Purpose: We analysed the radiographic course of anterior lumbar interbody fusion achieved via a minimal anterior extraperitoneal approach.

Material and methods: From January 1996 to December 2001, we operated 198 patients with this technique. Twenty-one patients were excluded from the analysis (two deaths, three tumours, 16 follow-ups less than 12 months). Mean age of the 177 patients retained for study was 53 years (range 22–78). Mean follow-up was 2.7 years. The 55 post-trauma cases involved essentially thoracolumbar junction. The 122 cases of degenerative lumbar spine included 14 cases of scoliosis, 26 cases of spondylolisthesis, 72 cases of unstable spines after primary posterior surgery, and 10 isolated degenerative discs. Only eight patients did not have posterior fixation. Fusion (globally 360 levels) concerned one disc in 89 patients, two discs in 71, three discs in 17. Cancellous autologous grafts were used with cages. Tricortical grafts were implanted after corporectomy (n=23). Radiological fusion was confirmed by the absence of a mobility chamber around the pedicular screws, the cages or the tricortical grafts, and by searching for loss of sagittal angles (digitalized scans and x-ray, Auto Cad L.T.2000).

Results: 1) Early postoperative status. For the post-trauma cases (65 fused levels, 55 patients), a simple callus was observed in 28. For the others, mean correction was 4° per level. 2) Angle loss. For the trauma cases, mean angle loss was 3.9° in 36 cases (29 grafts on a single level). There were two partial expulsions of the tricortical grafts implanted in osteoporotic patients; revision was not attempted. Mean angle loss for the 65 grafted levels was 2°. For the degenerative cases, mean angle loss was 3.7° for 172 fused levels (112 patients). Cage expulsion on a grade 3 spondylolisthesis did not warrant revision. Two cage impactions did not cause significant loss of angle. 3) Anatomic status of the grafts. Fusion was achieved at all levels without cage or tri-cortical graft rupture. We observed a partial but stable lucent line around the case in five cases.

Discussion: The rate of fusion reported after anterior lumbar interbody fusion has varied from 55 to 100% in the literature. This technique is an original approach for trauma victims avoiding the need for extensive posterior assemblies and/or the damage caused by a wide anterior approach. For the degenerative spine, the mediocre quality of the bone and the frequency of several level fusions is not a particular problem.

Conclusion: Anterior lumbar interbody fusion is an interesting method for reinforcing posterior fixation with a real efficacy in terms of effective fusion.