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Surgical Outcomes Research

Thoracoscopic Multilevel Anterior Instrumented Fusion in a Goat Model

Newton, Peter O. MD*†; Lee, Steven S. MD†; Mahar, Andrew T. MS*†; Farnsworth, Christine L. MS*; Weinstein, Craig H. MD*

Study Design. A survival study in a caprine model for evaluation of a thoracoscopic anterior scoliosis instrumentation construct for fusion.

Objective. To compare the efficacy of performing multilevel anterior thoracoscopic “scoliosis” fusion with both allograft and autograft bone.

Summary of Background Data. The use of minimally invasive thoracoscopic spinal surgery has been increasing. Until recently, instrumentation methods for correcting scoliosis entirely with a minimally invasive approach have not been available. Although multilevel thoracoscopic instrumentation and fusion now is in use clinically at some centers, reports of its effectiveness in an animal model are limited.

Methods. A thoracoscopically implanted multilevel screw–rod instrumentation construct was used in a goat survival model, with fusion quality evaluated 16 weeks after surgery. Autogenous iliac crest bone graft was compared with an allogenic bone graft substitute. The quality of fusion was evaluated both radiographically and biomechanically.

Results. Thoracoscopic insertion of a multilevel screw–rod construct was demonstrated to be technically feasible. However, with regard to the quality of fusion, only 47% of the disc space “fusion ratings” with the use of autogenous iliac crest graft were considered fully fused by computed tomography scan evaluation. This compares with no ratings of full fusion in the allograft demineralized bone group and only a single rating of full disc space fusion in the control group, which received no bone graft. Torsional range of motion was the smallest in the group receiving iliac crest bone graft and the greatest in the control animals that did not undergo bone grafting.

Conclusions. The lack of complete fusion at 4 months in the autogenous iliac crest group emphasizes the importance of the discectomy and bone grafting technique. The use of demineralized bone allograft as a sole source of interbody fusion is not supported.

 

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Spine: 15 July 2003 – Volume 28 – Issue 14 – pp 1614-1619