腰椎后路减压术后预后及稳定性的相关因素分析

[目的]探讨腰椎后路手术不同程度地切除后部结构与术后脊柱稳定性的关系,以及在腰椎后部结构切除后的机体反应和机械稳定性改变,分析机体对自身稳定性损伤修复的能力及机制.[方法]对腰椎术后稳定性表现进行临床回顾分析.[结果]对临床病例的总结显示腰椎板切除减压手术对退行性腰椎管狭窄症效果满意,通过对手术改善率低者的影像学检查,未见手术节段椎间不稳定发生;腰椎板切除减压手术临床结果与术前JOA评分、年龄、手术涉及的小关节数、椎板减压节段数没有相关性;术后功能恢复率与术后时间长短及病史长短有统计学负相关性.[结论]在术前无失稳存在时不同范围和程度的腰椎后部结构切除均可获得满意的临床效果,并未造成随访时限内的腰椎不稳定的发生,提示机体对损伤具有修复代偿的能力.     

寰椎齿状突人工关节置换的生物力学研究

[目的]测试寰椎齿状突人工关节置换后寰枢椎的稳定性和功能.[方法]将10例新鲜的成人头颈部标本制备成生物力学实验模型,对每一标本分别测定完整状态、减压术后、人工关节置换术后以及疲劳实验后4种状态下的运动范围、中性区和刚度.[结果]减压术后,在前屈、后伸、左右侧屈及左右旋转等方向较完整状态运动范围、中性区明显增大(P＜0.05).而刚度则显著减弱(P＜0.05);人工关节置换术后及疲劳实验后与减压术后相比前屈、后伸、左右侧屈及左右旋转的运动范围和中性区明显减小(P＜0.05),刚度显著增强(P＜0.05);人工关节置换术后及疲劳实验后与完整状态相比前屈、后伸、左右侧屈的运动范围和中性区明显减小(P＜0.05),刚度显著增强(P＜0.05),与完整状态相比左右旋转的运动范围无显著差异(P＞0.05),中性区增大(P＜0.05),刚度减小(P＜0.05).[结论]实验证实作者设计、制造出的人工寰椎齿状突关节在形态学和动力学两方面进行仿生,具有置放稳定、操作简便、不易造成副损伤以及低磨损等特点,对以往齿状突切除、脊髓减压后需要使用前路或(和)后路寰枢椎融合的患者,提供了另一种术式的选择.     

后部结构分级切除对下腰椎稳定性影响的实验研究

目的 探讨小尾寒羊L5,6后部结构分级切除对腰椎稳定性的影响.方法 选取14只小尾寒羊,截取L4～L7脊柱标本.实验前摄正、侧位X线片以排除脊柱疾患,CT定位关节突关节分级切除.对L5,6节段后部结构依次分级切除如下:Ⅰ正常→Ⅱ全椎板减压→Ⅲ左侧关节突切除1/2→Ⅳ左侧关节突全部切除→Ⅴ右侧关节突切除1/2→Ⅵ右侧关节突全部切除→结束.利用Instron 8874液压伺服动态生物力学测试系统依次测试标本六个自由度上椎间运动的变化,计算平均刚度.利用SPSS 11.5行单因素方差分析,检验水准α值取0.05.结果 全椎板减压和左侧关节突的全部切除对于前屈或后伸的稳定性影响不大;当再切除右侧关节突1/2时,前屈或后伸的平均刚度比正常时分别下降32.33%和30.83%.腰椎后路结构的切除对于腰椎侧弯的稳定性影响不大.全椎板减压即出现左和右扭转失稳,平均刚度分别比正常时下降26.13%和26.20%,关节突关节与扭转的稳定性亦具有重要意义,特别是对对侧扭转的稳定性.结论 行腰椎后路手术时,在保证手术视野的情况下,力求做到微创,尽量保留后部结构的完整性.     

