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Radiculopathy and Myelopathy at Segments Adjacent to the Site of a Previous Anterior Cervical Arthrodesis.

·J Bone Joint Surg Am·1999·1,674 citations·Spine
DOI·PubMed
SummaryAbstract on PubMed →

Prospective cohort study of 374 patients followed up to 21 years after anterior cervical arthrodesis. Defines the incidence, prevalence, and risk factors for symptomatic adjacent-segment disease — new radiculopathy or myelopathy at a motion segment immediately adjacent to a prior fusion. Answers the question: how often does this happen, to whom, and when?

Study Snapshot

Design
Retrospective cohort
Setting: Single center, Cleveland (Case Western Reserve)
Funding: None
Objective
Determine whether symptomatic adjacent-segment disease develops after anterior cervical arthrodesis
Outcome(s)
Annual incidence and 10-year prevalence of symptomatic adjacent-segment disease
Subjects
374 patients, 409 anterior cervical arthrodeses
Inclusion
  • Anterior cervical arthrodesis for cervical spondylosis
  • Radiculopathy or myelopathy indication
  • Survived >6 months post-index procedure
Exclusion
  • Died within 6 months post-index procedure (n=9)
  • Acute fracture or dislocation
  • Planned concomitant posterior arthrodesis
Follow-up
Maximum 21 years
Statistics
Kaplan-Meier survivorship analysisLogistic regressionChi-square analysisLife-table methods

Key Findings

  • Kaplan-Meier analysis predicts a 25.6% chance of developing symptomatic adjacent-segment disease within 10 years — roughly 1 in 4 patients who undergo anterior cervical fusion will require evaluation or potential reoperation at an adjacent level.
  • The annual incidence remains constant at 2.9% per year throughout the first decade, with no early clustering — risk persists long-term, not just in the first few postoperative years.
  • Risk varies sharply by level, tracking the normal range of motion at each segment:
    –C5-6: prevalence 13.8% (high risk)
    –C6-7: prevalence 13.0% (high risk)
    –C3-4, C4-5: intermediate risk (3.2× relative risk vs. low-risk levels)
    –C2-3, C7-T1: low risk
    –Relative risk at high-risk levels is 4.9× that of low-risk levels (p < 0.0001)
  • Counterintuitively, single-level fusion carried higher adjacent-segment disease risk than multilevel fusion (18% vs. 12%, OR 0.64, p < 0.001) — multilevel constructs incorporate the naturally high-risk C5-6 and C6-7 levels, leaving only lower-risk segments adjacent to the construct.
  • Preexisting grade IV degeneration at an adjacent level predicted symptom onset in under 2 years vs. over 7 years with no preoperative changes — over two-thirds of affected patients ultimately failed nonoperative management and required reoperation.
Board PearlOne in four patients develops symptomatic adjacent-segment disease within 10 years of anterior cervical fusion, at a constant rate of 2.9% per year.

Clinical Relevance

Tell every patient before anterior cervical fusion: there is approximately a 1-in-4 chance of developing new radiculopathy or myelopathy at an adjacent level within 10 years, requiring potential reoperation.

When you review preoperative MRI and see grade III or IV degeneration at a level adjacent to your planned fusion — especially at C5-6 or C6-7. That level is at high risk for rapid symptom onset (under 2 years). Strongly consider including it in the initial arthrodesis if clinical findings support it.

The counterintuitive finding here drives modern practice: do not stage operations by fusing one level and watching the others. Addressing all symptomatic, compressive levels in a single procedure reduces adjacent-segment disease risk, because multilevel constructs end adjacent to the naturally lower-risk C2-3 or C7-T1 segments.

This paper is the foundational reference for cervical disc arthroplasty trials. The Prestige and Bryan disc studies used the 2.9%-per-year benchmark to test whether motion preservation reduces adjacent-segment disease rates.

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|

Radiculopathy and Myelopathy at Segments Adjacent to the Site of a Previous Anterior Cervical Arthrodesis.

·J Bone Joint Surg Am·1999·1,674 citations·Spine
DOI·PubMed
SummaryAbstract on PubMed →

Prospective cohort study of 374 patients followed up to 21 years after anterior cervical arthrodesis. Defines the incidence, prevalence, and risk factors for symptomatic adjacent-segment disease — new radiculopathy or myelopathy at a motion segment immediately adjacent to a prior fusion. Answers the question: how often does this happen, to whom, and when?

Study Snapshot

Design
Retrospective cohort
Setting: Single center, Cleveland (Case Western Reserve)
Funding: None
Objective
Determine whether symptomatic adjacent-segment disease develops after anterior cervical arthrodesis
Outcome(s)
Annual incidence and 10-year prevalence of symptomatic adjacent-segment disease
Subjects
374 patients, 409 anterior cervical arthrodeses
Inclusion
  • Anterior cervical arthrodesis for cervical spondylosis
  • Radiculopathy or myelopathy indication
  • Survived >6 months post-index procedure
Exclusion
  • Died within 6 months post-index procedure (n=9)
  • Acute fracture or dislocation
  • Planned concomitant posterior arthrodesis
Follow-up
Maximum 21 years
Statistics
Kaplan-Meier survivorship analysisLogistic regressionChi-square analysisLife-table methods

Key Findings

  • Kaplan-Meier analysis predicts a 25.6% chance of developing symptomatic adjacent-segment disease within 10 years — roughly 1 in 4 patients who undergo anterior cervical fusion will require evaluation or potential reoperation at an adjacent level.
  • The annual incidence remains constant at 2.9% per year throughout the first decade, with no early clustering — risk persists long-term, not just in the first few postoperative years.
  • Risk varies sharply by level, tracking the normal range of motion at each segment:
    –C5-6: prevalence 13.8% (high risk)
    –C6-7: prevalence 13.0% (high risk)
    –C3-4, C4-5: intermediate risk (3.2× relative risk vs. low-risk levels)
    –C2-3, C7-T1: low risk
    –Relative risk at high-risk levels is 4.9× that of low-risk levels (p < 0.0001)
  • Counterintuitively, single-level fusion carried higher adjacent-segment disease risk than multilevel fusion (18% vs. 12%, OR 0.64, p < 0.001) — multilevel constructs incorporate the naturally high-risk C5-6 and C6-7 levels, leaving only lower-risk segments adjacent to the construct.
  • Preexisting grade IV degeneration at an adjacent level predicted symptom onset in under 2 years vs. over 7 years with no preoperative changes — over two-thirds of affected patients ultimately failed nonoperative management and required reoperation.
Board PearlOne in four patients develops symptomatic adjacent-segment disease within 10 years of anterior cervical fusion, at a constant rate of 2.9% per year.

Clinical Relevance

Tell every patient before anterior cervical fusion: there is approximately a 1-in-4 chance of developing new radiculopathy or myelopathy at an adjacent level within 10 years, requiring potential reoperation.

When you review preoperative MRI and see grade III or IV degeneration at a level adjacent to your planned fusion — especially at C5-6 or C6-7. That level is at high risk for rapid symptom onset (under 2 years). Strongly consider including it in the initial arthrodesis if clinical findings support it.

The counterintuitive finding here drives modern practice: do not stage operations by fusing one level and watching the others. Addressing all symptomatic, compressive levels in a single procedure reduces adjacent-segment disease risk, because multilevel constructs end adjacent to the naturally lower-risk C2-3 or C7-T1 segments.

This paper is the foundational reference for cervical disc arthroplasty trials. The Prestige and Bryan disc studies used the 2.9%-per-year benchmark to test whether motion preservation reduces adjacent-segment disease rates.

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