Wednesday, October 30, 2001 3:58–4:41 pm Concurrent Session 1A: Complex Cervical Reconstruction: 3:58 The effect of posterior cervical distraction on foraminal dimensions using a screw-rod system

Abstract

Purpose of study: Cervical spondylotic radiculopathy is a common degenerative problem manifesting as neck and arm pain. The pathogenesis of spondylotic radiculopathy often relates to foraminal narrowing resulting from uncovertebral and facet joint hypertrophy as well as disc height collapse. The surgical management of foraminal stenosis includes anterior and posterior options. An anterior cervical discectomy with interbody fusion allows for restoration of disc height, and a posterior laminotomy and foraminotomy allows for direct nerve root exposure and decompression. There are limitations with either approach, including the inability to perform complete decompression. The advent of new posterior cervical lateral mass screw-rod systems brings into question the possible role of forminal instrumented distraction to manage nerve root compression. The purpose of this study is to assess the effect of posterior instrumented distraction on foraminal dimensions.Methods used: Six human cadaveric cervical spines were obtained. A posterior midline exposure was performed with care not to disrupt the associated intersegmental ligamentous structures. Unilateral screw-rod fixation was placed in the lateral mass at C5 and C6 and pedicle fixation at C7 (Summit cervical screws, Johnson and Johnson/Depuy/Acromed). Computed tomography scans with reconstructed images were obtained initially and following 2 mm, 4 mm, 6 mm and 8 mm of distraction. The following measurements were analyzed: foraminal area, height, disc height and segmental angulation.of findings: The findings suggest that posterior cervical distraction increases foraminal dimensions. At the C5–C6 level, distraction of 6 mm significantly increased foraminal area, although mild segmental kyphosis was noted at 4 mm of distraction. At the C6–C7 level, similar findings were noted except that significant increase in area was noted at 2 to 4 mm of distraction and no significant segmental kyphosis until 8 mm of distraction.Relationship between findings and existing knowledge: Previous studies have suggested that posterior distraction in the lumbar spine of 6 mm allows for an increase in foraminal dimensions without causing segmental kyphosis [1]. To our knowledge, this is the first study to assess the potential role of posterior cervical distraction in increasing foraminal area.Overall significance of findings: The findings suggest that limited posterior cervical distraction may increase formaminal dimensions without causing segmental kyphosis. Clinical application of this technique may be warranted to assess the outcomes of patients with spondylotic radiculopathy.Disclosures: Device or drug: lateral mass screw fixation. Status: investigational.Conflict of interest: Louis Jenis, grant research support.