不同加载速度对大鼠骨生物力学特性的影响

本实验观察了在三点弯曲力学实验中,在不同运动速度（５ｍｍ／ｍｉｎ,２０ｍｍ／ｍｉｎ）的加载条件下,即在不同的加载速度时,大鼠肱骨最大载荷、弹性载荷、最大挠度、弹性挠度、最大应力、弹性应力、最大应变、弹性应变８项骨生物力学指标的变化特点。结果表明：与５ｍｍ／ｍｉｎ加载速度相比较,在２０ｍｍ／ｍｉｎ加载速度下,骨最大载荷、弹性载荷、最大挠度、弹性挠度显著增加（Ｐ＜０．０５）;骨最大应力、弹性应力、最大应变、弹性应变无明显变化。提示：三点弯曲力学实验中,在一定范围内提高加载速度,主要影响骨结构力学特性,而对骨材料力学特性无明显影响     

人体胫骨静力与冲击轴向载荷的生物力学特征

[目的]探讨人体胫骨在静力载荷与冲击载荷作用下发生胫骨骨折的区别。[方法] 20个新鲜人体胫骨标本,随机分为两组,每组10个,左侧和右侧各5个,分别施加静力轴向载荷与动态冲击装置轴向载荷,测量其力学参数。[结果]静力学对照组10个标本的测试表明左侧胫骨的屈服载荷、屈服位移、极限载荷、极限位移均显著大于右侧（P<0.05）。动力冲击组10个标本在冲击速度为2.5 m/s,冲击高度32 cm,落锤重量40 kg的冲击下测试结果表明,左右两侧胫骨标本在动态冲击试验的加速度、冲击极限载荷、动态变形和载荷作用时间脉宽的差异均无统计学意义（P>0.05）。两种加载试验相比较,动态冲击力作用下的胫骨极限载荷显著大于静态极限载荷（P<0.05）,动态冲击力作用下的胫骨动态形变大于静态极限位移（P<0.05）。[结论]与静态轴向载荷相比,胫骨标本在动态冲击载荷状态下的极限载荷和极限位移均显著增加。     

椎动脉的解剖研究及在上颈椎椎弓根置钉中的应用

目的：测量上颈椎椎弓根与椎动脉的位置关系,提高上颈椎椎弓根螺钉置入的安全性。方法：成人头颈部尸体标本6具（12侧）,解剖椎动脉,测量寰椎椎弓根螺钉进钉点处椎动脉下缘距椎动脉沟底部的距离,枢椎横突孔內缘与椎动脉內缘的距离,横突孔内椎动脉的外径,记录数据并进行统计学处理。结果：寰椎椎弓根螺钉进钉点处椎动脉下缘距椎动脉沟底部的距离为左侧（1.96±0.72）mm,右侧（1.99±0.61）mm,枢椎横突孔內缘与椎动脉外缘的距离为左侧（2.23±0.43）mm,右侧（2.30±0.39）mm,横突孔内椎动脉的外径为左侧（3.03±0.48）mm,右侧（2.98±0.75）mm。结论：除了椎动脉高跨病例外,正确置入上颈椎椎弓根螺钉无损伤椎动脉之虞,椎弓根钉置入时应尽量个体化。     

下颌骨截骨术耳后入路保留耳大神经的解剖学研究

目的：为下颌骨截骨术提供解剖学基础,建立二维坐标系,使得行下颌骨截骨美容术耳后入路时能够有效地保护耳大神经的主干及分支。方法：取常规固定头部标本20侧,取一张厚度为0.5mm的透明塑料膜,用圆规在塑料薄膜上建立直角坐标系,其最小刻度为0.2cm,将带有刻度的软塑料薄膜铺于标本的面侧区,坐标原点正对下颌角后下方的最凸点,y轴垂直于该连线（颧弓向外的最凸点与眼裂外侧点之间线段的延长线）。用油画笔将耳大神经比较完整的描点到薄膜上。最后将薄膜平铺于玻璃上,测量得出坐标参数指标。结果：耳大神经各分支的坐标值选三点,腮腺支坐标为：（34.0±2.6,-42.6±3.8）mm,（24.0±4.2,-33.0±4.5）mm,（14.0±2.8,-13.6±3.6）mm。耳后支坐标为：（34.0±2.6,-44.0±5.2）mm,（30.0±3.6,-31.0±5.6）mm,（28.0±2.8,-44.0±5.2）mm。耳垂支坐标为：（12.0±2.8,-44.0±2.6）mm,（14.0±4.6,-36.4±3.0）mm,（16.0±2.7,-31.0±4.6）mm。耳前支坐标为：（-8.0±2.8,54.0±3.4）mm,（8.0±3.6,36.2±3.4）mm,（16.0±2.7,-18.0±4.7）mm。结论：临床医生行下颌骨截骨美容术耳后入路时：①耳后切口线不低于耳廓根部后缘中点与乳突尖连线,可避免损伤耳大神经的耳后支;②游离过程中,经胸锁乳突肌鞘膜深面,紧贴胸锁乳突肌向前游离可减少耳大神经主干损伤。     

