Department of Orthopedic Surgery, Research Institute MOVE, VU University Medical Center, De Boelelaan 1117, P.O. Box 7057, 1081 HV, Amsterdam, The Netherlands.
Eur Spine J. 2012 Mar;21(3):530-6. doi: 10.1007/s00586-011-1968-2. Epub 2011 Aug 24.
Laminectomy is a standard surgical procedure for elderly patients with symptomatic degenerative lumbar stenosis. The procedure aims at decompression of the affected nerves, but it also causes a reduction of spinal shear strength and shear stiffness. The magnitude of this reduction and the influence of bone mineral density (BMD) and disc degeneration are unknown. We studied the influence of laminectomy, BMD, and disc degeneration on shear force to failure (SFF) and shear stiffness (SS).
Ten human cadaveric lumbar spines were obtained (mean age 72.1 years, range 53-89 years). Laminectomy was performed either on L2 or L4, equally divided within the group of ten spines. BMD was assessed by dual X-ray absorptiometry (DXA). Low BMD was defined as a BMD value below the median. Intervertebral discs were assessed for degeneration by MRI (Pfirrmann) and scaled in mild and severe degeneration groups. Motion segments L2-L3 and L4-L5 were isolated from each spine. SFF and SS were measured, while loading simultaneously with 1,600 N axial compression.
Low BMD had a significant negative effect on SFF. In addition, a significant interaction between low BMD and laminectomy was found. In the high BMD group, SFF was 2,482 N (range 1,678-3,284) and decreased to 1,371 N (range 940-1,886) after laminectomy. In the low BMD group, SFF was 1,339 N (range 909-1,628) and decreased to 761 N (range 561-1,221). Disc degeneration did not affect SFF, nor did it interact with laminectomy. Neither low BMD nor the interaction of low BMD and laminectomy did affect SS. Degeneration and its interaction with laminectomy did not significantly affect SS.
In conclusion, low BMD significantly decreased SFF before and after lumbar laminectomy. Therefore, DXA assessment may be an important asset to preoperative screening. Lumbar disc degeneration did not affect shear properties of lumbar segments before or after laminectomy.
对于有症状的退行性腰椎管狭窄的老年患者，椎板切除术是一种标准的手术治疗方法。该手术旨在对受影响的神经进行减压，但也会导致脊柱剪切强度和剪切刚度降低。这种降低的程度以及骨密度（BMD）和椎间盘退变的影响尚不清楚。我们研究了椎板切除术、BMD 和椎间盘退变对失效剪切力（SFF）和剪切刚度（SS）的影响。
我们获得了 10 个人体腰椎尸体标本（平均年龄 72.1 岁，范围 53-89 岁）。10 个脊柱标本中，一半在 L2 进行椎板切除术，另一半在 L4 进行。通过双能 X 射线吸收法（DXA）评估骨密度。低 BMD 定义为 BMD 值低于中位数。通过 MRI（Pfirrmann）评估椎间盘退变，并分为轻度和重度退变组。从每个脊柱上分离出 L2-L3 和 L4-L5 的运动节段。在同时施加 1600N 轴向压缩的情况下，测量 SFF 和 SS。
低 BMD 对 SFF 有显著的负面影响。此外，还发现低 BMD 和椎板切除术之间存在显著的相互作用。在高 BMD 组中，SFF 为 2482N（范围 1678-3284），椎板切除术后降至 1371N（范围 940-1886）。在低 BMD 组中，SFF 为 1339N（范围 909-1628），椎板切除术后降至 761N（范围 561-1221）。椎间盘退变既不影响 SFF，也不与椎板切除术相互作用。低 BMD 或低 BMD 与椎板切除术的相互作用均不影响 SS。退变及其与椎板切除术的相互作用并未显著影响 SS。
总之，低 BMD 显著降低了腰椎椎板切除术前和术后的 SFF。因此，DXA 评估可能是术前筛选的重要依据。腰椎间盘退变既不影响椎板切除术前也不影响椎板切除术后脊柱节段的剪切性能。
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