畸形愈合的跟骨在不同步态位相应力分布的三维有限元研究

目的 对后关节面压缩的跟骨与距骨在步态过程中的应力变化进行生物力学分析。方法 在跟骨有限元模型上切割部分后关节面，模拟跟骨骨折后的后关节面压缩畸形。利用模拟畸形愈合的跟、距骨有限元模型模拟跟距骨在步态过程中三个位相(落地相、中立相、起步相)时的受力状况，进行有限元计算，并与正常状况进行分析。结果 获得了模拟畸形愈合的跟、距骨在三个位相时的应力分布和应力增高区，与正常状况时明显不同。结论 模拟畸形愈合的跟、距骨的应力分布变化对临床研究有重要意义，可对许多临床病理现象做出解释。     

正常与畸形愈合跟骨应力分布的比较研究

 目的 探讨在静力载荷作用下,正常与畸形愈合跟骨的应力分布差异。方法 将正常跟骨有限元模型的后关节面由内向外、由前向后楔形切除,模拟骨折后距下关节面塌陷的畸形愈合模型。切除前B?hler角为35°,切除后为0°。自足跟及跟腱附着点处分别垂直向上对模型施加320 N和160 N的载荷,观察畸形愈合跟骨的Vonmises应力分布,并与正常模型进行比较。结果 畸形愈合跟骨的距下关节面应力降低,应力分布特点为从正常的跟骨前中关节面为主要应力区转为跟骨外侧紧靠跟骰关节处,外侧主要应力区要高于内侧,是支撑载荷的主要部位。从跟骨结构的细化比较来看,首先,距下关节面顶部的塌陷造成跟骨主要应力区部分后移,转至跟腱附着点处由正常的(1.51±0.22) MPa增至(3.11±0.24) MPa,而距下关节面顶部的应力由正常的(6.71±0.37) MPa减至(2.83±0.49) MPa。其次,跟骨前侧近跟骰关节处应力明显加大,由正常的(0.46±0.15) MPa增至(2.13±0.15) MPa,载距突应力由5.18 MPa减少至1.41 MPa。结论 跟骨骨折距下关节面塌陷是多数病理变化的主因,在临床治疗中应先解决距下关节面的塌陷问题,恢复跟骨正常高度,跟骨内部应力的分布对解决跟骨骨折后期出现的相关部位疼痛至关重要。     

跟骨三维有限元模型的建立及其骨折发生机制

目的:建立跟骨三维有限元模型,探讨跟骨骨折发生机制。方法:通过扫描正常人跟骨螺旋CT,精确模拟边界条件,并运用Sap93计算软件运算建立跟骨有限元模型,模型由1959个节点,1496个单元组成。在跟骨有限元模型上模拟踝关节在中立位和背伸20°时的状况后对模型施以500N的垂直轴向载荷,观察模型应力分布和位移情况。结果:跟骨在踝关节中立位时通过跟距外侧的关节面,并且由内后斜向前外方向的跟骨处遭受应力最大。背伸20°受力时除上述位置遭受应力最大外,从跟骨体部走向后距关节面与跟腱之间的部位遭受应力也比较大。结论:高处坠落踝关节中立位时跟骨骨折的发生将从跟距关节面的外侧向内后方向走行;当坠落时踝关节处于背伸位时除产生上述骨折线外,跟骨体部走向后距关节面方向也将发生骨折,同时跟腱附着点附近也会形成撕脱性骨折。     

正常步态下距骨关节面接触特征的有限元分析

[目的]通过有限元法分析正常步态下距骨各关节面软骨应力变化,了解各关节面软骨应力分布的生物力学特征.[方法]利用正常男性的足踝部螺旋 CT 扫描数据,运用三维建模软件,建立足踝部三维几何模型,并对其进行有限元网格划分,分析正常步态下距骨各关节面接触应力及 Von Mises 应力分布.[结果]建立包括骨、软骨、韧带在内的正常人体足踝部三维有限元模型,共21 865 个节点、73 440 个单元,较客观地反映了人体足踝的解剖结构和力学特性.不同位相距骨各关节面接触应力及 Von Mises 应力分布区域和应力值不同.[结论]采用有限元法分析关节软骨应力的生物力学特征是一种可行、有效的方法.     

跟骨Boehler角改变对跟骨应力影响的有限元分析

目的以有限元分析方法探讨Boehler角改变不同角度后跟骨应力的变化情况,为B6hler角作为l临床判定骨折严重程度和评估疗效提供理论依据。方法建立正常足踝模型,并在此基础上建立Boehler角减少5°、10°、15°、20°时的有限元模型,研究5种模型的应力分布、应力峰值及位置。结果正常模型跟骨的应力集中出现在后关节面后内方、后关节面前内方及跟骰关节面,最大应力出现在后关节面后内方,最大应力值16．608MPa。B6hler角减小后跟骰关节面处应力集中消失,B6hler角减少5°、10°、15°、及20°时,应力峰值分别为18．492MPa、18．603MPa、19．674MPa及19．8999MPa。结论Boehler角可作为临味上判定跟骨骨折严重程度和评估跟骨骨折治疗效果的一项指标,且术中应尽可能将B6hler角恢复至正常,若复位困难时至少应复位到减少15。以内。     

