Lumbar spinal mobility after short anterior interbody fusion

Study Design. Segmental deformations of the lumbar spine in asymptomatic volunteers measured radiologically were compared with those in patients who underwent anterior interbody fusion. 

Objective. To determine the effects of anterior lumbar interbody fusion on the juxta-fused segments. 

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 spine, from maximum extension to maximum flexion, in 30 asymptomatic volunteers and 52 pain-free patients who had single-level L4-L5 or double-level L4-S1 fusion were measured and compared. 

Results. The total flexibility of the lumbar spine was decreased after a single-level fusion and further decreased after double-level fusions. The segmental deformations of the juxta-fused segments also were decreased after either a single-or double-level fusion. 

Conclusions. During normal flexion and extension of the lumbar spine, the juxta-fused segments were not deformed beyond their physiological limits after fusion. Thus, accelerated degeneration observed at a juxta-fused segment is unlikely to be attributable to hypermobility. Copyright © 1995 Lippincott-Raven Publishers.