Risk factors for mechanical failure involving the cervicothoracic junction following posterior cervical instrumentation

OBJECTIVE The risk profile of posterior cervical decompression and fusion (PCDF), particularly at the cervicothoracic junction (CTJ), remains a topic of ongoing investigation. The goal of this study was to determine whether construct-specific factors affect mechanical failure in patients undergoing PCDF at or beyond the CTJ. METHODS A retrospective chart review was conducted at a single quaternary care center from 2011 to 2023. Patients undergoing PCDF with 3 or more operative levels, long-term follow-up, and lowest instrumented vertebra (LIV) at C7, T1, or T2 were included. Demographic information, surgery indication, instrumentation characteristics, and secondary surgical outcomes were evaluated. Statistical analysis was performed in Python. RESULTS In total, 485 patients were included. The mean age for the cohort was 62.2 (SD 12.1) years, 296 patients (61.0%) were male, and the mean BMI was 30.0 (SD 7.4). Regarding comorbidities, 24.5% of patients had diabetes, 23.9% had heart disease, and 4.5% had osteoporosis. The most common upper instrumented vertebra (UIV) was C2 (58.1%) and the most common LIV was T2 (55.9%). Nineteen patients (3.9%) experienced mechanical failure. On multivariate analysis, a UIV at C2 was associated with decreased odds of mechanical failure compared with C3–4 (OR 0.08, 95% CI 0.02–0.24; p < 0.001). Furthermore, pedicle screw placement at C7 was associated with significantly decreased odds of mechanical failure (OR 0.23, 95% CI 0.02–0.79; p = 0.02). Additionally, compared to an LIV at C7, an LIV at T2 significantly decreased the odds of mechanical failure (OR 0.17, 95% CI 0.04–0.55; p < 0.001). A C7 pedicle screw remained protective in this regression, with significantly decreased odds of mechanical failure (OR 0.22, 95% CI 0.04–0.90; p = 0.03). In a subgroup of patients with 2-year follow-up, a C2 UIV (OR 0.07, 95% CI 0.01–0.32; p < 0.001) and C7 pedicle screw placement (OR 0.06, 95% CI 0.001–0.51; p = 0.01) remained associated with decreased odds of mechanical failure. CONCLUSIONS In the largest single-institution experience to date, this study identified construct-specific factors, including the UIV, LIV, and C7 pedicle screw placement, as independent predictors of mechanical failure in patients undergoing PCDF with constructs ending at or beyond the CTJ.