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1.
目的探讨静力位正常骨盆在垂直载荷下的生物力学情况,为骨盆骨折各种生物力学测试提供生物力学参数.方法5具骨盆标本应用应变电测法,在不同载荷作用下对正常国人骨盆应变分布、刚度及位移进行测定,采集8个反复1500N载荷情况下骨盆的各个部位的应变值进行比较.结果骶髂关节处应变最大,骨盆能承受2000N以上的载荷,在8次1500N的反复载荷下,骨盆的刚度和应变未出现明显改变.结论垂直载荷下,骶髂关节处应变最大,为骨折的好发部位,正常骨盆的极限失效点在2000N 以上,1500N 的垂直载荷位于骨盆的弹性区间之内.  相似文献   

2.
目的设计一种与胫骨平台后内髁解剖形态匹配的钢板,比较其与5孔L型有限接触动力加压钢板(LCDCP)和7孔直型重建接骨板治疗胫骨平台后内侧骨折的稳定性。方法将18具胫骨平台后内侧骨折的标本随机分为3组,每组6具。其中,A组标本模型采用前内侧5孔L型LC-DCP固定,B组标本模型采用后内侧7孔直型重建接骨板固定,C组标本模型采用新设计的胫骨平台后内侧锁定钢板固定。分别测量各组标本在轴向载荷为500、1000、1500 N下的垂直位移及失效载荷。结果 A组标本分别在500、1000、1500 N下的垂直位移是(1.035±0.140)mm、(1.721±0.149)mm、(2.263±0.134)mm,B组标本分别在500、1000、1500 N下的垂直位移是(0.268±0.702)mm、(0.788±0.507)mm、(1.518±0.111)mm,C组标本分别在500、1000、1500 N下的垂直位移是(0.180±0.049)mm、(0.578±0.103)mm、(0.760±0.055)mm。在同一载荷下,三组标本骨折块垂直位移组间比较差异均有统计学意义(0.05)。A组标本失效载荷为(1234.3±56.009)N,B组标本失效载荷为(2065.8±102.098)N,C组标本失效载荷为(2544.2±92.982)N,三组间比较差异均有统计学意义(0.05)。结论新设计的胫骨平台后内侧锁定钢板在治疗胫骨平台后内侧骨折上,较5孔L型LC-DCP和7孔直型重建接骨板具有更好的生物力学优势。  相似文献   

3.
采用生物力学实验的方法研究骨盆骨的轴向刚度、不同部位骨盆骨的压缩及拉伸弹性模量以及强度,从而为骨盆的临床及实验研究提供理论依据.试验采用12具防腐骨盆骨,利用万能材料试验机测量不同载荷下骨盆骨的位移,计算其轴向刚度;之后截取耻骨、坐骨、髋臼骨前柱及后柱、以及骶髂关节两侧骨,制成10 mm×5mm×10mm大小试件,分成12组,利用杠杆引伸仪、万能材料试验机、电阻应变仪上分别进行压缩及拉伸弹性模量以及强度的测定.在静态载荷状态下,500 N的生理载荷时,骨盆刚度值为181.28±21.4 N.mm-1,1500N时,刚度值增加到352.32 N.mm-1;耻骨、坐骨、髂骨、髋臼前、后柱以及骶髂关节两侧骨质的压缩弹性模量依次为26.7、18.4、31.7、21.3、23.1、31.7、29.6 GPa;压缩强度均值依次为64.27、124.26、91.73、94.22、50.39、107.37、84.23 GPa;拉伸弹性模量依次为29.3、20.4、25.4、23.3、21.2、19.3、17.6 GPa;拉伸强度均值依次为132.53、93.26、95.72、74.22、40.39、84.23、64.27 GPa.静态载荷状态下,刚度值随着载荷的增加逐渐加大;坐骨的抗压缩强度最大,而耻骨的抗拉伸强度最大,髋臼前柱抗压缩及拉伸的强度(94.22、74.22)均明显高于髋臼后柱.  相似文献   

