颈椎终板抗压强度分布规律的生物力学研究

[目的]研究颈椎终板不同位点抗压强度及其分布规律。[方法]选用5具成年男性新鲜颈椎标本(C3～7),共25个椎体50个终板。对终板平面49个测试点用直径1.5 mm的平底压头以12 mm/min的速度进行连续压缩加载试验,获得最大压缩力,进行统计分析。[结果](1)抗压强度自C3～7逐渐减小(P﹤0.05);(2)下终板抗压强度大于上终板(P=0.000);(3)椎间隙相邻面上一椎体下终板的抗压强度大于下一椎体上终板抗压强度(P<0.05);(4)随着压力点逐渐外移,抗压强度逐渐增大(P﹤0.05);(5)处于不同角度的压力点,其抗压强度存在差异(P=0.029);(6)终板后部强于前部(P=0.003)。上终板后部抗压强度大于前部(P=0.000)。[结论]颈椎终板抗压强度自C3～7逐渐减小,下终板强于上终板,外周大于中央,后部强于前部。椎间隙相邻面上一椎体下终板的抗压强度大于下一椎体上终板抗压强度。     

青少年胸12腰1段椎体楔形变在下腰椎间盘退变发病中的意义

目的探讨胸12腰1段椎体楔形变在腰椎间盘退变发病中的意义,为预防青少年腰椎间盘早发退变 提供临床及理论依据。方法 随机选取腰痛青少年患者40例,均行腰椎X线和MRI检查,其中有胸12腰1段椎 体楔形变19例,无椎体楔形变21例;并根据T2加权像信号强度强弱将椎间盘分为以下三型:Ⅰ型:椎间盘呈强 信号;Ⅱ型:椎间盘呈不规则信号;Ⅲ型:椎问盘呈低信号。测量青少年腰骶角统计各型病例数,进行统计学处理。 结果 青少年胸12腰1段椎体楔形变组下腰椎间盘(L4-5、L5-S1)Ⅱ型、Ⅲ型椎间盘例数明显多于无椎体楔形变组 青少年患者,有显著性差异(P<0.01)。胸12腰1段椎体楔形变患者较无楔形变患者腰骶角明显增大,具有显著性 差异(P<0.01)。结论胸12腰1段椎体楔形变是青少年下腰椎间盘早发退变的重要诱因,防止胸12腰1段椎体楔 形变,是预防、减缓青少年腰椎间盘突出症发病的重要措施。     

L5新型自稳定人工椎体生物力学性能的有限元分析

目的:采用有限元分析评估L5椎体次全切术后置入新型自稳定人工椎体的力学性能以及对周围组织的影响,为腰骶段脊柱结核等疾病的治疗提供新的选择。方法:提取1名健康志愿者腰骶段CT薄层扫描数据进行三维重建,构建腰骶段(L3-S1)脊柱生理组有限元模型并进行有效性验证。将L5椎体及邻近椎间盘切除后,分别置入新型自稳定人工椎体和钛笼联合侧前方钉棒固定,构建新型假体组和钛笼组有限元模型。对所有模型的S1椎体下表面进行全部自由度约束,在L3椎体上表面给予400N的轴向载荷模拟生理压缩,然后再在L3椎体上表面施加8Nm的弯矩载荷,模拟腰椎前屈、背伸、左右侧弯及左右扭转六种运动,统计分析在不同运动方向上三组模型L4～S1的活动度及L4下终板和S1上终板的最大Von mise应力。结果:新型假体组和钛笼组L4～S1在前屈、背伸、侧弯、扭转方向上的活动度分别为0.38°～0.56°与0.53°～1.41°,较生理组(4.48°～10.12°)同部位活动动度明显减小。新型假体组和钛笼组L4下终板与S1上终板在前屈、背伸、左右侧弯、左右扭转方向上的最大Von Mises应力较生理组均明显增大,新型假体组在上述方向上终板的最大Von Mises应力较钛笼组明显减小。结论:自稳定人工椎体可以较好地重建手术部位的即刻稳定性,有效降低手术部位邻近终板的局部应力,理论上可以降低术后假体的下沉率,但其长期稳定性、抗疲劳性等力学性能尚需进一步研究。     

