Patient-specific mechanical properties of a flexible multi-body model of the scoliotic spine

The flexibility of the scoliotic spine is an important biomechanical parameter to take into account in the planning of surgical instrumentation. The objective of the paper was to develop a method to characterisein vivo the mechanical properties of the scoliotic spine using a flexible multi-body model. Vertebrae were represented as rigid bodies, and intervertebral elements were defined at every level using a spherical joint and three torsion springs. The initial mechanical properties of motion segments were defined fromin vitro experimental data reported in the literature. They were adjusted using an optimisation algorithm to reduce the discrepancy between the simulated and the measured Ferguson angles in lateral bending of three spine segments (major or compensatory left thoracic, right thoracic and left lumbar scoliosis curves). The flexural rigidity of the spine segments was defined in three categories (flexible, nominal, rigid) according to the estimated mechanical factors (α). This approach was applied with ten scoliotic patients under-going spinal correction. Personalisation of the model resulted in an increase of the initial flexural rigidity for seven of the ten lumbar segments (1.38≤α≤10.0) and four of the ten right thoracic segments (1.74≤α≤5.18). The adjustment of the mechanical parameters based on the lateral bending tests improved the model's ability to predict the spine shape change described by the Ferguson angles by up to 50%. The largest differences after personalisation were for the left lumbar segments in left bending (4⁰±3⁰). Thein vivo identification of the mechanical properties of the scoliotic spine will improve the ability of biomechanical models adequately to predict the surgical correction, which should help clinicians in the planning of surgical instrumentation manoeuvres.     

补肾中药佳蓉片对去势小鼠骨丢失的预防作用

目的　研究补肾中药佳蓉片 (JRP)对模型小鼠骨质疏松的影响 .方法　雌性昆明小鼠 6 0只随机分为 6组 ,行去卵巢术或假手术 .处理后分组为 :去卵巢组 (OVX) ,假手术组(Sham) ,去卵巢分为佳蓉片低剂量组 (JRP- L,10 0 mg·d- 1 ) ,佳蓉片中剂量组 (JRP- M,2 0 0 mg· d- 1 ) ,佳蓉片高剂量组 (JRP- H,40 0 mg· d- 1 )和 17β雌二醇组 (E2 ,10 μg·d- 1 ) .手术后灌胃上述药物 2 8d,测定股骨密度、骨生物力学性能、血清碱性磷酸酶 (AL P)、骨钙素 (BGP) .结果　各中药组的股骨骨密度均高于去卵巢对照组 (P<0 .0 5 ) ,与假手术组无差异 ;灌胃中药后骨结构力学参数显著性改善 (P<0 .0 5 ) ,同时 AL P,BGP显著性降低 (P<0 .0 5 ) .结论　补肾中药方剂可预防去卵巢引起的骨丢失 ,改善骨的生物力学性能     

沈氏装置稳定性的生物力学评价

评价沈氏经椎弓根内固定装置的生物力学稳定性。方法采用５具新鲜尸体脊柱标本,制造Ｌ１损伤模型,测量并比较标本在完整状态,损伤状态、沈氏装置固定、沈氏装置疲劳及ＣＤ装置固定下的Ｔ１２和Ｌ２之间的三维运动范围,并将沈装置与ＣＤ装置固定下的运动范围进行,经统计学处理,评价沈氏装置的稳定性。     

尸体植入新型人工腰椎间盘腰椎节段生物力学测试

目的:评价植入新型人工腰椎间盘的腰椎节段的稳定性和压缩力学性能。方法:将人工腰椎间盘植入6具新鲜青壮年尸体标本的L4-5椎间隙,进行三维运动范围和压缩刚度测试,并与植入前和髓核切除后进行比较。结果:新型人工腰椎间盘植入后,腰椎节段的三维运动范围为前屈146°,后伸66°,左侧弯79°,右侧弯89°,左轴向旋转85°,右轴向旋转87°。其压缩刚度比髓核切除后高(P<005)。结论:新型人工腰椎间盘植入后既保证了腰椎节段的三维运动功能,又起到了稳定脊柱的功能。     

