Is Preoperative Cervical Kyphosis a Fixed Structural Deformity in Compressive Myelopathy? A Longitudinal Dynamic Radiographs Analysis

BACKGROUND AND OBJECTIVES: Conventional selection for cervical laminoplasty relies on the neutral-position C2-7 Cobb angle. Preoperative kyphosis is often considered a relative contraindication because of concerns regarding impaired spinal cord shift. However, this may reflect compensatory functional posture to minimize cord compression. We investigated preoperative kyphosis reversibility and the longitudinal cervical alignment changes after laminoplasty. METHODS: We retrospectively analyzed 850 consecutive patients undergoing cervical laminoplasty for myelopathy (2015-2023). Serial standing lateral radiographs in neutral, flexion, and extension positions were analyzed preoperatively through 5 years postoperatively (mean follow-up, 29.6 ± 27.7 months). Patients were stratified by preoperative alignment (lordosis, straight, and kyphosis) and diagnosis (cervical spondylotic myelopathy and cervical myelopathy with ossification of the posterior longitudinal ligament). The C2-7 Cobb angle, C7 slope, and C2-7 sagittal vertical axis were measured at each time point in all 3 positions. RESULTS: Overall, the neutral-position C2-7 angle showed no significant change immediately after laminoplasty (mean difference, 0.38°; P = .31) and remained stable through 5 years (mean difference, 0.12°; P = .52). In subgroup analysis, the kyphosis subgroup (n = 32) demonstrated a significant gain of lordosis, shifting from +13.99° preoperatively to +2.35° within 1 month (P < .001), and this corrected alignment was maintained at +1.96° up to 5 years (P = .668). The straight and lordosis subgroups achieved lordotic alignment 1 month postoperatively, maintained up to 5 years. C7 slope and C2-7 sagittal vertical axis markedly decreased across all subgroups in the early postoperative period, followed by a gradual increase throughout the 5-year follow-up. The cervical myelopathy with ossification of the posterior longitudinal ligament group consistently maintained a smaller range of motion compared with the cervical spondylotic myelopathy group across all time points, yet both subgroups exhibited comparable longitudinal patterns. CONCLUSION: Mild preoperative kyphosis of the cervical spine on neutral position may represent a potentially reversible condition rather than a fixed deformity. This aspect warrants careful consideration when selecting a posterior decompressive surgery.