Results of skip laminectomy - Minimum 2-year follow-up study compared with open-door laminoplasty

Study Design. Results of skip laminectomy and open-door laminoplasty for cervical spondylotic myelopathy were compared. Objectives. To verify that skip laminectomy is less invasive to the posterior extensor mechanism of the cervical spine including the deep extensor muscles than conventional laminoplasty and is effective in preventing postoperative problems often seen after conventional laminoplasty of the cervical spine such as persisting axial pain, restriction of neck motion, and loss of cervical lordosis. Summary of Background Data. A preliminary short-term follow-up study on skip laminectomy demonstrated that the procedure successfully prevented such postoperative problems, while achieving adequate decompression of the spinal cord. Methods. Since December 1998, more than 100 patients with cervical spondylotic myelopathy underwent skip laminectomy, and 43 who were followed for more than 2 years (average of 2 years and 6 months) (Group A) were included in this study. Fifty-one patients who underwent open-door laminoplasty (Group B) in the authors' institutes before December 1998 served as controls. Japanese Orthopaedic Association scores and incidence of newly developed or deteriorated axial pain were recorded. Preoperative and postoperative ranges of neck motion were measured on lateral flexion and extension radiographs. Preoperative and postoperative cervical curvature indices were calculated according to Ishihara's method. For quantitative analysis of damage to the posterior cervical muscles, atrophy rates were calculated from cross-sectional areas of the deep extensor muscles on preoperative and postoperative axial magnetic resonance images. Results. Using Japanese Orthopaedic Association scores, the average recovery rates were 59.2% for Group A and 60.1% for Group B. Only one patient (2%) in Group A had newly developed axial pain, whereas 33 patients (66%) in Group B had postoperative development or deterioration of axial pain. Postoperative range of neck motion averaged 98% of the preoperative measurement in Group A and 61% in Group B. There was no significant difference between preoperative and postoperative cervical curvature index in Group A, whereas the mean value of postoperative index (16.0) was significantly smaller than that of preoperative one (11.8) in Group B (P < 0.05). The atrophy rate of the deep extensor muscles in Group A averaged 13%, whereas that in Group B was 59.9%. Conclusions. Skip laminectomy was less invasive to the posterior extensor mechanism including the deep extensor muscles than open-door laminoplasty. This new procedure was effective in preventing postoperative morbidities often seen after conventional laminectomy and laminoplasty with adequate decompression of the spinal cord.