3.5. Bone and Joint TB

Bone and Joint TB roughly accounts for 5-15% of all EPTB and 2-5% of all TB in children and adults. It occurs due to the reactivation of bacilli which had seeded the bones during the initial mycobacteremia. The symptomatic disease usually develops within 1-3years of infection, but TB dactylitis can have an early manifestation (usually one month). Typical presentations of Bone and Joint TB are Potts spine (50% of osteoarticular TB), Dactylitis, Arthritis (as an extension from the metaphysitis), Osteomyelitis. A few uncommon ones are reactive arthritis (Poncet’s arthritis), tenosynovitis and bursitis. 

 

3.5.1. Dactylitis (Spina ventosa)

Tuberculous osteitis, the dactylitis form, often affects children. It may involve multiple or consecutive bones. In children, short tubular bones of the hands and feet are usually affected, typically involving the proximal phalanx of the index/middle fingers and middle/ring finger metacarpals. It often follows a benign course without pyrexia and acute inflammatory signs. On X-Ray, the involved bones show a diaphyseal expansile lesion, a periosteal reaction is uncommon, and healing is by sclerosis.

 

3.5.2. Spinal TB or Pott’s Spine

The most common site of Pott’s Spine is thoracic, followed by lumbar/ cervical areas. Pain may be localized over the involved vertebra or could be referred to due to root pains. There can be local tenderness or deformity. Fever and constitutional symptoms are present in one among three cases. Neurological complications include paraparesis (20-50% cases), and cauda equina syndrome. Moreover, about 15% of patients can have a paradoxical response with increased neurologic deficit following therapy. However, this entity is diagnosed only after ruling out other causes of non-response like DRTB, pus collection, etc. There is a risk of kyphosis later in life, especially in children below 7-10 years.

Plain X-Ray of the spine is less sensitive in early disease as it does not reveal any abnormality till about 30-50% of bone loss has occurred. The typical findings are one more of the following: endplate erosion decreased vertebra height, collapse and narrowing of discal space and paravertebral soft tissue shadow. MRI is the most sensitive for picking up abnormalities (nearly 100%). Features in MRI are marrow oedema, destruction of adjacent vertebral bodies and opposing endplates, destruction of the intervening disc, occurrence of prevertebral, paravertebral, and epidural abscesses. 

Microbiology should always be attempted for definitive diagnosis and to pick up MDR-TB. One should look for the coexistence of pulmonary TB. If surgery is not planned, a CT-guided biopsy of the paravertebral soft tissue/ vertebral body should be carried out and subjected to histopathological examination (HPE), culture, or NAAT. Diagnostic yield varies with various methods from 50-70%.

 

3.5.3. TB Arthritis

TB arthritis occurs from intra-articular spread from osteomyelitis. Usually, it involves the weight-bearing joints such as the hip and knee (90%). There is single joint involvement commonly. Pain is the first symptom (usually at night) later followed by local tenderness and restriction of joint movement. Fever and constitutional symptoms may be absent. Often, TB arthritis may be confused sometimes with oligoarticular Juvenile Rheumatoid Arthritis (JRA). Plain X-ray shows soft tissue swelling, osteopenia, periarticular bone destruction and periosteal reactions. Moreover, MRI is very sensitive. However, joint fluid aspiration or synovial biopsy should be carried out for a definitive diagnosis and subjected to HPE or culture or CBNAAT.