4.
目的 探究髋臼四边体骨折的最优内固定方式。 方法 采用半骨盆标本制作髋臼四边体骨折模型12具,按内固定方式随机分成3组,A组:骨盆缘下重建接骨板,B组:骨盆缘下锁定重建接骨板,C组:前柱重建接骨板结合方形区螺钉。将柳叶状压敏片贴于股骨头上,通过垂直加载依次测量生理体重600 N下完整髋臼I组(未制作骨折线)和A、B、C 3组的臼顶接触特性,及连续分级负载下A、B、C 3组的水平位移和纵向位移。 结果 生理体重600 N下3组内固定的髋臼负重区接触特性未能恢复至正常,负重面积、平均应力、峰值应力及分级载荷下水平位移和纵向位移均存在统计学差异(P<0.05,200 N除外),且水平位移和纵向位移都随载荷的增加而增大,而在1800 N时A组纵向位移达到失效标准。 结论 对髋臼四边体骨折予以3种不同内固定,前柱重建接骨板结合方形区螺钉内固定的稳定性及接触特性均优于骨盆缘下接骨板内固定,可以减少创伤性关节炎的发生率。  相似文献   

5.
目的 探讨新型镍钛(Ni-Ti)记忆合金掌指关节假体的轴向压缩刚度特征,为该假体的临床应用提供生物力学依据。方法 选用10侧完整成人新鲜手标本,按数字表法随机分为假体组和对照组,每组5侧。假体组分别在第2~5掌指关节置入新型Ni-Ti记忆合金掌指关节假体,对照组标本只做切开及缝合处理。假体组和对照组手标本分别解剖游离出第2~5掌指关节,分别以伸直位、屈曲30°、屈曲60°固定于BOSE材料试验机上,分别在载荷为50、100、150、200、250、300、350 N时记录标本的轴向压缩位移,计算垂直和屈曲载荷状态下的轴向压缩刚度。所有标本实验后使用X线机透视,观察有无骨折,有无假体松动、断裂等情况。在假体组和对照组的组内和组间,分别比较第2~5指掌指关节在伸直位和屈曲30°、60°位时轴向压缩刚度。结果 所有标本实验后X线机透视检查显示,无明显骨折,假体无松动、断裂等情况。假体组和对照组第2~5掌指关节的轴向压缩刚度均随着掌指关节屈曲角度的增大而逐渐减小。假体组与对照组比较,第2~5指掌指关节伸直位时轴向压缩刚度差异均无统计学意义(P值均>0.05);屈曲30°、60°时假体组轴向压缩刚度均大于对照组,差异均有统计学意义(P值均<0.05)。假体组和对照组组内比较,在伸直位和屈曲30°、60°位时,不同掌指关节间轴向压缩刚度差异均无统计学意义(P值均>0.05)。结论 新型Ni-Ti记忆合金掌指关节假体轴向压缩刚度符合正常掌指关节的生物力学特征。置入该假体后,不同掌指关节在不同屈曲角度下均具有良好的稳定性。  相似文献   

6.
目的构建侧方静态应力作用下骨盆骨的尸体模型,运用生物力学试验技术在垂直应力试验机上对单纯侧方受力导致的旋转不稳定骨盆骨折的生物力学特点及其发病机制进行初步探讨。方法选取正常成人骨盆试验标本12具,其中男性7例,女性5例;年龄45~68岁,平均年龄57.32岁。分为2组,每组6具。构建侧方撞击的生物力学模型,测量单纯静态侧方应力作用于髂嵴或股骨大粗隆时,不同工况下骶髂关节、髋臼、耻骨支等骨盆常见骨折部位的受力状况,用应变仪获得各试验点的主应变、主方向、垂直位移,以及测量静态应力下骨盆骨折阈值,并构建应变-时间曲线。结果①500 N静态侧方应力作用于髂嵴时,骨盆环结构中固定侧髂骨翼,对侧耻骨上支承载压(397±43)、拉应变(113.2±11.4)最大,受力侧坐骨支应变最小(23±7);髂骨翼位移最大(4.6 mm),髂嵴在静态侧方应力作用下的极限载荷(3 752±425)N;②股骨大粗隆在500 N静态侧方应力作用下,在骨盆环结构中,对侧耻骨上支承载压(277±31)、拉应变(401±53)最大,受力侧髂骨应变值最小(35±11);左耻骨支位移最大(2.3 mm)。股骨大粗隆在侧方应力作用下的极限载荷(4 207±617)N;③静态侧方应力作用于股骨大粗隆时产生的骨盆各点位移均小于作用于骨盆髂嵴时产生的位移。结论①耻骨支及耻骨联合等骨盆前环结构对于维持侧方应力下骨盆环旋转稳定性至关重要。②生物力学试验能较好地反映静态侧方应力撞击下骨盆骨的生物力学特性。  相似文献   

