Reoperation for proximal adjacent segment pathology in posterior cervical fusion constructs that fuse to c2 vs c3

BACKGROUND: Few studies have described rates of proximal clinical adjacent segment pathology (CASP) after posterior cervical decompression and fusion (PCDF). OBJECTIVE: To investigate rates of proximal CASP at C2 vs C3 in PCDFs for degenerative spine disease. METHODS: A retrospective review of 380 cases of PCDF for degenerative disease with proximal constructs ending at C2 vs C3 was performed. Minimum follow-up was 12 mo. The primary outcome was proximal CASP requiring reoperation. Variable analysis included demographic, operative, and complication data. RESULTS: There were 119 patients in the C2 group and 261 in the C3 group with no significant differences in age, gender, comorbidities, presenting symptoms, or complications. Vertebral artery injury rates were 0.8% in the C2 group and 0.0% in the C3 group (P =. 12). No patients in the C2 group had reoperation for proximal CASP, while 5.0% of patients in the C3 group did (P =. 01). Patients with arthrodesis up to C3 had an increased risk of proximal failure when the fusion construct crossed the cervicothoracic junction (P =. 03). Multivariate logistic regression analysis showed no factors that were independently associated with re-instrumentation for proximal CASP. CONCLUSION: Instrumenting to the C2 level reduces the risk for proximal CASP compared to fusion only up to C3. The type of instrumentation used at these 2 levels, form of ASP disease at C1-C2, and natural motion of the relevant proximal adjacent joint may contribute to this difference. Furthermore, within the C3 cohort, fusion across the cervicothoracic junction increased the risk for proximal CASP.