Adjacent Segment Disease
DC 5242Medical Rationale
Lumbar spinal fusion eliminates motion at the fused segment(s), redistributing mechanical stress to the adjacent unfused levels, a phenomenon known as adjacent segment disease (ASD). Biomechanical studies demonstrate 30-45% increases in intradiscal pressure and facet joint loading at the level immediately above a lumbar fusion. This accelerated mechanical demand exceeds the degenerative tolerance of the adjacent disc and facet joints, producing disc herniation, stenosis, spondylolisthesis, or facet hypertrophy at rates significantly higher than age-matched natural history. Radiographic ASD develops in 30-40% of patients within 5 years of fusion, with symptomatic ASD requiring additional surgery in 15-20%. The longer the fusion construct and the younger the patient, the higher the ASD risk.
Key Studies
Hilibrand AS & Robbins M (2004) Spine J (adjacent segment degeneration and disease, systematic review); Lee CS et al. (2009) Spine (risk factors for adjacent segment pathology after lumbar fusion).
Filing Tips
Post-fusion MRI or CT demonstrating disc degeneration, herniation, or stenosis at the level immediately above or below the fusion. Comparison with pre-fusion or immediate post-operative imaging showing the adjacent levels were previously intact. Neurosurgery or orthopedic spine surgeon nexus letter is ideal, the biomechanics of ASD are well-established and nexus letters are routinely granted. 38 CFR 4.71a assigns DC 5243 (intervertebral disc syndrome) only when there is disc herniation with compression and/or irritation of the adjacent nerve root, and assigns DC 5242 (degenerative arthritis, degenerative disc disease other than intervertebral disc syndrome) for all other disc diagnoses, so adjacent-level degeneration is filed under DC 5242 unless the imaging shows herniation compressing or irritating the nerve root, in which case DC 5243 applies. 38 CFR 4.71a rates DC 5235 to 5243 on one General Rating Formula for Diseases and Injuries of the Spine, and Note (6) evaluates the thoracolumbar and cervical segments separately rather than individual levels within a segment, so adjacent-level degeneration in the fused segment is evaluated within that segment. Service connection for the new level is a separate question from a second evaluation. (capture cfr-4.71a)
