Favorable cervical extension capacity preventing loss of cervical lordosis after laminoplasty due to spontaneous restoration of initial lordosis

Abstract

Background ContextCervical laminoplasty is a common approach for the treatment of multilevel cervical spondylotic myelopathy (CSM). Postoperative loss of cervical lordosis (LCL) was associated with lower extension motion of the cervical spine before laminoplasty. PurposeTo analyze the possible causes of preoperative cervical extension capacity affecting LCL after laminoplasty by evaluating the changes in cervical lordosis (CL) at different stages. Study Design/SettingRetrospective study. Patient SampleSeventy-two patients undergoing laminoplasty due to multilevel CSM. Outcome MeasuresRadiographic parameters included CL, extension CL (eCL), flexion CL (fCL), range of motion (ROM), extension ROM (eROM), flexion ROM (fROM) and LCL. Clinical outcomes were assessed using the Japanese Orthopedic Association (JOA) and neck disability index (NDI) score. MethodsThe data were recorded before surgery and at 3- and 24-month follow-up. All patients completed a cervical extension test preoperatively. A receiver operating characteristic (ROC) curve of eROM was constructed to discriminate the patients with and without postoperative kyphotic deformity. ResultsAccording to the optimal cut-off value of eROM, the patients were divided into two groups: extension group (eROM≥9.3°) and control group (eROM<9.3°). The radiographic outcomes demonstrated no significant differences in CL, eCL, fCL and ROM between the two groups. Both eROM and fROM were significantly different in the two groups. There was a significant change in CL in the extension group at 3-month follow-up and in the control group at 24-month follow-up. The extension group exhibited significantly lower LCL compared with the control group at follow-up. No significant difference between the two groups was noted in the JOA recovery rate, while the NDI score was significantly different at 24-month follow-up. The positivity ratio of the extension test was significantly greater in the extension group than that in the control group. ConclusionseROM in patients with favorable preoperative cervical extension capacity (eROM≥9.3°) consisted of the actual extension capacity and compensatory flexion. The cervical alignment would be spontaneously restored to its initial lordosis in the short term after laminoplasty. These patients had no substantial LCL at 24-month follow-up and would be good candidates for laminoplasty.