MATERIAL and METHODS: This study included 75 patients consisted with 32 of CSM (group A) and 43 of OPLL (group B) presenting a preserved cervical sagittal balance who underwent multi-level laminoplasty for cervical myelopathy. The radiological outcomes were analyzed with the following radiological parameters: C2?C7 Cobb angle in neutral (C2-7AN), flexed (C2-7AF), and extended (C2-7AE) neck postures; C2?C7 range of motion (C2-7ROM); T1 slope (T1S); and C2?C7 sagittal vertical axis (C2-7SVA). The functional outcomes were analyzed with the modified Japanese Orthopedic Association (mJOA) score, Nurick grade, and recovery rate. The radiological and functional outcomes between the two groups were evaluated at 12-month postoperatively.

RESULTS: There were statistically significance increase of C2-7SVA in group A; and decrease of C2-7AF and C2-7ROM in group A and C2-7ROM in group B postoperatively (p<0.05). However, C2-7AN showed no statistically significant inter-group differences and postoperative intra-group changes in both groups (p>0.05). There were no statistically significant differences in the postoperative functional outcomes including mJOA score (p=0.251), Nurick grade (p=0.316), and recovery rate (p=0.435) between the two groups.

CONCLUSION: Although there were no statistically significant differences in functional outcomes between the two groups, the group A showed a greater deterioration in sagittal balance with an increase of C2-7SVA than the group B after multi-level laminoplasty. Keywords : Cervical spondylotic myelopathy, OPLL, Laminoplasty, Cervical spine