Abstract
BackgroundThe association of lumbar spine instability between laminectomy and laminotomy has been clinically studied, but the corresponding in vitro biomechanical studies have not been reported. We investigated the hypothesis that the integrity of the posterior complex (spinous process-interspinous ligament-spinous process) plays an important role on the postoperative spinal stability in decompressive surgery.MethodsEight porcine lumbar spine specimens were studied. Each specimen was tested intact and after two decompression procedures. All posterior components were preserved in Group A (Intact). In Group B (Bilateral laminotomy), the inferior margin of L4 lamina and superior margin of L5 lamina were removed, but the L4–L5 supraspinous ligament was preserved. Fenestrations were made on both sides. In Group C (Laminectomy) the lamina and spinous processes of lower L4 and upper L5 were removed. Ligamentum flavum and supraspinous ligament of L4–L5 were removed. A hydraulic testing machine was used to generate an increasing moment up to 8400 N-mm in flexion and extension. Intervertebral displacement at decompressive level L4–L5 was measured by extensometerResultsThe results indicated that, under extension motion, intervertebral displacement between the specimen in intact form and at two different decompression levels did not significantly differ (P > 0.05). However, under flexion motion, intervertebral displacement of the laminectomy specimens at decompression level L4–L5 was statistically greater than in intact or bilateral laminotomy specimens (P = 0.0000963 and P = 0.000418, respectively). No difference was found between intact and bilateral laminotomy groups. (P > 0.05).ConclusionWe concluded that a lumbar spine with posterior complex integrity is less likely to develop segment instability than a lumbar spine with a destroyed anchoring point for supraspinous ligament.
Highlights
The association of lumbar spine instability between laminectomy and laminotomy has been clinically studied, but the corresponding in vitro biomechanical studies have not been reported
Each of the eight porcine lumbar spines was tested in intact form, after bilateral laminotomy and after laminectomy at different levels of decompressive surgery (Fig. 1 and Fig. 2)
The results suggest that bilateral laminotomy is generally effective in lumbar spine decompressive surgery
Summary
The association of lumbar spine instability between laminectomy and laminotomy has been clinically studied, but the corresponding in vitro biomechanical studies have not been reported. Various studies have proposed technical modifications of the standard laminectomy procedure, applicable to the cervical, thoracic and lumbar spines [5,6,7]. These techniques have evolved from attempts to adequately decompress spinal stenosis in patients while preserving spinal integrity. Clinical studies indicate that neurologic compression occurs most frequently at the level of the interlaminar window This window has been used to afford adequate decompression by excision of ligamentum flavum, resection of laminar margins and trumpeted "undercutting" techniques of partial facetectomy while maintaining residual lamina, pars and facet joint stability. Decompressing the ipsilateral foramen and lateral recess requires further facet joint resection, which compromises spinal stability
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