Pathogenesis and evolution of the lesion
The development of osteoarticular tuberculosis always occurs against the background of general hematogenous dissemination from the primary focus. Mycobacteria are carried by the bloodstream into the spongy bone, where a specific granuloma—primary tuberculous ostitis—is formed.
The evolution of the lesion goes through several regular stages:
- Formation: a bone cavity (a cavity with an isolating wall) is formed. Caseous or purulent masses accumulate inside, and bone sequestra develop.
- Spread period: the most dangerous stage. Mature tuberculous inflammation ruptures beyond the bone. When it breaks into a joint or intervertebral disc, secondary arthritis or discitis develops, and when it extends into soft tissues, a cold migration abscess is formed.
- Progression: massive destruction of cartilage and bone tissue occurs, leading to disfiguring deformities.
- Outcomes: the process may subside after scarring and the discharge of necrotic masses (sometimes via fistulas), however, a complete cure is not achieved. A protracted course with a high risk of relapse is typical.
Tuberculous spondylitis: prespondylitic phase
Tuberculous involvement of the spine occupies a special place due to the severity of its consequences. The clinical picture strictly follows pathological and anatomical changes and begins with the prespondylitic phase (development of primary ostitis in the vertebral body).
At this stage, general symptoms predominate over local ones. In children, unmotivated restlessness, loss of appetite, weight loss, and decreased mobility are noted. Adults complain of rapid fatigue, stiffness, and lumbago-like pain that worsens after exertion.
Objectively (status localis), the clinical picture is extremely sparse. One can notice a slight smoothing of physiological curves, a slight increase in the tone of the back extensor muscles, and moderate tenderness upon palpation of paravertebral points without strict localization. The neurological status remains normal. Standard radiography in this phase is uninformative; the most reliable method for early diagnosis is MRI, which reveals specific bone marrow edema.
Spondylitic phase: height of the disease
When the vertebral body is destroyed and the process spreads to adjacent structures, the spondylitic phase sets in. It is characterized by the classic triad: local pain, impaired mobility, and the development of deformities.
The pain syndrome becomes localized and constant. A specific sign in children is nighttime pain. Due to the pain, a protective myogenic contracture develops, visually manifested as the "reins" sign. Patients lose normal mobility: they cannot bend, they turn with their entire torso ("wolf-like" gait), and they prefer to sit leaning on their arms. When the thoracolumbar region is affected, iliopsoas rigidity is revealed.
During the peak period, the temperature can reach 40°C, and intoxication increases. A local deformity—spondylitic gibbus—forms. Against this background, symptoms of spinal cord compression (paresis, paralysis) often appear, the severity of which directly depends on the magnitude of the deformity and the presence of peridural abscesses. Neutrophilic leukocytosis, eosinophilia, and a sharp acceleration of ESR are recorded in the blood.
Remission and postspondylitic phase
In a favorable course, which is rare without treatment, the process passes into the remission stage. The intensity of pain decreases, becoming aching, and the myogenic contracture weakens. Neurological complications may regress, but the resulting kyphotic deformity persists permanently.
In the postspondylitic phase, a period of relative well-being begins. General manifestations of infection disappear, blood counts normalize, and radiographs show signs of fusion of the affected vertebrae (marginal, focal, or total destruction).
The decrease in working capacity in this period is associated with severe residual deformities of the spine, chest, and contractures. It is important to remember that "dormant" tuberculosis foci remain in the body, so the risk of relapse persists constantly.
Briefly: answers to topical questions
What radiological signs are characteristic of the spondylitic phase of tuberculous spondylitis?
The spondylitic phase of tuberculous spondylitis is characterized by destructive changes in the vertebral bodies, a decrease in intervertebral disc height, local kyphosis, and the formation of a cold abscess.
- Radiography — isolated cavity with destruction of the compact plates of the vertebral body, decreased height of the adjacent disc, and local kyphosis; soft tissue thickening indicates the formation of a cold abscess.
- MRI — in case of signs of spinal cord compression, it allows for clarifying the localization of the compressing factor, its extent, and the degree of the vertebromedullary conflict.
- CT — lytic destructive foci in the vertebral bodies may be detected.
Marginal, focal, and total destruction of vertebral bodies are distinguished.
What are the typical localizations of osteoarticular tuberculosis in the musculoskeletal system?
In the musculoskeletal system, tuberculosis most frequently affects the spine and large joints. The following typical localizations are distinguished:
- Spine — tuberculous spondylitis (accounts for up to 40–45% of cases).
- Hip joint — tuberculous coxitis (about 20% of cases).
- Knee joint — tuberculous gonitis (15–20% of cases).
- Bones — epiphyses of long tubular bones and diaphyses of finger phalanges.
Which diseases require differential diagnosis with tuberculous spondylitis?
Differential diagnosis of tuberculous spondylitis must be carried out with bacterial osteomyelitis of the spine, which can also involve multiple vertebral bodies.
What are the indications for surgical treatment of tuberculous spondylitis?
Surgical treatment of tuberculous spondylitis is indicated when conservative therapy is ineffective for 1.5–2 months and complications develop. The main indications include:
- Destruction and sequestration of vertebrae, spinal instability, and spinal column deformity.
- Marginal and destructive forms with the formation of para- or prevertebral abscesses.
- Well-circumscribed foci with caseous contents.
- Spinal cord compression and pronounced neurological disorders (emergency surgery is required).
- Presence of fistulas and severe pain syndrome.
Which first-line drugs are used for etiotropic therapy of osteoarticular tuberculosis?
First-line (primary) anti-tuberculosis drugs are used for the etiotropic therapy of osteoarticular tuberculosis.
- Isoniazid
- Rifampicin
- Pyrazinamide
- Ethambutol
- Streptomycin
In the intensive phase, a combination of four drugs (isoniazid, rifampicin, pyrazinamide, ethambutol) is prescribed. In the continuation phase, at least three drugs are used (isoniazid, rifampicin, and either pyrazinamide or ethambutol).
The pathogenesis of nighttime pain in spondylitis is a vicious cycle: deep sleep $\rightarrow$ relaxation of back muscles $\rightarrow$ onset of mobility in the destroyed segment $\rightarrow$ acute pain (patient cries out) $\rightarrow$ reflexive muscle spasm $\rightarrow$ pain subsides $\rightarrow$ patient falls asleep.
Class and exam questions
Why does the "reins" sign occur in tuberculous spondylitis?
This is a visual and palpation manifestation of protective myogenic contracture. The body reflexively increases the tone of the back extensor muscles to immobilize the tuberculosis-affected spinal segment and reduce pain.
What is the value of MRI in the prespondylitic phase?
MRI is the most reliable method for early diagnosis because it allows the detection of bone marrow edema and inflammation even before gross bone destructions, which are visible on conventional radiographs, appear.
Does the onset of the postspondylitic phase mean complete recovery?
No, a complete cure is not achieved. The subsidence of the process is accompanied by scarring, but uneliminated foci and cold abscesses remain in the tissues, creating a constant threat of relapse.
What else to study on this topic
- Mechanism of formation and pathways of spread of cold "migrating" abscesses
- Specific forced postures of patients in the spondylitic phase
- Radiological variants of vertebral destruction (marginal, focal, total)
- Neurological complications and the mechanism of vertebromedullary conflict
- Features of peripheral blood changes in the active phase
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