Is arthrodesis, posterior non-segmental instrumentation, and spinal bone autograft (Spinal Bone Graft) medically indicated for a patient with lumbar spinal stenosis L4-5 and degenerative spondylolisthesis, who has low back pain radiating to the right leg, interfering with Activities of Daily Living (ADLs) and work, and had relief from a transforaminal Epidural Steroid Injection (ESI)?

Medical Necessity Assessment for Arthrodesis with Posterior Instrumentation and Spinal Bone Autograft

Yes, arthrodesis with posterior non-segmental instrumentation and spinal bone autograft is medically indicated for this patient with L4-5 lumbar spinal stenosis and degenerative spondylolisthesis who has failed conservative management including transforaminal ESI. 1, 2

Evidence-Based Rationale for Fusion

The presence of degenerative spondylolisthesis at L4-5 with stenosis constitutes a Grade B indication for decompression combined with fusion rather than decompression alone. 1, 2 Class II medical evidence demonstrates that 96% of patients with spondylolisthesis and stenosis treated with decompression plus fusion reported excellent or good outcomes, compared to only 44% with decompression alone. 1, 2

Key Clinical Criteria Met:

• Documented spinal instability: Degenerative spondylolisthesis at L4-5 represents biomechanical instability that warrants fusion following decompression 1, 2

• Symptomatic stenosis: Low back pain radiating to the right leg with interference in ADLs and work activities correlates with imaging findings of L4-5 stenosis 1

• Failed conservative management: The patient underwent transforaminal ESI with temporary relief, demonstrating adequate conservative treatment before surgical consideration 1, 3

• Functional impairment: Pain interfering with ADLs and work activities represents significant functional limitation justifying surgical intervention 1

Rationale for Instrumentation (Pedicle Screws)

Pedicle screw fixation improves fusion success rates from 45% to 83% (p=0.0015) compared to non-instrumented fusion in patients with degenerative spondylolisthesis. 1, 2 The American Association of Neurological Surgeons recommends instrumentation when preoperative spinal instability exists, as in this case with documented spondylolisthesis. 1, 2

Biomechanical Advantages:

• Instrumented fusion provides optimal biomechanical stability with fusion rates up to 95% 1
• Prevents progression of spinal deformity, which is associated with poor outcomes following decompression alone 1, 2
• Reduces risk of iatrogenic instability from extensive decompression required for adequate neural element decompression 2, 4

Justification for Spinal Bone Autograft

Autologous bone graft remains the gold standard for achieving solid arthrodesis in lumbar fusion procedures. 1 Local autograft harvested during laminectomy combined with allograft provides equivalent fusion outcomes and is appropriate for single-level instrumented fusion procedures. 1

Graft Material Considerations:

• Fusion rates of 89-95% are achievable with local autograft combined with allograft or bone graft substitutes in instrumented single-level fusion 1
• Grade B evidence supports the use of rhBMP-2 as a bone graft extender when performing fusion with structural interbody graft, though this carries higher complication rates including postoperative radiculitis (14% incidence) 1
• Iliac crest bone graft harvesting is associated with donor-site pain in up to 58-64% of patients at 6 months post-operatively 1

Critical Distinction: Why Fusion is Necessary

Decompression alone in the setting of degenerative spondylolisthesis carries unacceptable risk of progression and poor outcomes. 1, 2 Studies demonstrate that patients with spondylolisthesis who undergo decompression alone have up to 73% risk of progressive slippage and significantly higher rates of poor outcomes. 2

Evidence Against Decompression Alone:

• Preoperative spondylolisthesis is a documented risk factor for 5-year clinical and radiographic failure after decompression alone 2
• Patients with degenerative changes and low back pain combined with spondylolisthesis achieve statistically significantly less back pain (p=0.01) and leg pain (p=0.002) with fusion compared to decompression alone 1
• Extensive decompression without fusion can lead to iatrogenic instability in approximately 38% of cases 2

Common Pitfalls to Avoid

Do not perform decompression alone in patients with documented spondylolisthesis and stenosis, as this creates unacceptable risk of progression requiring revision surgery. 1, 2 The temporary relief from transforaminal ESI does not negate the need for definitive surgical treatment when structural instability is present. 1

Additional Considerations:

• Ensure adequate decompression of neural elements while preserving as much facet joint integrity as possible to minimize iatrogenic instability 4
• Postoperative CT with fine-cut axial and multiplanar reconstruction is superior to plain radiographs for assessing fusion status (sensitivity 70-90%) 1
• Instrumented fusion procedures carry higher complication rates (31-40%) compared to decompression alone (6-12%), requiring appropriate patient counseling and postoperative monitoring 1

Expected Outcomes

Clinical improvement occurs in 86-92% of patients undergoing instrumented fusion for degenerative spondylolisthesis with stenosis, with significant reductions in Oswestry Disability Index scores and pain levels. 1 The patient can expect resolution of radiculopathy, improved functional capacity, and return to work activities in the majority of cases. 1