The relationship between preoperative cervical sagittal balance and clinical outcome of laminoplasty treated cervical ossification of the posterior longitudinal ligament patients

Abstract

Background context: Laminoplasty is a common surgical method used to treat patients with cervical ossification of the posterior longitudinal ligament (OPLL). Although laminoplasty is preferred over traditional laminectomy, the factors affecting the complications and outcomes are unclear. Recently, sagittal balance indexes have been revealed to be predictors of clinical outcomes in patients with cervical degenerative diseases, but their relationships with laminoplasty-treated OPLL outcomes remains unknown.

Purpose: The purpose of this study is to evaluate the relationship of preoperative cervical sagittal balance indexes and clinical outcome in laminoplasty treated OPLL patients.

Study design: This is a retrospective case study.

Patient population: Between January 2015 and January 2017, 181 consecutively included patients who underwent cervical laminoplasty for OPLL were enrolled (male:female ratio=126:75; mean age=60.2 years). Cervical spine lateral radiographs in neutral, flexion, and extension positions were taken before and 2 years after the surgery.

Outcome measures: The C2-C7 Cobb angle, T1 slope, C1-C7 sagittal vertical axis (SVA), C2-C7 SVA, CGH (center of gravity of the head)-C7 SVA, cervical JOA (Japanese Orthopedic Association) score, and neck VAS (visual analogue scale) score were measured preoperatively and postoperatively at the 2-year follow-up.

Methods: The patients were divided into two groups according to changes in the lordotic angle or the recovery rate of the JOA score. The relationships between the postoperative lordosis loss or the clinical outcome and the preoperative variables, including the patient's age, JOA score, C2-C7 Cobb angle, T1 slope, C1-C7 SVA, C2-C7 SVA, and CGH-C7 SVA, were investigated.

Results: The patients were divided into two groups according to the postoperative change in the C2-C7 Cobb angle. There were no differences in the age, preoperative C2-C7 Cobb angle, C1-C7 SVA, or C2-C7 SVA; there was only a difference in the preoperative CGH-C7 SVA and T1 slope level (p=.038, p=.042). The postoperative JOA and JOA recovery rate were related to the postoperative lordosis loss in cervical alignment (p=.048, p=.031). We again divided the patients into two groups according to the JOA recovery rate and found that only the preoperative CGH-C7 SVA and C1-C7 SVA were related to the neurological outcome (p=.011, p=.047). According to the multivariate logistic regression analysis, higher preoperative CGH-C7 SVA levels were significantly associated with decreases in the lordosis angle postoperatively and the clinical outcome (p=.018, OR=1.225; p=.034, OR=1.654). The ROC (receiver operating characteristic) analysis revealed that the proper cutoff value of preoperative CGH-C7 SVA for predicting the postoperative loss of lordosis and clinical outcomes is 3.8 cm.

Conclusion: Preoperative cervical sagittal balance indexes are related to the outcomes of OPLL patients after laminoplasty. Patients with high preoperative CGH-C7 SVA levels have a high probability of developing sagittal imbalances and neurological symptoms of the cervical spine, and this measurement can be used as a predictor of outcomes in laminoplasty-treated cervical OPLL patients.

Keywords: CGH-C7 SVA; Clinical outcome; Complications; Laminoplasty; OPLL; Sagittal balance.