7.
目的研究股骨近端锁定板内固定在动力髋固定粗隆间骨折术后再骨折内固定模型力学情况。方法选取10对老年尸体股骨近端标本,制作双侧股骨粗隆间骨折标本。动力髋螺钉固定后取出固定材料,选择左侧为对照组,用防旋髓内钉进行内固定,选择右侧为观察组,用股骨近端锁定板进行内固定。检测2组骨折模型不同载荷下骨块的垂直位移情况、轴向刚度以及旋转刚度。结果不同载荷作用下,观察组股骨头的垂直位移距离和股骨粗隆的垂直位移距离均明显短于对照组(P0.05);观察组股骨头、股骨粗隆的轴向刚度和旋转刚度均明显高于对照组(P0.05)。结论股骨近端锁定板内固定有助于提高应力载荷,增强轴向刚度以及旋转刚度,是治疗动力髋固定粗隆间骨折术后再骨折的理想内固定材料。  相似文献   

8.
目的比较防腐与聚甲基丙烯酸甲酯(PMMA)人工股骨标本之间的生物力学特性的差异。方法选择单足站立位受力模型,在Instron-8874液压伺服力学实验测试机上对各标本(防腐与PMMA人工股骨)行预加载处理5次,消除股骨松弛、蠕变等时间效应影响后,开始对各标本进行正式实验,每个标本测试5次,各次测试之间应间隔20min,待应变仪上的数值变化小于3με时再记录数据。施加在模型上的总载荷为1200N,以100N分级增量方式加载,实验机压头下降速度为10mm/min。观察防腐与PMMA人工股骨标本近端的载荷-应变关系、股骨头的载荷-位移关系和股骨头的轴向刚度。结果防腐与PM-MA人工股骨标本在2倍于人体体质量的载荷下的载荷-应变关系都基本呈线性变化;在载荷为1200N时,PMMA人工股骨标本的位移明显大于防腐股骨标本的位移(P〈0.01);防腐股骨标本的轴向刚度大于PMMA人工股骨标本(P〈0.01)。结论在进行轴向生物力学实验研究中,往往需要大量的股骨标本,在股骨标本获得日益困难的情况下,PMMA人工股骨标本在一定程度上可以替代防腐股骨标本进行轴向生物力学研究。  相似文献   

9.
目的建立髋臼前壁骨折模型,比较4种内固定方式的生物力学稳定性。方法选取20个防腐成人半骨盆标本,建立髋臼前壁骨折模型。将骨折模型随机分为4组,A组采用真骨盆上缘重建接骨板固定,B组采用真骨盆内缘重建接骨板固定,C组采用顺行拉力螺钉固定,D组采用逆行拉力螺钉固定。对各组标本进行轴向压缩实验,测量骨折断端水平位移,计算剪切刚度,比较4组不同内固定方式的稳定性。结果相同加载载荷下,骨折断端水平位移:A组B组C组D组,内固定剪切刚度:D组C组B组A组。载荷为400 N时各组水平位移及内固定剪切刚度差异均无统计学意义(P0.05),载荷为800 N至2000 N时,除C组与D组间水平位移及内固定剪切刚度差异无统计学意义外(P0.05),其余各组间比较差异均有统计学意义(P0.05)。结论髋臼前壁骨折模型可用于髋臼前壁骨折的生物力学分析,采用拉力螺钉固定髋臼前壁骨折的稳定性高于重建接骨板固定方式,其中顺行拉力螺钉固定与逆行拉力螺钉固定的稳定性相似。  相似文献   

