Abstract
Introduction: Wide laminectomy has been the accepted treatment of choice for stenosis in the lumbar spine. Recently, bilateral laminotomy has been proposed as an alternative decompressive technique for spinal canal stenosis. There have been no biomechanical studies to determine the in vitro difference in stability between these techniques.
Objective: To determine the in vitro difference in stability in a functional spinal unit (FSU) following bilateral laminotomy, and compare it to the instability resulting from laminectomy.
Methods: Six fresh human cadaver lumbar spines were injured sequentially at the L4-5 level: bilateral laminotomy and laminectomy. The normal and injured spines were subjected to flexion, extension, lateral bending and torsional moments. The three-dimensional motion behaviour of each spine before and after the two injuries was recorded using a magnetic motion sensor. The data from all five spines was pooled for statistical analysis.
Results: With flexion and extension loading, bilateral laminotomy induced significantly less sagittal angulation and translation in the FSU than did laminectomy. Significant increases in coronal translation occurred with laminectomy in spines subjected to lateral bending loads. There were no significant differences between the two techniques in coronal plane angulation with lateral bending loads and torsional loads.
Discussion: Adequate exposure of the lateral recesses requires limited medial facetectomy with both laminotomy and laminectomy. With laminotomy, the lamina and posterior ligamentous structures are preserved. This is aimed at decreasing the potential late development of spinal instability associated with laminectomy. The increase in motion seen with laminectomy in sagittal angulation / translation, and coronal translation in this in vitro model, may represent clinical instability, and may be responsible for continued symptomatology in these patients. Preservation of the lamina, spinous processes, and the posterior ligamentous structures significantly enhances the biomechanical stability of the FSU.
The abstracts were prepared by Dr P Dolan. Correspondence should be addressed to him at the British Orthopaedic Association, Royal College of Surgeons, 35-43 Lincoln’s Inn Fields, London WC2A 3PN.
