Effect of Lamina Open Angles in Expansion Open-door Laminoplasty on the Clinical Results in Treating Cervical Spondylotic Myelopathy

Study Design: A retrospective study. Objective: To evaluate and compare the relation of the efficacy and clinical results of expansion open-door laminoplasty (EOLP) with different angles in lamina open-door. Summary of Background Data: EOLP is currently the most widely adopted surgical treatment for cervical spondylotic myelopathy. Although many long-term clinical follow-up studies have reported that most patients recover satisfactorily after EOLP, there have been numerous reports regarding postoperative complications, such as stubborn axial symptoms (AS) and C5 palsy. The lamina open-door angles in EOLP play a decisive role in determining the openness of the door that affects clinical outcomes. Nonetheless, no thorough studies on different angles in EOLP have been published. Method: A total of 198 cervical spondylotic myelopathy patients who underwent posterior cervical EOLP and at least 24 months follow-up treatment between July 2006 and January 2009 were selected as case studies. Among the 198 cases used, there were 39 double-segment cases with the location being C3-C5 in 11 cases and C4-C6 in 28 cases, 97 three-segments (C4-C7) and 62 four segments (C3-C7). All of the patients underwent x-ray, computed tomography, and magnetic resonance imaging images for evaluation of the cervical spine. According to different opening angles, measured by computed tomography scan after operation 1 week, the patients were divided into 2 groups, group A (> 30 degrees, 76 patients including 44 males and 32 females) and group B (15-30 degrees, 122 patients including 71 males and 51 females). All patients were followed up for over 24 months, clinical results including operative duration, intraoperative bleeding volume, postoperative complications, C2-C7Cobb angle, cervical curvature index (CI), range of motion (ROM), and values after the spinal cord backward shift were analyzed statistically, evaluating the neurological function at final follow-up and calculating the improvement rate of nerve function recovery. Results: There was no statistically significant difference (P > 0.05) between the 2 groups in the following areas: the Japanese Orthopedic Association scores, C2-C7Cobb angle, cervical CI, and ROM. In addition, operative duration and intraoperative bleeding volume between A group and B group showed no significant differences (P> 0.05). After surgery, 51 patients (67.1%) in group A had AS, 8 patients (10.4%) had C5 palsy, and 1 patient had mild cervical kyphosis. Whereas post-operatively group B contained 37 cases (10.5%) with AS, 3 (2.4%) with C5 palsy, and in 4 cases (3.28%) the lamina open-door had reclosed. The rate of patients with AS and C5 palsy in group A was higher than group B. The incidence of postoperative complications between the 2 groups have a significant difference (P < 0.05). The rate of improvement of Japanese Orthopedic Association scores in last follow-up between group A and group B did not reach statistical significance (P > 0.05). At the 1-month follow-up the range of the value of spinal cord backward shift was 0-7.95mm with the average being 2.41 +/- 0.46 mm. C2-C7Cobb angle, CI, and ROM between the 2 groups revealed no statistical significance (P > 0.05). ROM comparisons preoperatively and postoperatively between the 2 groups were significantly different (P < 0.05). Conclusions: In different angles of lamina open-door, the improvement rate of neurological function after surgery had no statistically significant difference between 2 groups. When the open-door angle is maintained between 15 and 30 degrees, it can reduce the incidence of C5 palsy in the hinge side and AS, but we should prevent reclosure of the lamina open-door.