Can preoperative spino-cranial angle predict cervical sagittal imbalance after laminoplasty?

This study aimed to determine whether the preoperative spino-cranial angle (SCA) predicts cervical sagittal imbalance (CSI) after laminoplasty (LP).

We retrospectively screened 298 consecutive patients with degenerative cervical myelopathy (DCM) who underwent LP at our hospital from January 2018 to June 2021. Of these, 116 met the inclusion criteria and were analyzed. Radiographic and clinical parameters were collected preoperatively and at the last follow-up. Patients were stratified based on the change in cervical sagittal vertical axis (cSVA), calculated as ΔcSVA = postoperative-preoperative, into three categories: improvement (ΔcSVA≤ - 10 mm), stability (-10 mm < ΔcSVA≤10 mm), and deterioration (ΔcSVA>10 mm). Group comparisons were conducted using the χ ² test, t-test, analysis of variance, or non-parametric equivalents, as appropriate. Multivariable logistic regression was used to identify factors associated with postoperative CSI (ΔcSVA>10 mm). Receiver operating characteristic (ROC) analysis was performed to determine the SCA cutoff.

Patients in the deterioration group exhibited the lowest preoperative SCA, along with poorer JOA recovery and worse postoperative neck pain compared to the improvement group. In the adjusted model, a lower SCA independently predicted postoperative cSVA deterioration (OR = 0.575, 95%CI: 0.372-0.808, p = 0.012), while other preoperative variables were not significant. The ROC analysis showed fair discrimination (AUC = 0.662), and an SCA threshold of 81.8° yielded 62.6% sensitivity and 96.0% specificity.

The preoperative SCA influences postoperative cervical alignment after LP. Patients with a low SCA are at increased risk for CSI and may benefit from enhanced preoperative counseling and strategies that preserve alignment during LP.