膝关节前交叉韧带胫骨止点的软组织解剖标记

背景：膝关节前交叉韧带（ACL）重建时,胫骨骨道定位不准会产生重建韧带与髁间窝的撞击或起不到维持膝关节稳定性的作用。因此,确定ACL胫骨止点的位置非常重要。目的：研究膝关节ACL胫骨止点前内束（AMB）和后外束（PLB）与软组织标记后交叉韧带（PCL）和外侧半月板前角的距离,从而明确ACL胫骨止点在胫骨平台的位置,为ACL损伤双束重建提供理论支持。方法：解剖18个膝关节尸体标本（左膝10个,右膝8个）,测量ACL中点、AMB中点、PLB中点与PCL和外侧半月板前角的距离,并分析左、右膝关节是否存在差异。结果：AMB中点与PCL和外侧半月板前角的距离分别为（15.00±3.97）mm和（19.78±4.10）mm;PLB中点与两者的距离分别为（10.17±5.56）mm和（19.50±4.40）mm;ACL中点与两者的距离分别为（12.67±4.52）mm和（19.61±3.87）mm。左右膝关节ACL中点、AMB中点、PLB中点与软组织解剖标记的距离无明显统计学差异。结论：膝关节ACL损伤行手术重建时,可采用PCL和外侧半月板前角作为定位标记。     

特发性胸椎左侧凸患者的临床及影像学特征

目的探讨特发性胸椎左侧凸患者的临床及影像学特征。方法通过对病史、查体、X线、全脊髓MRJ等检查,回顾性分析11例特发性胸椎左侧凸患者（A组）的临床资料,测量冠状面及矢状面影像学参数,并将相关指标与特发性胸椎右侧凸患者（B组）进行比较分析。结果特发性胸椎左侧凸以男性多见,男：女为7：4。11例患者弯型分布为：三弯1例,双弯（胸主弯／代偿性腰弯）2例,单胸弯8例。主弯的上端椎分布于T5-T8,下端椎分布于T11～L3,平均跨度达7．1＋1．4节,顶椎分布于T8～T11,单胸弯（75％）型患者中6例顶椎位于T9。与右侧凸型相比,特发性胸椎左侧凸型患者胸椎后凸角（T5-T12）较大（31．20±21．8°VS12．8°±9．4°）,差异有显著统计学意义（P〈0．01）,其余影像学参数两组间比较均无统计学差异。结论特发性胸椎左侧凸患者影像学上具有一定的特征性：在冠状面上,特发性胸椎左侧凸的侧凸模式与右侧凸型相似,呈“镜像”模式;但在矢状面上,特发性胸椎左侧凸型患者胸椎后凸角趋于正常,甚至呈过度后凸,与右侧凸型不同。     

椎弓根劈裂对内固定稳定性影响的生物力学研究

目的探讨椎弓根螺钉内固定时椎弓根皮质劈裂对骨折椎体稳定性的影响。方法取新鲜成年羊胸腰椎脊柱标本(T14~L2)20具,随机分为A、B两组。在A组和B组标本的L1椎体上分别制作单椎体压缩骨折模型,再单独对B组标本T14胸椎任意一侧的椎弓根行外侧(1/4~1/2)切除,作为椎弓根劈裂椎体骨折模型。然后对A、B两组分别置钉,进钉深度为钉道全长。标本模型固定后,在HY-3080微机控制电子万能材料试验机上,以频率为1.5 Hz的载荷对两组标本模型行10 000次疲劳实验,分别测量疲劳实验后两组标本前屈、后伸、左侧弯、右侧弯4个方向运动范围的大小和疲劳实验后两组标本模型螺钉拔出力大小,并比较两组差异。结果疲劳实验后A组各个方向活动范围:前屈(1.81±0.14)mm,后伸(1.68±0.37)mm,左侧弯(4.08±0.41)mm,右侧弯(4.18±0.12)mm;B组各个方向活动范围大小:前屈(4.49±0.40)mm,后伸(3.72±0.51)mm,左侧弯(6.67±0.64)mm,右侧弯(6.73±0.58)mm;A组各个方向活动范围均小于B组(P0.01)。疲劳实验后A组螺钉最大拔出力为(252.34±51.27)N,B组螺钉最大拔出力为(115.50±36.74)N,最大拔出力A组大于B组(P0.01)。结论椎弓根皮质劈裂将严重影响骨折椎体内固定的稳定性。     

