Anterior Lumbar Stabilization

Published on 09/05/2015 by admin

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Last modified 09/05/2015

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Chapter 41 Anterior Lumbar Stabilization

INTRODUCTION

In the anterior reconstruction of the lumbar spine, there are several anatomical and biomechanical features unique to the lumbar spine.1 The important points are the large size and high weight-bearing demand of the lumbar vertebral bodies; greater mobility than the thoracic spine; lordotic curvature; restricted access to the lower lumbar spine because of the pelvic ring; and functional importance of the lumbar nerve roots compared with those of the thoracic spine. Although the upper lumbar segment (L1, L2 level) is considered to be the transitional zone between the rigid thoracic spine and the mobile lumbar spine, thoracolumbar instability is not a common problem after anterior-only reconstruction or circumferential decompression and stabilization at these levels. For L5 lesions, it is impossible to apply anterior stabilization because of the pelvic ring, which may be the case even in L4 lesions. In these cases, the stabilization should be performed with the posterior approach. The commonly used fixation site is the lateral surface of the vertebral body in the lumbar spine because of the midline location of the great vessels.

TECHNIQUE

PSOAS MUSCLE DISSECTION

The stabilization procedure is carried out after retroperitoneal exposure of the lateral surface of the vertebral bodies. When the anterior instrument is implanted on the lateral surface of the lumbar vertebral body, the psoas muscle should be dissected. The psoas muscle covers the lateral surface of the vertebral body from the base of the transverse process to the lateral margin of the anterior longitudinal ligament (Fig. 41-1). The anatomical safe zone is the middle one-third of the width of the psoas muscle belly. In the anterior margin, the sympathetic chain lies underneath the psoas muscle and the exiting nerve roots are around the foramen. There are two ways to dissect the psoas muscle from the bony surface. First, the dissection starts from the anterior margin of the psoas muscle and continues to the foraminal side (see Fig. 41-1). Second, the dissection starts from the midline of the psoas muscle belly and retracted mediolateral side. During dissection of the psoas muscle, it is important not to injure the underlying extraforaminal nerve roots.

CORPECTOMY

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