Study Design.This is a retrospective study of the morphologic limitations of posterior decompression for ossification of the posterior longitudinal ligament in the cervical spine.Objectives.To determine the morphologic limitations of the posterior approach in the management of ossification of the posterior longitudinal ligament.Summary of Background Data.Thirty-eight patients who underwent laminoplasty by midsagittal splitting for ossification of the posterior longitudinal ligament were reviewed. Fifteen patients were included in the noncontact group, in which the spinal cord was free of the ossified lesion after posterior decompression. Twenty-three patients were included in the contact group, in which the spinal cord was not free of the ossified lesion even after posterior decompression.Methods.The preoperative sagittal alignment of the cervical spine and preoperative maximal thickness of ossification were compared between the two groups. In addition, the morphologic limitations of posterior decompression for ossification of the posterior longitudinal ligament were investigated.Results.The following factors were found to contribute significantly to contact between the spinal cord and ossification of the posterior longitudinal ligament after posterior decompression: 1) lordosis of less than 10° or kyphosis in the preoperative sagittal alignment, and 2) preoperative maximal thickness of ossification of more than 7 mm.Conclusions.Patients who exhibit significant risk factors for continued contact of the spinal cord should be morphologically considered for anterior decompression.