Effect of plantar flexor muscle stiffness on selected gait characteristics

Although plantar flexor muscle strength is known to affect gait characteristics, the effect of plantar flexor (PF) muscle stiffness on gait is unknown. The purpose of this study was to determine the effect of PF muscle stiffness, in addition to PF strength, on the gait characteristics of subjects with diabetes and peripheral neuropathy (DM & PN) and age-matched controls. Thirty-four subjects were tested (17 DM & PN, 17 controls), 10 males and seven females in each group. PF muscle strength (concentric peak torque) explained a significant amount of variance in all gait variables (20–37%). Passive stiffness added a unique contribution to plantar flexor peak moment and walking speed (10–11%). Plantar flexor stiffness, in addition to strength, may be an important factor contributing to gait characteristics. Treatment techniques designed to preserve or increase stiffness may be indicated for patients with limited PF strength.     

Reduction of gait data variability using curve registration

Timing in peak gait values shifts slightly between gait trials. When averaged, the standard deviation (S.D.) in gait data may increase due to this inter-trial variability unless normalization is carried out beforehand. The objective of this study was to determine how curve registration, an alignment technique, can reduce inter-subject variability in gait data without perturbing the curve characteristics. Twenty young, healthy men participated in this study each providing a single gait trial. Gait was assessed by means of a four-camera high-speed video system synchronized to a force plate. A rigid body three-segment model was used in an inverse dynamic approach to calculate three-dimensional muscle powers at the hip, knee and ankle. Curve registration was applied to each of the 20 gait trials to align the peak powers. The mean registered peak powers increased by an average of 0.10±0.13 W/kg with the highest increases in the sagittal plane at push-off. After performing curve registration, the RMS values decreased by 13.6% and the greatest reduction occurred at the hip and knee, both in the sagittal plane. No important discontinuities were reported in the first and second derivatives of the unregistered and registered curves. Curve registration did not have much effect on the harmonic content. This would be an appropriate technique for application prior to any statistical analysis using able-bodied gait patterns.     

Assessment of patellar maltracking using combined static and dynamic MRI

Between January 1995 and Jul 1997, 474 patients with anterior knee pain resistant to conservative treatment were referred for MR of the knee. The MR examination consisted of routine sequences with an additional patellofemoral dynamic examination using a technique that has been developed at this institution. The dynamic study examines both knees simultaneously, with the patient supine and the quadriceps loaded. No gating or restraint apparatus is needed. Patellar subluxation or tilt was present in 188(40 %) of cases, bilateral in 104 and unilateral in 84 cases (right 39, left 45). It was classified as mild in 51 %, moderate in 39 % and severe in 10 %. Subluxation was more prevalent in females than males (42 % vs. 37 %) and this was most obvious in the severe group where 68 % were female. In 90 knees selected at random, four measurements of patellofemoral morphology were obtained using reconstructed images from a volume gradient echo sequence. These measurements were correlated with the degree of subluxation or tilt. A tibial tubercle distance greater than 20 mm, a femoral sulcus angle greater than 150 degrees, sulcus depth less than 4 mm were specific for subluxation but no measurement proved to be sufficiently sensitive to preclude a tracking study. MRI can be used to define more precisely the anatomy of the extensor mechanism and its relationship to the femur and tibia, in both a static and dynamic setting. In this way, patients with anterior knee pain can be classified more accurately and the outcomes of treatment more reliably assessed. Received: 17 September 1999; Revised: 31 January 2000; Accepted: 4 February 2000     

不同承力点前牵引颅面骨骼的三维有限元研究

目的：从生物力学的角度比较分析,不同部位承力颅面骨骼前牵引的生物力学变化特点。方法：采用三维有限元方法,建立颅面复合体三维有限元模型,在模型上分别以牙列承力前牵引和梨状孔底骨骼承力的前牵引,比较分析其生物力学变化。结果：以梨状孔底骨骼承力的前牵引,矢向位移面中上1／2前移比牙列承力的前牵引多,面中下1／2位移相对较少,垂直向及侧向位移值均小于牙列承力的前牵引,等效应力集中范围明显小于牙列承力的前牵引,鼻根区压应力减少明显。结论：与传统的牙列承力的前牵引比较,以梨状孔底骨骼承力的前牵引可整体前移上颌,减少上颌的逆向旋转,减少硬腭前部压缩现象。     

骶髂关节不同固定方式对骶部影响的生物力学研究

背景:长节段固定治疗腰椎退变性侧凸取得了良好的矫形效果.目前对于骶髂关节不同固定方式对骶部影响的生物力学研究尚少..目的:研究骶髂关节不同固定方式对S1螺钉应力分布的影响,为腰椎退变性手术方式的选择提供依据.方法:抽取6具成人新鲜尸体按照三种不同固定方式分成T12-S1组(T12-S1固定)、T12-S2组(T12-S...     

