Tuberculosis of ankle joint is relatively uncommon. The incidence of ankle tuberculosis is less than 5 percent of all osteo-articular tuberculosis.
Pathophysiology of Tuberculosis of Ankle
The mycobacteria reaches the ankle joint via bloodstream. The initial focus may start in the synovium, especially in children, or as an erosion in the distal end of tibia, malleoli or talus. Rarely tuberculosis of calcaneum may reach the ankle joint after involvement of subtalar joint and the talus.
Relevant Anatomy of Ankle Joint
The ankle is a hinge joint formed by talus bone and socket formed by formed by the distal ends of tibia and fibula called ankle mortise.
The mortise is deepened posteriorly by the transverse tibiofibular ligament.
Interosseous ligaments hold tibia and fibula together. Other connecting ligaments are the antero-inferior and posteroinferior tibiofibular ligaments.
Ankle joint is stabilized by various ligaments. Anteriorly it is wide, membranous, extending from the distal anterior part of tibia to the neck of talus. The posterior ligament is short and thin extending from the distal posterior surface of tibia to the posterior surface of talus.
Medially deltoid ligament is attached above to the medial malleolus and distally radiates anteriorly to the tuberosity of navicular, the spring ligament and the neck of talus, directly below to the sustentaculum tali, and posteriorly to the body of talus.
Synovial membrane lines the inner surface of the capsule and is attached to the articular margins.
[Read more about Ankle joint anatomy]
Patient may present with pain and swelling which may be accompanied by limp. The onset is insiduous and initially the pain may be ignored or treated by over the counter medication. The patient may seek consultation as the symptoms advance.
On examination, there would be swelling in the joint as marked by fullness around the malleoli and tendo-Achilles insertion.
In cases of long standing with gross destruction of bones and ligaments the ankle joint may show pathological anterior dislocation.
Imaging in Tuberculosis of Ankle Joint
Initial stages would show normal xray or generalized osteoporosis around the ankle joint. As the disease progresses to arthritis, reduction in joint space occurs.
If there is a bony focus, it may be visible as radiolucent shadow in juxta-articular region.
More advanced cases would show destruction in the bones.
If the swelling is larger enough, it may perforate the skin and result in sinus formation.
MRI would show reveals soft tissue involvement in a better way. MRI is especially useful in cases where synovium and other tissues are involved and xrays are normal.
If infection is suspected, an early MRI helps in reaching the diagnosis and differentiation. With increasing health awareness, the patients now present early and MRI has got increasing role in the diagnosis of various conditions.
Routine Lab Tests
Complete blood count, ESR and CRP would indicate inflammation though the levels may not correlate with severity of the disease.
Joint Fluid Study
The joint fluid is aspirated under aseptic conditions and is subjected to biochemical, cytological and microbiological studies.
Read about normal joint fluid
Fluid can be subjected to studies like PCR and culture for mycobacteriae.
Synovial biopsy may be taken in cases where there is difficulty in diagnosis to help differentiate from other diseases.
- Rheumatiod arthritis
- villonodular synovitis
Treatment of Tuberculosis of Ankle Joint
Like other TBs, ankle tuberculosis is managed by chemotherapy and rest. Patient is put on antitubercular drugs, which are mainstay of the treatment. To provide the rest , the joint is splinted in functional position for 6-12 weeks.
If the disease responds well and local signs become quite gentle active and assisted exercises are begun.
The ankle is a complex joint with high degree of weight bearing and locomotion. Ideally the treatment should restore pain free mobile ankle that is able to sustain weight of the person.
If the patient is treated in synovitis stage, the patient does recover almost completely. But in cases, where the arthritis has set in, some loss of motion with varying degrees of pain may be expected even after completion of treatment. The loss of motion and residual pain is dependent upon the destruction of the bone.
In cases with advanced arthritis where the joint is expected to be very painful, painless ankylosis of the joint in neutral position is the aim of treatment, which can be achieved in majority of the cases by antitubercular drugs and immobilization in a below-knee plaster cast.
Isolated ankylosis of ankle joint does little or no disability in normal activities when compared to hip or knee joint.
For achieving this ankylosis, the patient is put on below knee plaster cast and allowed to ambulate with help of crutches with affected limb non weight bearing.
This continues for 8 to 12 weeks. After this period, the patient is encouraged to start guarded weight bearing while plaster is still on. After six months, the plaster may be replaced by an orthosis that is worn for 2 years to prevent recurrence of infection and deformity.
Patients who are not responding to antitubercular drugs and rest might need surgery.
Following surgical treatments may be considered from patient to patient.
Synovectomy With or Without Joint Debridement
This is done in the stage of synovitis, and early arthritis.
Arthrodesis of Ankle Joint
Arthrodesis may be considered for advanced disease or for painful ankylosis. It is also a choice in cases of pathological subluxation or dislocation.
If secondary infection is present, it is better to perform arthrodesis following the joint debridement.
This is indicated when there is an unacceptable deformity of the ankle. It mostly happens when ankylosis occurs in an awkward position.
A supramalleolar osteotomy would correct the position in such cases.
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