Radiculopathy after laminoplasty of the cervical spine.

STUDY DESIGN

The risk factors of patients with and without radiculopathy after laminoplasty of the cervical spine were compared retrospectively.

OBJECTIVES

To study the association between risk variables and postlaminoplastic radiculopathy to clarify the pathogenesis of radiculopathy and to devise preventive measures.

SUMMARY OF BACKGROUND DATA

Radiculopathy after cervical laminoplasty on the expanded side has been attributed mainly to traumatic surgical techniques, whereas radiculopathy on the hinged side has been attributed to traction, tethering, or kinking of the nerve root that has resulted from posterior shift of the spinal cord from the preoperative position. There is still much divergence of opinion concerning the risk factors for the outbreak as well as the prevention.

METHODS

Of 365 patients who had undergone laminoplasty, 20 patients (5.5%) developed postoperative radiculopathy. Using data from postoperative computed tomography scans and other sources, these patients were compared with 211 patients with no radiculopathy, who had undergone laminoplasty during the same period, to identify risk factors related to patient characteristics and surgical techniques.

RESULTS

Of various risk factors studied, the narrowest level of the spinal canal, preoperative symptomatic severity, flatness of the spinal cord assessed by computed tomography myelography at C4-C5, cervical curvature, anterior protrusion of the superior articular process as assessed by computed tomography scan, laterality of the osteophytes, and ossification of the posterior longitudinal ligament could not significantly discriminate between patients with and without postoperative radiculopathy. The angle of lamina as measured by using computed tomography scans obtained after expansion in the patients with radiculopathy was greater than 68 degrees on the opened and hinged sides and was significantly greater than the angle in patients without radiculopathy (P < 0.05). The incidence of radiculopathy on both the opened and hinged sides was significantly higher in patients in whom the bony gutter had been cut on the lateral side of the medial aspect of the zygapophyseal joint.

CONCLUSION

Any one of patients' characteristics could not be correlated with postoperative cervical radiculopathy in this study. To prevent postoperative radiculopathy, it may be important during surgery to place the bony gutter on the medial side of the zygapophyseal joint and to keep the slope of the opened lamina within 60 degrees.