Spinal Tuberculosis — Debridement and Fusion

Pott disease is primarily an anterior column infection. Anti-tubercular therapy (ATT) cures the infection; the operation addresses the three mechanical consequences — progressive kyphotic deformity, neurological deficit, and instability. The two treatments are complementary: surgery is never a substitute for a full course of ATT, and most patients are cured by ATT alone. Absolute indications. Operate without delay when any of the following is present: - Progressive or severe neurological deficit (Frankel C or worse) despite adequate ATT — surgical decompression is urgent.

• Neurological deterioration while on ATT — the most urgent surgical indication.
• Failure of medical management — progression of deformity or increase in pain after 4 to 6 weeks of adequate ATT.
• Severe kyphosis (Cobb angle greater than 40 degrees) at presentation, or progressive kyphosis on treatment.
• Instability — translational movement on dynamic radiographs or segmental collapse with loss of normal sagittal alignment.
• A large abscess not resolving on ATT, with significant thecal sac compression or causing dysphagia and airway compromise in the cervical spine. Relative indications. - Moderate kyphosis (20 to 40 degrees) in children — risk of progression with growth; combined anterior-posterior surgery is recommended.
• Multi-level disease (more than two contiguous vertebral bodies) — associated with instability and deformity progression.
• Persistent severe pain attributed to mechanical instability despite adequate ATT.
• Tissue diagnosis required — when imaging is atypical or malignancy cannot be excluded.
• Late-onset paraplegia (greater than two years after quiescent disease) — mechanical compression from internal kyphosis. Contraindications. Absolute: active pulmonary TB with positive sputum (treat with ATT first until sputum conversion, usually 4 to 8 weeks, before elective surgery — urgent decompression for neurological deficit overrides this); multi-drug resistant (MDR) TB without an effective drug regimen (extremely high risk of implant infection and non-union); poor nutritional status (albumin less than 25 g/L or severe cachexia — correct first); active miliary TB (prioritise medical treatment). Relative: advanced age with multiple comorbidities; severe pulmonary compromise where thoracotomy may not be tolerated (consider costotransversectomy or a posterior approach); irreversible complete paraplegia of more than 6 months duration (Frankel A) — surgery rarely improves motor function and is then for deformity and pain only. The one decision that matters — operate, or continue ATT alone. The Medical Research Council Working Party trials established when surgery changes the outcome:

Key conclusion. Chemotherapy alone is sufficient for patients without neurological deficit, without significant deformity (kyphosis less than 20 degrees), and with disease limited to one or two vertebral bodies. Surgical intervention improves kyphosis correction and gives more reliable neurological recovery in patients with a deficit, with the radical resection plus graft (the Hong Kong operation) performing best long-term.

Approach selection — the level drives the approach. Because the disease is anterior, the debridement is anterior; the level determines which anterior exposure is used. - Thoracic (T2-T10): a RIGHT-sided thoracotomy — the aorta lies on the left and the segmental vessels are easier to control from the right.

• Thoracolumbar (T10-L2): a combined thoracoretroperitoneal approach, dividing the diaphragm 2 to 3 cm from its costal insertion.
• Lumbar (L1-L5): a LEFT retroperitoneal approach — the aorta is easier to mobilise than the IVC.
• Cervical: an anterolateral Smith-Robinson approach.
• Costotransversectomy: an alternative for lateral or paravertebral disease, or when a thoracotomy is contraindicated; it gives limited anterior access.

Anti-tubercular therapy is the foundation. The standard short-course regimen follows pulmonary TB principles but runs longer because the vertebral body is poorly perfused with a high organism burden and relapse rates rise with shorter courses. - Intensive phase (2 months): four drugs — rifampicin, isoniazid, pyrazinamide, ethambutol.