踝关节周围韧带损伤对距骨稳定性影响的有限元分析

目的有限元法分析踝关节周围韧带损伤对距骨生物力学稳定性的影响,为临床踝关节周围韧带损伤的治疗提供理论依据。方法基于正常男性的足踝部螺旋CT扫描数据,运用三维重建软件,建立足踝部三维几何模型,最后导入Abaqus 6.9软件中,模拟人体踝关节内旋、外旋的受力状况,分析踝关节周围韧带损伤后距骨各关节面的接触压力及VonMises应力分布。结果建立包括骨、软骨、韧带在内的正常人体足踝部三维有限元模型,踝关节周围韧带在踝关节内旋、外旋时对距骨的生物力学影响不同。结论在外旋作用力下胫距后韧带对踝关节的稳定性具有重要作用,而在内旋作用力下跟腓韧带对踝关节的稳定性具有重要作用。     

跟骨外侧壁切除距下关节融合治疗跟骨骨折畸形愈合

跟骨骨折早期处理不当常会造成畸形愈合,主要表现为跟骨增宽,并由此产生足外侧疼痛、跟腓撞击、肌腱神经卡压等及距下关节炎、后足畸形导致步态改变,临床治疗困难.自2005年3月～2009年10月,笔者采用跟骨外侧壁切除联合距下关节融合手术治疗此类患者7例(9足),其中6例(8足)获得随访,现报告如下. 1 临床资料 1.1一般资料本组6例(8足),男5例,女1例;年龄21～68岁,平均42.5岁.病程8～21个月,平均12.5个月.8足均以跟骨外侧疼痛为主,疼痛点封闭试验阳性,伴有不同程度跛行.跟骨轴位X线片显示跟骨骨折畸形愈合,跟骨增宽,CT显示后关节面不平整.跟骨骨折畸形愈合Sanders分型[1]:Ⅱ型4例6足,Ⅲ型2例2足.6例均无系统疾病.     

跟骨骨折后距下后关节面应力改变的实验研究

目的研究载荷条件下跟骨后关节面骨折后,所受应力的改变对距下关节的影响,为临床治疗提供理论依据。方法取6具包括完整足和胫腓骨远端15～20cm的新鲜标本。剔除皮肤、肌肉和跟腱,保留除外距下关节后方的关节囊部分,保持韧带和关节囊的完整。将压敏片插入距下关节的后关节间隙,中立位状态下分别在500N载荷下,对6具标本的距下关节进行加载,完成完整足的测试。然后模拟原始骨折线用微型摆动锯将跟骨后关节面分为前内和后外2块,接着按解剖复位、后外侧骨折块向跖侧移位2、5、10mm等条件重复上述实验,记录距下后关节面所受应力的改变。结果完整的距下后关节面承载的平均应力为(1.83±0.56)MPa。跟骨后外侧骨折块向跖侧移位2mm时,后关节面所承载的应力为(2.41±0.84)MPa,较完整跟骨承载应力显著增加(P<0.01)。结论跟骨距下关节后关节面骨折跖侧移位≥2mm即应手术复位。     

载距突螺钉内固定治疗SandersⅡ型跟骨骨折的生物力学研究

 目的 探讨载距突螺钉内固定在SandersⅡ型跟骨骨折治疗中的作用及必要性。方法 将跟骨CT扫描后的Dicom数据输入Mimics 12.0软件及Ansys 13.0软件中构建跟骨三维有限元数字模型。而后,将此模型导入Solidworks 2010软件中,根据Sanders分型切割跟骨,建立SandersⅡ型跟骨骨折模型。将AO跟骨钢板及螺钉的几何参数输入Solidworks 2010软件中,在跟骨模型的基础上建立两种内固定模拟,一种为钢板放于跟骨外侧面,在钢板后关节面下方2枚螺钉孔、钢板后方2枚螺钉孔、钢板下方1枚螺钉孔、钢板前方2枚螺钉孔分别垂直跟骨打入松质骨螺钉;另一种为在前一种固定方式的基础上再在钢板后关节面最下方螺钉孔向载距突打入1枚皮质骨螺钉。在相同条件下分别对两种内固定模型加载,行非线性有限元分析,分别计算两种内固定模型的应力分布情况。结果 在相同条件的加载下两种内固定跟骨模型的最大主应力均集中于载距突皮质骨,载距突螺钉内固定模型在骨缝间位移值、跟骨最大主应力值、钢板螺钉内固定系统的最大主应力值方面均较无载距突螺钉内固定模型小,且应力更分散。结论 载距突螺钉内固定治疗跟骨骨折符合生物力学稳定性,可很好地用于临床。     

