Medical Necessity Assessment for CPT 20936 and 20939
Direct Answer on Medical Necessity
For this 48-year-old patient with degenerative anterolisthesis L4-5, moderate-to-severe bilateral foraminal stenosis, facet arthropathy with facet cyst, and failed conservative management requiring laminectomy with posterolateral fusion L4-L5, both spinal bone autograft (CPT 20936) and bone marrow aspiration (CPT 20939) are medically necessary to optimize fusion success in the setting of documented spinal instability.
Clinical Justification for Fusion with Bone Grafting
Established Indication for Fusion
The presence of degenerative anterolisthesis L4-5 with facet arthropathy represents documented spinal instability that warrants fusion in addition to decompression, as the American Association of Neurological Surgeons recommends fusion as a treatment option when there is evidence of spinal instability 1
Patients with spondylolisthesis are at significant risk for delayed clinical and radiographic failure after decompression alone, with preoperative spondylolisthesis identified as a main risk factor for 5-year clinical and radiographic failure 1
For patients with degenerative spondylolisthesis and stenosis, studies demonstrate better outcomes with decompression and fusion compared to decompression alone 1
The combination of facet arthropathy with synovial cyst formation indicates advanced degenerative instability that increases the risk of iatrogenic instability following extensive decompression 1
Risk of Iatrogenic Instability
Extensive decompression without fusion can lead to iatrogenic instability in approximately 38% of cases, particularly when bilateral facetectomies and foraminotomies are performed 1
The planned bilateral partial facetectomies at L4 will further destabilize an already unstable segment, making fusion mandatory rather than optional 1
Medical Necessity for Autograft (CPT 20936)
Evidence Supporting Autograft Use
Autologous bone is considered the best option whenever possible for fusion procedures, as it provides the gold standard for achieving solid arthrodesis 1
Spinal bone autograft obtained from local decompression (lamina, spinous process) is appropriate to achieve solid arthrodesis in posterolateral fusion 1
Autograft remains the gold standard bone graft material due to its osteogenic, osteoinductive, and osteoconductive properties, though alternatives exist due to supply limitations 2
Clinical Rationale in This Case
In a 48-year-old patient with documented instability requiring fusion, maximizing fusion success is critical to prevent revision surgery, and local autograft harvested during decompression provides osteogenic cells without additional donor site morbidity 1, 2
The presence of spondylolisthesis with instability creates a biomechanically challenging environment for fusion, justifying the use of all available autograft material 1
Studies demonstrate fusion success rates are significantly improved when autograft is utilized, with pedicle screw fixation improving fusion success from 45% to 83% when combined with adequate bone graft 1
Medical Necessity for Bone Marrow Aspiration (CPT 20939)
Evidence Supporting Bone Marrow Aspiration
The osteogenicity of bone marrow has been well documented in the literature, with bone marrow serving as a source of osteoprogenitor cells for spinal fusion surgery 3
Bone marrow aspirate contains mesenchymal stem cells and osteoprogenitor cells that enhance the osteoinductive potential of the graft construct 3, 2
Correct aspiration technique from the iliac crest is imperative to successful use of bone marrow with various grafting combinations, as improper technique can lead to dilution and reduction in osteoprogenitor cells 3
Clinical Justification in This Patient
In a patient with documented instability requiring posterolateral fusion, bone marrow aspiration provides critical osteoprogenitor cells to augment the fusion mass, particularly when combined with local autograft and allograft 3
The combination of morselized allograft (osteoconductive matrix) with local autograft and bone marrow aspirate (osteoinductive and osteogenic components) creates an optimal biological environment for fusion 2
Recent attention has focused on osteoinductive materials such as bone marrow aspirates, which may be combined with osteoconductive carriers and are clearly finding a place in the clinical arena 2
Risk-Benefit Analysis
Complications from bone marrow aspiration are rare, while the potential benefit of enhanced fusion success in a patient with instability is substantial 3
The risk of pseudarthrosis (failed fusion) in this patient with spondylolisthesis would necessitate revision surgery, making the minimal risk of bone marrow aspiration clearly justified 1, 3
Algorithmic Approach to Bone Graft Selection
Decision Tree for This Case
Fusion indicated? YES - documented anterolisthesis with instability 1
Adequate local autograft available? YES - from laminectomy, but quantity may be limited given single-level decompression 1
High-risk fusion environment? YES - spondylolisthesis with instability increases pseudarthrosis risk 1
Augmentation needed? YES - combine local autograft + allograft + bone marrow aspirate for optimal fusion environment 3, 2
Rationale for Multimodal Graft Strategy
The planned use of morselized allograft (CPT 20930 - already approved) provides osteoconductive scaffold 2
Local autograft (CPT 20936) provides osteogenic cells and osteoinductive factors 1, 2
Bone marrow aspirate (CPT 20939) provides concentrated osteoprogenitor cells to enhance fusion potential 3, 2
Common Pitfalls and Caveats
Critical Considerations
Do not perform posterolateral fusion in a patient with documented instability without optimizing the biological environment for fusion, as pseudarthrosis rates are unacceptably high and would necessitate revision surgery 1
The presence of facet arthropathy and synovial cyst indicates advanced degenerative disease that may compromise local bone quality, further justifying bone marrow augmentation 1
Instrumentation alone (CPT 22840 - already approved) does not guarantee fusion success; adequate bone graft with osteogenic potential is essential 1
Documentation Requirements
The surgical plan appropriately documents the use of local autograft from decompression, morselized allograft, and bone marrow aspiration from iliac crest 3
This multimodal approach aligns with evidence-based practice for achieving solid arthrodesis in patients with spinal instability 1, 3, 2
Comparison to Payer Policy
Policy Gap Analysis
While CPB 0411 does not specifically address CPT 20936 or 20939, the approved fusion procedure (CPT 22612) cannot succeed without adequate bone graft material 1
The approval of posterolateral fusion with instrumentation creates a medical necessity for bone graft materials that will achieve that fusion 1
Surgical decompression with fusion is recommended as an effective treatment for symptomatic stenosis associated with degenerative spondylolisthesis (Grade B recommendation), and this recommendation implicitly requires adequate bone graft 4, 5
Evidence-Based Justification
Studies demonstrate 60-85% of properly selected patients have satisfactory symptomatic improvement with surgical treatment of lumbar stenosis with spondylolisthesis, but this outcome depends on achieving solid fusion 6
The best surgical results in patients with degenerative spondylolisthesis were obtained by laminectomy with instrumented fusion, with excellent results in 91% of patients when adequate fusion was achieved 5