severe cases, combined with cuneometatarsal joint arthrodesis);

For midfoot flatfoot (pes planovalgus) deformity, Lisfranc joint arthrodesis and/or Evans calcaneal osteotomy can be performed.

Evans calcaneal osteotomy is a surgical procedure in which a linear incision is made in the anterolateral part of the calcaneus, followed by bone graft insertion to lengthen the lateral column of the foot.

In the presence of severe osteoarthritic changes in the ankle joint, surgical treatment should be approached as for its isolated pathology.

Comments: The described surgeries do not represent the full spectrum of existing and applied surgical methods. Due to the high variability of the deformity, the choice of surgical treatment methods is always individual and determined by the attending physician. In some situations, percutaneous procedures are possible, as well as the use of external fixation devices with gradual deformity correction over time. Postoperative management is determined on an individual basis.

• Surgical interventions for acquired clubfoot (cavovarus deformity) are recommended in the following situations:

  1. Progressive foot deformity causing functional impairment [155, 156].

  2. Severe pain syndrome resistant to conservative treatment [157], [158, 159].

  3. Recurrent ankle sprains and foot instability.

  4. Skin ulcerations caused by uneven weight distribution.

  5. Ineffectiveness of orthotic correction [160].

GPP CLOE 4Grade of Recommendation C (Level of Evidence – 4).

Comments: The choice of surgical intervention is determined by the components and rigidity of the deformity. Surgical methods are rarely used in isolation; the choice of combination is determined individually by the attending physician taking into account the deformity.

• Correctable (flexible) form — predominantly soft-tissue procedures.

• Rigid form — more frequently bone and joint interventions.

Tenotomies and tendon lengthenings – these methods aim to reduce excessive muscle tone and restore balance between antagonistic muscles, and include:

• Achilles tendon lengthening – used for pronounced equinus foot positioning, including as a component of other interventions [161, 162].

• Posterior tibial tendon and digital flexors lengthening – used to correct foot adduction and supination and to correct clawtoe deformity [157].

Tendon transfers – used to redistribute tendon pull and improve foot position, for example:

• Split anterior tibialis tendon transfer (SPLATT) – allows balancing the pull of foot inverters and everters, improving walking posture; during surgery, the tendon is split longitudinally, one part remains intact, while the second is sutured to the tendon of the peroneus tertius or peroneus brevis to enhance foot eversion [162, 163].

• Lateralization of the tibialis anterior tendon – allows correction of midfoot and forefoot supination.

• Transfer of the peroneus longus tendon to the peroneus brevis tendon or to the lateral cuneiform bone is used to correct foot varus positioning [2, 162].

Osteotomies can be used to correct foot deformity components when joint condition is good. For example, to correct hindfoot varus positioning, a calcaneal osteotomy variant (Dwyer osteotomy) can be used.

Surgical treatment methods for this group of patients can also include:

• Plantar fascia release.

• Joint arthrodesis.

• Neuro-orthopedic methods are used to reduce muscle spasticity and improve functional status. Selective neurotomy – sectioning of the motor branches of the tibial nerve, which reduces hypertonus (performed according to individual indications) [158].

The choice of surgical treatment for such complex pathology as drop foot syndrome is often a very challenging task. Currently, there are a number of surgical interventions most commonly performed for this pathology. The choice of surgical intervention depends not only on the severity of the deformity, but also on the patient's functional demands, anatomical features, presence of comorbid conditions, and osteoarthritic changes in the ankle and foot joints. Given the variety of existing surgical techniques and the need to account for patient factors, there is no single universally accepted algorithm for surgical selection. The optimal treatment method should be selected individually. In common peroneal nerve (CPN) compression, when conservative therapy is ineffective or in case of pronounced neurological deficit, surgical decompression is the primary treatment method [69]. Nerve decompression is performed by incising the two fascial layers surrounding the nerve, proximally and distally to the fibular head, where compression most frequently occurs [164], [165, 166]. For superficial peroneal nerve (SPN) compression at the level of the anterior muscular compartment of the leg, open or arthroscopic surgical treatment is considered.