节段内固定治疗腰椎峡部裂的生物力学研究

在8具成人新鲜腰椎标本上,通过脊柱三维运动实验机,研究了横突棘突钢丝捆绑法、钩螺钉固定法及Buck螺钉固定法对峡部裂腰椎三维稳定性的影响。实验结果表明：三者均能显著地恢复脊柱的稳定性,且三者之间无显著差别。     

Improved Bone Biomechanical Properties in Rats after Oral Xylitol Administration

The effects of 5, 10, and 20% dietary xylitol supplementations on the biomechanical properties, histological architecture, and the contents of collagen, pyridinoline, and deoxypyridinoline in long bones of rats were studied. Tibiae were used for the three-point bending test, and femurs were used for the torsion and loading test of the femoral neck. The 10 and 20% oral xylitol administrations caused a significant increase of tibial stress, femoral shear stress, and stress of the femoral neck as compared with the controls. Parallel, but not significant, effects were also seen in the 5% xylitol supplementation group. No significant differences in strain or Young's modulus of the tibiae were detected between the groups. An increased shear modulus of elasticity in femurs was detected in the 20% supplementation group as compared with the controls. The histomorphometrical data for the secondary spongiosa of the proximal tibia revealed that trabecular bone volume was significantly greater in all dietary xylitol supplementation groups as compared with the controls. The bone volume increased along with increasing xylitol content. No significant differences between the groups were detected concerning the amount of collagen per dry weight of organic matrix, the concentrations of pyridinoline or deoxypyridinoline in collagen, or the ratio of these crosslinks. This suggests no xylitol-dependent selective changes in these structures of bone collagen. In conclusion, dietary xylitol supplementation in rats improves the biomechanical properties of bone and increases the trabecular bone volume dose dependently. Received: 30 January 1997 / Accepted: 1 October 1998     

仙灵骨葆改善去卵巢骨质疏松模型大鼠松质骨骨质量的实验研究

目的:探讨仙灵骨葆对去卵巢骨质疏松模型大鼠松质骨骨质量的影响。方法:将40只Wistar雌性大鼠随机分为正常组、模型组、倍美力组和仙灵骨葆组,每组10只。正常组仅行假手术,其余3组行卵巢切除术,术后91 d开始给药,连续90 d,处死,取出腰椎,用电镜观察第2、3腰椎形态结构,测定第2、3腰椎的骨质密度、第2腰椎骨质的钙、磷、有机质含量,并进行第3腰椎骨质的生物力学性能测定与分析。结果:仙灵骨葆能明显提高大鼠第2、3腰椎骨的骨质密度和第2腰椎骨质钙、磷含量,调整有机质含量,修复骨小梁三维结构,改善第3腰椎骨生物力学性能。结论:仙灵骨葆能够提高去卵巢骨质疏松模型大鼠松质骨的骨质量。     

The design of a cervical vertebra titanium plate-interbody fusion cage

Objective： To study the biomechanical feature of a newly designed cervical vertebra internal fixation device and its clinical applications. Methods： Some functional spinal units were fixed respectively with titanium plate, fusion cage and new device designed by ourselves, then a controlled biomechanical study including flexion, extension, torsion and lateral bending was performed and the results were analyzed. Results： As to the mechanical performance, fusion cage showed poor performance in extension test and so did the titanium plate in the distortion test. However, the new device showed good performance in every test. Conclusion： Both simple titanium plate fixation and simple fusion cage fixation have biomechanical defaults, but they are complementary. The titanium plate-interbody fusion cage avoids the defaults and has specific advantages.     

