Are posterior lumbar interbody fusion with an expandable cage and Mazor Medtronic (robotic-assisted surgery system) robotic placed pedicle screws medically necessary for a patient with lumbar stenosis and neurogenic claudication?

Medical Necessity Assessment for Posterior Lumbar Interbody Fusion at L4-5

Direct Recommendation

The requested posterior lumbar interbody fusion (PLIF) with expandable cage and robotic-assisted pedicle screw placement at L4-5 is medically necessary for this patient with lumbar stenosis, neurogenic claudication, and documented dynamic instability (12 mm translation on flexion-extension films), provided that adequate conservative management has been completed. However, the critical deficiency in this case is the lack of documentation confirming completion of formal physical therapy within the past year, which is required by established guidelines before surgical intervention can be approved 1.

Key Clinical Findings Supporting Fusion

The patient presents with compelling indications for surgical intervention:

• Dynamic instability at L4-5: 12 mm of translation on flexion-extension films (versus 7 mm) clearly exceeds the 4 mm threshold that defines pathologic instability requiring fusion 2, 1
• Severe stenosis: Large disc herniation at L4-5 causing severe canal stenosis correlates with bilateral lower extremity symptoms 1
• Neurogenic claudication: Constant right lower extremity pain with burning/throbbing character worsened by walking/standing is classic for neurogenic claudication 1
• Functional disability: Pain level 8/10 with inability to function represents significant impairment 1

Conservative Management Requirements - CRITICAL GAP

The patient does NOT currently meet medical necessity criteria due to incomplete conservative management documentation 1. Guidelines require:

• Formal physical therapy for at least 6 weeks within the past year 1
• The patient reports "physical therapy in the past but not recently" - this is insufficient 1
• While the patient had one epidural steroid injection that provided some relief, and has tried ibuprofen and stretching, these do not substitute for structured physical therapy 1

The patient must complete a minimum 6-week course of formal, supervised physical therapy before fusion can be approved, unless there is documented progressive neurological deficit or cauda equina syndrome (neither is present here) 2, 1.

Fusion is Appropriate Once Conservative Management is Complete

When conservative management is properly documented, fusion is strongly indicated based on Class I and II evidence:

• Patients with dynamic instability ≥4 mm who undergo fusion have significantly better outcomes than those treated with decompression alone, with statistically significant reductions in both back pain (p=0.01) and leg pain (p=0.002) 1
• Fusion rates of 92-95% are achieved with interbody techniques combined with posterior instrumentation 1
• Decompression alone would be inadequate given the 12 mm of pathologic motion - removing additional bone would worsen instability and lead to poor outcomes 2, 1

Specific Surgical Techniques Requested

Posterior Lumbar Interbody Fusion (CPT 22633)

PLIF is medically appropriate for this indication 2, 3:

• PLIF provides anterior column support, addresses the disc pathology directly, and achieves higher fusion rates (95%) compared to posterolateral fusion alone (80%) 2, 3
• For spondylolytic instability with stenosis, adding PLIF to posterolateral fusion reduces nonunion rates from 7.5% to 0% and provides better reduction maintenance 3
• PLIF allows direct decompression of neural elements while simultaneously stabilizing the segment 3

Expandable Cage Technology

The use of an expandable interbody cage is a reasonable surgical option 4:

• Recent 24-month outcomes data shows expandable cages significantly improve segmental lordosis by 5.3° and lumbar lordosis by 4.2° (p<0.0001 and p=0.049 respectively) 4
• Disc height improved by 49% (6.1 mm) with no device-related complications or subsidence at 2-year follow-up 4
• Clinical outcomes showed 55% improvement in ODI and 72-79% reduction in VAS pain scores (p<0.0001) 4

Robotic-Assisted Pedicle Screw Placement (Mazor/Medtronic System)

Robotic guidance for pedicle screw placement is medically reasonable but not medically necessary 5, 6:

• The Mazor X system provides increased accuracy by eliminating 4 of 6 degrees of freedom, potentially reducing severe complications from misplaced screws 5
• A 2024 pilot study of 27 robot-assisted TLIF cases showed high pedicle screw accuracy with low complication rates comparable to conventional O-arm navigation 6
• However, this technology is an adjunct that improves accuracy but does not change the fundamental indication for surgery - traditional fluoroscopic or navigation-guided techniques achieve similar clinical outcomes 6

Allograft Bone Graft Material (CPT 20930)

Allograft bone graft material is medically necessary for spinal fusion per Aetna policy 1:

• Cadaveric allograft and demineralized bone matrix are considered medically necessary for spinal fusions regardless of implant shape
• Allograft materials that are 100% bone meet criteria for this indication

Posterior Instrumentation (CPT 22840)

Pedicle screw fixation is medically necessary given the documented instability 2, 1:

• Class I evidence shows pedicle screw fixation improves fusion rates from 45% to 83% in patients with stenosis and instability (p<0.05) 2
• Instrumentation provides optimal biomechanical stability with fusion rates up to 95% 1
• Per Aetna policy exception, pedicle screws may be certified with any spinal fusion if the fusion surgery meets criteria

Imaging Clarification Required

The question of spondylolisthesis must be definitively answered:

• The clinical documentation describes "abnormal motion at L4-5 with 12 mm versus 7 mm flexion versus extension of the posterior vertebral body" 1
• This 12 mm of translation represents dynamic instability, which meets fusion criteria regardless of whether static spondylolisthesis is present 2, 1
• Request the actual flexion-extension radiographs or formal radiology report to document: (1) degree of static listhesis if present, and (2) millimeters of translation between flexion and extension views
• The iSuite history shows a certified CPT 72148 (lumbar MRI) with DOS 10/10/2025-04/08/2026 at a different facility - obtain these imaging studies for review

Inpatient vs Outpatient Setting

The request does not specify setting, but this procedure requires inpatient admission 1:

• Combined interbody fusion with instrumentation has complication rates of 31-40% compared to 6-12% for simpler procedures 1
• Multi-component procedures requiring decompression, interbody fusion, and bilateral pedicle screw placement necessitate close postoperative neurological monitoring 1

Final Determination

DENY pending completion of conservative management, then APPROVE with conditions:

1. Patient must complete minimum 6 weeks of formal, supervised physical therapy documented within the past year before surgical approval 1
2. Once physical therapy is documented, approve CPT 22633 (PLIF), 20930 (allograft), and 22840 (pedicle screws) based on documented dynamic instability of 12 mm at L4-5 2, 1
3. CPT 61783 (robotic guidance) is reasonable but not medically necessary - may approve as surgeon preference but not required for medical necessity 5, 6
4. Require submission of actual flexion-extension radiographs to document the 12 mm translation measurement
5. Obtain the prior MRI from iSuite reference 8650584 to ensure complete imaging review
6. Approve for inpatient setting given procedural complexity 1

Common Pitfalls to Avoid

• Do not approve fusion without documented completion of formal physical therapy - "physical therapy in the past" is insufficient; must be within past year and minimum 6 weeks duration 1
• Do not confuse dynamic instability (12 mm translation) with static spondylolisthesis - either condition can independently justify fusion when symptomatic 2, 1
• Do not deny based on age - at 51 years old, this patient is appropriate for fusion if criteria are met 1
• Verify the facility (Swedish Medical Center/Cherry Hill) is on the Nuance list as noted in the request - follow Nuance list directions if applicable