Tuberculosis of Bone and Joint

Question 1

Pott’s Disease
Epidemiology

Answer 1

• Increased incidence in immunocompromised patients
• HIV positive populations susceptible [CD4+ 50 to 200 counts]
• 5% of all TB patients have spine involvement
• Thoracic spine most common extrapulmonary TB site of infection

15% of all TB patients have extrapulmonary involvement

Pott’s disease is an infection of the spine caused by Tuberculosis. It is an extrapulmonary manifestation of TB and can lead to Osteomyelitis, Kyphosis deformity and Spinal mechanical instability/neurological deficits

Question 2

Pott’s Disease
Etiology

Answer 2

Early Disease:
- Metaphysis of vertebral body
- Under Anterior Long. ligament spread [contiguous spread/non-contiguous segments/paraspinal abscess formation usually anterior and large - unique to TB in early disease]
- Initially does not involve disc space [pyogenic osteomyelitis involves disc space]

Chronic Disease:
- Most often diagnosed at this stage
- Severe Kyphosis

Mycobacterium tuberculosis is the pathogen

Question 3

Pott’s Disease
Presentation

Answer 3

Incidious onset:
- Chronic illness
- Malaise
- Night sweats
- Weight loss
- Back pain [often late symptom, after significant bone deformity]

Physical Exam:
- Kyphotic deformity
- Neurological deficits: Abscess/granulation tissue/tubercular debris/caseous tissue puts mechanical pressure on cord | Mechanical instability [subluxation/dislocations - paraplegia from healed disease can occur] | Stenosis from ossification of Ligamentum Flavum adjacent to severe kyphosis

Question 4

Pott’s Disease
Imaging

Answer 4

CXR:
- 66% have abnormal CXR
- ordered in patients with TB possibility

Spine Radiographs:
- Early disease: Anterior vertebral body involvement with spared disc spaces
- Late disease: Disk space destruction, lucency, compression of adjacent vertebral bodies, severe kyphosis development
- Buckling collapse risk, presence of Retropulsion, Subluxation, Lateral translation, toppling

MRI with Gadolinium contrast:
- Preffered method for dx and tx
- Dx of adjacent levels
- Smooth wall abscess in pre/paravertebral/intraosseous septate with subligamentous extension and breaching of epidural space

CT:
- < 1,5 cm lesions seen better
- Destruction of bone can be seen [fragmentary, osteolytic, subperiosteal, sclerotic]

Nuclear Medicine studies:
- Tc99m and Gallium combinations
- Highest sensitivity for detecting infection

Question 5

Pott’s Disease
Studies

Answer 5

• CBC
• ESR
• PPD [Purified Protein Derivative of tuberculin]: positive in ~80% of patients

Dx:
- CT guided biopsy with cultures and staining for Acid-Fast Bacilli [AFB]/PCR for faster identification but lower sensitivity [??]

AFB takes 10 weeks to yield cultures

Question 6

Pott’s Disease
Treatment

Answer 6

Non-operative:
- no neurological deficits
- Pharmacological Tx +/- Spinal Orthosis
- Isoniazid + Rifampin + Ethambutol + Pyrazinamide for 2 months then Isoniazide + Rifampin for 9-18 months

Operative:
- Neurological deficits present [worsening/acute severe paraplegia/ panvertebral involvement
- Spinal Instability
- Kyphosis correction
- Failure of nonop tx for 3-6 months
- Anterior Decompression/Corpectomy, Strut Grafting +/- posterior instrumented stabilization +/- posterior column shortening
- Advantages of above methods: earlier healing, less progressive kyphosis, improved neurologic recovery with early debridement and decompression
- Pharma management is continued
- Halo Traction, Anterior Decompression, Bone grafting, Anterior plating
- Direct Decompression

Spinal Orthosis is like a corset/back brace

Question 7

Pott’s Disease
Complications

Answer 7

• Deformity [kyphosis/gibbus] highest after Ant decompression and grafting alone, lowest after both ant and post fusion
• Retropharyngeal Abscess
• TB arteritis, pseudoaneurysms
• Resporatory compromise if costopelvic impingement
• Sinus formation
• Pott’s paraplegia

Question 8

Atypical Spinal Tuberculosis

Answer 8

Compressive myelopathy without visible spinal deformity or typical radiological apprearance

Etiology:
- Intraspinal Granuloma
- Neural arch involvement
- Sclerotic vertebra with bridging of vertebral bodies

Tx:
- Laminectomy [Extradural extraosseous granuloma, Subdural granuloma]
- Decompression and Myelotomy [Intramedullary granuloma]

Question 9

TB of Bones and Joints

Answer 9

Types:
- Caseous Exudate [bone destruction, swelling, abscess]
- Granular

Clinical Features:
- Pain and swelling [if in superficial joint]
- Synovial thickening [visible in Xray]
- Muscle wasting
- Limited movement
- Articular erosion [joint space narrowing, stiffness and deformity]
- Peri and Panarticular osteoporosis