可视化角膜生物力学分析仪评价FS-LASIK、SBK、LASEK术后生物力学变化

目的：研究3种角膜屈光手术在手术前后角膜生物力学的变化及不同术式间的差异。方法：前瞻性研究。对2016年2-4月南京医科大学附属南京医院眼科行准分子激光手术的患者64例（125眼）手术前后的角膜生物力学参数进行分析,其中55眼行飞秒激光制瓣准分子激光原位角膜磨镶术（FS-LASIK）,47 眼行准分子激光前弹力层下角膜磨镶术（SBK）,23眼行准分子激光上皮下角膜磨镶术（LASEK）。应用可视化角膜生物力学仪（CST）对患者进行测量,选取其中第一压平时间（AT1）、第二压平速度（Vout）、最大压陷曲率半径（HC-radius）、最大压陷幅度（DA）、眼压（IOP）进行分析。术后1 d、1 周、3 个月进行随访。采用单因素方差分析、Pearson相关分析、配对t检验进行数据分析。结果：FS-LASIK组中各项生物力学参数与中央角膜厚度（CCT）（ AT1：r=0.455,P<0.001;Vout：r=-0.286,P=0.034;HC-radius：r=0.357,P=0.007;DA：r=-0.341,P=0.011;IOP：r=0.436,P=0.001）、角膜剩余基质床厚度（RST）（ AT1 r=0.563,P<0.001;Vout：r=-0.417,P=0.007;HC-radius：r=0.552,P<0.001;DA：r=-0.395,P=0.012;IOP：r=0.516,P<0.001）、最大切削深度（AD）（ AT1：r=-0.721,P<0.001;Vout：r=0.466,P=0.002;HC-radius：r=-0.407,P=0.009;DA：r=0.596, P<0.001;IOP：r=-0.612,P<0.001）均有较强相关性。SBK组中各项生物力学参数均与CCT（AT1：r=0.364,P=0.012;Vout：r=0.408,P=0.004;HC-radius：r=0.326,P=0.025;DA：r=-0.362,P=0.012;IOP：r=0.387,P=0.007）有较强的相关性。LASEK组中仅AT1（r=0.625,P=0.001）、IOP（r=0.624,P=0.001）与CCT有相关性。3 组的AT1、HC-radius、IOP和CCT较术前均减小（均P<0.05）,Vout、DA较术前均增加（均P<0.05）。3组间比较,术后1 周时FS-LASIK组的AT1、IOP值明显大于LASEK组（AT1：F=7.313,P=0.001;IOP：F=4.979,P=0.009）,Vout和DA值明显小于LASEK组（Vout：F=3.420,P=0.038;DA：F=9.024,P<0.001）,SBK组的各项参数值位于2 组之间,与FS-LASIK组差异无统计学意义;术后3 个月时,3 组间差异无统计学意义。结论：在角膜厚度足够时,3 种手术方式均能安全可靠地矫正近视。FS-LASIK由于飞秒激光切削的精确性和优越性,术后能够更快恢复生物力学的稳定性。LASEK的生物力学变化与剩余基质床厚度和切削深度的相关性较低,在患者近视度数较高,角膜相对较薄时,可以优先考虑该术式。     

单枚椎间融合器并对侧经皮椎弓根螺钉固定的生物力学研究

目的对单枚融合器联合单侧钉棒系统固定的生物力学性能进行评价。方法5具新鲜小牛腰椎标本,建立以下力学模型：A组：双侧开窗＋双枚融合器置入＋双侧椎弓根钉棒固定;B组：单侧小关节切除＋单枚融合器斜向置入＋同侧椎弓根钉棒固定;C组：单侧开窗＋单枚融合器置入＋同侧椎弓根钉棒固定;D组：单侧开窗＋单枚融合器置入＋对侧椎弓根钉棒固定。在生物力学平台上测试各试验组在不同工况下的ROM值。结果A组的固定最稳固,各工况下ROM值最低。B组的前后抗弯ROM值与A组差异无显著性,其左右侧弯和旋转方向的稳定性较A组有所降低。与B组比较,D组的前后弯曲性能与B组差异无显著性,其左右侧弯方向的ROM低与B组。两组的抗旋转ROM值差异无显著性。C组的左右抗弯及抗旋转性能均差于B、D组。结论单枚椎间融合器联合对侧椎弓根钉棒固定是一种力学性能较为优良组合,可以替代单侧斜向融合器并同侧椎弓根钉棒技术用于下腰椎微创手术。