Isotretinoin induced achilles tendinopathy: Histopathological and biomechanical evaluation on rats

Objective

The aim of the present study was to evaluate histopathological and biomechanical effects of isotretinoin on Achilles tendon.

Effectiveness of posterior structures in the development of proximal junctional kyphosis following posterior instrumentation: A biomechanical study in a sheep spine model

IntroductionProximal junctional kyphosis – PJK has been defined by a 10 or greater increase in kyphosis at the proximal junction as measured by the Cobb angle from the caudal endplate of the uppermost instrumented vertebrae (UIV) to the cephalad endplate of the vertebrae 1 segments cranial to the UIV. In this biomechanical study, it is aimed to evaluate effects of interspinosus ligament complex distruption and facet joint degeneration on PJK development.Materials and methodsPosterior instrumentation applied between T2 – T7 vertebrae using pedicle screws to randomly selected 21 sheeps, divided into 3 groups. First group selected as control group (CG), of which posterior soft tissue and facet joints are protected. In second group (spinosus group, SG) interspinosus ligament complex which 1 segment cranial to UIV has been transected, and third group (faset group-FG) was applied facet joint excision. 25 N, 50 N, 100 N, 150 N and 200 N forces applied at frequency of 5 Hertz as 100 cycles axial to the samples. Then, 250 N, 275 N and 300 N forces applied static axially. Interspinosus distance, kyphosis angle and discus heights was measured in radiological evaluation. Abnormal PJK was defined by a proximal junctional angle greater than 10⁰ and at least 10⁰ greater than the corresponding preoperative measurement.ResultsIn CG group, average interspinosus distance was 6,6 $\pm$ 1.54 mm and kyphosis angle was 2,2 $\pm$ 0.46° before biomechanical testing, and they were measured as 9,4 $\pm$ 1.21 mm and 3,3 $\pm$0.44° respectively after forces applied to samples. In SG group, average interspinosus distance was 6,2 $\pm$ 1.72 mm and kyphosis angle was 2,7 $\pm$ 1.01° before experiment, and they were measured as 20,8 $\pm$ 5.66 mm and 15,1 $\pm$ 2.34° respectively after forces applied to samples. In FG group, average interspinosus distance was 4,8 $\pm$ 1.15 mm and kyphosis angle was ?1 $\pm$ 4.14° before experiment, and they were measured as 11,1 $\pm 1.96$mm and 11 $\pm$ 2.87° respectively after forces applied to samples. In comparison to group CG, statistically significant junctional kyphosis was seen on both FG and SG group after statistical analysis. (p < 0.05). PJK was seen statistically significant more on SG group than FG group. (p < 0.05). Not any statistically significant difference was seen on measurement of disk distances among three groups. (p > 0.05)ConclusionsProtecting interspinosus ligament complex and facet joint unity during posterior surgical treatment for spine deformation is vital to prevent PJK development. Based on our literature review, this is the first biomechanical study that reveals interspinosus ligament complex are more effective on preventing PJK development than facet joints.     

Biomechanics of the deltoideus

The objective of this study was to determine the direction of the migration engendered by the middle deltoideus on the upper end of the humerus. Eleven patients suffering from shoulder pathology underwent an MRI examination (3 mm thick slices). From these MRI slices, 3D reconstructions were obtained for each patient by using a manual data capture system (SliceOmatic^®). From this geometry, a mechanical model of the deltoideus was produced, taking into account the contacts between the latter and the following anatomical parts: supraspinatus, infraspinatus and humeral head. For the 11 shoulders, we have obtained a deltoideus showing a global resultant oriented upwards. There was, however, a component oriented downwards (at the level of the humeral head), its intensity being 40–80% less than the component oriented upwards (at the level of the deltoideus V). It is important to note that this study is valid only in the initial degrees of lateral elevation. The deltoideus is an elevator muscle of the humeral head in the glenoid, presenting nevertheless a component oriented downwards. The deltoideus would, therefore, intervene to recenter the shoulder during an abduction movement.     

后路短螺丝钉固定术治疗骶髂关节骨折脱位实验研究与临床

目的:探讨后路短螺丝钉固定治疗骶髂关节骨折脱位的安全性和疗效。方法:骶骨应用解剖,骶髂关节脱位模型生物力学实验,11例病人手术方法及疗效分析。结果:应用解剖,(1)骶骨耳状面下缘在S_(2、3)后孔连线中下1/3以下者占86.6％;(2)S_(2、3)侧柱呈直角梯形。S_2侧柱横截面前后径(28.3±1.7)mm,S_3侧柱横截面前后径中部为(21.4±1.5)mm,中下1/3处为(8.4±1.1)mm;(3)骶后中间嵴到耳状面中轴垂直距离:S_2水平处(26.7±2.6)mm,S_3水平处(27.2±2.8)mm。骶后孔连线:S_(1、2)间(17.4±1.6)mm,S_(2、3)间(17.6±2.1)mm。生物力学:(1)2枚短螺丝钉固定可以控制骶髂关节的移位,同时前部固定后明显增加骨盆的强度和刚度,并可以对抗剪切力。临床部分:治疗11例病人平均随访5.4年,优7例,良4例。结论:后路短螺丝钉经过骶骨侧柱中上部,不超过骶孔连线固定骶髂关节,不但能获得牢固的固定,同时能有效的避免神经损伤,骶髂关节植骨融合其远期疗效好。     

