What is the approach to fusion therapy?

Approach to Fusion Therapy for Degenerative Lumbar Disease

Lumbar fusion is recommended as a treatment for carefully selected patients with disabling low-back pain due to one- or two-level degenerative disease when specific criteria are met: documented instability (any degree of spondylolisthesis), failed comprehensive conservative management for at least 3-6 months, and imaging findings that correlate with clinical symptoms. 1, 2

Patient Selection Criteria

Fusion should only be added to decompression when specific biomechanical instability is present, including:

• Any degree of spondylolisthesis documented on imaging 2, 3
• Radiographic instability on flexion-extension films 2
• Significant deformity such as scoliosis or kyphotic malalignment 2
• Evidence that extensive decompression will create iatrogenic instability (requiring bilateral facetectomy or extensive facet removal) 2

For isolated stenosis without instability, decompression alone is the recommended treatment, as multiple studies demonstrate no improvement in outcomes with the addition of fusion in this population 1, 2

Conservative Management Requirements

Before considering fusion, patients must complete:

• Formal supervised physical therapy for at least 6 weeks 1, 3
• Trial of anti-inflammatory medications 3
• Consideration of neuroleptic medications (gabapentin or pregabalin) for radicular symptoms 3
• Activity modification and potentially epidural steroid injections 3

The duration of conservative treatment should be 3-6 months with documented failure before proceeding to surgical fusion. 1, 3

Surgical Approach Algorithm

When Stenosis WITHOUT Spondylolisthesis:

• Perform decompression alone 1, 2
• Fusion adds no benefit and increases operative time, blood loss, and complications 2
• Only 9% of patients without preoperative instability develop delayed slippage after decompression 2

When Stenosis WITH Spondylolisthesis:

• Perform decompression plus fusion 2, 3
• Class II evidence shows 96% excellent/good outcomes with fusion versus 44% with decompression alone 2, 3
• Statistically significant reductions in back pain (p=0.01) and leg pain (p=0.002) compared to decompression alone 3

When Extensive Decompression Required:

• Add fusion if bilateral facetectomy or extensive facet removal is necessary 2
• Risk of iatrogenic instability approaches 38% with extensive decompression 2

Instrumentation Decisions

Pedicle screw fixation should be used when fusion is indicated in the presence of spondylolisthesis or instability, as it improves fusion success rates from 45% to 83% (p=0.0015) compared to non-instrumented fusion 2, 3

Instrumentation is NOT recommended for stenosis without deformity or instability, as it increases complications without proven benefit 2

Interbody Fusion Considerations

Interbody fusion techniques (TLIF, PLIF, ALIF, OLIF) demonstrate fusion rates of 89-95% compared to 67-92% with posterolateral fusion alone in patients with degenerative disc disease and spondylolisthesis 3

• TLIF offers high fusion rates (92-95%) with unilateral approach minimizing dural retraction 3
• ALIF with posterior instrumentation provides superior outcomes at L5-S1 3
• OLIF demonstrates comparable clinical outcomes to TLIF/PLIF with less blood loss and operative time 4

Critical Pitfalls to Avoid

Do not perform fusion for isolated stenosis without documented instability, as this increases surgical risk without improving outcomes 1, 2

Do not perform multilevel fusion unless each level independently meets fusion criteria (documented instability, failed conservative management, and imaging correlation with symptoms) 3

Avoid fusion in patients with significant psychological comorbidities including personality disorders, severe depression, or high neuroticism scores, as these patients respond more favorably to conservative management 5

Ensure adequate documentation of conservative treatment failure, as inadequate conservative management is a common reason for denial of medical necessity 3

Expected Outcomes

When appropriate criteria are met:

• 93-96% of patients report excellent or good outcomes with decompression plus fusion for stenosis with spondylolisthesis 3
• Fusion rates of 89-95% are achievable with appropriate instrumentation and technique 3
• Patients with less extensive surgery have better outcomes than those with extensive decompression and fusion when instability is absent 2

Biological Optimization

Consider patient-specific factors that affect fusion success:

• Smoking cessation is critical for fusion success 6
• Optimize bone mineral density in patients with osteoporosis 6
• Use of bone graft substitutes (rhBMP-2, β-tricalcium phosphate) as extenders has Grade B-C evidence 3
• Local autograft combined with allograft provides equivalent outcomes to iliac crest harvest while avoiding donor site morbidity (58-64% donor site pain at 6 months) 3