The relative spinal cord float back distance might be associated with C5 palsy after posterior cervical decompression.

Objective: To investigate the independent risk factors for C5 palsy (C5P) after cervical posterior decompression. Methods: Between 2020 and 2023, 97 patients with multisegmented cervical spondylotic myelopathy (CSM) who underwent posterior cervical decompression surgery at our hospital were retrospectively reviewed. Clinical features and radiological data of patients with and without C5P were analyzed. The clinical features of the patients who underwent two different surgeries were analyzed. Then the parsimonious multivariable logistic regression was conducted. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of the relative spinal cord float back distance (RSD) and intervertebral foramen diameter (IFD). Kaplan-Meier analysis was used to compare C5P recovery time between different surgical approaches and RSD subgroups. Results: Patients in C5P group had higher RSD and narrower IFD than non-palsy group. Patients in laminoplasty group had lower postoperative VAS scores for axial pain and lower incidence of C5P. Parsimonious multivariate binary logistic regression analysis showed that RSD was associated with increased odds of C5P. ROC analysis further demonstrated that an RSD > 6.91 mm predicted postoperative C5P with an accuracy of 85.00%. Kaplan-Meier analysis revealed that, in the laminoplasty group, patients presenting with C5P and RSD < 6.91 mm experienced significantly shorter recovery times compared to the laminectomy group. Conclusion: RSD might be associated with increased odds of C5P, and the IFD might be associated with decreased odds of C5P. These results indicated that any potential factor that may induce traction on the C5 nerve root could contribute to the development of C5P. Laminoplasty might have lower odds of C5P compared with laminectomy.