LUMBAR SPINAL MOBILITY AFTER SHORT ANTERIOR INTERBODY FUSION

Study Design. Segmental deformations of the lumbar spine in asymptomat ic volunteers measured radiologically were compared with those in pati ents who underwent anterior interbody fusion. Objective. To determine the effects of anterior lumbar interbody fusion on the juxta-fused seg ments. Summary of Background Data. Stiffness of a spinal segment after fusion was thought to be the cause of the degeneration process at the juxta-fused segments. Methods. Segmental deformations of the lumbar s pine, from maximum extension to maximum flexion, in 30 asymptomatic vo lunteers and 52 pain-free patients who had single-level L4-L5 or doubl e-level L4-S1 fusion were measured and compared. Results. The total fl exibility of the lumbar spine was decreased after a single-level fusio n and further decreased after double-level fusions. The segmental defo rmations of the juxta-fused segments also were decreased after either a single- or double-level fusion. Conclusions. During normal flexion a nd extension of the lumbar spine, the juxta-fused segments were not de formed beyond their physiological limits after fusion. Thus, accelerat ed degeneration observed at a juxta-fused segment is unlikely to be at tributable to hypermobility.