Comparative Analysis of Outcomes and Kyphotic Risk Factors After Cervical Laminoplasty in 2 Different Ossification of the Posterior Longitudinal Ligament Groups and Cervical Spondylotic Myelopathy

BACKGROUND AND OBJECTIVES: Cervical laminoplasty is commonly used to treat cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL). Postoperative kyphotic changes can restrict spinal cord dorsal shift, leading to poor neurological outcomes. This study analyzes risk factors for loss of cervical lordosis (LCL) after laminoplasty in 3 groups: CSM, continuous OPLL, and other OPLL. It also evaluates postoperative changes in cervical spine parameters: C2-7 sagittal vertical axis, C2-7 Cobb angle (CA), T1 slope, and C2 slope. METHODS: This retrospective study included 154 patients who underwent cervical laminoplasty from January 2018 to January 2023. Patients were categorized into 3 groups: CSM (Group 1), continuous OPLL group (Group 2), and noncontinuous OPLL group (Group 3). Preoperative and postoperative radiographic parameters were measured. Analysis of variance and Tukey HSD post hoc tests identified significant differences among the groups. Receiver operating characteristic analysis determined the cutoff value of K-line tilt. RESULTS: Kyphotic changes (>10°) were observed in 18.2% of patients postoperatively: 23.8% in Group 1, 1.7% in Group 2, and 28.3% in Group 3. Significant differences were found among the groups in preoperative K-line, C2-7 CA, extension C2-7 CA, and C2 slope ( P < .05). Univariate and multivariate analyses revealed that greater age, higher K-line tilt, lower preoperative CA-extensor CA, and lower extensor muscle volume were significant risk factors of LCL in Groups 1 and 3. In Group 2, higher preoperative K-line tilt and K-line negative status were associated with greater LCL. Receiver operating characteristic analysis showed that K-line tilt is a strong predictive parameter with a threshold of 15.15°. CONCLUSION: The continuous OPLL group had a lower likelihood of postoperative kyphosis due to structural support. K-line tilt, dynamic extension reserve, and extensor muscle volume were significant predictors of LCL in CSM and segmental OPLL groups. K-line tilt is a valuable radiographic parameter for predicting outcomes and guiding surgical decisions in cervical laminoplasty patients.