• Hematogenous spread of organisms from a distant site of infection or by direct spread from bone.
• Most commonly affected area: 50% of cases in the spine; next most commonly affected area: large joints (knee and hip).
• Primary infection beginning in the lungs and spreading to the highly vascular synovium.
• Tuberculous osteomyelitis commonly involving an adjacent joint.
• In peripheral joints, a granulomatous reaction in the synovium causing joint effusion and eventual destruction of underlying bone.
• In the spine, infection of the intervertebral disk spreading to adjacent vertebrae.
• Osteomyelitis of vertebrae causing collapse, kyphosis, or gibbous deformity, and possibly paraspinal “cold” abscess.
The prototype of granulomatous arthritis is tuberculous arthritis. Atypical mycobacteria, sarcoidosis, and sporotrichosis can cause granulomatous involvement of the synovium, but these entities are much less common.
Around 1% of patients with tuberculosis develop joint and/or bone involvement. It occurs as the primary disease in children. In adults, it is usually due to haematogenous spread from secondary pulmonary or renal lesions. The onset is insidious and diagnosis often delayed. The organism invades the synovium or intervertebral disc. There are caseating granulomas and rapid destruction of cartilage and adjacent bone. Some patients develop a reactive polyarthritis (Poncet’s disease). The hip or knee (30%) is quite commonly affected, but around 50% develop spinal disease. The patient is febrile, has night sweats, is anorexic and loses weight. The usual risk factors for tuberculosis apply - debility, alcohol abuse or immunosuppression. HIV-positive/AIDS patients are at particular risk.
EPIDEMIOLOGY & DEMOGRAPHICS
INCIDENCE (IN U.S.): Unknown
PREVALENCE (IN U.S.): Unknown
PREDOMINANT SEX: Male = female
PREDOMINANT AGE: Rare in childhood
PEAK INCIDENCE: No seasonal predilection
PHYSICAL FINDINGS & CLINICAL PRESENTATION
• Often no constitutional symptoms (fever and weight loss).
• Possibly no clinical or radiographic evidence of pulmonary TB.
• Spinal infection most often in the thoracic or upper lumbar area, with back pain as the most common symptom.
• Considerable local muscle spasm possible.
• Kyphosis and neurologic symptoms resulting from spinal cord compression in advanced disease.
• Chronic monoarticular arthritis in the peripheral joints.
• Single joint involved in 85% of patients.
• Pain, swelling, limitation of motion, and joint stiffness less dramatic than in acute bacterial arthritis; possibly present for months to years.
• Seen more often in persons from developing countries, elderly patients, and hemodialysis patients.
• Fungal arthritis
• Metastatic cancer
• Primary or metastatic synovial tumors
• High index of suspicion needed.
• Gold standard: synovial biopsy.
• Joint aspiration and culture of the synovial fluid performed while awaiting biopsy.
• Positive synovial fluid smear for acid-fast bacilli in 20% of cases; positive culture in 80%.
• Elevated synovial fluid protein, low glucose.
• Considerable variation in synovial fluid WBC count, but values of 10,000 to 20,000 cells/mm3 typical; may be predominantly polymorphonuclear leukocytes.
• Usually positive tuberculin skin test.
• Anergy in elderly patients or in advanced disease.
• In spinal infections, percutaneous or open biopsy to obtain accurate C&S data.
Peripheral WBC count and ESR are elevated but nonspecific.
• Plain radiographs of the affected joint.
1. Typically demonstrate bony destruction with little new bone formation.
2. Osteopenia and soft tissue swelling in early infections.
3. Later, erosions at the joint margins.
4. In the spine, disk space narrowing with vertebral collapse (wedging) causing characteristic kyphosis.
• CT scan: useful in early diagnosis of infections of the spine and to detect paraspinal abscess.
• Technetium and gallium scintigraphic scans: may be positive, but do not permit differentiation from inflammation or osteoarthritis.
Encourage range-of-motion exercises of the affected joint to prevent contractures.
ACUTE GENERAL Rx
• Combination chemotherapy.
1. If sensitive TB suspected, give isoniazid 5 mg/kg/day (maximum 300 mg/day) plus rifampin 10 mg/kg/day (maximum 600 mg/day) for at least 6 mo and pyrazinamide 15 to 30 mg/kg/day (maximum 2 g/day) for at least the first 2 mo plus ethambutol 15 to 25 mg/kg/day until sensitivity results are available.
2. Most patients are treated successfully with chemotherapy alone.
3. Urgent surgical intervention is necessary if spinal cord compression causes neurologic changes.
• Surgical debridement in cases of extensive bone involvement.
In long-standing extensive disease, arthrodesis of weight-bearing joints.
Loss of cartilage and destruction of underlying bone if treatment is not initiated promptly.