Relationship between postoperative axial symptoms and the rotational angle of the cervical spine after laminoplasty

Introduction: An axial symptom is one of the postoperative problems after cervical laminoplasty. The range of motion (ROM) of the cervical spine decreases after laminoplasty. It is speculated that the reduction in neck ROM is one of the causes of axial symptoms. However, most reports have focused on ROM of the cervical spine in flexion and extension, and few papers describe the rotational motion after surgery. It is impossible to assess the rotational motion in plain X-rays. This study was undertaken for the following two purposes: (1) to compare segmental rotational angles of the cervical spine between control subjects and patients with cervical laminoplasty ; (2) to analyze the relationship between postoperative axial symptoms and the range of cervical rotational angle after laminoplasty. Methods: Eleven young volunteers (control 1 group) and 10 elderly subjects (control 2 group) who did not have any neck problems and 23 patients who had en bloc cervical laminoplasty due to cervical spondylotic myelopathy were included. Dynamic CT scan was conducted in neutral, right, and left maximum rotational positions from C1 to T1. We measured the rotational angle in each vertebral segment. The axial symptoms, such as limited neck motion and neck stiffness, were assessed by a questionnaire. The rotational angle of the cervical spine was compared between the patients with axial symptoms and the subjects without. Results: The rotational angle in control 1 group was greater than that in control 2 group. The rotational angle was markedly decreased in the patients with cervical laminoplasty compared to that in control 2 group. The reduction was observed at the upper vertebral segment. Twelve patients were judged to have axial symptom after cervical laminoplasty (symptom + group), and 11 patients did not have symptoms (symptom - group). The rotational angle in the symptom + group was significantly smaller than that in symptom - group. The reduction in the rotational angle was found below C2 level, whereas the C1-2 angle was not significantly different in the two symptom groups. Conclusion: Reduction of the rotational angle in the cervical spine was clearly observed in patients with cervical laminoplasty, compared to that in the controls. The marked reduction might be related to the axial symptoms after laminoplasty.