• Continuation phase (10 months): two drugs — rifampicin and isoniazid.
• Total duration: 12 months minimum; 12 to 18 months with extensive disease, neurological involvement, or after surgery.
• Typical adult doses: rifampicin 450 to 600 mg daily, isoniazid 300 mg daily, pyrazinamide 25 mg/kg daily, ethambutol 15 mg/kg daily.
• Monitoring: monthly clinical assessment (pain, neurology, weight, ESR and CRP); radiographs at 3, 6 and 12 months; MRI if neurological deterioration or unsatisfactory response. Give at least 2 to 4 weeks of four-drug ATT before elective surgery to reduce bacterial load and implant-infection risk. In urgent cases (progressive neurological deficit), surgery may proceed after 1 to 2 weeks of ATT — do not delay decompression for a "full course". For MDR-TB, use second-line agents (fluoroquinolones, aminoglycosides, ethionamide, cycloserine) under infectious-diseases guidance for 18 to 24 months, and obtain drug-sensitivity testing from a pre-operative biopsy (GeneXpert, line probe assay or culture). Consent specifically for the risk of neurological deterioration (1 to 3%), graft or cage subsidence, implant failure, recurrence or reactivation, approach-specific complications (intercostal neuralgia, dural leak, vascular injury, pleural effusion, chylothorax), and the need to complete a 12-month ATT course. Setup. Anterior stage: lateral decubitus — right side down for a right thoracic approach (left side up) for upper and mid-thoracic disease; left side down for a left retroperitoneal approach to the lumbar spine. Flex the table slightly to open the intercostal space or the space between iliac crest and rib cage; place an axillary roll and pad all bony prominences; confirm access to the iliac crest for graft harvest without repositioning. Posterior stage: prone on a Jackson table (or four-poster frame) with the abdomen free to reduce venous pressure and blood loss, arms at less than 90 degrees abduction, and C-arm positioned for AP and lateral imaging before draping.

The goal is direct anterior access to the diseased vertebral body, radical debridement of all caseous and necrotic material back to healthy bleeding bone, decompression of the thecal sac, reconstruction of the anterior column with a structural graft or cage, and stabilisation of the segment with posterior pedicle-screw instrumentation to hold the correction and protect the graft. The exposure is laid out in full as the first steps below — it is the heart of the operation.

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Immediate post-operative phase (day 0 to 3). High-dependency or ICU monitoring for the first 24 to 48 hours (respiratory status after thoracotomy, haemodynamics, hourly neurological observations for the first 24 hours then 4-hourly). Manage the chest tube on underwater seal at 20 cm H2O suction and remove when drainage is less than 100 to 150 mL per 24 hours with no air leak (typically day 2 to 4), with a routine chest radiograph after removal. Give perioperative IV cefazolin for 24 hours (longer only if active infection is suspected), restart the full four-drug ATT on day 1 (via nasogastric tube if needed), begin mechanical thromboprophylaxis immediately and chemical prophylaxis (LMWH) at 24 to 48 hours, and mobilise out of bed to chair on day 1 to 2 and walking on day 2 to 3 with physiotherapy. Bracing. A custom thoracolumbosacral orthosis (TLSO) for thoracic and lumbar disease, or a cervical-thoracic brace (SOMI or Halo-vest) for cervical disease, worn for 3 to 6 months — full-time (removed only for showering and sleeping once skin tolerance develops) for the first 3 months, then weaned over 4 to 6 weeks, with daily skin checks over bony prominences. Anti-tubercular therapy after surgery. Continue for 12 months total (counting from the start of treatment): four drugs for the first 2 months then rifampicin plus isoniazid for 10 months. Monitor monthly LFTs (rifampicin and isoniazid are hepatotoxic), visual acuity (ethambutol optic neuritis) and clinical response; use directly observed therapy where compliance is a concern; for MDR-TB, second-line agents continue for 18 to 24 months under ID guidance. Follow-up schedule.

Obtain an MRI for neurological deterioration (new or progressive deficit), recurrent pain at the surgical site, suspected recurrence or reactivation, or suspected implant-related complications. Return to function. Walking on day 2 to 3 with the brace and physiotherapy; driving at 6 to 8 weeks (free of opiate analgesia and able to perform an emergency stop); sedentary work at 6 to 12 weeks; manual work and heavy lifting at 6 to 9 months only after solid radiographic fusion; non-contact sports (swimming, cycling) at 6 months and contact sports at 12 months with confirmed solid fusion. Complications.

Epidemiology. Spinal tuberculosis is the most common form of skeletal tuberculosis and a major cause of debilitating kyphosis and paraplegia in TB-endemic regions; it predominantly affects the thoracic and thoracolumbar spine of young and middle-aged adults and is closely linked to overcrowding, malnutrition and immunosuppression. The three-column spine in Pott disease. - Anterior column (anterior longitudinal ligament plus the anterior two-thirds of the vertebral body): the primary site of disease. Infection begins paradiscally in the anterior vertebral body, spreads through the disc to the adjacent body, and destroys the disc early. The anterior longitudinal ligament (ALL) is usually stripped off the bodies by the abscess but often remains intact as a sleeve that can be preserved and closed over the graft to contain the reconstruction.