新型钢丝弹力夹板的生物力学测试及临床应用研究

目的:钢丝弹力夹板是我们自行研制的,一种以钢丝为主要材料的夹板。取中医传统夹板帘子的优点,摒弃其在材料方面的局限性,而设计的一种新型夹板,本文通过对钢丝弹力夹板的生物力学测试及其临床应用研究去探讨钢丝弹力夹板的性能,为临床应用提供依据。方法:(1)取6套新型弹力钢丝夹板和6套柳木夹板,随机分为6组,每组由一套新型弹力钢丝夹板和一套柳木夹板组成。每组再随机编号,根据力学原则,不同力的作用下测量出两种夹板对应的纵向位移及其在撤销相应外力后两种夹板弹回后相应的残余位移,绘制相应曲线图,对其进行分析。(2)60例科雷氏骨折患者随机分为2组,钢丝弹力夹板组30例,柳木夹板组30例。经复位、固定后,分别在4 w后摄x线片观察骨折固定效果、患肢功能恢复情况、并以比正常骨折愈合时间提前多少为疗效判定标准评定疗效。比较两种夹板的临床效果。结果:新型钢丝弹力夹板强度及其弹性明显优于柳木夹板(P<0.05,P<0.01)。在治疗固定效果、患肢功能恢复(P<0.05,P<0.05)也优于传统柳木夹板。结论:新型钢丝弹力夹板是一种理想的外固定材料。     

髋关节发育不良髋臼内壁内移截骨全髋置换术的三维有限元分析

目的利用三维有限元力学分析方法,研究髋关节发育不良患者行髋臼内壁内移截骨全髋关节置换术对髋臼假体-骨界面间的应力分布情况的影响。方法选取髋关节发育不良患者的骨盆为实验对象,用螺旋CT做全长连续扫描,然后利用计算机仿真技术对CT图像进行三维重建,建立髋关节发育不良骨盆模型。利用计算机辅助设计(CAD)功能,在计算机环境中对重建模型进行髋臼内壁内移截骨全髋关节置换的模拟手术,利用有限元分析软件SolidWorks对重建模型进行有限元网格化,最后使用SolidWorks软件中的力学分析工具包COSMOS对网格化的模型进行力学分析,得到髋臼假体-骨界面间的应力分布情况的实验结果,对实验结果进行统计和分析,观察术后髋臼假体-骨界面间的应力分布情况。结果术后髋臼压应力分布符合后上象限最大,前下象限最小,前上象限、后下象限居中的趋势。剪切应力分布情况为后上象限剪切应力最大,其他象限无差异。结论髋臼内壁内移截骨术没有改变正常髋臼的应力分布情况。     

不同牵引重量对颈椎髓核内压力影响的研究

目的:通过测试不同牵引力量对颈椎标本髓核内压力的影响,探讨牵引对颈椎影响的机制。方法:利用生物力学材料实验机使用150N、200N、300N3种牵引力对6例新鲜人体颈椎标本进行力学加载,同时利用微型压力传感器测试加载过程中各节段髓核内压力的变化。结果:模拟头部重量及加载牵引力后均出现C5,6,C6,7髓核内压力高于C3,4,C4,5髓核内压力(P0.05),加载牵引力后所有标本髓核内压力均出现降低(P0.05)。结论:牵引通过增大颈椎椎间隙,降低外力对椎间盘髓核内的压力;同时在进行旋转手法时应配合适当的牵引力以增加旋转手法的安全性。     

胸腰椎不稳定骨折前后路短节段内固定有限元生物力学研究

目的通过建立前、后路内固定模型,比较前、后路固定后的力学稳定关系,指导临床选择前路或后路固定。方法分别建立胸腰椎三维有限元力学模型和前、后路固定器械模型及L1骨折模型,分别加载,对不同固定组的L1前柱、中柱、前中柱骨折的应力进行比较。结果①椎体前柱损伤的工况下,前路固定组的L1平面的Mises stress小于后路固定;②椎体前中柱共同损伤的工况下,前路固定组也优于后路固定组。结论胸腰椎前柱与前中柱不稳定骨折损伤,前路固定都优于后路。     

解剖结构逐级损伤对Hangman骨折稳定性影响的生物力学研究

目的测试C2、3椎间解剖结构逐级损伤对Hangman骨折稳定性的影响并探讨其临床意义。方法8具新鲜C1～4颈椎标本,按Hangman骨折病理诊断标准模拟C2、3椎间解剖结构逐级损伤,并在脊柱三维运动实验机上依次按照:①对照组(正常状态);②切断双侧椎弓峡部组;③切断双侧椎弓峡部及后纵韧带组;④切断双侧椎弓峡部及前、后纵韧带组顺序测试其三维运动范围(ROM),对结果进行统计学分析。结果随着解剖结构逐级破坏,ROM值逐渐增大。切断双侧椎弓峡部组与对照组相比除旋转有显著性差异外,余均无显著性差异;而切断双侧椎弓峡部及后纵韧带组、切断双侧椎弓峡部及前后纵韧带组与对照组相比均有显著性差异。切断双侧椎弓峡部及后纵韧带组与切断双侧椎弓峡部组相比除后伸无显著性差异外,余均有显著性差异;切断双侧椎弓峡部及前后纵韧带组与其他组相比均有显著性差异(P<0.05)。结论对旋转运动影响最大的是峡部,前后纵韧带对屈伸运动影响明显,而侧弯运动则随着各椎间结构的破坏逐步下降;准确判断Hangman骨折的具体损伤部位对骨折稳定性的认识和手术方法的选择有着重要作用。