后部结构对腰椎前屈／后伸稳定性的影响

目的：探讨小尾寒羊L5／6后部结构分级切除对腰椎前屈／后伸稳定性的影响。方法：利用改良的定位移生物力学测试方法,对L5／L6后部结构依次分级切除：Ⅰ正常→Ⅱ全椎板减压→Ⅲ左侧关节突切除1／2→Ⅳ左侧关节突全部切除→Ⅴ右侧关节突切除1／2→Ⅵ右侧关节突全部切除,Instron8874试验机依次测试标本前屈／后伸椎间运动的变化。结果：全椎板减压和左侧关节突的全部切除对于前屈／后伸的稳定性影响不大（P〉0．05）;当再切除右侧关节突1／2时,稳定性影响明显（P〈0.05）。结论：在保证手术视野的情况下,腰椎后路手术力求做到微创,尽量保留后部结构的完整性。     

保留脊柱后韧带复合结构多椎板切除的临床应用

本文报道196例腰椎管狭窄症患者采用保留脊柱后韧带复合结构多椎板切除减压术。男121例,女75例。并通过生物力学方法评价其对腰椎稳定性的影响。实验结果表明:(1)多椎板切除减压术明显破坏腰椎的稳定性(p<0.01)。(2)保留脊柱后韧带复合结构将明显提高腰椎的抗弯强度(p<0.01和降低腰椎术后屈伸活动度(p<0.01)。(3)脊柱后韧带复合结构对维持腰椎的稳定,减轻术后腰椎过度屈曲和后凸畸形具有重要作用。本文还简介了该手术基本方法和临床效果,认为手术简单易行,安全有效,符合尽量减少后柱破坏的手术原则。     

计算机辅助设计腰椎融合器的生物力学评价

目的探讨新型计算机辅助设计腰椎椎间融合器和2种常用的椎间融合器在PLIF附加椎弓根螺钉术后的生物力学稳定性。方法选用经过检查无损伤(肿瘤、外伤、手术)的10具成人新鲜冰冻尸体脊柱标本(L4~S1)进行实验分组:①完整标本组;②行腰椎后路L4,5全椎板切除减压合并椎间隙单纯植骨组;③行腰椎后路L4,5全椎板切除减压、椎间隙单纯植骨合并L4,5椎弓根螺钉组;④行腰椎后路L4,5全椎板切除减压、椎间隙植骨CAPSTONE融合器植入合并L4,5椎弓根螺钉组;⑤行腰椎后路L4,5全椎板切除减压、椎间隙植骨OIC融合器植入合并L4,5椎弓根螺钉组;⑥行腰椎后路L4,5全椎板切除减压、椎间隙植骨CAD-CAGE融合器植入合并L4,5椎弓根螺钉组。各组随机顺序进行7项非损伤性加载,运用数字相关法对不同处理组术后腰椎即刻生物力学指标进行测定,并运用统计学方法分析。结果腰椎后路L4,5全椎板切除术后,与完整标本组和其他固定组相比,在屈曲、左右侧弯、左右旋转6个方向的动态加载下角位移和运动范围显著增大(P<0.01);行PLIF附加椎弓根螺钉固定术后各组,与完整标本和不附加椎弓根螺钉固定组相比,6个方向的动态加载下角位移和运动范围显著减小(P<0.01);使用椎弓根螺钉各个固定组之间比较,单纯椎间隙植骨组仅在屈曲方向的动态加载下角位移和运动范围显著增大(P<0.01),其他各个方向的动态加载下角位移和运动范围差异无统计学意义(P>0.05)。使用椎间融合器的3组之间比较,6个方向的动态加载下角位移和运动范围差异无统计学意义(P>0.05)。结论①腰椎全椎板切除后,腰椎稳定性显著降低。②附加椎弓根螺钉固定可以得到比完整状态更好的腰椎稳定性。③PLIF术式中,采用椎间融合器比不采用融合器,能够使腰椎得到更可靠的稳定性。④融合器外形设计的区别对稳定性影响甚微。     

单侧小关节分级切除对同节段腰椎间孔形态影响的实验研究

[目的]了解单侧腰椎小关节分级切除对不同运动状态下同节段腰椎间孔形态变化的影响机制.[方法]取8例新鲜尸体脊柱腰段完整标本,依次进行分级切除L4j的后部结构,造成5种减压情况,依次测量加载前后各组L4、5椎间孔高度及最大、最小宽度值并比较分析.[结果]①完整组标本负载荷状态下,L4、5椎间孔各孔径均减小而且变化存在显著性差异;以扭力矩加载时,L4、5椎间孔高度及最大、最小宽度分别在中立位、后伸、同侧弯状态下三者均显著减小,在前屈、对侧弯状态下明显增大;②在中立位、后伸位和同侧弯体位负载时,当腰椎单侧小关节切除大于1/2后,L4、5椎间孔孔径均有显著性差异.[结论]在外科操作进行后部结构切除手术时,尤其是小关节切除手术应严格掌握指征.     

