This narrative review distinguishes adjacent segment degeneration (radiographic only) from adjacent segment disease (symptomatic) after cervical and lumbar fusion. It synthesizes long-term follow-up and biomechanical data to ask whether fusion itself drives adjacent pathology or whether it reflects natural disease progression.
When you counsel a patient before ACDF, you need a number: adjacent segment disease develops at roughly 3% per year, reaching about a quarter of patients by 10 years. The central teaching point is separating degeneration from disease. Radiographic changes adjacent to a fusion are common and often silent, so do not treat the film. Treat the symptomatic patient.
The most important critical-appraisal lesson: this review presents evidence on both sides and refuses to declare fusion the cause. Multilevel fusions had lower disease rates than single-level, and non-fused foraminotomy patients degenerated at similar rates. Both findings undercut the pure mechanical stress hypothesis.
Practically, do not extend a fusion into an adjacent degenerated disc based on MRI alone. Outcomes were actually worse when patients were fused next to normal discs, and imaging degeneration did not predict the need for reoperation. Whether adjacent segment pathology is iatrogenic or natural history remains debated, which is exactly why motion-preserving disc arthroplasty was proposed.
This narrative review distinguishes adjacent segment degeneration (radiographic only) from adjacent segment disease (symptomatic) after cervical and lumbar fusion. It synthesizes long-term follow-up and biomechanical data to ask whether fusion itself drives adjacent pathology or whether it reflects natural disease progression.
When you counsel a patient before ACDF, you need a number: adjacent segment disease develops at roughly 3% per year, reaching about a quarter of patients by 10 years. The central teaching point is separating degeneration from disease. Radiographic changes adjacent to a fusion are common and often silent, so do not treat the film. Treat the symptomatic patient.
The most important critical-appraisal lesson: this review presents evidence on both sides and refuses to declare fusion the cause. Multilevel fusions had lower disease rates than single-level, and non-fused foraminotomy patients degenerated at similar rates. Both findings undercut the pure mechanical stress hypothesis.
Practically, do not extend a fusion into an adjacent degenerated disc based on MRI alone. Outcomes were actually worse when patients were fused next to normal discs, and imaging degeneration did not predict the need for reoperation. Whether adjacent segment pathology is iatrogenic or natural history remains debated, which is exactly why motion-preserving disc arthroplasty was proposed.