Study design: A retrospective review with long-term clinical and radiologic assessment was conducted.
Objective: To assess the severity and reasons for the reduction of disc space distraction after successful autograft fusion of the lumbar spine and its clinical consequences.
Summary of background data: Anterior lumbar interbody fusion is an established treatment for lumbar disc degeneration. It is not firmly established whether the grafted level narrows after surgery, and if so, what the clinical consequences are.
Methods: This study assessed 67 patients who underwent anterior lumbar interbody fusion at L4-L5 with autologous iliac crest graft. The disc space height and angle between L4 and L5 were serially measured. Times until fusion and the presence of symptoms before and after surgery and at the latest follow-up assessment were noted.
Results: The mean follow-up period was 14 years (range, 2.5-32 years). The fusion rate was 96% (64 of 67 patients), and the mean time to fusion was 9 months. In the group that had successful fusion, there was an initial increase in disc space distraction followed by a reduction in 55 patients (86%). The mean preoperative disc space height was 12.1 mm, which increased immediately after surgery to 16.2 mm, but had been reduced to 12.6 mm at the latest follow-up assessment. The reduction in distraction occurred within the first 3 months after surgery and was correlated with age, but not with recurrence of symptoms, the amount of initial distraction, or the gender of the individual. A similar trend was seen with L4-L5 segmental angulation.
Conclusions: Reduction of disc space distraction after anterior lumbar interbody fusion using tricortical iliac crest bone graft is a common finding. Despite this, the fusion rate is high, and there is no association with symptom recurrence.