Kinematic Effects of Cervical Laminoplasty for Cervical Spondylotic Myelopathy on the Occipitoatlantoaxial Junction.

STUDY DESIGN: A retrospective evaluation of sagittal angular motion from cervical spinal flexion to extension.

OBJECTIVE: To evaluate the kinematic effects of cervical laminoplasty for cervical spondylotic myelopathy (CSM) on the occipitoatlantoaxial junction.

SUMMARY OF BACKGROUND DATA: The kinematic effects of cervical laminoplasty for CSM on the occipitoatlantoaxial junction remain controversial.

METHODS: A total of 65 CSM patients who were treated with cervical laminoplasty ranging from the C3 to C7 vertebrae were included in the study. After surgery, all patients wore a Philadelphia collar for the first week and began cervical range of motion exercises as soon as possible. Functional plain radiographs were obtained preoperatively and at 1 and 3 years postoperatively. Sagittal angular motion from cervical spinal flexion to extension was measured using the Cobb technique at 7 cervical segments (Oc-C1, C1-C2, C2-C3, C3-C4, C4-C5, C5-C6, and C6-C7). We defined the contribution of each segment's mobility to the total angular mobility of the cervical spine as percent segmental mobility.

RESULTS: Total cervical angular mobility significantly decreased after cervical laminoplasty. There were no significant differences in Oc-C2 angular mobility; however, C2-C7 angular mobility had significantly decreased by 3 years postoperatively. No significant differences in percent segmental mobility were observed at 1 year postoperatively except at the C3-C4 segment. By 3 years postoperatively, percent mobility at the Oc-C1 and C1-C2 segments had significantly increased, whereas that at the C3-C4 and C5-C6 segments had significantly decreased.

CONCLUSIONS: Our results suggest that, although the contribution of occipitoatlantoaxial junctional mobility to total cervical mobility increases, dynamic mechanical stress to the occipitoatlantoaxial junction does not increase following laminoplasty, and no adjacent segmental disorder at the occipitoatlantoaxial junction was observed within 3 years postoperatively. We hypothesized that early removal of the cervical collar and early cervical range of motion exercises may contribute to these kinematic changes.