前交叉韧带胫骨平台止点的MRI测量及临床意义

目的应用MRI测量前交叉韧带（ACL）胫骨平台止点,为临床生理等长重建ACL提供参考。方法选择100例正常的膝关节磁共振检查结果,在适当的切面上绘制并测量胫骨平台前缘至后交叉韧带（PCL）前缘之间直线距离（AP）、在该径线上ACL胫骨侧止点中心至胫骨平台前缘之间距离（IA）、ACL胫骨止点中心至PCL前缘切线距离（DL）,并计算IA/AP的比值。结果IA为（19.5±2.8）mm,AP为（38.5±3.6）mm,IA/AP为（50.6±4.8）%,DL为（16.3±2.0）mm。结论MR I可用于测量ACL胫骨侧止点,重建ACL胫骨侧止点定位于胫骨平台中点稍后方可能更为合理。     

人体股骨应力分布的研究

目的 :测试人股骨在相同载荷状态下不同截面和部位的应力分布情况。方法 :取健康成人新鲜股骨标本 4只 ,将其自上而下四等分 ,在其等分点划周线 ,并将截面周长四等分 ,确定各面的后内前外 ,4个标志点。用MTS试验机进行各面各点的纵向压缩、三点弯曲及轴向扭转测试。结果 :测试结果显示 ,股骨干在相同载荷时各个截面所承受的载荷不同 ,纵向压缩 10 0 0N时 ,压应变在近端 1/4内侧点最大 ,平均值为 - 1.0 5E - 0 3(mm/mm) ,张应力在其外侧点最大 ,平均值为 6 .6 3E - 0 4 (mm/mm)。三点弯曲在 30 0N压力时 ,股骨中间 1/2端 ,内侧点为最大张应变 ,平均值为 1.18E - 0 3(mm/mm)。轴向扭转对股骨下段以N·m·s的速度施加N·m外翻扭矩时 ,近端 1/4前侧点 ,扭转角度最大为 1.85°。结论 :在相同载荷下股骨干不同部位所受力不同 ,揭示了股骨干各种骨折类型的创伤机理。     

站位活动腰椎小关节三维CT测量

[目的]分析站立活动时腰椎小关节（lumbar facet joint, LFJ）在体三维运动学特征。[方法]招募10名无腰椎疾病的志愿者。通过高分辨CT获取志愿者腰椎模型并与双荧光透视成像系统获取的图像相匹配,可再现LFJ瞬时运动状态,并分析其位移和旋转角度等运动学特征。[结果]屈伸运动中,在L4～L5节段的旋转范围最大（3.6±2.7）°（P>0.05）。平移范围在L5S1节段最大（P>0.05）。左右平移范围在前后方向上（Y轴方向） L3～L4右侧显著大于左侧[(0.9±0.5)mm vs (0.4±0.5)mm, P<0.05],L4～L5节段左侧显著大于右侧[(1.6±0.8)mm vs (1.1±0.4)mm, P<0.05]。侧弯运动中,在L3～L4节段的旋转范围最大（4.9±4.4）°（P<0.05）。平移范围在L3～4节段最大（P>0.05）。L4～L5水平的左右LFJ平移范围在左右方向（X轴方向）左侧显著大于右侧[(0.7±0.5)mm vs (0.6±0.4)mm, P<0.05]。旋转运动中,L3～L4节段的旋转范围最大...     

