L4-L5 Posterior Lumbar Interbody Fusion is Medically Indicated
For this 46-year-old male with L4-L5 spondylolisthesis and stenosis causing radicular pain that has failed comprehensive conservative management for over 6 weeks, posterior lumbar interbody fusion is medically indicated and represents the evidence-based standard of care. 1
Evidence Supporting Surgical Intervention
The SPORT trial provides Level II evidence demonstrating that patients with stenosis associated with degenerative spondylolisthesis who undergo decompression and fusion experience superior outcomes in every clinical measure compared to nonoperative management, with benefits maintained for at least 4 years. 1 Specifically, 96% of patients treated with decompression plus fusion reported excellent or good outcomes, compared to only 44% with decompression alone. 2
The presence of spondylolisthesis fundamentally changes the surgical algorithm—fusion is specifically recommended when decompression coincides with any degree of spondylolisthesis, as this represents documented spinal instability. 2, 3
Conservative Management Requirements Met
This patient has completed appropriate conservative therapy including:
- Fluoroscopic guided epidural steroid injection 2
- NSAIDs for pain management 2
- Gabapentin for neuropathic pain 2
- Physical therapy for more than 6 weeks 1, 2
The 6-week threshold for formal physical therapy satisfies guideline requirements before considering surgical intervention. 2 The patient's persistent functional impairment with activities of daily living despite this comprehensive approach meets criteria for surgical consideration. 2
Why Decompression Alone is Inadequate
Decompression alone in the setting of spondylolisthesis carries unacceptable risks. 1, 3 Studies demonstrate that preoperative spondylolisthesis is a documented risk factor for 5-year clinical and radiographic failure after decompression alone, with up to 73% risk of progressive slippage. 3 Compression alone can result in progression of vertebral misalignment. 1
The guidelines are explicit: in situ posterolateral lumbar fusion is NOT recommended as a treatment option in patients with lumbar stenosis in whom there is no evidence of preexisting spinal instability. 1 However, this patient HAS documented instability (spondylolisthesis), which reverses this recommendation. 3
Fusion Technique Selection
The SPORT investigators found no differences in outcome between different fusion techniques (noninstrumented PLF, instrumented PLF, and 360° approaches including interbody grafts) when surgeons selected the technique they deemed most appropriate. 1 Posterior lumbar interbody fusion (PLIF) represents an appropriate technique offering high fusion rates of 92-95%. 2
Pedicle screw instrumentation is appropriate in this case given the presence of spondylolisthesis and the need to prevent progression of deformity. 1, 2 Instrumentation improves fusion success rates from 45% to 83% (p=0.0015) compared to non-instrumented fusion. 3
CPT Codes 20937 and 20936 Assessment
CPT 20937 (morselized autograft) and 20936 (structural allograft) represent bone graft materials used during the fusion procedure. Local autograft harvested during laminectomy combined with allograft provides equivalent fusion outcomes and is appropriate for single-level TLIF procedures. 2 These codes are medically necessary components of achieving solid arthrodesis. 3
Expected Outcomes
Patients undergoing fusion for stenosis with spondylolisthesis achieve statistically significant reductions in back pain (p=0.01) and leg pain (p=0.002) compared to decompression alone. 2 Ninety-three percent of patients treated with decompression/fusion report satisfaction with their outcomes, with statistically significant improvements in ability to perform activities, participate socially, sit, and sleep. 2
Clinical improvement occurs in 86-92% of patients undergoing interbody fusion for degenerative pathology with spondylolisthesis. 2 Fusion rates of 89-95% are achievable with appropriate instrumentation and graft materials. 2
Critical Pitfalls to Avoid
Do not perform decompression alone in patients with documented spondylolisthesis. 3 This creates risk of progression requiring subsequent fusion surgery. 3 The presence of spondylolisthesis is a risk factor for delayed clinical and radiographic failure after lumbar decompressive procedures. 3
Do not deny fusion based on absence of "severe" spondylolisthesis—any degree of spondylolisthesis constitutes instability warranting fusion when combined with stenosis requiring decompression. 2, 3
Facility and Network Considerations
The note that "the facility is not on the Nuance list" requires clarification with the payer, but does not change the medical necessity determination. The procedure itself meets evidence-based criteria for medical necessity regardless of facility designation. 1, 2