Interspace distraction and graft subsidence after anterior lumbar fusion with femoral strut allograft.

The authors performed a retrospective review of 32 patients who had undergone a single-level anterior lumbar fusion with femoral strut allograft as an isolated procedure. The goal of the study was to use clinical radiographs to measure interspace distraction, graft subsidence, interspace collapse, the nature of allograft incorporation, and to correlate these results with successful arthrodesis. Results were categorized according to plain radiographic appearance and flexion/extension stability. Sixty-six percent of the group exhibited radiographic union with flexion/extension stability. Twenty-two percent exhibited stability on the flexion-extension analysis but less than complete arthrodesis was present. Twelve percent exhibited radiographic non-union and flexion-extension instability. Interspace distraction of 11 mm was obtained initially with a follow-up distraction of 5.5 mm. Graft subsidence was noted posteriorly in 27 patients with an average subsidence of 4 mm. The authors' conclusions were: 1) Interspace distraction can be achieved with anterior lumbar fusion if appropriate interbody grafts are used. 2) Despite a solid arthrodesis rate of only 66%, "functional arthrodesis" was achieved in 88%. In a retrospective review of patients who underwent anterior lumbar fusion with femoral strut allograft, interspace distraction, graft subsidence, and incorporation and arthrodesis status were measured. A solid arthrodesis was achieved in 66% of the patients, and functional arthrodesis in another 22%. Interspace distraction was maintained in 59% of cases.