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Tuberculosis of the Hip

Epidemiology

  • 2nd most common location of musculoskeletal TB after the spine
  • Most common in children and adolescents
  • More common in developing countries

Etiology

  • Causative organism – Mycobacterium tuberculosis
  • Due to haematogenous spread of pulmonary TB
  • Can also spread through lymphatics

Pathogenesis

  • Initial lesion
    • Is usually in the bone adjacent to the joint – in acetabulum or the head of the femur (osseous TB)
    • In the minority of cases it begins in the synovium (synovial TB)
  • The initial bony focus, which contains the infected granulation tissue, erodes the overlying cartilage and reaches the joint
  • Results in synovial hypertrophy and effusion
  • The Pannus of hypertrophies synovium around the articular cartilage gradually extends – destroys the cartilage
    • Joint becomes full of pus and granulation tissue
  • Multiple cavities form in the femoral head and acetabulum – they eventually become partially absorbed
    • The remaining head of the femur dislocates from the acetabulum to the ilium – due to the pull of muscles acting on the hip (gives rise to ‘  wandering acetabulum ’)
  • In the later stages, pus bursts through the joint capsule – presents as a cold abscess in the groin

Stages of TB of the Hip

Stage I – stage of synovitis

  • Joint effusion – hip joint assumes a position of flexion, abduction and external rotation
  • Affected limb appears longer (apparent lengthening)

Stage II – stage of arthritis

  • Articular cartilages becomes involved
  • Hip assumes a position of flexion, adduction and internal rotation
  • Affected limb appears shorter (apparent shortening)

Stage III – stage of erosion

  • Cartilage is destroyed and the femoral head and/or acetabulum is eroded
  • Pathological dislocation of the hip may occur
  • There is true shortening of the affected limb due to destruction of bone

Clinical features

  • Insidious onset
  • Stiffness of the hip – leads to a limp
  • Initially pain may be referred to the knee
  • Antalgic gait
  • Wasting of thigh and gluteal muscles
  • Shortening of lengthening – depending on the stage (see above)
  • Swelling around the hip due to the cold abscess
  • Limited range of motion

Diagnosis

  • X-ray – shows reduction of joint space, irregular outline of articular bone, acetabular dislocation (wandering acetabulum), sclerosis
  • MRI
  • Tc99 bone scan

Treatment

Pharmacological

  • Drugs – Isoniazid (H), Rifampin (R), Ethambutol (E), Pyrazinamide (Z)
    • Regimen – HRZE for 2 months, followed by HR for 9-18 months

Operative

  • Joint debridement – pus, necrotic tissue, inflamed synovium and dead cartilage is removed from the joint
  • Girdlestone arthroplasty
    • Excision of head and neck of femur, necrotic tissue, granulation tissue
    • Post-operative traction and immobilisation
  • Arthrodesis
  • Total hip replacement
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