Comparison of disc space heights after anterior lumbar interbody fusion.

Thirty-one consecutive patients underwent anterior interbody fusion of 40 levels of the lumbar spine using autogenous, autologous, or mixed iliac crest graft. Each patient's disc space height was measured preoperatively, immediately postoperatively, and an average of 29 months postoperatively. The immediate postoperative radiograph demonstrated an average increase in disc space height of 89%, or 9.5 mm for each operated level. The late radiographic evaluation, from 7 to 54 months postoperatively, showed an average decrease of 1%, or 0.1 mm for each level. At late follow-up, no correlation could be found between the time from the operation and disc space height. One hundred percent of patients developed disc space height decreases during the postoperative period, with 46% of levels being narrower than their preoperative height at last follow-up. Loss of distraction is a normal postoperative occurrence of the procedure. Disc space distraction is temporary with anterior interbody fusion.