腰骶椎终板生物力学特性的实验研究

目的:研究腰骶椎终板不同位点的生物力学特性及其分布规律。方法:选用成人新鲜尸体腰骶椎标本(L1～S1)5具,共30个椎体55个终板,应用电子万能实验机(型号CSS-2205)对终板平面49个测试点用直径1.5mm的平底压头以12mm/min的速度进行连续压缩加载实验,记录最大压缩力,并对数据进行统计分析。结果:(1)L1～S1上终板最大压缩力从68.81±8.12N增加至120.41±34.33N,各节段间差异有显著性(P<0.05);L1～L4下终板最大压缩力从78.66±5.57N增加至120.44±29.27,L5降为106.65±16.10N,各节段间差异有显著性(P<0.05)。(2)L1～S1上终板中央至外周最大压缩力从65.02±6.40N增加至110.61±10.63N,下终板中央至外周最大压缩力从68.09±9.43N增加至162.69±16.46N,差异有显著性(P<0.05);上终板前侧最大压缩力为87.30±6.42N,后侧为89.25±14.30N,下终板前侧最大压缩力107.63±4.84N,后侧最大压缩力109.82±18.66N,差异均无显著性(P>0.05)。(3)L3/4、L4/5上下终板的最大压缩力的差异均有显著性(P<0.05),余间隙差异无显著性。结论:L1～S1上终板强度逐渐增大;L1～L4下终板强度逐渐增大,L4～L5减小;腰骶椎上、下终板强度从中央至外周逐渐增大,前、后侧无差异;L3/4、L4/5间隙上位椎体下终板强度大于下位椎体上终板。     

少儿脊柱结核的临床特点分析

目的:总结少儿脊柱结核的临床特点,为其诊断和治疗提供参考。方法:对2006年1月~2012年12月我院收治的112例少年儿童脊柱结核患者归纳分析其首诊原因、病程、受累节段、受累椎体数、后凸Cobb角、瘫痪情况,并分析病程、受累椎体数和后凸Cobb角之间的相关性,同时根据年龄将患者分成婴幼儿(0~3岁)、学龄前儿童(4~6岁)、学龄儿童(7~12岁)、少年(13~17岁)四组并进行比较。将脊柱分为脊柱上段(颈段、颈胸段、胸段)和脊柱下段(胸腰段、腰段、腰骶段和骶段)并对其所占的比例进行比较。根据脊髓神经功能将患者分为瘫痪组和非瘫痪组,比较两组的病程、受累椎体数和后凸Cobb角。根据后凸Cobb角,以30°为界分为两组,比较其瘫痪发生率。结果:少儿脊柱结核最常见首诊原因为疼痛,病程平均5.3±10.9个月(1.5~72个月),受累椎体数平均2.9±1.0个(1~6个),累及胸椎最为常见。后凸Cobb角平均15.7°±17.0°(0~90.5°),后凸Cobb角、受累椎体数、病程之间有相关性(r为0.384~0.666,P0.05)。瘫痪组的Cobb角角度、受累椎体数和病程均显著大于非瘫痪组(P0.05);Cobb角≥30°组发生瘫痪的比率(11/18,61.1%)明显高于Cobb角30°组(12/70,17.1%)。比较四个年龄组的患者,疼痛和瘫痪在首诊原因中所占的比率具有显著性差异(X~2=32.695,P0.05);瘫痪发生率具有显著性差异,婴幼儿组(8/19,42.1%)和学龄前儿童组(8/31,25.8%)发生瘫痪的比率明显高于学龄儿童组(4/39,10.3%)和少年组(3/23,13.0%)。四个年龄组患者的病程、脊柱上段和脊柱下段的发病率、受累椎体数、后凸Cobb角无显著性差异(P0.05)。结论:少儿脊柱结核以疼痛首诊和病变累及胸椎最为常见,其后凸Cobb角、受累椎体数和病程之间具有相关性。少儿脊柱结核中瘫痪患者的后凸Cobb角、受累椎体数和病程均显著大于非瘫痪患者。幼儿和学龄前儿童以及后凸Cobb角≥30°者发生瘫痪的几率较高。     