The surgical approach involves an incision on the dorsum of the foot and nerve release in the area of the inferior extensor retinaculum [167]. If conservative treatment is ineffective for an average of 6–12 months or earlier in case of pronounced neurological deficit, as well as if decompression fails or the peroneal nerve is injured, nerve grafting is considered. In 2018, a meta-analysis of publications and studies on peroneal nerve grafting for compression was performed [168]. The sural nerve, tibial nerve, or superficial peroneal nerve branches were chosen as donors. Studies included in the meta-analysis showed varying results [168]. Another type of surgical treatment is tendon transfer. In peroneal nerve neuropathy, the tibialis posterior is transferred through the interosseous membrane and fixed to the cuneiform bone of the foot [169]. However, the transfer technique may vary depending on muscle weakness [169]. This method is performed when full range of motion is present in the ankle and foot joints.

• All patients are recommended to wear an immobilizing orthosis or plaster cast after tendon transfer to ensure stability for 6 weeks [170].

Level of Evidence CReliability of Evidence 5Level of Recommendation Consensus: C (Reliability of Evidence – 5).

Another surgical treatment method for ankle dorsiflexor weakness, including due to peroneal nerve injury, is ankle arthrodesis. This method is performed, for example, in post-traumatic nerve injuries and foot and ankle deformities when there is a significant reduction in range of motion. The essence of the intervention is to ensure ankle joint stability and restore weight-bearing function [171].

Comments: The combination of techniques may vary depending on the specific clinical case; the main goal is to solve the tasks of surgical treatment. Many of the above-described surgeries require the use of internal and/or external fixation. It is possible to use external fixation combined with internal fixation, or to transition from one to the other. The choice of fixation method remains at the discretion of the surgeon. Most of the discussed surgical techniques can be performed openly or percutaneously using minimally invasive techniques [171], as well as in combination. The method of surgery is determined individually depending on the severity of the deformity, and the surgeon's preferences and experience.

3.3 Analgesic therapy

General principles and approaches to pain management in adult patients with acquired foot deformities are outlined earlier in Section 3.1.2 – "Pharmacotherapy".

• For patients with acquired foot deformities, if surgical treatment is indicated, it is recommended to provide adequate pain management using various multimodal analgesia approaches, which may include parenteral administration of nonsteroidal anti-inflammatory and antirheumatic drugs (NSAIDs), paracetamol**, opioids, and/or local infiltration anesthesia [187, 188, 189, 190].

Level CLevel 5Level of recommendation evidence C (reliability level of evidence – 5).

Comments: Selection of medications depends on the severity of acquired foot deformities and the intensity of pain, and may include the administration of NSAIDs, paracetamol**, opioids either as monotherapy or as multimodal analgesia (MMA), which involves the use of several analgesics with different mechanisms of action and non-pharmacological interventions aimed at targeting peripheral and/or central parts of the nervous system [172]. As an adjuvant during MMA, a single intravenous administration of #dexamethasone** at a dose of 1.25–20 mg can be used in the perioperative period, which provides a significant reduction in pain [189]. It must be remembered that the duration of parenteral administration of most NSAIDs (ketorolac**, ketoprofen**, diclofenac**) is limited to two days, which requires timely switching of the patient to oral administration, changing the drug, or coordinating its further use with the medical commission. The specific choice of local anesthesia method and medicinal products is made by the attending physician individually in accordance with the patient's characteristics, local protocols, and the equipment of the healthcare facility.

3.4 Dietary Therapy

At the time of these clinical guidelines creation, no specific dietary therapy has been developed or proposed for patients with acquired foot deformities.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

This section presents the principles and approaches to medical rehabilitation of adult patients with acquired foot deformities who have undergone surgical treatment. The corresponding rehabilitation approaches for relevant patients receiving conservative treatment are presented in these clinical guidelines in Section 3.1.1 – Non-pharmacological therapy.

The goal of rehabilitation in patients after surgical interventions is full functional, social, domestic, and professional recovery. Rehabilitation includes medical rehabilitation (or restorative treatment), social rehabilitation aimed at social and domestic adaptation, and professional rehabilitation, which consists of vocational guidance, vocational education, and occupational adaptation [175].

