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

OBJECTIVE: 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.

METHODS: 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.

RESULTS: Postoperative ASD developed in 68 of 283 patients. 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.

CONCLUSIONS: 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.