改良钉棒系统治疗垂直不稳定骨盆骨折的生物力学研究

目的 探讨改良钉棒系统治疗垂直不稳定型骨盆骨折,并分析其生物力学性质.方法 在8例尸体骨盆标本上造模成垂直不稳定型骨盆骨折,分别行TOS术式固定、骶髂螺钉固定、改良钉棒系统固定,检测1000 N载荷下骨盆刚度、骨折分离移位距离及局部应变改变.结果 骨盆标本骨折模型采用各种不同固定方式,经生物力学测试,改良钉棒系统在载荷1000 N下刚度(224.3±18.3)N/mm及骨折分离移位距离(1.98±0.24)mm,明显优于骶髂螺钉固定(169.10±17.60)、(8.08±0.71)mm,差异有统计学意义(P＜0.01),与TOS(233.20±12.90)、(1.62±0.31)mm比较,差异无统计学意义(P＞0.05).结论 改良钉棒系统是一种生物力学性能较好的治疗垂直不稳定型骨盆骨折的新方法.     

种植体骨界面形成研究进展

随着种植牙越来越广泛的应用,种植义齿的生物力学研究已成为种植义齿研究中很重要的一方面。种植义齿的生物力学影响因素有种植体材料、形态结构、表面处理、颌骨结构和受力情况等。目前研究仍不深入,有待进一步研究。     

胸腰段三维非线性有限元建模及临床意义

目的建立胸腰段三个椎体节段的三维非线性有限元模型并对模型的有效性进行验证。方法建立T12/L1/L2三个椎体节段的三维非线性有限元模型,该模型分别在垂直压缩力800N作用下,屈曲、后伸、侧弯、扭转力矩作用下,最大力矩皆为16N·m,分析模型的平均刚度、屈曲和后伸力矩与旋转角度的关系,观察椎间盘纤维环上的应力分布情况。结果模型的平均刚度及力矩-旋转角度关系曲线和其他作者的实测法所得结果基本一致;椎间盘纤维环上应力符合临床和其他作者有限元分析所得结果。结论本研究通过一种改良的测量建模法建立的胸腰段有限元模型符合脊柱生物力学的一般特点,可以对胸腰段和胸腰段内固定的生物力学进行研究。     

腰椎节段内固定后相邻下位间隙即刻运动范围的测试

目的 :观测腰椎滑脱固定后即刻其相邻下位间隙的运动范围 ,探讨与固定节段相邻间隙退变加剧的可能原因。方法 :7具新鲜成人尸体脊柱标本 ,取L2～S2节段。每一标本在 5种状态 (组 )下进行L5 /S1三维运动测试 :完整组、L4滑脱组、两节段HOIST器械固定L4～L5组、两节段Dick器械固定L4～L5组、三节段Dick器械固定L3～L5组。结果 :除前屈运动时三节段Dick系统固定组L5 /S1间隙的运动范围显著大于完整组和L4滑脱组外 ,其他各组相邻下位间隙的不同方位运动范围差异不明显。结论 :三节段固定后相邻下位间隙即刻的前屈运动范围明显增加 ,这可能是相邻间隙退变的的原因之一。     

非线性三维有限元法分析腰椎间盘退变

目的 探讨椎间盘退变对腰椎活动节段生物力学的影响.方法 采用新型的基于CT图像的CAD建模方法精确建立L4-L5运动节段的三维非线性有限元模型,并通过改变椎间盘材料特性和椎间盘高度等参数,建立正常椎间盘模型和轻、中、重度椎间盘退变模型,分别对4种有限元模型进行生物力学测试,比较4种模型之间刚度、髓核内压、后部结构力、纤维环基质最大应力的差异,并比较椎体、终板的应力分布变化.结果 各种载荷条件下,退变椎间盘模型刚度均与正常椎间盘模型不同,其中轻度退变模型刚度小于正常模型,而中度退变模型和重度退变模型刚度大于正常模型,且重度退变模型刚度大于中度退变模型;与正常模型比较,轻度退变模型的后部结构力略有增大,而中度退变和重度退变模型的后部结构力逐渐减小;随着椎间盘退变程度的增加,髓核内压逐渐减小,纤维环基质最大von Mises应力渐行性增大,各指标在5种载荷下表现一致;随着椎间盘退变的加重,椎间盘承载向纤维环分散,椎体、终板外缘出现应力集中现象.结论 椎间盘退变可导致腰椎活动节段刚度改变,轻度椎间盘退变引起腰椎刚度下降,而中、重度椎间盘退变时腰椎刚度增加;椎间盘退变时腰椎间盘承载与腰椎后部结构力呈现负相关变化;退变椎间盘的承载模式发生改变,椎间盘、椎体、终板应力分布存在向外周扩散的趋势.