胸腰椎爆裂骨折三种后路内固定方法的稳定性生物力学研究

[目的]比较长节段固定术、短节段固定术和短节段结合椎体成形固定术治疗胸腰椎爆裂骨折的稳定性。[方法]收集6具新鲜尸体的脊柱(T9～L5)标本,对每一具标本依次按完整状态、骨折状态、长节段固定、短节段固定和短节段结合椎体成形的顺序进行测试,计算其在屈曲、背伸、左右侧弯和左右旋转6个方向的运动范围,比较各组间差异。[结果]骨折后脊柱在6个方向上的运动范围均增加(P<0.05);各内固定组的运动范围均小于完整组(P<0.05);长节段固定和短节段结合椎体成形固定的运动范围小于单纯短节段固定组(P<0.05);短节段结合椎体成形固定在屈曲和左右侧屈方向上的运动范围与长节段固定无差别(P>0.05),而在背伸和左右旋转方向上的运动范围短节段结合椎体成形固定则大于长节段固定(P<0.05)。[结论]通过延长固定节段与联合椎体成形均能够增加短节段固定的稳定性,在屈曲和左右侧屈方向上短节段联合椎体成形已经能够达到长节段固定所能够达到的稳定性。     

脊柱颈胸段前路内固定手术相关的影像学测量及其临床意义

目的:通过影像学方法测量脊柱颈胸段前路内固定手术相关的重要参数,为脊柱颈胸段前路手术术前计划的制定以及钢板螺钉内固定物的设计提供参考。方法:自2012年6月至11月,随机选取120例正常成人颈椎MRI正中矢状面影像,男58例,女62例;年龄20～78岁,平均(48.3±13.7)岁。利用PACS系统工作站自带的测量工具,分别测量各个椎体的前、中、后高度和上、中、下矢状径以及各个不同节段的前高度和Cobb角。结果:脊柱颈胸段椎体从头侧向尾侧,前、中、后高度以及上、中、下矢状径逐渐增大(P<0.01)。对单个椎体而言,后高度>前高度>中高度(P<0.01),下矢状径>上矢状径>中矢状径(P<0.01),上位椎体的下矢状径与下位椎体的上矢状径数值较接近。男性受试者脊柱颈胸段Cobb角为(7.61±3.85)°,女性受试者脊柱颈胸段Cobb角为(5.58±2.59)°。结论:在行脊柱颈胸段前路内固定时,建议上位椎体进钉点在椎体中下1/3,螺钉可稍向头侧倾斜,下位椎体的进钉点在椎体的中上1/3,螺钉可稍向尾侧倾斜,并可根据正常成人的Cobb角对钢板进行预弯。     

脊柱外周型原始神经外胚层肿瘤影像学表现(7例报告)

目的观察脊柱外周型原始神经外胚层肿瘤(pPNET)的影像学表现。方法回顾性分析7例经病理证实的脊柱pPNET患者的影像学资料。结果 7例脊柱pPNET病例中,男性4例,女性3例。病变位于颈段(C2~7)1例,颈胸段(C7~T2)1例,胸段(T10~12)1例,腰段(L3~4、L4~5)2例,腰骶段(L1~S2)1例,骶段(S1~4)1例;其中,髓外硬膜内1例,硬膜外6例。MR(n=7)和CT(n=4)检查表现为硬膜内或硬膜外肿块,信号/密度不均,T1WI为等或稍低信号,T2WI为稍高信号,CT为等密度,增强扫描呈不同程度不均匀强化。肿瘤位于髓外硬膜内者可伴有多发蛛网膜下腔转移,硬膜外pPNET肿瘤的主体部分多位于椎骨或椎旁组织,肿块椎管内部分累及多个椎体平面,并通过椎间孔、骶孔与椎旁部分沟通。结论脊柱pPNET可表现为髓外硬膜内或硬膜外肿瘤,确诊依赖病理及免疫组化检查。     

脊柱颈胸段螺钉固定技术的研究现状

颈胸段(cervicothoracic junction,CTJ)主要是指C6～T2脊柱节段或包括其邻近的脊柱节段.创伤、肿瘤、结核等原因导致的椎体破坏以及广泛椎板切除造成的颈胸段脊柱不稳,加上该区域解剖及生物力学的特殊性给临床治疗带来很大挑战.     