跳跃式椎板切除术和多节段椎板切除术的生物力学评价

跳跃式椎板切除术和多节段椎板切除术的生物力学评价王秋根１王建华１年申生１丁祖泉２杨国标２卢太生１李文军１从生物力学角度探讨多节段椎板切除与跳跃式椎板切除对脊柱稳定性影响的差异。材料和方法取急性颅脑外伤致死的新鲜成年男性完整腰椎离体标本７具（无脊柱疾病...     

Wallis棘突间固定结合改良小关节植骨术后的即刻稳定性生物力学评估

目的研究Wallis动态固定系统结合改良小关节植骨术的术后即刻稳定性,为临床应用提供生物力学依据。方法取7节新鲜小牛腰椎椎间节段,采用自身前后对照,标本完整状态设为完整组,标本单纯安装Wallis为单纯Wallis组,在Wallis组的基础上进行改良双侧小关节植骨术为Wallis植骨组。分别测试在前屈、后伸、左右侧屈、左右选转6种状态下的活动度(ROM),中性区(NZ)。结果在屈伸状态下Wallis组和Wallis植骨组的运动范围与中性区均较完整组减少,差异有统计学意义(P0.05)。屈伸状态下,Wallis组与Wallis植骨组ROM没有统计学意义。中性区Wallis植骨组较Wallis组增大(P0.05),与完整组无统计学差异。在侧屈和旋转状态下所有组间运动范围与中性区均无统计学差异。结论 Wallis结合改良小关节植骨术后的屈伸即刻稳定性增加,但是较单纯Wallis固定减少,患者术后应该佩戴支具。     

胸腰椎骨折伤椎短椎弓根钉固定的生物力学研究

[目的]通过生物力学测试对胸腰椎爆裂性骨折伤椎单侧短椎弓根钉固定的稳定性及刚度进行评价.[方法]取18具新鲜小牛胸腰段(T11 ～L3)标本,制作成胸腰椎爆裂性骨折模型,测试跨节段4枚椎弓根钉固定(4钉组)、伤椎单侧短椎弓根钉固定(5钉组)、伤椎双侧椎弓根钉固定(6钉组)标本模型的轴向压缩刚度及三维6个方向的运动范围(ROM).[结果]4钉组、5钉组、6钉组三种固定方式,均能提高骨折模型的稳定性及刚度;5钉组、6钉组模型刚度均明显高于4钉组,差异有统计学意义(P＜0.05),5钉组、6钉组模型在屈伸、侧弯、旋转6个方向的运动范围(ROM)均明显低于4钉组,差异有统计学意义(P＜0.05);而5钉组与6钉组模型之间的刚度比较差异无统计学意义(P＞0.05),5钉组与6钉组模型在屈伸、侧弯、旋转6个方向的运动范围(ROM)的比较差异无统计学意义(P＞0.05).[结论]对于胸腰椎爆裂性骨折,伤椎置钉固定能明显提高脊柱的刚度及稳定性,经伤椎单侧短椎弓根钉固定与伤椎双侧椎弓根钉固定对脊柱刚度及稳定性的影响无明显差异.     

Biomechanical analysis of posterior instrumentation systems after decompressive laminectomy. An unstable calf-spine model

Mechanical non-destructive cyclical testing in rotation, axial compression, and flexion were performed on twelve fresh spinal segments from calves. Each segment contained five motion segments. Each spine was destabilized with bilateral laminectomy and facetectomy of the fourth and fifth lumbar vertebrae, resection of the pars interarticularis of the fourth lumbar vertebra, and resection of the disc between the fourth and fifth lumbar vertebrae. Sequential stabilization of each spine was used to compare the stiffness of: (1) Harrington distraction instrumentation of five levels, (2) Luque rectangular instrumentation of five levels, (3) modified Steffee transpedicular notched-rod instrumentation of three and five levels, and (4) Cotrel-Dubousset transpedicular instrumentation of three and five levels with and without transverse approximating rods. This in vitro study of a calf-spine model led to three reproducible conclusions: (1) after laminectomy and discectomy, the instrumented spine was more unstable in rotation and flexion than when it was subjected to axial compressive loads; (2) the most rigid implant was the Cotrel-Dubousset transpedicular instrumentation of five vertebral levels (p less than 0.05); and (3) with the Steffee or the Cotrel-Dubousset transpedicular instrumentation of three vertebral levels, it was possible to restore torsional, compressive, and flexural rigidity to the destabilized spine of the calf. Furthermore, transpedicular fixation of only three vertebral levels provided more in vitro stability than either traditional Harrington or Luque rectangular instrumentation, which require fixation of five vertebral levels to stabilize a spine after laminectomy.     

