The Association Between Clival Axial Angle and Distal Junctional Failure After Craniocervical Fusion

Study DesignRetrospective Cohort.ObjectivesCraniovertebral instability can arise from various congenital or acquired conditions, but definitive management often requires craniocervical fusion. This study evaluates whether postoperative clivo-axial angle (CXA) can predict distal junctional failure in patients undergoing craniocervical fusion. While postoperative alignment of the head and cervical spine can be quantified via the CXA, it is unclear whether the CXA can predict distal junctional failure.MethodsAll patients undergoing craniocervical decompression and fusion (CCF) for craniovertebral instability between 2012 and 2023 at a single institution were identified. Patients experiencing adjacent segment disease (ASD) were identified and compared to those without said pathology based on CXA, Grabb-Oakes line (pBC2), and the presence of cervical kyphosis, cervical disc degeneration, or subluxation on pre- and postoperative imaging. Statistical analysis included Shapiro-Wilk tests for normality, followed by independent t-tests or Mann-Whitney U tests with FDR adjusted <i>P</i> values as appropriate, and univariable logistic regression.Results71 patients were included, of whom ten (14.3%) developed distal junctional kyphosis and 3 (4.3%) developed cervical spondylolisthesis. The median postoperative CXA was significantly lower in non-ASD patients (144° [IQR: 140-148°] vs 158° [IQR: 153-162°]; <i>P</i> < .001) and logistic regression showed that each 10° degree increase in CXA was associated with a 6.7-fold higher odds of ASD.ConclusionsWe found craniocervical alignment, as assessed by CXA, independently predicted distal junctional disease in patients undergoing craniocervical fusion, possibly due to low preoperative CXA in these patients. Large increases in CXA may contribute to postoperative instrumentation failure.