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Reduction of Vertebral Blood Flow by Segmental Vessel Occlusion: An Intraoperative Study Using Laser Doppler Flowmetry

Hempfing, Axel MD*; Dreimann, Marc MD*; Krebs, Stefan MD*; Meier, Oliver MD*; Nötzli, Hubert MD†; Metz-Stavenhagen, Peter MD*

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Abstract

Study Design. During anterior spinal surgery, vertebral perfusion was assessed by laser Doppler flowmetry. Blood flow changes were assessed after unilateral ligation and contralateral compression of the segmental vessels.

Objective. To assess the influence of unilateral and bilateral segmental vessel occlusion on vertebral blood flow.

Summary of Background Data. During anterior spinal surgery, segmental vessels are frequently being ligated. The reduced blood supply to the vertebrae may impair intervertebral fusion, and the decreased spinal cord perfusion may lead to ischemic myelopathy. To our knowledge, this is the first in vivo study to investigate vertebral blood flow.

Methods. There were 10 patients who underwent anterior release for adult idiopathic scoliosis (n = 6), Scheuermann disease (n = 3), and posttraumatic kyphosis (n = 1). A high-power laser Doppler flowmeter was used to assess vertebral blood flow. Measurements were performed in 19 thoracic and 4 lumbar vertebrae (n = 23) after unilateral segmental vessel ligation and additional temporary digital compression of the contralateral vessels.

Results. Initial mean blood flow was 49.1 ± 27.6 arbitrary units, and all signals were pulsatile. The blood flow decreased by a mean of 8% after unilateral ligation of the segmental vessels. With additional compression of the contralateral vessels, the signal heights decreased significantly by 54% (mean 18.3 ± 7.8 arbitrary units, P = 0.00003), and a loss of the pulsatile pattern was observed in 75% of the vertebrae. On release of digital compression, the signal height as well as the pulsatility promptly returned.

Conclusions. Unilateral ligation of segmental vessels led only to a slight decrease of the vertebral blood flow. Future studies may show whether sparing the segmental vessels during anterior fusion enhances bone graft incorporation, thus decreasing the rate of pseudarthrosis. According to clinical data, the risk of neurologic injury through unilateral ligation is negligible. Bilateral segmental vessel occlusion markedly reduced vertebral bloodflow. Therefore, when treating patients with a higher neurologic risk or in revision cases, the surgeon should always consider sparing the segmental vessels.

© 2005 Lippincott Williams & Wilkins, Inc.

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