Does zoledronate therapy make mandibular bone susceptible to fracture? A radiographical and biomechanical study in rats

IntroductionThe aim of this study was to evaluate the effect of zoledronate therapy on susceptibility of mandibular bone to fracture in rats.MethodsFifty rats were randomly allocated to two groups of 25 animals. The rats in group Z received monthly intravenous infusion of 0.06 mg/kg zoledronate for 6 months. The rats in the group C were injected with an equal volume of saline in the same manner. A month after the last zoledronate/saline administration, all 50 rats were euthanized. Using a cone beam computed tomography, the cortical thickness of inferior border of mandible and the mandibular bone mineral density were calculated, and using a three-point bending test, the peak load failure and the ultimate stress of mandibular bone were determined.ResultsThe mean mandibular inferior cortical bone thickness and the mean bone mineral density were significantly larger in zoledronate-treated rats (0.30 ± 0.02 mm and 1045.00 ± 185.79, respectively) compared to control rats (0.21 ± 0.01 mm and 878.66 ± 166.53, respectively). The peak load and the ultimate stress were lower in the zoledronate-treated hemimandibles (84.61 ± 33.62 N and 1.76 ± 0.72 MPa, respectively) compared to the control hemimandibles (98.36 ± 16.5 9 N and 2.03 ± 0.44 MPa, respectively).ConclusionZoledronate therapy reduced the mechanical strength of the mandibles, implying an increased risk of mandibular fracture in rats.     

Evaluation of anatomical axis-joint center distance and anatomical axis-joint center ratio in distal femur and proximal tibia in coronal plane of Indian population

BackgroundRadiographic evaluation of the anatomical geometry of the bone is important for executing reconstructive surgeries like deformity correction, limb lengthening and joint replacements. Various studies have been done in the past to define the anatomic placement of implant inside the bone. The aim of this study is to evaluate the distance between the anatomical axis and joint center of the distal femur (aJCD-f) and proximal tibia (aJCD-t) along with the ratio of anatomical axis-joint center distance of distal femur (aJCR-f) and proximal tibia (aJCR-t) of the skeletally mature individual of Indian population along with its application in day to day practice.MethodsData is procured from the standard radiographs of the knee on large films. The anatomical axis is drawn on both sides of tibia and femur in a standard fashion. These lines intersect the horizontal drawn line at the intercondylar notch of femur and joint orientation line of the tibia. The aJCD-f, aJCD-t, aJCR-f, aJCR-t are then measured. Also the center of the inter-spinous distance of the tibia is measured from the anatomical axis (aSCD-t).ResultsA total of 182 x-rays of skeletally mature individual were included with mean age of 46.35 ± 13.93 years. Of them 81 were males and 101 were females. There were 89 x-ray of left side and 93 x-ray of right side. The mean width of the femur at the intercondylar notch is found to be 76.78 mm (±7.40). The mean aJCD-f is found to be 3.87 mm (±2.44), aJCR-f to be 0.50 (±0.06). The mean width of the tibia is found to be 76.80 mm (±6.48). The aJCD-t is found to be 2.20 mm (±1.41), aJCR-t to be 0.50 (±0.03). The aSCD-t at the level of tibial spine is found to be −0.23 mm (±2.84). There was significant difference in the width of the femoral condyle of males 82.13 mm (±0.65) and females 72.48 mm (±0.55). Males showed mean aJCD-f of 3.59 mm (±2.42) and females showed 4.10 mm (±2.46). The aJCR-f is found to be significantly different between males 0.49 (±0.05) and females 0.51 (±0.07). There is significant difference between the width of the proximal tibia between males 80.83 mm (±0.68) and females 73.56 mm (±0.46). The aJCD-t of males and females is found to be 2.28 mm (±1.25) and 2.16 mm (±1.54) respectively. The aJCR-t is found to be significantly different between males 0.49 (±0.03) and females 0.50 (±0.04). While the mean distance of the anatomical axis from the lateral tibial spine is 0.23 mm lateral to the center of the inter-spinous distance and is found to be same in both males and females −0.23 mm (±2.84).ConclusionThe coronal plane parameter like aJCD, aJCR of femur and tibia and aSCD-t of tibia can be a useful parameter to calculate in the ‘real world’ settings for reconstructive surgeries like deformity correction, nailing through the knee for femur and tibia as well as replacement surgeries around knee.     

