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OR4.1 | Skeletal Tuberculosis — PBL Case

CLINICAL SETTING

Mr. Suresh Kumar, a 48-year-old subsistence farmer from a rural district, is brought to the orthopaedic outpatient clinic by his son. He reports 10 months of progressive midthoracic backache that has worsened to the point where he can no longer work in the fields. Over the past 8 weeks, he has noticed weakness in both legs, difficulty climbing stairs, and has begun to have episodes of urinary urgency that twice led to incontinence. He has lost approximately 9 kg over the past year and has been experiencing low-grade fever and night sweats. There is no cough. He was treated for pulmonary TB 12 years ago and completed a full course at the district health centre. He is a non-smoker, drinks alcohol occasionally, and has no known diabetes. His family history is unremarkable. On general examination he appears cachectic and pale. Vital signs: temperature 37.9°C, BP 104/68 mmHg, pulse 92/min. Spine examination reveals a sharply angular kyphosis at the D8–D9 level (gibbus). Neurological examination of the lower limbs shows power 3/5 in both hip flexors and knee extensors bilaterally, brisk knee and ankle jerks, bilateral extensor plantar responses, and reduced pinprick sensation below the umbilicus. Rectal tone is reduced. Upper limb examination is normal.

Trigger 1: Initial Presentation and Differential Diagnosis

Investigations ordered at first contact: CBC — Hb 9.8 g/dL (normocytic), TLC 7,200/mm3 (lymphocyte predominant 58%), platelets 340,000. ESR: 92 mm/hr. CRP: 48 mg/L. Blood glucose fasting: 94 mg/dL. HIV ELISA: non-reactive. Plain X-ray thoracic spine AP and lateral: destruction of D8 and D9 vertebral bodies with disc space obliteration, anterior wedge collapse, and bilateral paraspinal soft-tissue shadow. The posterior elements appear intact.

DISCUSSION POINTS

  • What is your working diagnosis and what features in the history, examination, and initial investigations support it?
  • How does the clinical and radiological presentation distinguish Pott's disease from pyogenic spondylodiscitis and metastatic spinal disease? List specific differentiating features.
  • What is a gibbus, and what is the mechanism of its formation in spinal TB?
  • Why is neurological involvement (upper motor neuron signs + sphincter dysfunction) ominous in this case, and what is the anatomical explanation for anterior cord compression in Pott's disease?
Click to reveal Trigger 2: Confirmatory Investigations and Classification of Paraplegia (discuss previous trigger first!)

Trigger 2: Confirmatory Investigations and Classification of Paraplegia

MRI thoracic spine with contrast (T1, T2, STIR, post-gadolinium): destruction of D8–D9 vertebral bodies and intervening disc; large anterior and bilateral paraspinal soft-tissue collection extending from D7 to D10 (cold abscess); anterior extradural component compressing the cord at D8–D9 with cord signal change (T2 hyperintensity). The thecal sac is severely narrowed anteriorly. Posterior elements (laminae, pedicles) are intact. CT-guided biopsy of the paravertebral collection is performed under local anaesthesia. CBNAAT (GeneXpert MTB/RIF) on biopsy material: MTB DETECTED, Rifampicin resistance: NOT DETECTED. Histopathology: caseating granulomas with Langhans giant cells. Culture on LJ medium: pending (expected 6–8 weeks).

DISCUSSION POINTS

  • Classify this patient's paraplegia — is it paraplegia of active disease or paraplegia of the healed phase? What is the significance of this distinction for prognosis and surgical decision-making?
  • The CBNAAT shows rifampicin-sensitive TB. What anti-tubercular regimen would you prescribe? Name the drugs, phases, duration, and the specific adverse effects to monitor for each drug.
  • The MRI shows T2 cord signal change at the level of compression. What does this finding imply about cord viability and prognosis?
  • The paraspinal collection is large. What is the appropriate management of the cold abscess — and what is the classic error to avoid when managing a cold abscess in skeletal TB?
Click to reveal Trigger 3: Surgical Decision and Postoperative Management (discuss previous trigger first!)

Trigger 3: Surgical Decision and Postoperative Management

Mr. Suresh is started on 2HRZE/4HR with pyridoxine supplementation. LFT and visual acuity are baseline-checked. At the 6-week review, lower limb power has not improved (still 3/5 bilaterally) and urinary urgency persists. He is still unable to walk independently. A multidisciplinary meeting involving orthopaedic surgery, neurosurgery, anaesthesia, and physiotherapy decides to proceed with anterior surgical decompression. The procedure: left anterolateral thoracotomy, excision of D8–D9 vertebral bodies, removal of cold abscess and caseous material, anterior strut graft reconstruction, and instrumented spinal fusion (Hong Kong operation). Intraoperatively, a large sequestrum compressing the anterior cord is identified and removed. Post-operative MRI at 48 hours shows complete decompression with no residual anterior cord compression.

DISCUSSION POINTS

  • What were the indications for surgery in this case, and at what point should the surgical decision have been triggered?
  • Explain precisely why posterior laminectomy is contraindicated in Pott's paraplegia, and what risks it carries at this level of spinal instability.
  • Outline the post-operative rehabilitation plan: sequence of physiotherapy interventions, bladder rehabilitation, and return-to-activity milestones.
  • What prognostic factors will determine the degree of neurological recovery in Mr. Suresh? How does the finding of cord signal change on MRI affect his prognosis for full motor recovery?

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [OR4.1] What are the clinical stages of TB arthritis of major joints (hip and knee), the Phemister triad, and how do these differ radiologically and clinically from pyogenic arthritis?
  2. [OR4.1] What is the pathological basis of Pott's paraplegia in the active phase vs the healed phase, and how does this distinction influence surgical approach and prognosis?
  3. [OR4.1] What is the complete ATT regimen for drug-sensitive skeletal TB, including drug names, dosing phases, and monitoring for organ-specific adverse effects (hepatotoxicity, optic neuritis, peripheral neuropathy)?
  4. [OR4.1] Why is posterior laminectomy contraindicated in Pott's paraplegia, and what is the anatomical rationale for anterior surgical decompression (Hong Kong operation)?
  5. [OR4.1] What is the correct management of a cold abscess in skeletal TB — and what classic surgical error (open incision) must be avoided and why?