Cervical stability after foraminotomy. A biomechanical in vitro analysis.

Laminectomy or facetectomy of the cervical spine, or both, may be needed for decompression of the spinal cord or of the nerve-roots. Acute stability of the cervical spine was tested after laminectomy and progressive staged foraminotomies in an in vitro model. Twelve cervical spines from human cadavera were used in the experiment. Biomechanical testing included the application of an axial load, the application of a flexion and extension moment, and the application of a torsional moment. Each specimen was tested intact, after laminectomy of the fifth cervical vertebra, and after progressive foraminotomy of the sixth cervical root. Foraminotomy was performed by resection of 25, 50, 75, and 100 per cent of the facet joint and capsule. Torsional stiffness decreased dramatically when more than 50 per cent of the facet had been resected. Statistically equivalent subsets were the intact specimen, laminectomy, 25 per cent facetectomy, and 50 per cent facetectomy in one subset, and 75 and 100 per cent facetectomy in the least-stiff subset. Flexion-moment testing showed that the posterior strain did not differ among three groups: the intact specimens, those that had been treated with laminectomy, and those that had been treated with a 25 per cent facetectomy. The 50 per cent facetectomy resulted in a 2.5 per cent increase in posterior strain, and the 75 or 100 per cent facetectomy, in a 25 per cent increase in posterior strain compared with the intact specimen. Segmental hypermobility of the cervical spine results if a foraminotomy involves resection of more than 50 per cent of the facet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dynamics of an Intervertebral Disc Prosthesis in Human Cadaveric Spines

Low-back pain is a common, disabling medical condition, and one of the major causes is disc degeneration. Total disc replacements are intended to treat back pain by restoring disc height and re-establishing functional motion and stability at the index level. The objective of this study was to determine the effect on range of motion (ROM) and stiffness after implantation of the ProDisc®-L device in comparison to the intact state. Twelve L5–S1 lumbar spine segments were tested in flexion/extension, lateral bending, and axial rotation with axial compressive loads of 600 N and 1,200 N. Specimens were tested in the intact state and after implantation with the ProDisc®-L device. ROM was not significantly different in the implanted spines when compared to their intact state in flexion/extension and axial rotation but increased in lateral bending. Increased compressive load did not affect ROM in flexion/extension or axial rotation but did result in decreased ROM in lateral bending and increased stiffness in both intact and implanted spine segments. The ProDisc®-L successfully restored or maintained normal spine segment motion.     

Effect of the Total Facet Arthroplasty System after complete laminectomy-facetectomy on the biomechanics of implanted and adjacent segments

Background contextLumbar fusion is traditionally used to restore stability after wide surgical decompression for spinal stenosis. The Total Facet Arthroplasty System (TFAS) is a motion-restoring implant suggested as an alternative to rigid fixation after complete facetectomy.PurposeTo investigate the effect of TFAS on the kinematics of the implanted and adjacent lumbar segments.Study designBiomechanical in vitro study.MethodsNine human lumbar spines (L1 to sacrum) were tested in flexion-extension (+8 to ?6 Nm), lateral bending (±6 Nm), and axial rotation (±5 Nm). Flexion-extension was tested under 400 N follower preload. Specimens were tested intact, after complete L3 laminectomy with L3–L4 facetectomy, after L3–L4 pedicle screw fixation, and after L3–L4 TFAS implantation. Range of motion (ROM) was assessed in all tested directions. Neutral zone and stiffness in flexion and extension were calculated to assess quality of motion.ResultsComplete laminectomy-facetectomy increased L3–L4 ROM compared with intact in flexion-extension (8.7±2.0 degrees to 12.2±3.2 degrees, p<.05) lateral bending (9.0±2.5 degrees to 12.6±3.2 degrees, p=.09), and axial rotation (3.8±2.7 degrees to 7.8±4.5 degrees p<.05). Pedicle screw fixation decreased ROM compared with intact, resulting in 1.7±0.5 degrees flexion-extension (p<.05), 3.3±1.4 degrees lateral bending (p<.05), and 1.8±0.6 degrees axial rotation (p=.09). TFAS restored intact ROM (p>.05) resulting in 7.9±2.1 degrees flexion-extension, 10.1±3.0 degrees lateral bending, and 4.7±1.6 degrees axial rotation. Fusion significantly increased the normalized ROM at all remaining lumbar segments, whereas TFAS implantation resulted in near-normal distribution of normalized ROM at the implanted and remaining lumbar segments. Flexion and extension stiffness in the high-flexibility zone decreased after facetectomy (p<.05) and increased after simulated fusion (p<.05). TFAS restored quality of motion parameters (load-displacement curves) to intact (p>.05). The quality of motion parameters for the whole lumbar spine mimicked L3–L4 segmental results.ConclusionsTFAS restored range and quality of motion at the operated segment to intact values and restored near-normal motion at the adjacent segments.     

