Posterior Lumbar Decompression and Fusion (PLDF)

Indication. Symptomatic lumbar spinal stenosis with instability that has failed at least 3-6 months of conservative care. The commonest single indication is degenerative spondylolisthesis Grade I-II at L4-L5 (with neurogenic claudication or radiculopathy and dynamic translation on flexion-extension radiographs), but PLDF is also used for: - Spinal stenosis with instability — central or lateral recess stenosis with spondylolisthesis, dynamic translation greater than 3-4 mm, or angulation greater than 10 degrees on flexion-extension views.

• Anticipated iatrogenic instability — when an adequate decompression requires removal of more than 50 percent of a facet joint.
• Recurrent stenosis after prior decompression with progressive instability.
• Degenerative scoliosis with stenosis (curves greater than 15-20 degrees) requiring decompression and realignment. The one decision that matters. Every case begins with the same posterior midline exposure and a thorough decompression. The only real question is whether the segment is unstable enough to warrant adding an instrumented fusion:

Contraindications. Absolute: active infection at the surgical site, severe medical comorbidity precluding safe anaesthesia, or inability to tolerate prone positioning. Relative: severe osteoporosis (T-score less than minus 3.5 — may need cement augmentation), active smoking (raises pseudarthrosis risk three- to four-fold), morbid obesity (BMI greater than 40), severe vascular disease, and previous fusion at adjacent levels. Pre-operative planning. Standing AP and lateral lumbar radiographs with flexion-extension views to assess alignment and instability; MRI for stenosis severity, disc degeneration and nerve root compression; CT where bone detail matters (facet arthritis, spondylolysis, prior hardware). Decompress every symptomatic stenotic level; fuse only unstable segments. Plan pedicle diameter on axial imaging (typically 6-8 mm in the lumbar spine, smaller at L5), screw length 35-45 mm (about 80 percent of vertebral body depth), and a 5.5 mm rod.

The goal: through a single posterior midline incision, expose the posterior elements subperiosteally, decompress the central canal and both lateral recesses/foramina, insert pedicle screws at the Magerl point with five-wall probing, decorticate the transverse processes, pack local autograft to create a posterolateral fusion, and connect the construct with lordotic rods. The exposure is laid out in full below (and in depth on the posterior approach to the lumbar spine page).

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Rehabilitation | Phase | Timing | Milestones and restrictions | |-------|--------|------------------------------| | Recovery room | 0-24 h | Neurovascular checks every 2 h; log-roll; IV then oral analgesia; mobilise day 0-1 (bed rest 24-48 h if a dural tear was repaired) | | Early mobilisation | Weeks 0-6 | Walking only; NO bending, lifting greater than 5 kg or twisting (BLT) for 3 months; drain out when less than 30 mL per 8 h | | Therapy | Weeks 6-12 | Gentle range of motion from week 2-4; core strengthening from week 6-8; avoid flexion-loading and favour neutral-spine postures | | Consolidation | 3-6 months | Light activities and driving from about 3 months; radiographs at 6 weeks, 3 and 6 months | | Fusion maturation | 6-12 months | CT at 12 months to confirm fusion (the gold standard); return to heavy labour once fused | Bracing is NOT routine for instrumented PLDF — it is reserved for osteoporotic bone, obesity, or non-compliance risk (a rigid TLSO for 6-12 weeks when used). Return to work: desk duties at 6-12 weeks, light physical work at 3-4 months, heavy labour at 6-12 months when the fusion is solid. Bone health matters — vitamin D supplementation (target greater than 75 nmol/L), calcium 1200 mg daily, and smoking cessation are critical; thromboprophylaxis is risk-based (early mobilisation and stockings for low risk; enoxaparin or rivaroxaban for 10-14 days when age greater than 60, obese, or prior VTE). Complications

Other complications. Wrong-level surgery (0.5-1 percent) is prevented by preop and intraop fluoroscopy counting from the sacrum, skin marking and a time-out; management is immediate reoperation at the correct level with full documentation and disclosure. Hardware failure (screw or rod breakage, usually from pseudarthrosis or an under-sized screw) and junctional problems (proximal junctional kyphosis) are revised if symptomatic or if deformity progresses.

Epidemiology. Degenerative spondylolisthesis — most often L4 on L5 — is the single commonest indication for PLDF; it predominates in women and older adults (the SLIP trial cohort averaged 67 years and was about 80 percent women). Martin and colleagues (2019) tracked United States lumbar fusion procedure rates and hospital costs for degenerative spinal disease across 2004-2015, documenting the scale and utilisation patterns of fusion practice. Pathoanatomy. Degenerative spondylolisthesis arises from facet-joint and intervertebral-disc degeneration that allows one vertebra to slip forward on the next, narrowing the spinal canal and lateral recesses and producing neurogenic claudication and radiculopathy. The medial pedicle wall (1-3 mm, thinnest at L5) and the valveless epidural venous plexus are the two structures that most dictate operative danger. Pedicle screw breach — the Gertzbein-Robbins grading. The classification that still frames how breaches are reported and probed:

Key evidence — the central exam controversy is whether to fuse. SPORT (Weinstein) established durable benefit for operative over nonoperative management of symptomatic degenerative spondylolisthesis with stenosis. The SLIP trial (Ghogawala, NEJM 2016) then showed that adding instrumented fusion to laminectomy for stable Grade I slip gave a small but clinically meaningful quality-of-life gain and roughly halved the reoperation rate (14 percent versus 34 percent). Published in the very same issue, the Swedish Spinal Stenosis Study (Forsth, NEJM 2016) reached the opposite conclusion — fusion added morbidity and cost without clinical benefit for stenosis with or without a low-grade slip. The reconciling principle: reserve fusion for demonstrable instability or deformity, not for stenosis alone. A SPORT substudy (Abdu) further showed no durable clinical difference between posterolateral in-situ, instrumented posterolateral, and 360-degree interbody fusion at four years — justifying instrumented posterolateral fusion (PLDF) as the standard construct, with interbody reserved for slip reduction, foraminal height restoration or revision.