• Middle column (posterior one-third of the vertebral body plus the posterior longitudinal ligament): the key to neurological status. Retropulsion of the posterior body wall or disc into the canal compresses the thecal sac; the posterior longitudinal ligament (PLL) may be elevated by caseous material and should be opened at surgery to inspect the canal and confirm complete decompression.
• Posterior column (pedicles, laminae, facets, spinous process, ligamentum flavum): rarely involved in pure Pott disease — the posterior elements are typically spared. Posterior-element involvement suggests very advanced disease or alternative pathology (pyogenic infection, malignancy). The posterior column provides the fixation points (pedicle screws) for the stabilisation construct; the facet joints at the affected level are usually preserved. Pattern of spread.

Abscess anatomy. A paravertebral abscess in the thoracic spine lifts the parietal pleura and paravertebral fascia, appearing as a fusiform paravertebral soft-tissue shadow on a chest radiograph; it can track up and down beneath the ALL for several levels (the characteristic sausage shadow) and drain spontaneously into the pleural space (empyema), through the skin (sinus), or through the diaphragm into the retroperitoneum (psoas abscess). In the lumbar spine, pus tracks along the psoas sheath and can present as a groin mass, hip-flexion deformity or referred hip pain — the psoas is intimately related to the kidney, ureter, renal vessels and lumbar plexus. A cold abscess (no heat or erythema, distinct from a pyogenic abscess) contains caseous material, liquefied pus and granulation tissue and may hold 100 to 500 mL of pus while causing surprisingly few systemic symptoms. Rajasekaran's spine at risk signs. Four plain-radiograph signs predict progressive kyphotic deformity in children: (1) separation of the facet joint; (2) posterior vertebral body height greater than anterior body height; (3) lateral translation at the affected level; (4) toppling of the upper vertebra. Any one sign identifies a spine at risk of progression to severe kyphosis (greater than 60 degrees) without surgical stabilisation. Rajasekaran's kyphosis-prediction formula, based on the initial vertebral body loss, guides the threshold for surgery: - Loss of less than one and a half vertebral bodies — predicted final kyphosis less than 30 degrees: may be managed with chemotherapy alone.

• Loss of one and a half to two bodies — predicted final kyphosis 30 to 60 degrees: combined anterior-posterior surgery recommended.
• Loss of greater than two bodies — predicted final kyphosis greater than 60 degrees: combined surgery is mandatory with extended posterior instrumentation. The Hong Kong operation and its modern evolution. Hodgson and Stock's 1956 landmark contribution at the University of Hong Kong recognised that the disease is primarily anterior, that an anterior approach gives direct access to the pathology, and that radical debridement with autogenous bone grafting achieves both disease clearance and mechanical reconstruction. Their original description — a transthoracic approach, resection of the affected body and adjacent discs back to healthy bleeding bone, and a tricortical iliac crest autograft under compression, without posterior instrumentation — gave solid bony fusion in 92% of 100 patients. Upadhyay's long-term follow-up (1996) confirmed 94% fusion at a mean of 15 years, with a mean loss of 6 degrees of correction during graft incorporation and late neurological deterioration in fewer than 2%. The modern addition of posterior pedicle-screw instrumentation gives immediate rigid stabilisation for early mobilisation without external bracing, offloads the anterior graft to reduce subsidence, improves kyphosis correction to a mean of 15 to 20 degrees (versus 5 to 10 degrees with anterior alone), and raises fusion rates to greater than 95% in modern series. Applied surgical anatomy.

Special situations. Paediatric disease: the growing spine compensates poorly for anterior column loss, so progressive kyphosis occurs as the posterior elements keep growing while the anterior column is fused; a combined anterior-posterior reconstruction is justified for any child with more than 20 degrees of kyphosis or spine at risk signs, autograft (rib or iliac crest) is preferred over a cage because it remodels with growth, posterior instrumentation should use growth-friendly or short constructs, and follow-up continues annually until skeletal maturity. Multi-level disease (more than two vertebral bodies): a long strut graft or cage spanning the diseased segment is at greater risk of subsidence, so combined surgery is mandatory with posterior instrumentation extended 2 to 3 levels above and below and consideration of a staged procedure. Drug-resistant spinal TB: MDR-TB requires 18 to 24 months of second-line therapy, surgery carries an elevated implant-infection risk (10 to 20%), a titanium implant is better tolerated than stainless steel, more radical debridement is necessary, and post-operative wound surveillance is essential.