Effects of hormonal conditions and drugs on both muscle and bone strength can be assessed in a single rat test

Strength of both muscles and bone are important for fracture prevention in osteoporotic individuals. Therefore, drugs that are preclinically tested in animals for preventing or treating osteoporosis, and reducing fracture risk, should not only be checked for their effects on bone strength, but also for those on muscle strength. We developed a rat model to measure both in the same animal, using a single test. The model is based on an in vivo, ventral three-point bending test of the lower leg (Nordsletten L. and Ekeland A. J Orthop Res 11:299-304; 1993). This model was developed to test the contribution of triceps surae muscle contraction to the strength of the tibia. We hypothesized that this same test can be applied to determine bone and muscle strength independently, in an absolute sense. To investigate this possibility, the muscle contribution to bone stresses was estimated from mechanical analyses, based on direct assessment of muscle strength in a separate test. Sixteen mature female Wistar rats were used, half of which were ovariectomized. After 12 weeks, the rats were tested in vivo in three-point bending of the right lower leg during muscle contraction, and then the isolated triceps surae muscle strength in the left lower leg was measured separately, in another model. The rats were then killed, and the left nude shafts were tested mechanically in three-point bending in vitro to determine structural strength of the bone alone. Ultimate external bending moments of the in vivo and in vitro tests, maximal muscle force, and geometrical parameters formed the basis for the analysis. While contracting, the triceps surae loads the tibia in axial compression and bending. We found that the axial compressive stress on the bone due to muscle contraction was less than 2.5% of the bending stress this produced. This indicates that muscle contribution to lower leg strength is due almost entirely to the bending moment it produces, counteracting the external moment put on the leg by the testing device. Thus, the difference between the in vivo (lower leg) and in vitro (nude tibia) failure bending moments is approximately equal to the maximal muscle bending moment. This information can be applied to test the effects of hormonal conditions and drugs on both muscle and bone strength independently, in a single rat test, using the aforementioned procedure.     

Stress-Protection After External Fixation on the Intact Rabbit Tibia

Bone loss due to the stress-protecting effect of a metal plate on intact bone is a well-known phenomenon. The purpose of the present study was to find whether a similar effect is caused by external fixation.

External mini-fixation was applied on the intact rabbit tibial diaphysis of one leg. The other tibia served as control. The animals were sacrificed after 6 or 12 weeks, and both tibiae biomechanically tested in three-point bending. The bone mineral content was measured by photon absorptiometry.

No significant changes in bone strength, stiffness or mineral content were found after 6 weeks. The strength and stiffness were significantly reduced after 12 weeks. The median strength and stiffness at that time were 87 and 88 per cent, respectively, in relation to the control bones. The mineral content in the bone segment which had been stabilized by external fixation was significantly reduced after 12 weeks (median 90 per cent of the values for the control bones). No significant change in the mineral content occurred at a level in the tibial diaphysis distal to the external fixation device.

It is concluded that the stress-protecting effect caused by external mini-fixation on the rabbit tibia occurs later, and is less pronounced, than that caused by metal plates.     

Standardization of tibial fractures in the rat.

The influence of the fracture level on the biomechanical properties of healing rat tibial fractures has not been investigated so far, despite the widespread use of rats in fracture healing studies. Fractures were produced in four different zones in the right rat tibia and immobilized with a K-wire. A fifth group of rats was not fractured. After 40 days of healing the fractures and the non-fractured bones were tested in three-point bending. A distinct correlation was found between fracture level and mechanical parameters: maximum load, maximum stiffness, and maximum stress decreased the more distal the fracture was located. In the non-fractured bones, maximum load and maximum stress were constant in all four zones tested, whereas energy absorption increased in the distal part of the tibia. No influence of the healing fracture was found on the contralateral, non-fractured tibia, compared with the animals left undisturbed, and the mechanical properties of the right and the left tibia were found to be symmetrical in terms of mean values. Four different methods of determining the area moment of inertia were investigated, and the simple method of approximating the cross section to an elliptical annulus was found to correlate well with the area moment of inertia, determined from computer tracings of bone slices prepared from the test specimens after the bending test. The computer tracings were corrected for the compression of the specimens caused by the mechanical test.     

