Skeletal Tuberculosis

INTRODUCTION:
  • Tuberculosis of bone, one form of what is known as "extrapulmonary tuberculosis," occurs when the germ (mycobacterium tuberculosis) spreads from the lungs (always its first site of infection) to bones like the spine, usually via the bloodstream. 
  • Weight-bearing joints (spine 40%, hips 3% and knees 10%) are most commonly affected.
  • Triple deformity of the knee is a complication of tuberculosis of knee
  • A paravertebral "cold" abscess in chest may form
  • Vertebral tuberculosis is the most common form of skeletal tuberculosis in children, accounting for 50% of all cases in reported series.
  • Progression to kyphosis deformity is least with lumbar lesions in children
  • Approximate distribution in the skeleton are spine (50%), hip (20%), knee (10%), ankle and foot (5%), hand and wrist (3%), elbow (2%), shoulder (1 %), bursal sheaths and other bones (8%)
SYMPTOMS OF POTT'S DISEASE:
  • Spinal tuberculosis (Pott's disease or tuberculous spondylitis) often involves two or more adjacent vertebral bodies.
  • In spinal tuberculosis, the commoner route of spread is blood
  • Pott's Disease is usually located in the thoracic, or upper, spine.
  • Commonest spine involved in spine TB is Thoracolumbar/Dorsolumbar T12-L1 (Lower thoracic to be precise)
  • Early signs oftuberculosis are fever, night sweats and weight loss.
  • Severe back pain is the most common indication that the TB has spread to the spine.
  • Pott disease, also known as tuberculous spondylitis, refers to vertebral body and intervertebral disc involvement with tuberculosis (TB).
  • The spine is the most frequent location of musculoskeletal TB, and commonly related symptoms are back pain and lower limb weakness/paraplegia.
  • As the disease worsens, patients will have difficulty standing.
  • Collapse of vertebral bodies results in kyphosis (gibbus)
  • Chronic retropharyngeal abscess is associated with tuberculosis of spine
DIAGNOSIS
  • Blood tests
CBC:
  1.  leukocytosis
  2. Elevated erythrocyte sedimentation rate: >100 mm/h
Tuberculin skin test
  • Tuberculin skin test (purified protein derivative [PPD]) results are positive in 84–95% of patients with Pott disease who are not infected with HIV.
Radiographs of the spine
  1. Radiographic changes associated with Pott disease present relatively late. The following are radiographic changes characteristic of spinal tuberculosis on plain radiography: Lytic destruction of anterior portion of vertebral body
  2. Increased anterior wedging
  3. Collapse of vertebral body
  4. Reactive sclerosis on a progressive lytic process
  5. Enlarged psoas shadow with or without calcification
Additional radiographic findings may include the following:
  • Vertebral end plates are osteoporotic.
  • Intervertebral disks may be shrunk or destroyed.
  • Vertebral bodies show variable degrees of destruction.
  • Fusiform paravertebral shadows suggest abscess formation.
  • Bone lesions may occur at more than one level.
  • Bone scan
  • CT of the spine
  • Bone biopsy
  • MRI(Investigation of choice)
PROGNOSIS:
  • Prognostic factors in Pott’s paraplegia
  • Age of the patient: Children respond to the treatment better than adults
  • Duration of the paraplegia: Long standing paraplegia has a worse prognosis
  • Severity: Motor paralysis alone has a better prognosis. Sphincter involvement i.e urinary or bowel incontinence are bad prognostic indicators.
  • Onset of paraplegia: Acute onset paraplegia has a better prognosis
  • Sudden onset of paraplegia: has a bad prognosis
Grades of paraplegia:
  • On the basis of degree of motor involvement, Pott’s paraplegia has been divided into four grades. Grade IV is most severe and grade I is least severe.
  • In Grade IV pott’s paralysis patient is unable to walk, and has paraplegia in flexion with severe muscle spasm. There is near complete loss of sensation with sphincter disturbances as already mentioned sphincter disturbances indicate poor prognosis.
Exam Question
  • Earliest sign in X-ray in TB spine is Narrowing of disc space
  • Pott's spine is commonest at Thoracolumbar spine
  • Old age,Long standing cases, Sphincter involvement, sudden onset are the indicators of poor prognosis of tuberculosis of spine
  • Most common cause of cold abscess of chest wall is Pott's spine
  • Chronic retropharyngeal abscess is associated with tuberculosis of spine
  • Triple deformity of the knee is a complication of tuberculosis of knee
  • Commonest presenting symptom of Pott's spine is back pain
  • In spinal tuberculosis, the commoner route of spread is blood
  • Tuberculosis in Pott's disease involves spine
  • Large paravertebral abscess ,Marked collapse of vertebra & Deceased joint space are radiological features of tuberculosis of spine
  • Progression to kyphosis deformity is least with lumbar lesions in children
  • Spine is the most common skeletal tuberculosis site
  • Investigation of choice for spinal TB is MRI

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