While waiting for space in a shelter, the homeless patient was hospitalized — a fortuitous event.
A homeless, young, recent immigrant from Mexico came to the ER. He attributed his worsening left hip pain to a leg injury sustained while lifting a heavy couch a few months earlier. The hip was exquisitely tender with a decreased range of motion. X-ray revealed avascular necrosis (AVN) of the femoral head and associated degenerative joint changes (Figure 1). The man reported no fever, chills, cough, night sweats, weight loss, history of TB, surgery, or past consumption of corticosteroid medications or herbs. He did not smoke, drink alcohol, or use illicit drugs. There was no family history of joint problems.
CLINICAL EXAMINATION
The patient was of normal height and weight. Vital signs as well as lung, heart, abdominal, and neurovascular examinations were unremarkable. A chemistry profile and complete blood counts, including neutrophil and lymphocyte counts, were within normal limits. A chest x-ray revealed nothing unusual.
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The patient was prescribed analgesics, ambulation with crutches, and clinic follow-up. Since he was homeless, he remained in the hospital pending shelter placement. By the fourth hospital day, tuberculin testing with purified protein derivative (PPD) was positive (20-mm induration). He developed low-grade fever (101ºF), bilateral ankle and left-knee swelling, and pain. Ticarcillin/clavulanic acid was started (later changed to cephalexin), and subsequent joint x-rays revealed soft-tissue swelling with no evidence of arthritis.
Infective and rheumatologic causes of arthritis and avascular necrosis were sought. Tests for HIV, gout, sickle cell disease, Lyme disease, rheumatoid factor, syphilis, lupus anticoagulant, hepatitis B and C, smooth-muscle ribonucleoprotein, as well as antinuclear, anticardiolipin, anti-smooth-muscle, Sjögren, anti-DNA, and antineutrophilic cytoplasmic antibodies (both c-ANCA and p-ANCA) were negative. Urine and blood cultures as well as parvovirus titers were also negative. The patient was immune to varicella zoster. Liver function tests and albumin were normal, but total protein and an erythrocyte sedimentation rate (104 mm) were elevated. Serum protein electrophoresis was consistent with inflammation.
Lower-extremity duplex scanning was negative for deep venous thrombosis, and an echocardiogram excluded vegetations. Chest CT scan showed minimal right lower atelectasis or scarring but no evidence of active infiltrates or lymphadenopathy. A repeat x-ray and subsequent CT (Figure 2) confirmed AVN and further degeneration of the left femoral head. Nuclear bone scans failed to reveal increased hip uptake. Gallium scans showed increased uptake in the acetabulum, ischium, and inferior pubis ramus.
Follow-up MRI revealed extensive soft-tissue swelling, joint destruction, and septic arthritis with multiple abscesses involving gluteal muscles and the vastus lateralis and obturator internus. After a nondiagnostic CT-guided hip biopsy, an open hip biopsy revealed necrotizing granulomatous lesions with acid-fast positive bacilli in the synovial specimen and a focus of granulomatous reaction in the femoral-head specimen. Antitubercular four-drug therapy (isoniazid, rifampicin, pyrazinamide, and ethambutol) yielded clinical improvement.
Discussion
TB can affect almost all organ systems. Skeletal TB accounts for approximately 10% of extrapulmonary cases. The weight-bearing joints (spine, hips, and knees) are most often affected. Hip TB manifests as synovitis, arthritis, joint destruction, osteomyelitis, cold abscess, joint dislocation, sclerosis, pseudoarthrosis, and infection of a prosthetic joint.
Presenting symptoms of hip TB include fever, night sweats, and joint pain. Symptoms are typically worse at night. Reduced appetite, weight loss, and cold abscess with or without drainage are also seen. TB usually affects a single joint and can mimic worsening osteoarthritis, rheumatoid arthritis, or pyogenic arthritis. Common causes of AVN are trauma, corticosteroid use, pancreatitis, systemic lupus erythematosus, alcoholism, gout, sickle cell disease, and infiltrative diseases (e.g., Gaucher’s disease).
A high index of clinical suspicion is often needed to diagnose TB of the hip. Radiologic findings that arouse high suspicion are periarticular osteopenia, joint-space narrowing, soft-tissue inflammation with minimal periosteal reaction, multiple subarticular cysts, bone destruction or sclerosis without evidence of bone formation, and sequestrum affecting both bones of the joint. MRI is the preferred imaging modality. It provides excellent details of the joint anatomy, tenosynovial involvement, and location of abscesses.
DIAGNOSIS
Aspiration of a tuberculous joint reveals leukocytosis with lymphocytic predominance and may reveal TB bacilli on acid-fast stain or culture. When aspiration is insufficient for diagnosis, joint biopsy reveals classic TB granuloma with TB bacilli on stain and culture. New techniques, such as polymerase chain reaction, permit rapid confirmation of the diagnosis and an estimation of drug sensitivity.
Immunosuppressed patients pose a diagnostic challenge. The presenting symptoms can be very nonspecific and insidious, and overt clinical symptoms, such as fever, leukocytosis, joint pain, swelling, erythema, and reduced range of motion, may not be evident until later in the disease. In addition, PPD skin testing may be falsely negative in immunosuppressed patients. TB has a higher incidence and greater extrapulmonary involvement in patients suffering from AIDS.
TREATMENT
The primary approach to hip TB uses at least three antimycobacterials, including a bactericidal agent. The CDC currently recommends four drugs: isoniazid, rifampicin, pyrazinamide, and ethambutol or streptomycin, depending on susceptibility results. Treatment must be continued for at least 12 months. Surgery is an option for refractory cases or those with severe osteoarticular involvement. Excision arthroplasty of the hip is well established as a primary or a salvage procedure. Most patients recover with a relatively painless and stable joint, although some have limb-length discrepancy and altered gait. Arthrodesis to fix the greater trochanter to the iliac wing carries the risk of complications, such as nonunion, partial union, and ipsilateral knee and back pain. Total hip replacement is recommended when there is extensive joint damage or AVN of the femoral head. In this situation, surgery is coupled with at least 12 months of chemotherapy to prevent recurrence of TB in the joint.