脊柱颈胸段螺钉固定技术的研究现状

颈胸段(cervicothoracic junction,CTJ)主要是指C6～T2脊柱节段或包括其邻近的脊柱节段.创伤、肿瘤、结核等原因导致的椎体破坏以及广泛椎板切除造成的颈胸段脊柱不稳,加上该区域解剖及生物力学的特殊性给临床治疗带来很大挑战.     

Mapping the structural properties of the lumbosacral vertebral endplates

STUDY DESIGN: A biomechanical investigation using indentation tests in a human cadaveric model to seek variation in the structural properties across the lower lumbar and sacral endplates. OBJECTIVES: To determine 1) if there are regional differences in endplate strength and 2) whether any differences identified are affected by spinal level (lumbar spine vs. sacrum) or endplate (superior vs. inferior). SUMMARY OF BACKGROUND DATA: It has been postulated that some regions of the vertebral body may be stronger than others. Conclusive data, either supporting or disproving this theory, would be valuable for both spine surgeons and implant designers because one mode of failure of interbody implants is subsidence into one or both adjacent vertebrae. METHODS: Indentation tests were performed at 27 standardized test sites in 62 bony endplates of intact human vertebrae (L3-S1) using a 3-mm-diameter, hemispherical indenter with a test rate of 0.2 mm/sec to a depth of 3 mm. The failure load and stiffness at each test site were determined using the load-displacement curves. Three-way analyses of variance were used to analyze the resulting data. RESULTS: Both the failure load and stiffness varied significantly across the endplate surfaces (P < 0.0001), with posterolateral regions being stronger and stiffer than the central regions. Characteristic distributions were identified in the lumbar superior, lumbar inferior, and sacral endplates. The failure load distributions were found to differ in 1) the superior lumbar and sacral endplates (P = 0.0077), 2) the inferior lumbar and sacral endplates (P = 0.0014), and 3) the superior and inferior lumbar endplates (P < 0.0001). The sacral and inferior lumbar endplates were both found to be stronger than the superior lumbar endplates (sacrum, P = 0.054; inferior, P = 0.008) but were not themselves significantly different (P = 0.89). CONCLUSIONS: Highly significant regional strength and stiffness variations were identified in the lumbar and sacral endplates. The center of the bone, where implants are currently placed, is the weakest part of the lumbar endplates and is not the strongest region of the sacral endplate.     

颈椎终板结构的生物力学研究

目的 研究颈椎终板不同位点生物力学特性的分布规律。方法 运用人体新鲜颈椎标本66椎，对终板平面上的20个特定测试点进行压缩试验，用直径2mm的半球形压头以0.03mm/s的速度垂直终板平面下压2mm，由所得的压缩力-位移线计算最大压缩力及刚度，采用析因分析对实验数据进行统计处理。结果 （1）颈椎各节段之间最大压缩力及刚度的差异有显著性（P＜0.01)，且由上而下呈逐渐减小趋势。终板矢状方向中各点之间最大压缩力及刚度的差异有显著性（P＜0.01），且椎体后部是最大压缩力及刚度较大的区域；终板冠状方向上各点之间最大的压缩力及刚度（除下终板最大压缩力外）的差异均无显著性（P＞0.05)。（2）下颈椎相邻终板之间的最大压缩力及刚度的差异有显著性（P＜0.05），下终板的最大压缩力及刚度比上终板大。矢状方向上相邻板的最大压缩力差异有显著性（P＜0.05）。结论 颈椎上终板后都、下终板后外侧区是椎体力学强度最大的区域。在进行颈前路融合术时下颈椎较易发生塌陷，且塌陷多发生于颈椎上终板平面。     

