adjacent segment disease
Also written as: ASD — adjacent segment disease
Accelerated degeneration or instability occurring at spinal levels adjacent to a previously fused segment.
Full Definition
Adjacent segment disease (ASD) refers to the development of new symptoms, degeneration, or instability at spinal levels immediately above or below a previously fused segment. This phenomenon is thought to result from altered biomechanics and increased stress transfer to adjacent levels following spinal fusion. ASD can manifest as disc degeneration, facet arthropathy, instability, or stenosis. The condition typically develops months to years after initial fusion surgery and may require additional surgical intervention. Understanding ASD is crucial for patient counseling regarding long-term outcomes and for surgical decision-making regarding fusion extent.
Usage
Usage note: Distinguish from natural aging processes; requires evidence of accelerated degeneration.
In Context
- "Five years post-fusion, the patient developed adjacent segment disease at L3-L4." — follow-up consultation
- "Revision surgery was necessary to address symptomatic adjacent segment disease." — operative indication