Influence of SCA on clinical outcomes and cervical alignment after laminoplasty in patients with multilevel cervical spondylotic myelopathy

Background To study the impact of changes in spino-cranial angle (SCA) on sagittal alignment and to investigate the relationship between SCA and Neck Disability Index (NDI) scores after laminoplasty (LP) Material and methods In total, 72 patients with multilevel cervical spondylotic myelopathy (MCSM) after laminoplasty (LP) were retrospectively enrolled. Based on the optimal cut-off values of preoperative SCA, patients were classified into low SCA and high SCA groups. Radiographic data were measured, including spino-cranial angle (SCA), T1-slope (T1s), C2–7 lordosis (CA), T1s minus CA (T1sCA), and C2–7 sagittal vertical axis (cSVA). JOA and NDI scores were both applied to assess postoperative and follow-up clinical efficacy. Pearson correlation coefficient and linear regression analysis were respectively calculated between radiographic data and between SCA and NDI. Results The preoperative SCA was significantly correlated with T1s (r = − 0.795), CA (r = − 0.857), and cSVA (r = 0.915). A receiver operating characteristic (ROC) curve model predicted a threshold of SCA (value of 85.2°). At the follow-up period, patients with lower SCA had a higher T1s and CA and a lower cSVA, simultaneously accompanied by greater △T1s, △CA, and △cSVA. The linear regression model demonstrated that SCA in the higher group was positively correlated with NDI, and patients with higher SCA had worse NDI scores (pre: p p p = 0.003) and greater changes of NDI (post: p p = 0.002). Conclusion SCA may be a good predictor of evaluating sagittal balance and planning surgery. Changes in sagittal alignment in the low SCA group were affected more easily, and a higher SCA was associated with worse quality of life. Laminoplasty could be a good choice for patients with lower SCA.