Foot anatomy

X-ray anatomy of the midfoot and hindfoot

The assessment of deformity-free foot anatomy relies on strict geometric parameters. In the lateral view, the relationships of the axes of the talus, calcaneus, and first metatarsal bone play a key role:

• Lateral midfoot mechanical angle: formed by the intersection of the mechanical axis of the 1st metatarsal bone and the line of the talar trochlea at its posterior point. The normal value is 23.4 (+3.02°).
• Lateral midfoot anatomical angle: the point of intersection of the anatomical axis of the 1st metatarsal bone and the line of the talar trochlea is calculated using the formula (length of the trochlear line) × 0.49. The normal value is 26.1 (+3.5°).
• Lateral hindfoot angle: the anatomical axis of the calcaneus intersects the anteriorly extended line of the talar trochlea (the point is calculated as trochlear line length × 1.87). The normal value is 17.7 (+5.1°).

In the axial view, the posterior tibiocalcaneal angle is evaluated. Normally, the anatomical axis of the calcaneus is shifted laterally from the axis of the tibia by up to 10 mm and has a valgus deviation of up to 10°. It is also important to consider that the line of Chopart's joint intersects at its center at an angle of 90.3 (+3.9°), opening medially. The choice of specific parameters always depends on the components of the deformity in a given patient, and methodologies may slightly differ across literary sources.

Clinical anatomy of the tarsal and metatarsal bones

Knowledge of the anatomy of individual bones is critically important for diagnosing osteochondropathies—diseases that progress over years and cause localized pain, limping, and restricted movement. Self-healing often occurs, but deforming arthrosis may develop.

1. Talus: forms the apex of the arch. Assessment of its vascularity is extremely important after trauma. The appearance of subchondral radiolucent zones of the arch (Hawkins sign) in the Mortise view (internal joint rotation of 15–20°) is a favorable prognostic sign that reduces the risk of avascular necrosis.
2. Navicular bone: a short spongy bone. In children aged 3–10 years, it can be affected (Köhler disease I), which manifests as pain at the level of the tarsus and mild swelling on the dorsum of the foot without signs of inflammation. The disease lasts 8–12 months and, with adequate treatment, often ends with complete restoration of the anatomical picture.
3. Metatarsal heads: when affected (Köhler disease II) in adolescents aged 10–20 years, pastosity arises at the base of the toes. Due to pain, the walking pattern changes—the patient is forced to rely on the lateral arch of the foot or the heel.

Features of injuries and postoperative anatomy

The anatomy of the phalanges of the toes in children is distinguished by the presence of active growth plates. For intra-articular fractures of the 1st and 5th toes, precise anatomical reduction of bone fragments is strongly recommended. This is necessary to prevent irreversible bone growth disorders and the development of early osteoarthritis.

In adult patients after foot bone surgery (e.g., in talar fractures), a strictly individualized approach is required. Restriction of weight-bearing can last from 1.5 to 4 months, depending on the localization of the injury, the extent of the intervention, and signs of consolidation. The timing for initiating range-of-motion exercises in adjacent joints and the duration of immobilization depend on the stability of fragment fixation and radiographic data. The goal is to achieve the best functional outcomes.

Imaging methods for anatomical structures

A set of instrumental methods is used to study foot anatomy and detect pathologies. The gold standard is radiography of the feet in two projections, which is mandatory with weight-bearing.

Various types of examinations are used in traumatology: radiography of the tarsus, metatarsus, phalanges, and calcaneus. For open wounds of the leg and foot, the following are used to evaluate soft tissues:

• Ultrasound: allows for increased diagnostic sensitivity and finding radiolucent foreign bodies (wood, plastic, glass fragments).
• CT and MRI: used to visualize tiny fragments (less than 0.5 mm) and search for occult sources of infection of unknown origin.
• Soft tissue radiography: effective for radiopaque objects (bone, metal, teeth from animal bites, glass, and stone).

If initial radiography shows no convincing osteo-traumatic changes, but the wound is open, repeat X-ray examination is indicated to clarify the diagnosis.

Class and exam questions

What else to study on this topic

• Radiological parameters and classification of flatfoot-valgus foot deformity
• Biomechanics of compensatory gait in Köhler disease II
• Stages and radiation diagnostics of navicular bone osteochondropathy
• Criteria for initiating weight-bearing after talar osteosynthesis
• Algorithm for postoperative instrumental control of foot bones in adults

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.