Rehabilitation of patients of this profile is based on well-known principles of rehabilitation after surgical treatment for musculoskeletal pathology: early initiation once the patient achieves an adequate level of analgesia through the multimodal use of both various pharmacological agents and non-pharmacological methods, continuity, consistency, comprehensiveness, and an individualized approach to therapeutic measures [176].

• Following inpatient surgical interventions, adult patients with acquired foot deformities are recommended to undergo rehabilitation measures (medical rehabilitation services for a patient with a lower limb deformity, medical rehabilitation services for a patient with a musculoskeletal system disorder) in medical rehabilitation departments, outpatient clinics, sanatoriums, or at home [175, 176, 177, 178, 179].

Level CLevel 5Level of recommendation evidence C (reliability level of evidence – 5).

Comments: postoperative patient management must always be individualized and depends on both the performed surgical intervention and the condition of the specific patient, taking into account their comorbid conditions.

• Rehabilitation measures are recommended to begin in the hospital immediately after surgery and continue throughout the hospitalization period (stage one of rehabilitation). After discharge from the hospital, if necessary, it is advisable to continue restorative treatment (if feasible) in rehabilitation departments (stage two of rehabilitation), and finish it in day-patient medical rehabilitation departments, sanatoriums, outpatient clinics, or at home (stage three of rehabilitation) [175, 176, 177, 178, 179].

Level CLevel 5Level of recommendation evidence C (reliability level of evidence – 5).

Comments: the entire course of postoperative restorative treatment consists of three periods: early (0–4 weeks), late (4–8 weeks) postoperative periods, and the recovery period (8–12 weeks). Throughout all these periods of postoperative rehabilitation, exercise therapy (therapeutic exercise for joint diseases and injuries) [180, 181] and massage (foot and lower leg massage) [181] are of great importance.

Comments: the tasks of physiotherapy in the early period are the application of physical factors to achieve analgesic, anti-inflammatory, anti-edematous, and reparative-regenerative effects in the affected tissues of the operated limb. For this purpose, if clinically necessary, a wide range of modern physiotherapy methods can be used, taking into account the patient's comorbidity factors. The literature describes both classical physiotherapy techniques [178] and modern high-energy methods: extracorporeal shock wave therapy [182, 183], as well as contact diathermy (high-frequency electromagnetic current therapy — inductothermy), which have high efficacy.

In the late postoperative and recovery periods, an important task is to prevent scar formation, which is achieved by using both classical physiotherapeutic factors [178] and modern physiotherapeutic modalities, in particular, extracorporeal shock wave therapy [184, 185]. Manual therapy for bone diseases can also be used to increase the range of motion [181].

Comments: when using certain types of interventions (especially relevant for the midfoot and hindfoot) and fixators, as well as at the discretion of the attending physician, a mobilization regimen with complete offloading of the operated limb using crutches, walkers, or other devices may be prescribed. Patient verticalization can be performed either on the day of surgery or the next day, depending on the specifics of anesthesia and the patient's well-being; in specific cases, verticalization may be postponed to a later date. Knee and hip joint exercises are permitted at any time during postoperative rehabilitation. The prescription of specific exercises for the foot and ankle remains at the discretion of the attending physician or rehabilitation specialist (exercise therapy doctor, physical and rehabilitation medicine doctor, or medical rehabilitation doctor) and may begin as early as the first weeks after the intervention or be postponed until radiological confirmation of bone healing in the osteotomy or arthrodesis zones.

5. Prevention and Dispensary Observation

Comments: Prevention of acquired foot deformations in adults includes a set of non-pharmacological, orthopedic, and behavioral measures aimed at preserving the normal anatomy and function of the foot. One of the key methods is wearing orthopedic shoes with a fixed heel, wide toe box, and cushioning sole, which promotes even load distribution and prevents excessive pronation. Custom orthotics (inserts or arch supports) are selected based on the clinical and biomechanical assessment of the foot and help stabilize the longitudinal and transverse arches. Exercises for the foot and calf muscles, particularly those aimed at strengthening the short extensors and the tibialis posterior muscle, help maintain proper posture and dynamic foot stability [134].

