Postoperative Segmental Motion of the Unfused Spine Distal to the Fusion in 100 Adolescent Idiopathic Scoliosis Patients.

By London Spine

Postoperative Segmental Motion of the Unfused Spine Distal to the Fusion in 100 Adolescent Idiopathic Scoliosis Patients.

Spine (Phila Pa 1976). 2011 Oct 21;

Authors: Marks M, Newton PO, Petcharaporn M, Bastrom TP, Shah S, Betz R, Lonner B, Miyanji F

ABSTRACT: Study Design. A cross sectional study.Objective. The purpose of this study was to assess inter-vertebral segmental and cumulative motion in the distal un-fused segments of the spine in patients with Adolescent Idiopathic Scoliosis (AIS) following instrumentation as a function of the lowest instrumented level.Summary of Background Data. The implications of hyper or hypo-mobility in the un-fused segments of the spine following instrumentation are poorly understood. There is a paucity of research on changes in functional movement capabilities of the spine following thoracolumbar spinal fusion.Methods. Patients were prospectively offered inclusion into this IRB approved cross-sectional study at their routine 2, 3, 4 or 5 year post-operative visit at one of 5 participating centers. Motion was assessed by standardized radiographs acquired in maximum right, left and forwarding bending positions. The intervertebral angles were measured via digital radiographic measuring software at each level from T12 to S1. The relationship of the vertebral segmental motion for each interspace to the lowest instrumented vertebrae was evaluated with an ANOVA. The relationship between the cumulative preserved motion and each domain of the Scoliosis Research Society (SRS) questionnaire were evaluated using a Pearson’s correlation coefficient.Results: The data for 100 patients are included. The lowest instrumented vertebrae ranged from T10 to L4. In lateral bending, an association was detected between the lowest fused vertebral level and the degree of motion at the distal unfused segments. With a more distal instrumented vertebrae, there was significantly greater L2/L3, L3/L4, and L4/L5 segment motion (p = 0.002, 0.009 and 0.001 respectively). A similar trend was appreciated at L5-S1 level. In addition, the summed motion from L3 to S1 also increased with a more distal fusion (p = 0.001). Similar results were not found in forward bending. None of the domains of the SRS questionnaire correlated with the preserved L3-S1 motion.Conclusion: In a group of post-operative adolescent idiopathic scoliosis patients, evaluation of the distal unfused intervertebral motion showed that preservation of vertebral motion segments allowed greater distribution of functional motion across more levels. With each distal fusion level, motion was significantly increased at the L2/L3, L3/L4, and L4/L5 segmental levels in lateral bending. The relationship between the increased motion and subsequent disc degeneration with a more distal fusion is unknown, but suspected.

PMID: 22024909 [PubMed – as supplied by publisher]