Study design: Prospective study.
Objective: Evaluate the impact of the distal fusion level on overall spine motion in patients with adolescent idiopathic scoliosis.
Summary of background data: In the surgical treatment of adolescent idiopathic scoliosis, the impact of incorporating a single additional distal lumbar fusion level on residual spinal motion is unclear. This study uses radiographs and computerized motion capture technology to determine whether the addition of a single lumbar level in a posterior fusion construct produces a detectable alteration in spinal motion.
Methods: Twenty-three patients with adolescent idiopathic scoliosis were evaluated with standing radiographs and computerized motion analysis preoperatively and 1 year after fusion. Patients were divided into 2 groups: L1-L2 group (distal fusion ended at L1-L2) and an L3 group (distal fusion ended at L3). Cobb angle, coronal vertical alignment, sagittal vertical alignment, thoracic kyphosis, and lumbar lordosis were measured from radiographs. Three-dimensional motion data were obtained for static standing and repeated bending or twisting motions. Statistical analysis was performed with Student t test, analysis of variance, and Fisher exact methods.
Results: Both the L1-L2 and L3 groups demonstrated loss of spinal motion compared with preoperative values. The L1-L2 group showed a significant loss of rotational motion but no significant loss of motion in the sagittal and coronal planes. The L3 group demonstrated significant loss of motion in both the coronal plane and the rotational plane. When the 2 groups were compared, the L3 group showed a significant loss of coronal plane bending (18° ± 10°, P = 0.002).
Conclusion: Distal extension of a posterior spinal fusion construct to include L3 results in a significant decrease in spine motion in at least one plane. Preservation of a single lumbar segment may improve overall spine motion in the short term and may have implications for the long-term health of the unfused spine.
Level of evidence: 3.