Regular physical therapy (therapeutic exercise for joint diseases and injuries), including rolling the soles over massage rollers, balance exercises, and calf muscle stretching, improves blood circulation and tissue trophism. Body weight management reduces mechanical stress on the feet and slows down the progression of degenerative joint changes [134].

Dispanserization (clinical follow-up) of adult patients with acquired foot deformations is an essential component of complication prevention and timely decision-making regarding treatment strategy modifications. It includes regular orthopedic examinations to assess the dynamics of deformation, pain syndrome, and functional state of the foot. In the early stages of deformation, patients are indicated for follow-up on average every 6–12 months, evaluating the effectiveness of conservative therapy and selecting and adjusting orthopedic devices. The frequency of examinations may vary depending on the specific pathology [134].

As part of clinical follow-up, scheduled X-ray examinations are performed, including weight-bearing views, to assess the progression of foot axis changes, arch lowering, and secondary joint involvement. If signs of neuropathy, gait deterioration, increased pain syndrome, or decreased orthotic effectiveness are detected, an in-depth examination involving specialists from related disciplines—rheumatologist, endocrinologist, neurologist—is indicated. Follow-up also allows for timely evaluation of the need to transition to surgical treatment if conservative methods are ineffective, especially in later stages of the diseases [134].

In the postoperative period, dressing changes are necessary to monitor the wound condition and evaluate edema dynamics (the frequency of dressings is determined by the attending physician, on average twice a week). Follow-up X-rays are typically performed at 6 to 8 weeks post-surgery, which serves as the fundamental basis for deciding to lift activity restrictions, though the timing and frequency of X-rays may also vary depending on the specific clinical case. At 3 months, an examination is recommended to assess rehabilitation progress and potentially adjust the rehabilitation plan. The frequency and timing of examinations remain at the discretion of the attending physician.

6. Organization of Medical Care

Indications for planned hospitalization in a medical organization:

1) ineffectiveness of conservative treatment;

2) presence of indications for surgical correction of acquired foot deformations.

Indications for patient discharge from a medical organization:

1) completion of the course of treatment;

2) absence of complications from surgical treatment.

7. Additional Information

No additional information available.

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

1. S.A. Bozhkova, MD, Head of the Scientific Department of Prevention and Treatment of Wound Infection and Department of Clinical Pharmacology, Vreden National Medical Research Center of Traumatology and Orthopedics of the Russian Ministry of Health.

2. A.K. Vasilkin, PhD, Deputy Chief Physician for Medical Rehabilitation, Vreden National Medical Research Center of Traumatology and Orthopedics of the Russian Ministry of Health.

3. N.S. Konovalchuk, PhD, Junior Researcher, Traumatologist-Orthopedist of Department No. 15, Vreden National Medical Research Center of Traumatology and Orthopedics of the Russian Ministry of Health.

4. A.Yu. Kochish, MD, Professor, Chief Researcher, Vreden National Medical Research Center of Traumatology and Orthopedics of the Russian Ministry of Health.

5. E.A. Pashkova, PhD, Junior Researcher, Traumatologist-Orthopedist of Department No. 15, Vreden National Medical Research Center of Traumatology and Orthopedics of the Russian Ministry of Health.

6. E.P. Sorokin, PhD, Head of Traumatology and Orthopedics Department No. 15, Vreden National Medical Research Center of Traumatology and Orthopedics of the Russian Ministry of Health.

No conflict of interest declared.

Appendix A2. Methodology for Developing Clinical Guidelines

Description of methods used to gather evidence

The evidence base for these clinical guidelines includes relevant English- and Russian-language publications in electronic databases such as PubMed, WOS, and RSCI. The search depth covers 40 years.

Target audience of the clinical guidelines:

Orthopedic trauma surgeons.

In these clinical guidelines, information is ranked by the level of reliability (evidence) depending on the quantity and quality of studies on the given issue.