Stability of the whole lumbar spine after multilevel fenestration and discectomy.

STUDY DESIGN: An investigation of the in vitro biomechanical effects of multilevel fenestrations and discectomies on the behavior of whole lumbar spine motion, using a material testing system (Instron 1341, Instron Limited, High Wycombe, England) and Elite three-dimensional motion analysis system (BTS, Milano, Italy). OBJECTIVES: To investigate the effects of multilevel fenestrations and discectomies on the stability of the whole lumbar spine, including segmental stiffness and sagittal (horizontal and vertical) translation. SUMMARY OF BACKGROUND DATA: In the management of lumbar spinal stenosis, wide decompressive laminectomy with partial or total facetectomy has been the standard procedure for multilevel nerve decompression. Main complications with these procedures have been instability and chronic pain syndrome. Multilevel fenestration with undermining enlargement of the spinal canal has been selected for multilevel nerve decompression in recent years. However, the biomechanical effects of multilevel fenestration and discectomy have been controversial and difficult to validate. This study investigated the in vitro biomechanical effects of multilevel fenestrations and discectomies on motion behavior of the whole lumbar spine. METHODS: Seven fresh human specimens from L1 to sacrum were used in this study. The fenestrations and discectomies consisted of L3-L4 bilateral fenestration, L4-L5 bilateral fenestration, L5-S1 bilateral fenestration, L4-L5 discectomy, and L5-S1 discectomy. Flexion, lateral bending, and axial rotation (torsion) loading were applied. Ranges of motion were determined two-dimensionally by the Elite system with an infrared camera. The postoperation results were compared with the intact conditions. RESULTS: After multiple fenestrations, the sagittal ranges of motion at L4-L5 increased by 18% anteroposteriorly and 16% vertically under the flexion loads. At L5-S1, the motions increased by 19% and 45%, respectively. After fenestrations and discectomies, the ranges of motion in the sagittal plane increased by 28% horizontally and 71% vertically at L4-L5, and 14% and 166% at L5-S1. Motion increases were statistically significant (P < 0.05) in vertical translations. However, after the multilevel surgeries, no significant motions were found in each of the lumbar segments during lateral bending and axial rotation. CONCLUSIONS: The results demonstrate that multilevel fenestrations and discectomies affect lumbar spinal stability in flexion, but have no effect on the stability of the lumbar spine in lateral bending or axial rotation.     

Intradiscal pressure and kinematic behavior of lumbar spine after bilateral laminotomy and laminectomy.

