Mechanism of development and stages
The disease accounts for about 10% of all extrapulmonary forms of tuberculosis. The infection spreads sequentially: from the lungs, mycobacteria enter the lymph nodes and serous membranes, and are then carried via the bloodstream into the bone tissue.
In the fixation zone (usually the epiphyses of long tubular bones), a tuberculous tuberculum forms. Inflammation develops — primary osteitis. The tubercula undergo caseous necrosis, and granulations form around them, which also die off over time. Within the necrotic masses, the bone fragment completely separates from the healthy tissue, forming a bone sequestrum. When the process spreads to the joint, tubercula appear in the synovial bursa, and cartilage and bone are destroyed.
According to P.G. Kornev's clinical classification, three phases of the course are distinguished:
- Phase I (pre-arthritic) — formation of an isolated lesion in the bone (epiphysis).
- Phase II (arthritic) — breakthrough of inflammation into the joint cavity, development of secondary arthritis.
- Phase III (post-arthritic) — outcome and stabilization of the process.
Rarely (in 5% of cases), primary involvement of the synovial membrane occurs — tuberculous synovitis. It has a more favorable course and does not cause bone destruction.
Clinical presentation
The disease begins gradually. Against the background of positive tuberculin skin tests, general tuberculous intoxication syndrome develops: weight loss, low-grade fever, rapid fatigability, tiredness when walking, and decreased appetite.
An important diagnostic marker is the sequence in which local symptoms appear. First, limb function is impaired, and only after that pain develops (especially with movement, walking, or bending the torso).
Physical examination reveals pallor of the skin and mucous membranes, emaciation, and persistent muscle atrophy of the affected limb. Exacerbations can be triggered by trauma or previous infections, and the medical history often reveals contact with a patient suffering from active (open) tuberculosis.
Radiological diagnostics
Early changes are localized in the spongy bone of the metaepiphyseal region. Characteristic signs include:
- Osteoporosis (thinning of the bone tissue).
- Presence of sequestra, which look like a soft shadow against an area of radiolucency («melting sugar cube» sign).
- Complete absence of osteosclerosis and periostitis.
When the joint is involved, the radiological picture changes dynamically: initially, the joint space widens, then narrows, and a characteristic chewed-out and serrated appearance develops on the articular cartilage and bones.
Differential diagnosis
Most often, osteoarticular tuberculosis must be differentiated from chronic hematogenous osteomyelitis.
| Sign | Bone tuberculosis | Chronic osteomyelitis |
|---|---|---|
| Onset and localization | Gradual; metaphyses, epiphyses, vertebrae | Acute onset in history; diaphyses of long bones |
| Alexandrov's sign | Positive (thickening of the skin fold) | Negative |
| Local complications | Cold cold abscesses, joints are often affected | Joints are rarely involved, no cold abscesses |
| Radiography | Osteoporosis, no periostitis, melting sugar-like sequestra | Osteosclerosis, periostitis, involucrum and dense sequestra |
| Laboratory findings | Lymphocytosis, mycobacteria in pus, tests (+) | Neutrophilic leukocytosis, staphylococcus, tests (-) |
Briefly: answers to topical questions
What types of surgical operations are used to treat osteoarticular tuberculosis?
The following types of surgical interventions are used to treat osteoarticular tuberculosis:
- Necrectomy — a radical intervention preserving joint function.
- Limited conservative resections — radical interventions preserving joint function in the pre-arthritic phase or at the beginning of the arthritic phase.
- Wider joint resection with synovectomy — used during the height of the arthritic phase.
- Arthrodesis — may conclude the operation in a physiologically advantageous position to prevent postoperative joint instability.
- Corrective osteotomies and myotomies — used in the post-arthritic phase to eliminate contractures and pain syndrome.
- Opening and drainage of abscesses — used for cold abscesses of joints and in tuberculous spondylitis.
- Removal of sequestra and altered soft tissues, resection of vertebral bodies within healthy bone — used for tuberculous spondylitis.
- Transcorporal decompression — subtotal resection of vertebrae up to the posterior longitudinal ligament in spinal cord compression.
- Interbody fusion — osteoplastic replacement of vertebral body defects with the elimination of kyphotic deformity.
- Posterior spinal fixation with metal implants or devices — permitted to prevent the migration of bone grafts.
What complications, besides cold abscesses, are characteristic of osteoarticular tuberculosis?
In addition to abscesses, the following complications are characteristic of osteoarticular tuberculosis:
- Inflammatory: fistulas.
- Orthopedic: bone and limb deformation, reactive arthritis, contracture, pathological fractures, changes in limb segment length.
- Limb and joint deformities: varus and valgus deformities.
- Joint instability: dislocation, subluxation.
- Limitation of joint movement: contracture.
- Spinal deformities: pathological kyphosis, lordosis, scoliosis, mixed deformities.
- Spinal instability.
To remember the differences between tuberculosis and osteomyelitis, use the «Softness and Cold» association: tuberculosis begins gradually (softly), causes osteoporosis (bone softness) on X-rays, sequestra look like melting sugar, and abscesses form cold (cold abscesses).
Class and exam questions
Can bone tuberculosis develop as an independent primary disease?
No, bone and joint involvement is always secondary. Mycobacteria are disseminated hematogenously from pre-existing foci in the lungs, lymph nodes, or serous membranes.
How to differentiate pain in tuberculosis from the consequences of trauma?
In tuberculosis, symptoms develop in the reverse order of trauma: first, the patient notes impaired limb function (e.g., limp), and only later does pain during movement appear.
What is Alexandrov's sign?
This is a clinical sign of osteoarticular tuberculosis detected upon inspection: a noticeable thickening of the skin fold is observed on the side of the affected limb.
What else to study on this topic
- Pathogenesis of cold abscess formation
- Clinical features of tuberculous spondylitis and coxitis
- Surgical management in the pre-arthritic and arthritic phases
- Technique and evaluation of tuberculin tests (Mantoux, Pirquet)
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