Can laminoplasty maintain the cervical alignment even when the C2 lamina is contained?

Study Design. Retrospective case- controlled study of cervical laminoplasty. Objective. To evaluate the alignment and clinical result by laminoplasty when the C2 lamina is contained or retained. Summary of Background Data. Resection of the C2 lamina was reported to progress to kyphosis after laminectomy. Laminoplasty was reported to inhibit kyphosis. But no study has ever shown if the alignment is retained when laminoplasty also included the C2 lamina. Methods. Seventy- two patients with cervical spondylotic myelopathy undergoing laminoplasty were analyzed. Follow- up averaged 4.0 years. The outcome was assessed by the Cobb angle between C2 and C7, and the motor function scores of the upper and lower extremities for cervical myelopathy were made by the Japanese Orthopedic Association. Patients were stratified into three groups depending on the handling of the C2 lamina: fully split ( S group; n = 17), C2 dome- like laminotomy ( D group; n = 19), and intact ( I group; n = 36). Change of the C2 - C7 angle was compared by the analysis of variance and post hoc test. The association between the alignment and the motor scores was analyzed. Results. Upper/ lower score increased from 2.4/ 2.0 to 3.4/ 2.9, respectively. The C2 - C7 angle decreased in S group: - 8.3 °, D group: - 5.2 °, and I group: - 1.5 °. The cervical alignment deteriorated significantly in S group compared with the I group ( P < 0.01). The C2 - C7 angle change or postoperative C2 - C7 angle had no significant correlation with the postoperative upper and lower m-JOA scores or score change. Conclusions. Subaxial laminoplasty maintained the alignment. But if laminoplasty included the C2 lamina, the alignment worsened.