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 Specific Case
In a patient with spondylolisthesis requiring posterolateral fusion, bone marrow aspiration augments the limited volume of local autograft available from a single-level laminectomy 3
The combination of morselized allograft, local autograft, and bone marrow aspirate creates an optimal biological environment for fusion in a biomechanically challenging scenario 3, 2
Bone marrow aspirate is particularly valuable when local autograft volume is limited, as it provides osteoprogenitor cells without the morbidity of structural bone graft harvest 3
The incidence of complications from bone marrow aspiration is rare, making the risk-benefit ratio favorable in this high-stakes fusion case 3
Algorithmic Approach to Bone Graft Selection
Decision Tree for Graft Augmentation
Is fusion indicated? → Yes, due to degenerative anterolisthesis with instability 1
Is local autograft from decompression sufficient? → No, single-level laminectomy provides limited volume for posterolateral fusion bed 3
Should allograft alone be used? → No, allograft lacks osteogenic properties and should be augmented with autograft or bone marrow 2
Is structural iliac crest harvest necessary? → No, bone marrow aspiration provides osteoprogenitor cells without structural harvest morbidity 3
Final construct: Local autograft + morselized allograft + bone marrow aspirate = optimal biological environment 3, 2
Evidence Hierarchy and Quality Assessment
Strongest Supporting Evidence
The American Association of Neurological Surgeons guidelines provide Level III-IV evidence supporting fusion for spondylolisthesis with instability 1
Multiple studies demonstrate 91% excellent outcomes with decompression and fusion for degenerative spondylolisthesis with stenosis 4
60-85% of properly selected patients have satisfactory symptomatic improvement with surgical treatment for symptomatic lumbar spinal stenosis 5
Bone Graft Evidence Quality
The osteogenic properties of bone marrow are well-documented, though clinical studies on efficacy in spinal fusion were ongoing as of 2005 3
Autograft remains the gold standard with established superiority over alternatives, though supply limitations drive consideration of adjuncts 2
Critical Pitfalls to Avoid
Common Errors in Bone Graft Selection
Do not perform posterolateral fusion with allograft alone in a patient with spondylolisthesis, as the lack of osteogenic properties increases pseudarthrosis risk 2
Do not rely solely on limited local autograft from single-level laminectomy for posterolateral fusion, as inadequate graft volume compromises fusion success 3
Improper bone marrow aspiration technique (taking large volumes from single site) leads to dilution with peripheral blood and reduced osteoprogenitor cell concentration 3
Avoiding Revision Surgery
Pseudarthrosis in the setting of persistent instability leads to recurrent symptoms and need for revision surgery, making optimization of initial fusion biology critical 1
Patients with spondylolisthesis who undergo decompression alone have higher rates of poor outcomes due to progression of spinal deformity, emphasizing the importance of achieving solid fusion 1
Payer Policy Considerations
CPB 0411 Policy Analysis
While CPB 0411 does not specifically cover CPT 20939 (bone marrow aspiration), the policy explicitly considers allograft medically necessary for spinal fusions [@question context@]
The policy's approval of allograft (CPT 20930) for spinal fusion implicitly recognizes the need for adequate graft material to achieve fusion [@question context@]
The absence of specific exclusion criteria for autograft augmentation (CPT 20936) or bone marrow aspiration (CPT 20939) in a medically necessary fusion procedure supports their medical necessity [@question context@]
Clinical Override Justification
When the primary fusion procedure (CPT 22612) meets medical necessity criteria due to documented instability, the bone graft materials necessary to achieve that fusion are inherently medically necessary 1
The American Association of Neurological Surgeons guidelines emphasize that fusion should be performed when indicated for instability, and achieving solid arthrodesis requires adequate graft material 1