Loss of inter-vertebral disc height after anterior cervical discectomy.

Most surgeons undertaking anterior cervical discectomy (ACD) introduce a bone graft or cage into the disc space when the decompression is complete. This is done to prevent segmental collapse, preserve cervical spine alignment and to promote fusion. We have conducted a prospective observational cohort study to investigate the relationship between loss of disc height, cervical spine alignment and clinical outcome in 140 patients undergoing ACD without inter-body graft or cage. At a minimum of 12 months after operation changes in disc space height and cervical spine alignment were correlated with clinical outcome measured by SF36, Neck Disability Index, and visual analogue neck and arm pain scores. There was no relationship between loss of disc height and outcome. Loss of the overall cervical lordosis was present in 71 patients and segmental kyphosis was found in 69. Analysis of clinical outcome showed no significant differences between patients with preserved and abnormal cervical alignment. Neither loss of disc height nor disturbance of cervical alignment compromised clinical outcome in the first year following ACD.