The significance of postoperative stability for osseous repair of a multiple fragment fracture. Animal experiment studies

The significance of postoperative mechanical stability for bony repair of a comminuted fracture was investigated in an animal experimental study comparing four commonly applied operative methods of stabilizing fractures: (1) flate osteosynthesis combined with lag screw fixation after reduction of the fragments; (2) bridging plate osteosynthesis; (3) external fixation; (4) static interlocking intramedullary nailing. As the fracture model, a triple-wedge osteotomy of the right sheep tibia was used. The results of in vitro testing of stiffness (N/mm) of each of the four osteosyntheses was as follows: anatomical plate: 746 N/mm; bridging plate 434 N/mm; external fixation 625 N/mm; nailing 416 N/mm. Eight weeks after the operation, the tibiae were explanted and the contralateral tibiae of six sheep were taken as a control group. The three-point bending test revealed no significant difference in bending deviation: anatomical plate 47.58 +/- 22.57 microns; bridging plate 33.93 +/- 7.67 microns; external fixation 33.83 +/- 8.02 microns; nailing 33.0 +/- 17.23 microns. However, it was noted that there was a slightly higher tendency towards stiffness of the bones after bridging plate osteosynthesis, external fixation and interlocking intramedullary nailing and that the amount of stiffness resembled that in non-operated control animals (25.56 +/- 6.66 microns). On the other hand, anatomical plate osteosynthesis showed less stiffness. To assess the tensile strength at the osteotomy area, bone samples were prepared and tested for failure on a material testing machine. The tensile strength of the bone samples showed a distinct difference in all experimental groups according to their anatomical location.(ABSTRACT TRUNCATED AT 250 WORDS)     

Standardized bending and breaking test for the normal and osteoporotic metaphyseal tibias of the rat: effect of estradiol, testosterone, and raloxifene.

The fracture of bone plays a key role in osteoporosis. BMD measurement, however, is only an indirect parameter of this phenomenon. We therefore developed a highly sensitive three-point bending test for the metaphyseal tibias in rats to evaluate stiffness and strength. This was validated in a right-left comparison and a bioassay with soy-free food, estradiol, raloxifene, and testosterone in orchidectomized rats. INTRODUCTION: Osteoporosis becomes manifest predominantly in the metaphyseal rat tibia. The anti-osteoporotic character of substances should, therefore, be tested (mechanically) in this bone area. MATERIALS AND METHODS: We evaluated a new three-point bending test for the metaphyseal tibia in rats in a right-left trial. In an animal experiment, we studied the change of bone quality under estradiol (E)-, raloxifene (R)-, and testosterone (T)-supplemented food and compared it with trabecular BMD (qCT). RESULTS: In the right-left comparison, the mean difference between the metaphyseal loads of both tibias in 37 rats was 8.43% for the maximum load (Fmax) and 6.46% for the failure load (fL). These results show the high reproducibility of the test, because they are close to the usual intraindividual difference of the two extremities. In a second experiment, four groups of 11 3-month-old male orchidectomized rats were fed with soy-free food only (C) or with the additives E, T, or R for 12 weeks. E and R were similar for Fmax and fL. There were significant differences in the stiffness (E = 406.92 N/mm versus R = 332.08 N/mm), the yield load (yL; E = 99.17 N versus R = 83.33 N), and the ratio between yL and Fmax (E = 86.33% versus R = 76.37%). T was similar to the controls concerning F(max), fL, and stiffness. There were significant differences in yL (T = 49.00N versus C = 39.5N) and the ratio between yL and Fmax (T = 64.28% versus C = 51.28%). CONCLUSIONS: Estradiol is superior to raloxifene concerning stiffness and yield load, and both are superior to testosterone. We conclude that the described three-point bending test for the metaphyseal tibia is a highly sensitive method to study hormones and substances with regard to their osteoprotective character. The precision and the low SD of the presented results are superior to the data from qCT and the calculated index of stiffness (SSI).     

Peroneal artery safe zone in the posterolateral approach to the distal tibia: A CT angiogram based anatomical study