颈椎椎间盘退变对终板结构生物力学特性的影响

目的研究颈椎椎间盘对终板结构生物力学特性的影响。方法50节颈椎标本,采用Nachemson椎间盘分级标准将标本分为4组,正常组(n=22)、Ⅰ度退变组(n=10)、Ⅱ度退变组(n=9)、Ⅲ度退变组(n=9),对每一终板平面上20个特定的测试点进行压缩实验,直径2mm的半球形压头以003mm/s的速度垂直于终板平面下压2mm,由所得的力─位移曲线计算出最大压缩力及刚度,采用单因素方差分析、析因分析、SNK检验及相关分析对实验数据进行统计学分析。结果颈椎椎间盘退变可导致颈椎终板最大压缩力及刚度的显著性减小(P<001),且存在负相关关系(分别为rs=-0429,P<0001;rs=-0244,P<0001);上终板随着椎间盘退变的加重终板平面中央承力逐渐变弱,外周承力逐渐增强,下终板的力学分布无明显改变。结论颈椎椎间盘退变是影响终板结构生物力学特性的重要因素,在进行颈椎前路融合术时应警惕由于椎间盘退变引起的“植入物沉陷”。     

A morphological study of lumbar vertebral endplates: radiographic, visual and digital measurements

Purpose

Clinical observations suggest that endplate shape and size are related to complications of disc arthroplasty surgery. Yet, the morphology of the vertebral endplate has not been well defined. This study was conducted to characterize the morphology of lumbar vertebral endplates and to quantify their morphometrics using radiographic, visual and digital measures.

Methods

A total of 591 vertebral endplates from 76 lumbosacral spines of men were studied (mean age 51.3 years). The shape of the vertebral endplates was classified as concave, flat and irregular, and was evaluated from both radiographs and cadaveric samples. Each endplate was further digitized using a laser scanner to quantify diameters, surface area and concavity for the whole endplate and its components (central endplate and epiphyseal rim). The morphological characteristics and morphometrics of the vertebral endplates were depicted.

Results

In both radiographic and visual assessments, more cranial endplates (relative to the disc) were concave and more caudal endplates were flat at all disc levels (p < 0.001). On average, the mean concavity depth was 1.5 mm for the cranial endplate and 0.7 mm for the caudal endplate. From L1/2 down to L5/S1 discs, the vertebral endplate gradually changed into a more oval shape. The central endplate was approximately 70 % of the diameter of the whole endplate and the width of the epiphyseal rim varied from 3 to 7 mm.

Conclusions

There is marked morphological asymmetry between the two adjacent endplates of a lumbar intervertebral disc: the cranial endplate is more concave than the caudal endplate. The size and shape of the vertebral endplate also vary considerably between the upper and lower lumbar regions.     

The effects of bone density and disc degeneration on the structural property distributions in the lower lumbar vertebral endplates.

In this study, we hypothesized that vertebral bone density and disc degeneration would affect the structural property distributions of the lower lumbar vertebral endplates (L3-L5). The results may have implications for improving interbody implant designs to better resist subsidence. A 3 mm diameter hemispherical indenter was used to perform indentation tests at 0.2 mm/s to a depth of 3 mm at 27 standardized locations in 55 bony endplates of intact human lumbar vertebrae (L3-L5). The resulting load-displacement curves were used to extract the failure load and stiffness of each test site. Bone density was measured using lateral DEXA scans. Disc condition was determined using a four-point grading scale. Three-way analyses of variance were used to analyze the relationships between the data. The overall failure load decreased with bone mineral density (BMD) in the superior (p < 0.0001) and inferior (p = 0.011) lumbar endplates. In both endplates, the posterolateral regions were significantly stronger than more central regions. With increasing BMD, this difference became more pronounced in the superior endplates only (p = 0.005). Increased disc degeneration was associated with an overall failure load decrease in the inferior lumbar endplates (p = 0.002). The strength in the central regions of the superior endplates was reduced with increasing degeneration, but this was not observed peripherally (p = 0.001). Stiffness magnitude or distribution was not significantly affected by BMD or disc degeneration. The locations of the strongest regions of the endplate did not change with either bone density or disc degeneration. This implies that implant shapes designed using the basic structural property maps for the L3-L5 endplates are appropriate for use in patients with a wide range of pathologies, even though overall failure loads are generally lower in patients with reduced bone density and greater degrees of disc degeneration.     