10.
目的 研究半椎板切除、全椎板切除及椎板回植成形对颈椎稳定性的影响。方法 将14例新鲜成年绵羊颈椎标本(C2~7)分为两组,每组7例。每例标本均被施加前屈后伸、左右侧弯和左右轴向旋转6个方向3.0 N·m载荷,测量C3~6运动节段在不同载荷下的运动范围(range of motion, ROM)及中性区(neutral zone,NZ)。对第1组进行完整状态、C5半椎板切除和C4~6半椎板切除3种状态下标本ROM和NZ的测量。对第2组进行完整状态、C4~6全椎板切除和C4~6椎板回植成形3种状态下标本ROM和NZ的测量。结果 与完整状态比较,C5半椎板切除和C4~6半椎板切除状态下标本ROM和NZ没有明显差异,且C5半椎板切除和C4~6半椎板切除两种状态之间标本ROM和NZ也没有显著性差异。与完整状态比较,C4~6全椎板切除与C4~6椎板回植成形状态下在前屈后伸载荷下ROM有显著增大(P <0.05)。C4~6椎板回植成形与C4~6全椎板切除状态比较,标本在后伸载荷下ROM明显减小(P<0.05);而其余载荷下,椎板回植成形和全椎板切除ROM之间没有显著性差异。结论 半椎板切除后,颈椎标本ROM和NZ无明显增加,并不影响颈椎的稳定性。全椎板切除后,颈椎标本在前屈后伸载荷下的ROM和NZ明显增加,颈椎稳定性受影响。椎板回植成形术并没有明显改善椎板切除术后颈椎的稳定性。  相似文献   

11.
报道了模拟正常国人双肢站立位,骨盆在承受体重(300牛顿600牛顿和900牛顿静载荷)时,用应变电测法得到的应力、应变分布、以及各测点的实测线应变,并计算出骨 不同载荷下各测点的最大最小应变值。数据通过电子计算机处理,得出主应力σ1、σ2和主应力方向角度。  相似文献   

12.
Across the entire human body, postural tone might play its most critical role in the body's axis because the axis joins the four limbs and head into a single functioning unit during complex motor tasks as well as in static postures. Although postural tone is commonly viewed as low-level, tonic motor activity, we hypothesized that postural tone is both tonically and dynamically regulated in the human axis even during quiet stance. Our results describe the vertical distribution of postural muscle tone in the neck, trunk, and hips of standing human adults. Each subject stood blindfolded on a platform that axially rotated the neck, trunk, or pelvis at 1 degrees /s and +/-10 degrees relative to the neutral position (i.e., facing forward). The measured resistance to axial rotation was highest in the trunk and lowest in the neck and was characterized by several nonlinear features including short-range stiffness and hysteresis. In half of the subjects, axial muscle activity was relatively constant during axial rotation, and in the other half, muscle activity was modulated by lengthening and shortening reactions, i.e., decreasing activity in lengthening muscles and increasing activity in shortening muscles, respectively. Axial resistance to rotation was reduced in subjects whose muscle activity was modulated. The results indicate that axial tone is modulated sensitively and dynamically, this control originates, at least in part, from tonic lengthening and shortening reactions, and a similar type of control appears to exist for postural tone in the proximal muscles of the arm.  相似文献   

13.
Total hip arthroplasty is a widespread surgical approach for treating severe osteoarthritis of the human hip. Aseptic loosening of standard metallic hip implants due to stress shielding and bone loss has motivated the development of new materials for hip prostheses. Numerically, a three-dimensional finite element (FE) model that mimicked hip implants was used to compare a new hip stem to two commercially available implants. The hip implants simulated were a novel CF/PA12 carbon-fibre polyamide-based composite hip stem, the Exeter hip stem (Stryker, Mahwah, NJ, USA), and the Omnifit Eon (Stryker, Mahwah, NJ, USA). A virtual axial load of 3 kN was applied to the FE model. Strain and stress distributions were computed. Experimentally, the three hip stems had their distal portions rigidly mounted and had strain gauges placed along the surface at 3 medial and 3 lateral locations. Axial loads of 3 kN were applied. Measurements of axial stiffness and strain were taken and compared to FE analysis. The overall linear correlation between FE model versus experimental strains showed reasonable results for the lines-of-best-fit for the Composite (Pearson R(2)=0.69, slope=0.82), Exeter (Pearson R(2)=0.78, slope=0.59), and Omnifit (Pearson R(2)=0.66, slope=0.45), with some divergence for the most distal strain locations. From FE analysis, the von Mises stress range for the Composite stem was much lower than that in the Omnifit and Exeter implants by 200% and 45%, respectively. The preliminary experiments showed that the Composite stem stiffness (1982 N/mm) was lower than the metallic hip stem stiffnesses (Exeter, 2460 N/mm; Omnifit, 2543 N/mm). This is the first assessment of stress, strain, and stiffness of the CF/PA12 carbon-fibre hip stem compared to standard commercially-available devices.  相似文献   

14.