BACKGROUND CONTEXT: Bilateral laminotomy has been proposed as an alternative to laminectomy for decompression of lumbar spinal stenosis. Preservation of the posterior midline ligaments with laminotomy is presumed to maintain spinal segment stability. There have been no previous studies that directly compare the amount of destabilization and increase in disc pressures between the two procedures. PURPOSE: To quantify spinal segmental instability caused by bilateral laminotomy and laminectomy, and to compare the central and peripheral intradiscal pressures after the two procedures. STUDY DESIGN/SETTING: Mechanical testing of the lumbar motion segments of calf spines. METHODS: Nine fresh calf spines were tested under flexion, extension, lateral bending and axial rotation, intact first, then after laminotomy and laminectomy at the level of L4-L5. Four miniature pressure transducers were implanted in the central and peripheral disc at L4-L5 to measure intradiscal pressures. Three-dimensional motion was measured with motion analysis system. RESULTS: Comparing with bilateral laminotomy, laminectomy showed significant increase in segmental motion at the surgical level in flexion (16%, p<.05), extension (14%, p<.04) and right axial rotation (23%, p<.03). In flexion, the stress at the anterior annulus increased a nonsignificant 20% after laminotomy, but significant 130% after laminectomy (p<.02). In the intact spine, the posterolateral annulus experienced the highest stress with lateral bending to the same side when compared with other loading directions. This stress remained unchanged after laminotomy but increased 9% after laminectomy (p<.06). In rotation, axial intradiscal stresses were evenly distributed and unchanged after each procedure. CONCLUSIONS: Laminectomy causes more destabilization of a spinal motion segment than laminotomy and significantly increases disc stress in the anterior annulus.     

下腰椎不同融合方法的即刻与疲劳后稳定性

目的:观察下腰椎后路不同融合方法的即刻与疲劳后稳定性。方法:9具新鲜L1~S1尸体标本分别头尾端固定,在脊柱三维运动实验机上模拟人体行屈伸、左右侧弯及旋转活动,观察L4~L5节段运动范围(ROM),随后进行各种模拟手术并安装内固定,依次测定失稳腰椎、CD内固定(CD)、CD加椎体间植骨(CD-骨块)、CD加TFC(CD-TFC)状态下L4~L5的ROM值。随后在868Mini-MTS多轴生物力学实验机上对三种术式腰椎进行1500次疲劳加载,再观察L4~L5节段的ROM。结果:①失稳腰椎与正常腰椎比较在各运动方向上ROM均明显增加;②单纯CD内固定即刻稳定性好,但疲劳后呈不稳趋势,在屈伸及左右旋转方向明显失稳;③CD-骨块、CD-TFC稳定性好,疲劳后仍能维持良好的稳定性;④CD-骨块与CD-TFC疲劳组比较在屈伸及左右侧弯时ROM无明显差异,但CD-TFC在抗旋转方向优于CD-骨块组。结论:单纯后路短节段CD内固定和/或椎体间植骨融合均能提供良好的稳定性,但单纯后路短节段CD内固定抗疲劳性差,辅以椎间支撑(植骨或TFC)可有效提高抗疲劳稳定性。     

Biomechanics of healing of posterior cervical spinal injuries in a canine model

The authors performed an in vivo experiment in a canine model to study the natural history of spinal stability as a function of healing time post-injury. Three injuries, in addition to sham, were investigated: 1) transection of supra- and interspinous ligaments at C4-C5; 2) laminectomy at C4; and 3) bilateral facetectomy at C4-C5. Standardized functional flexion/extension stereo-radiographs of the cervical spine were obtained before injury and at 1, 3, 6, 9, 12, and 24 weeks postinjury. The authors found decreased ranges of motion (ROM) at the C4-C5 level for all injuries, including the sham. The decreases, in general, seemed to be in direct proportion to the severity of the injury. When the ROM were normalized to that of the sham at each time point, the relative ROM at C4-C5 increased for Injury 1, remained the same for Injury 2, and decreased for Injury 3. The relative ROM remained the same or increased at C3-C4, and increased at C5-6 for all injuries. It should be emphasized that care should be taken in extrapolating any data from this animal study to the human cervical spine.     

The biomechanical effects of multilevel posterior foraminotomy and foraminotomy with double-door laminoplasty

The aim of this study is to evaluate the biomechanical effects of multilevel foraminotomy and foraminotomy with double-door laminoplasty compared with foraminotomy with laminectomy. Using fresh human cadaveric specimens (C2-T1), sequential injuries were created in the following order: intact, bilateral foraminotomies (C3-C4, C4-C5, C5-C6), laminoplasty (C3-C6) using hydroxyapatite spacer, removal of the spacers, and laminectomy. Changes in the rotations of each vertebra in each injury status were measured in six loading modes: flexion, extension, right and left lateral bending, and right and left axial rotation. Foraminotomy alone and following laminoplasty showed no significant differences in motion compared with intact except in axial rotation. After removal of the spacers and following laminectomy, the motion increased significantly in flexion and axial rotation. The ranges of initial slack showed similar trends when compared with the results at maximum load. Clinical implications of these observations are presented.