Lumbar Decompression for Spinal Stenosis

Indication. Symptomatic degenerative lumbar spinal stenosis with neurogenic claudication — bilateral or unilateral leg pain, heaviness or numbness brought on by walking and standing and relieved by sitting or forward flexion (spinal flexion opens the canal) — that has failed conservative treatment (3 to 6 months of physiotherapy, neuropathic agents and epidural steroid injections) and causes significant functional limitation. Surgery relieves leg symptoms far better than back pain, so it is the claudication and radiculopathy that justify the operation, not axial back pain alone. Less common but important indications: - A progressive neurological deficit — new motor weakness (foot drop, knee buckling), dermatomal sensory loss, or bladder and bowel disturbance.

• Cauda equina syndrome — an emergency indication for urgent decompression. Imaging correlation is essential. The MRI must show anatomical stenosis that matches the clinical picture: - Central canal — AP diameter less than 10 millimetres (relative stenosis) or less than 8 millimetres (absolute).
• Lateral recess — height less than 3 millimetres (significant) or less than 2 millimetres (severe).
• Foramen — height less than 15 millimetres or width less than 8 millimetres.
• A Schizas Grade C or D dural sac (no CSF around the rootlets) predicts failure of conservative care and the need for surgery.
• Flexion-extension radiographs if spondylolisthesis is suspected, to assess mobility. Contraindications — relative: predominantly axial back pain without a radicular component (the strongest predictor of a poor outcome), mild non-limiting symptoms, poor imaging correlation, and adverse psychosocial factors (active litigation, secondary gain, depression, catastrophising, opioid dependence — all predict poor outcomes regardless of technical success). Optimise medical comorbidities first: uncontrolled diabetes (HbA1c more than 8 percent), active smoking (4-week cessation recommended), severe cardiac disease and coagulopathy. Contraindications — absolute: active spinal infection (pyogenic discitis, epidural abscess), medical instability precluding anaesthesia, and patient refusal or unrealistic expectations.

The one decision that matters — decompress alone, or add fusion? Every case begins with an adequate decompression. The only real choice is whether to add a fusion, and it rests on stability rather than on the degree of stenosis:

Setup. Prone on a Wilson frame (or a radiolucent Jackson table for optimal fluoroscopy) with 30 to 45 degrees of hip flexion to open the interspinous spaces, and the abdomen free-hanging to lower epidural venous pressure and bleeding. Arms less than 90 degrees abducted (protect the brachial plexus and ulnar nerve); pad every pressure point and protect the eyes.

The goal is to expose the stenotic level(s) through a posterior midline approach, remove the compressive bone and hypertrophied ligamentum flavum from all three zones while preserving more than 50 percent of each facet, confirm decompression by dural pulsation and root mobility, and close in a watertight layer. The exposure and stepwise decompression are the heart of the operation and are laid out in full below (and in depth on the posterior approach to the lumbar spine page).

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Rehabilitation | Phase | Timing | Activity | Milestones | |-------|--------|----------|------------| | 1 | 0 to 2 weeks | Log-roll initially; walk 10 to 15 minutes three times daily, increasing gradually | Pain control on oral medications; no bending, lifting or twisting (BLTs); no driving on opioids | | 2 | 2 to 6 weeks | Walking progressively further; gentle range of motion; scar care from 6 weeks | Sedentary work from 2 to 4 weeks; staples out at 7 to 14 days | | 3 | 6 to 12 weeks | Core-strengthening programme (multifidus, transversus abdominis); light duty work | No heavy lifting (more than 10 kilograms) before 6 weeks | | 4 | 3 months onward | Graded return to full activity and heavy labour (around 12 weeks) | If fusion performed, confirm fusion on imaging at 3 to 6 months | Neurogenic claudication improves gradually over 6 to 12 weeks; radiculopathy may transiently worsen from surgical irritation before settling. Expected outcomes are 60 to 80 percent good or excellent at one year, with 50 to 70 percent sustained at four or more years (some attrition from natural degeneration). Red flags for urgent return: new or worsening bilateral leg weakness, urinary retention or incontinence, saddle anaesthesia, fever more than 38.5 degrees Celsius with wound drainage, severe uncontrolled pain, or a clear wound leak (CSF).

Pathoanatomy. Degenerative lumbar spinal stenosis arises from age-related hypertrophy of the ligamentum flavum and facet joints, often with a disc bulge, narrowing the canal and the neural foramina. The ligamentum flavum (about 80 percent elastin, giving its yellow colour) normally measures 2 to 3 millimetres but thickens to 5 to 8 millimetres in stenosis through chronic mechanical stress, inflammation, fibrosis and (in 10 to 15 percent) calcification — it is frequently the dominant compressive element. Compression comes from three directions: the flavum posteriorly, a disc bulge anteriorly, and the hypertrophied facet laterally. The three zones. Stenosis is described by zone because each compresses a different neural element and each needs its own decompression:

Key evidence. The SPORT stenosis trial (Weinstein, 2008) showed decompression superior to continued non-operative care for neurogenic claudication with anatomical stenosis, with benefit maintained to 4 years — the cornerstone evidence justifying surgery. For a stable grade I degenerative spondylolisthesis the two 2016 NEJM trials deliberately differ and both must be quoted: the SLIP trial (Ghogawala) randomised 66 patients to laminectomy alone versus laminectomy plus instrumented fusion and found a greater SF-36 physical-component gain with fusion (15.2 versus 9.5 at 2 years) and a lower cumulative reoperation rate (14 percent versus 34 percent). The Swedish Spinal Stenosis Study (Forsth) randomised 247 patients (135 with a slip) and found NO difference in ODI or 6-minute walk at 2 and 5 years, with fusion meaning a longer stay (7.4 versus 4.1 days), more bleeding and higher cost. The reconciliation that satisfies an examiner: routine fusion is NOT mandatory for a stable grade I slip — reserve it for dynamic instability, a high-grade slip, deformity or iatrogenic destabilisation.

Further reading: Ciol MA, Deyo RA, Howell E, Kreif S. An assessment of surgery for spinal stenosis: time trends, geographic variations, complications, and reoperations. J Am Geriatr Soc. 1996;44(3):285-290. · Jones AA, Stambough JL, Balderston RA, Rothman RH, Booth RE Jr. Long-term results of lumbar spine surgery complicated by unintended incidental durotomy. Spine. 1989;14(4):443-446. · Atlas SJ, Keller RB, Wu YA, Deyo RA, Singer DE. Long-term outcomes of surgical and nonsurgical management of lumbar spinal stenosis: 8 to 10 year results from the Maine Lumbar Spine Study. Spine. 2005;30(8):936-943.