ObjectivesThe posterolateral approach to the distal tibia is commonly used for stabilisation of ankle fractures as it allows good visualisation and direct reduction of the posterior distal tibia and malleolar fragments. This approach can also be used for internal fixation of an associated lateral malleolus fracture. The aim of our study is to describe the surgical anatomy of the peroneal artery (PA) in relation to the tibial plafond and the distal fibula; thereby suggesting a safe zone during proximal dissection of posterolateral approach.MethodsUsing Computed Tomography Angiographic (CTA) study, the course of the PA in relation to the tibial plafond and distal fibula was analysed in 142 lower limbs (bilateral limbs of 71 adult patients; 43 males and 28 females). Axial, coronal, and sagittal CT sections were cross-linked to specify the position of the PA. The PA course was identified and the level of its distal bifurcation over the tibia was marked. Perpendicular measurements were made from this point to the tibial plafond and tip of distal fibula.ResultsThe PA bifurcated distally at mean 58.3±24.2mm (SD) (range: 37.0–115.0mm) proximal to the right tibial plafond and mean 81.9±24.4mm (range: 54.0–137.0mm) from the right distal fibular tip. In the contralateral side, the PA bifurcated at mean 57.9±23.3mm (range: 36.0–125.0mm) proximal to the left tibial plafond and 81.8±23.9mm (range: 54.0–147.0mm) from the left distal fibular tip. The difference between the right and the left side of distal bifurcation point diameter of the same patient was assessed, range (0.0–58.0mm) with median 2.0mm and IQR 10.0mm. Three different PA vasculature patterns were identified.ConclusionsIt is important for surgeons to be aware of the surgical anatomy of PA to avoid inadvertent injury during posterolateral approach to distal tibia. The PA may bifurcate as close as 36mm from the tibial plafond with possible variation bilaterally. Therefore, special attention needs to be considered by the operating surgeon while dissecting in this region due to the wide anatomical variation in vasculature. However, once the PA is mobilised, any fixation modality including posterior buttress plate could be safely performed.     

Biomechanical evaluation of retrograde docking nailing to a total hip arthroplasty stem in a periprosthetic femur fracture model

IntroductionSlotted nails allow a connection to a total hip arthroplasty (THA) stem and act as intramedullary load carrier. This study compares construct stiffness, cycles to failure and failure load between a retrograde slotted femur nail construct docked to a THA stem and a lateral locking plate in a human periprosthetic femur fracture model.Materials and methodsIn seven pairs of fresh-frozen human anatomic femora with cemented THA, a transverse osteotomy was set simulating a Vancouver type B1 fracture. The femora were instrumented pairwise with either a retrograde slotted nail coupled to the prosthesis stem, or a locking plate plus a locking attachment plate. Four-point mediolateral bending, torsional and axial bending construct stiffness was investigated via non-destructive tests. Cyclic testing under progressively increasing physiologic loading was performed at 2 Hz until catastrophic construct failure.ResultsMediolateral bending stiffness did not differ significantly between the two groups (P=0.17) but exhibited a biphasic profile with significantly increased stiffness in both groups (P<0.01). Nail constructs provided a significantly lower torsional stiffness (0.49 ± 0.66 Nm/°) than plate constructs (1.70 ± 0.86 Nm/°), P=0.03. Axial bending stiffness did not differ significantly between the groups (Nail: 605 ± 511 N/mm; Plate: 381 ± 428 N/mm), P=0.61. Cycles to failure and failure load were significantly higher for the plate constructs (25’700 ± 8’341; 3’070 ± 1334 N) compared with the nail constructs (20’729 ± 7’949; 2’573 ± 1295 N), P=0.04.ConclusionThe docking nail construct provides an intramedullary fixation with connection to the prosthesis stem; however, it is biomechanically weaker in stable fractures compared to the plate construct.     

小牛胸腰椎解剖、生物力学研究及其临床意义

目的　测量小牛胸腰椎相关解剖数据并测试其生物力学性能 ,探讨其作为胸腰椎前路内固定模型的可行性。方法　采集 1周以内的新鲜小牛胸腰椎脊柱标本 2 0具 ,测量椎体及椎间盘的最大横径、矢状径和前部高度。测试屈曲、伸展、侧屈及扭转状态下的载荷 -应变、载荷 -位移关系以及最大载荷时的应力强度及轴向刚度 ,并进行极限力学性能测试。结果　小牛胸腰椎椎体及椎间盘矢径、横径、高度自T10 至L5逐渐递增 ,椎体横径与矢径之比约为 1∶1,其T10 ～L5段椎间盘高度之和与椎体高度比值为 1∶0 .9。小牛胸腰椎载荷 -应变及载荷 -位移关系呈线性变化 ,生理载荷下屈曲、伸展及侧屈状态下的应力强度分别为 (2 .86± 0 .2 4 )N/mm2 ,(2 .17± 0 .2 0 )N/mm2 ,(5 .2 9± 0 .5 0 )N/mm2 。屈曲、伸展、侧屈及扭转状态下的轴向刚度分别为 (37.13± 4 .30 )N/mm ,(35 .38± 4 .2 0 )N/mm ,(34.5 6± 4 .2 0 )N/mm ,(5 1.6 9± 1.6 2 )N/mm。结论　小牛胸腰椎形态及大小可满足前路内固定模型的需要 ,以小牛标本作为体外非破坏性生物力学实验模型具有可行性。