Purpose

Among patients over 50 years of age, separate vertical wiring alone may be insufficient for fixation of fractures of the inferior pole of the patella. Therefore, mechanical and clinical studies were performed in patients over the age of 50 to test the strength of augmentation of separate vertical wiring with cerclage wire (i.e., combined technique).

Materials and Methods

Multiple osteotomies were performed to create four-part fractures in the inferior poles of eight pairs of cadaveric patellae. One patella from each pair was fixed with the separate wiring technique, while the other patella was fixed with a combined technique. The ultimate load to failure and stiffness of the fixation were subsequently measured. In a clinical study of 21 patients (average age of 64 years), comminuted fractures of the inferior pole of the patellae were treated using the combined technique. Operative parameters were recorded from which post-operative outcomes were evaluated.

Results

For cadaveric patellae, whose mean age was 69 years, the mean ultimate loads to failure for the separate vertical wiring technique and the combined technique were 216.4±72.4 N and 324.9±50.6 N, respectively (p=0.012). The mean stiffness for the separate vertical wiring technique and the combined technique was 241.1±68.5 N/mm and 340.8±45.3 N/mm, respectively (p=0.012). In the clinical study, the mean clinical score at final follow-up was 28.1 points.

Conclusion

Augmentation of separate vertical wiring with cerclage wire provides enough strength for protected early exercise of the knee joint and uneventful healing.  相似文献   

15.
Fins incorporated into the design of a dynamic cervical spine implant have been employed to enhance axial load- bearing ability, yet their true biomechanical advantages, if any, have not been defined. Therefore, the goal of this study was to assess the biomechanical and axial load-bearing contributions of the fin components of the DOC ventral cervical stabilization system. Eighteen fresh cadaveric thoracic vertebrae (T1-T3) were obtained. Three test conditions were devised and studied: Condition A (DOC implants with fins were placed against the superior endplate and bone screws were not inserted); Condition B (DOC implant without fins was placed and bone screws were inserted); and Condition C (DOC implant with fins were placed against the superior endplate and bone screws were inserted). Specimens were tested by applying a pure axial compressive load to the superior platform of the DOC construct, and load-displacement data were collected. Condition C specimens had the greatest stiffness (459 +/- 80 N/mm) and yield load (526 +/- 168 N). Condition A specimens were the least stiff (266 +/- 53 N/mm), and had the smallest yield loads (180 +/- 54 N). The yield load of condition A plus condition B was approximately equal to that of condition C, with condition A contributing about one-third and condition B contributing two-thirds of the overall load-bearing capacity. Although the screws alone contributed to a substantial portion of axial load-bearing ability, the addition of the fins further increased load-bearing capabilities.  相似文献   

16.
The biomechanics of bracing in adolescent idiopathic scoliosis is still not fully understood. Finite element models (FEM) have been used but the gravity forces were not included and the production of spinal stresses not evaluated. An improved FEM to simulate brace treatment was thus developed. The 3D geometry of the spine, rib cage, pelvis, and of the trunk external surface of five scoliotic patients was acquired using a multi-view X-ray technique and surface topography. A FEM of the patient’s trunk including gravity forces was created. Custom-fit braces were modeled and their installation simulated. Immediate geometrical corrections and pressures were computed and validated. The resulting compressive loads on the vertebral endplates were quantified. The influence of the strap tension, spine stiffness, and of the gravity forces was evaluated. Results showed that the brace biomechanical action was importantly to prevent the scoliotic spine from bending under the gravity forces. The immediate correction depended on the strap tension and spine stiffness. The distribution and amplitude of computed pressures were similar to those measured with the real braces. After the brace installation, the coronal asymmetrical compressive loading on the vertebral endplates was significantly reduced. In conclusion, the model developed presents improvements over previous models and could be used to better understand and optimize brace treatment.  相似文献   

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