Lumbar spine endplate fractures: Biomechanical evaluation and clinical considerations through experimental induction of injury

Lumbar endplate fractures were investigated in different experimental scenarios, however the biomechanical effect of segmental alignment was not outlined. The objectives of this study were to quantify effects of spinal orientation on lumbar spine injuries during single‐cycle compressive loads and understand lumbar spine endplate injury tolerance. Twenty lumbar motion segments were compressed to failure. Two methods were used in the preparation of the lumbar motion segments. Group 1 (n = 7) preparation maintained pre‐test sagittal lordosis, whereas Group 2 (n = 13) specimens had a free‐rotational end condition for the cranial vertebra, allowing sagittal rotation of the cranial vertebra to create parallel endplates. Five Group 1 specimens experienced posterior vertebral body fracture prior to endplate fracture, whereas two sustained endplate fracture only. Group 2 specimens sustained isolated endplate fractures. Group 2 fractures occurred at approximately 41% of the axial force required for Group 1 fracture (p < 0.05). Imaging and specimen dissection indicate endplate injury consistently took place within the confines of the endplate boundaries, away from the vertebral periphery. These findings indicate that spinal alignment during compressive loading influences the resulting injury pattern. This investigation identified the specific mechanical conditions under which an endplate breach will take place. Development of endplate injuries has significant clinical implication as previous research identified internal disc disruption (IDD) and degenerative disc disease (DDD) as long‐term consequences of the axial load‐shift that occurs following a breach of the endplate. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1084–1091, 2016.     

退行性胸腰椎/腰椎后凸椎体终板Modic改变与脊柱骨盆矢状位参数相关性分析

目的探讨退行性胸腰椎/腰椎后凸椎体终板Modic改变(Thoracolumbar degenerative kyphosis/Lumbar degenerative kyphosis,TLDK/LDK)与脊柱骨盆矢状位参数的相关性。方法回顾性分析自2016-03—2018-03诊治的116例TLDK/LDK,记录T₁₀至S₁椎体出现Moidc改变的情况,并测量矢状位全脊柱X线片下脊柱-骨盆参数,分析Modic改变终板数量与矢状面偏移(Sagittal vertical axis,SVA)、胸椎后凸角(Thoracic kyphosis,TK)、胸腰后凸角(Thoracolumbar kyphosis,TLK)、腰椎前凸角(Lumbar lordosis,LL)、骨盆入射角(Pelvis incidence,PI)、骶骨倾斜角(Sacral slope,SS)、骨盆倾斜角(Pelvic tilt,PT)的相关性。结果 116例共1856个椎体终板均顺利完成检查,共62例184个椎体终板出现Modic改变,6例共12个椎体终板出现Ⅰ型改变,50例共137个椎体终板出现Ⅱ型改变,36例共35个椎体终板出现Ⅲ型改变。相关性分析结果显示出现椎体Modic改变的终板数量与LL、SS呈负相关,与PT成正相关(P<0.05)。结论 TLDK/LDK的Modic改变以Ⅱ型多见,Modic改变与LL、SS、PT存在相关性。     

Effect of endplate reduction on endplate healing morphology and intervertebral disc degeneration in patients with thoracolumbar vertebral fracture

Objective

To determine the effect of endplate reduction on the final healing morphology and degenerative changes in intervertebral discs.

Methods

Forty-eight patients with single-level thoracolumbar fractures with endplate injury were included. All patients underwent posterior reduction and pedicle screw fixation, and postoperative imaging was used to determine whether endplate reduction was successful. The healing morphology of the endplate was divided into three types: increased endplate curvature, irregular healing and traumatic Schmorl node. MRI was performed at baseline and at the last follow-up evaluation to observe changes in disc degeneration (disc height and nucleus pulposus signal) and Modic changes.