Table 1. Levels of Evidence (LoE) grading scale for diagnostic methods (diagnostic interventions)

Table 2.  Scale for evaluating levels of evidence (LE) for methods of prevention, treatment, and rehabilitation, including those based on natural therapeutic factors (preventive, therapeutic, rehabilitation interventions)

Table 3. Grade of Recommendation (GoR) scale for methods of prevention, diagnosis, treatment, and rehabilitation, including those based on natural therapeutic factors (preventive, diagnostic, therapeutic, and rehabilitative interventions)

Procedure for updating clinical guidelines.

The mechanism for updating clinical guidelines provides for their systematic revision at least once every three years, as well as upon the emergence of new evidence-based medicine data on the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

These clinical guidelines were developed taking into account the following regulatory legal documents:

1. Order of the Russian Ministry of Health No. 203n dated May 10, 2017, "On Approval of Criteria for Assessing the Quality of Medical Care."

2. Decree of the Government of the Russian Federation No. 588 dated April 5, 2022 (as amended on February 3, 2025) "On the Procedure and Conditions for Recognizing a Person as Disabled" (along with the "Rules for Recognizing a Person as Disabled") (with amendments and additions, effective March 1, 2025).

3. Order of the Russian Ministry of Labor No. 585n dated August 27, 2019 (as amended on October 6, 2021) "On Classifications and Criteria Used in Carrying Out Medico-Social Expertise of Citizens by Federal State Institutions of Medico-Social Expertise". Order of the Russian Ministry of Labor No. 585n dated August 27, 2019 (as amended on October 6, 2021) "On Classifications and Criteria Used in Carrying Out Medico-Social Expertise of Citizens by Federal State Institutions of Medico-Social Expertise".

4. Federal Law No. 351-FZ dated December 9, 2010 "On Amendments to the Federal Law 'On Veterans' and Articles 11 and 11.1 of the Federal Law 'On Social Protection of Disabled Persons in the Russian Federation'.

5. Federal Law No. 178-FZ dated July 17, 1999 (as amended on October 29, 2024) "On State Social Assistance".

Appendix B. Physician Action Algorithms

Appendix C. Patient Information

Hallux valgus is a pathological condition in which weakness of the foot ligaments leads to the deviation of the first metatarsal bone and, consequently, the deviation of the big toe. In addition to an aesthetic defect in the form of a protruding bony "bunion", this can lead to difficulties in finding suitable shoes, periodic or constant pain, the formation of calluses, corns, and nail problems.

The diagnosis is established based on X-ray examinations of the foot and a physical examination by a physician.

Conservative treatment may include the use of orthopedic devices, therapeutic exercise, physical therapy, massage, and pharmacotherapy; however, it can only temporarily relieve symptoms and is often ineffective. When symptoms are pronounced, the question of surgical treatment inevitably arises.

During surgery, soft tissue manipulations and specialized bone osteotomies may be performed to restore the normal anatomy of the foot. Both internal and external fixators made of various materials can be used to fix the bones in the required position.

In the postoperative period, a specific orthopedic regimen must be followed. It is determined depending on the severity of the disease and the chosen technique. One of the most widely used devices is the Barouk shoe (complex and semi-complex orthopedic footwear for adults and children), which allows offloading of the forefoot and walking almost immediately after surgery without crutches. The duration of wearing the shoe is determined individually, but averages 4–6 weeks.

An important element of treatment is postoperative rehabilitation aimed at reducing edema, pain, and restoring joint mobility. Special attention should be paid to exercises to develop movement in the first metatarsophalangeal joint, which is located at the base of the big toe. It must be understood that normal walking will not achieve a full range of motion, and exercises should be performed regularly, as recommended during a consultation with a physical therapy specialist. They can also advise on when and how often to perform them. Returning to active sports, especially those involving running and jumping, is recommended no earlier than 6 months after surgical treatment.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

Appendix G1. Visual Analog Scale (VAS)

Russian title: visual analog scale (VAS)

Original title: Visual Analog Scale

Source: A. Williamson, B. Hoggart: Pain: a review of three commonly used pain rating scales. Journal of Clinical Nursing. 14:798-804 2005.

Type – assessment scale

Purpose: assessment of pain intensity

Content:

Visual Analog Scale (10 cm (100 mm) line)