Laminectomy alone vs laminectomy with posterior fusion in lumbar spinal stenosis: The role of instability

Table 1 Summary of the contributors to lumbar spinal instability in the context of lumbar spinal stenosis

Cause of instability	Imaging findings	Impact on stability	Surgical implications
Degenerative spondylolisthesis	Anterolisthesis of vertebral body; facet joint effusion (> 1.5-2 mm)	Abnormal translation; facet capsule laxity	May be considered for fusion if instability is demonstrable; decompression alone may risk progression of slip
Facet joint degeneration	Hypertrophy, joint space narrowing, subchondral sclerosis, osteophytes	Loss of posterior element constraint; possible capsular laxity	Preserve > 50% of facet during decompression to reduce risk of iatrogenic instability
LF thickening and buckling	LF buckles into canal; often secondary to facet arthropathy and loss of posterior tension	Contributes to stenosis; not a primary instability cause, rather a correlator	LF removal is part of decompression; does not necessitate fusion unless other instability indicators are present
Intervertebral disc degeneration	Disc height loss; Modic changes; vacuum phenomenon	Load shift posteriorly; increased facet strain	May predispose to instability after decompression; fusion only in combination with other signs
PLC laxity	Disruption or thinning of supraspinous/interspinous ligaments (MRI)	Reduced posterior tension band stability	If ≥ 2 spinal columns compromised, fusion is often considered, but thresholds and definitions vary
Iatrogenic resection	Postoperative facet removal > 50%	Immediate segmental hypermobility	High risk of postoperative instability; may require fusion during index surgery depending on stability assessment

LF: Ligamentum flavum; PLC: Posterior ligamentous complex; MRI: Magnetic resonance imaging.

Table 2 Summary of differences between laminectomy alone and laminectomy with fusion for lumbar spinal stenosis

Feature	Laminectomy alone	Laminectomy + fusion
Surgical approach	Midline posterior exposure; removal of lamina ± partial medial facetectomy; LF excision; unilateral or bilateral decompression	Midline posterior exposure; decompression followed by pedicle screw instrumentation ± interbody cage placement
Extent of bone resection	Limited to lamina ± < 50% facet joint to preserve stability	Often requires > 50% facet joint resection, especially with TLIF; posterior elements partially or fully decorticated
Stability preservation	Preserves motion segment; relies on intact posterior tension band	Eliminates motion at treated level; restores or maintains alignment
Graft/implant use	None	Pedicle screws, rods, bone graft with/or interbody cage
Common variations	Central laminectomy with bilateral decompression; unilateral laminotomy with bilateral decompression (“crossover” technique)	PLF; TLIF for anterior column support
Intraoperative considerations	Minimize facet removal to reduce risk of instability	Ensure adequate fixation and graft placement; navigation or neuromonitoring often used

LF: Ligamentum flavum; TLIF: Transforaminal lumbar interbody fusion; PLF: Posterolateral fusion.

Table 3 Comparison of international guideline recommendations for lumbar fusion in lumbar spinal stenosis according to instability status

Criterion/element	NASS	WFNS	CSORN (DSIC)	NICE	JOA
Definition of instability	Numerical thresholds: > 4-5 mm translation or > 10°-15° sagittal rotation (up to 20° at L4-L5). > 2 mm translation in stenosis	No numeric thresholds; based on radiographic and clinical judgement	Scoring system integrating translation ≥ 4 mm, kyphotic/neutral disc angle, disc height > 6.5 mm, facet effusion, and back pain severity	No numeric thresholds; not explicitly defined	Requires radiographic evidence; no specific motion cut-offs
Primary indication for fusion	Definitive radiographic instability; > 50% facet removal; recurrent herniation; ≥ 2 mm spondylolisthesis; symptomatic adjacent segment disease; pseudarthrosis	Radiographic or functional instability; extensive facet removal; recurrent stenosis; sagittal/coronal deformity; pseudarthrosis	Type III (unstable) DSIC score; some type II (borderline) cases based on clinical judgement	Only when instability is clearly present; decompression alone in most borderline cases	Radiographic instability is similar to NASS criteria
Controversial areas	Lower threshold for fusion in degenerative spondylolisthesis (grade B for < 20% slip)	Broader use of fusion for functional instability without measurable motion	Borderline (type II) category may lead to over- or under-treatment; lacks RCT validation	Most conservative; may undertreat subtle instability	No numeric thresholds may lead to variation in interpretation

NASS: North American Spine Society; WFNS: World Federation of Neurosurgical Societies; CSORN: Canadian Spine Outcomes Research Network; DSIC: Degenerative Lumbar Spondylolisthesis Instability Classification; RCT: Randomized controlled trial; NICE: National Institute for Health and Care Excellence; JOA: Japanese Orthopedic Association.