Results

The reduction rate in the central area was significantly lower than that in the peripheral area (P = 0.017). In patients with successful reduction, 90.9% (20/22) of the endplates healed with increased curvature. In patients with an unsuccessful endplate reduction, 63.4% (26/41) of the endplates healed irregularly, and 34.1% (14/41) of the endplates formed traumatic Schmorl nodes. Endplate reduction was closely related to the final healing morphology of the endplate (P < 0.001), which had a significant protective effect on the degeneration of the intervertebral disc. At the last follow-up evaluation, there was no statistically significant correlation between different endplate healing morphologies and new Modic changes.

Conclusions

The reduction rate in the central area is significantly lower than that in the peripheral area. Although all of the intervertebral discs corresponding to fractured endplates had degenerated to different degrees, successful endplate fracture reduction can obviously delay the degeneration of intervertebral discs.

     

Elevated synthetic activity in the convex side of scoliotic intervertebral discs and endplates compared with normal tissues.

STUDY DESIGN: We measured concentrations of specific molecules reflecting matrix synthesis and degradation in normal and scoliotic intervertebral discs and endplates. OBJECTIVES: The aim of this work was to quantitate markers of matrix turnover in normal versus adolescent idiopathic scoliotic intervertebral discs and cartilaginous endplates. SUMMARY OF BACKGROUND DATA: Changes in the intervertebral disc and endplate composition have been implicated as possible etiologic factors in the pathogenesis of adolescent idiopathic scoliosis. To better understand this process, it is important to compare the turnover of matrix components in scoliotic and normal intervertebral disc and endplate tissues. This comparison may help to improve our understanding of the role that disc and endplate tissues may play in the induction and/or progression of idiopathic scoliosis. METHODS: Fifteen scoliotic and 17 normal intervertebral discs and endplates were analyzed for their water, collagen, proteoglycan, and protein content. In addition, newly synthesized aggrecan and collagen Types I and II were measured. Percent total denatured collagen was also determined. RESULTS: The total collagen content was significantly lower in the scoliotic anulus and endplate regions, whereas glycosaminoglycan (GAG) content was significantly lower in the scoliotic endplates and nucleus regions. Conversely, total protein content was significantly higher in scoliotic endplates and elevated in scoliotic nucleus regions. Water content was significantly lower in the scoliotic anulus and endplate regions. When comparing the concave and convex regions of scoliotic endplates, there was no significant difference in concentration of any matrix component. The major difference in the synthetic marker levels relates to the synthesis of Type II collagen, which was higher in the nucleus, anulus, and endplate regions of scoliotic discs than in the corresponding regions of normal tissues. By contrast, the percent total denatured collagen was significantly elevated in the nucleus of normal tissues compared with the scoliotic ones. CONCLUSIONS: The higher collagen Type II synthetic levels and increased total protein content with no matrix turnover suggest that scoliotic changes are due to an altered and ineffective synthetic response to a pathologic mechanical environment.     

The relation between vertebral endplate shape and lumbar disc herniations.

STUDY DESIGN: Blinded review of selected and un-selected computed tomographic myelograms. OBJECTIVE: To determine whether shape of the vertebral body endplate margins is a risk factor for the development of symptomatic lumbar disc herniations. The law of LaPlace for a fluid-filled tube suggests that anular tension could be related to endplate shape and a propensity for disc herniation. SUMMARY OF BACKGROUND DATA: It was hypothesized that the law of Laplace could apply to the lumbar spine because of to the cylindrical shape of the lumbar disc and its high water content in nonelderly individuals. It was further hypothesized that differences in the radius of the curvature could place stresses on the anulus that would make posterior disc herniations more likely with "rounder" endplates. METHODS: Ninety-seven contrast computed tomography scans were reviewed at transitional L4-L5 and L5-S1 in patients under 60 years of age, without previous spine surgery and without spondylolisthesis. Determinations of disc herniations and measurements of endplates were performed by blinded observers. A ratio of these measurements was used to determine the relative circularity of the endplate. Height, weight, body mass index, and disc endplate size and shape were related to the presence of disc herniation. RESULTS: By multiple logistic regression, only endplate shape was strongly related to disc herniations. Endplate area was a less significant factor in men. CONCLUSIONS: The shape of the vertebral body margin at the endplate is an important factor contributing to the development of disc herniations at L4-L5 and L5-S1.