Incidence and Risk Factors of Postoperative Adjacent Segment Degeneration Following Anterior Decompression and Instrumented Fusion for Degenerative Disorders of the Cervical Spine.

Abstract

To explore incidence and risk factors of postoperative adjacent segment degeneration (ASD) following anterior decompression and instrumented fusion for degenerative disorders of the cervical spine. Medical records from January 2005 to September 2011 of 283 patients were retrospectively reviewed. Patients were divided into 2 groups based on occurrence of ASD at follow-up: ASD group and no ASD group. To investigate risk for occurrence of ASD, 3 sets of factors were analyzed statistically: patient characteristics, surgical variables, and radiographic parameters. Postoperative ASD developed in 68 of 283patients. There was no statistically significant difference between the 2 groups in patient characteristics or the surgical variables of surgical strategy, surgical time, and blood loss. The number of patients receiving 2-level spinal fusion was higher in the ASD group. Upper instrumented vertebra at C5 was more common in the ASD group. There was no difference between groups in all but 1 of the radiographic parameters; the plate-to-disc distance was much smaller in the ASD group. Logistic regression analysis revealed that upper instrumented vertebra at C5, plate-to-disc distance <3.0 mm, and 2-level anterior cervical fusion were independently associated with ASD. Patients with degenerative disorders of the cervical spine who receive 2-level cervical fusion and with upper instrumented vertebra at C5 are at high potential risk of ASD.