《中国骨伤》杂志2012年第2期继续教育试题

以下是有关跟骨骨折的选择题,有单选题和多选题。请选出正确答案的序号,填在答题卡中。1.引起跟骨骨折的应力方式有:A.垂直压缩应力B.足外翻应力C.足内翻应力D.撕脱应力E.复合应力2.下列哪种骨折波及跟距关节面:A.跟骨结节纵行骨折B.跟骨外侧跟距关节面塌陷C.载距突骨折D.跟骨前端骨折E.跟骨结节横行骨折3.跟骨骨折手法治疗的原则为:     

Sanders Ⅱ型跟骨骨折螺钉微创治疗的有限元优化分析

目的:探讨Sanders Ⅱ型跟骨骨折微创治疗时螺钉不同固定方式后的生物力学特点.方法:将CT 扫描后的跟骨Dicom 数据输入Mimics 21.0 软件及Ansys 15.0 软件中构建跟骨三维有限元数字模型;将此模型导入UG NX 10.0 软件中,根据Sanders 分型切割跟骨,建立后关节面塌陷的Sander...     

Congruity of the subtalar joint in tongue fracture of the calcaneus: an anatomical study

STUDY DESIGN: An anatomic study. OBJECTIVES: To evaluate the effect of displacement of the fractured posterior facet in tongue fracture of the calcaneus on the congruity of the subtalar joint. METHODS: Eleven feet were used in this study. Seven females and four males with age range from 59 to 78. The specimens were dissected from both the lateral and the medial aspects of the calcaneus to expose these surfaces. A primary fracture line was created first, then a secondary line was engineered to simulate tongue fracture. Displacement of the superio-lateral fragment was done with 5-mm increment. Radiography was performed and the graphs were scanned and studied on specific computer software to explore the effects of displacement on joint congruity. RESULTS: The anterior end of the fragment of the tongue fracture, when displaced, not only is depressed but also rotated in the sagittal plane in a downward or planterward direction. The articular surface of the posterior facet of the calcaneus and the inferior facet of the talus are maintained in congruence with each other despite the varying degree of displacement and rotation. CONCLUSION: Congruity of the subtalar joint in tongue fractures is maintained despite different degrees of displacement. This study explains why the non-surgical treatment outcome is comparable to that of the operative treatment in tongue fractures of calcaneus. It also explains why tongue fractures have a good outcome with closed reduction.     

循原骨折线截骨矫正跟骨骨折畸形愈合

目的 探讨循原骨折线截骨矫正跟骨骨折畸形愈合方法的可行性.方法 2004年8月至2007年5月,跟骨骨折畸形愈合患者25例28足,男23例26足,女2例2足;年龄22～56岁,平均31岁;受伤至手术时间1.5～12个月,平均4.6个月.采用循原骨折线截骨术进行治疗.按照Zwipp和Rammelt跟骨骨折畸形愈合的分类方法进行分类,其中Ⅲ型11例12足,Ⅳ型14例16足.术前均摄双足跟骨侧位、轴位X线片及行CT检查,12例患者(14足)行三维CT重建.根据Sander及Essex-Lopresti分类,参考原始X线片对不同骨折类型制定截骨线,重现原始骨折.根据CT轴位载距突及外侧骨块所带关节面的宽度和轴位骨折线的斜度从前外上到后内下斜行截骨,恢复跟骨的高度,将后关节骨折块向后上撬起,使塌陷的后关节面骨块复位.骨缺损处,用劈下的跟骨外侧壁填塞植骨,或取自体髂骨植骨,最后用钢板螺钉固定.结果 24例26足获得随访,随访时间10～16个月,平均12个月.骨折愈合时间10～14周,平均12周.2例发生伤口感染,经抗生素治疗后10周取出钢板伤口愈合.无一例发生钢板螺钉断裂和骨折再移位.按照Maryland足部评分标准,优10足,良12足,可4足,优良率84%.结论 循原骨折线截骨重现原始骨折,可恢复跟骨的骨性结构,能更好地矫正跟骨各方位畸形,同时保留距下关节,减少了手术对足踝功能的影响,近期疗效满意.     

跟骨骨折内固定方法的有限元模拟比较

目的：对应用不同钢板固定跟骨关节内骨折手术治疗方法进行比较检验。方法：应用三维有限元模拟跟骨关节内冠状面骨折。跟骨的形状与材料属性取自CT扫描图像。模型正确性已经尸体检验。对模型的距下关节面施加600N垂直载荷。检验H型、T型和Y型3种钢板对跟骨骨折的固定效果。结果：H型钢板对骨折固定最为牢固，但T型钢板固定的骨的应力分布最接近正常跟骨且其钢板与螺钉的应力集中程度最小。结论：应用有限元法对不同钢板固定跟骨骨折进行比较检验是切实可行的并能获取有益的信息。     

Stress Distributions and Micromovement of Fragment Bone of Pilon Fracture Treated With External Fixator: A Finite Element Analysis

Osteoporosis and osteoarthritis are common pathological problems of the human bone tissue. There are some cases of pilon fractures associated with these 2 pathological conditions. In terms of treatment, for a normal and healthy bone with pilon fracture, the use of the Delta external fixator is a favorable option because it can allow early mobilization for patients and provide stability for the healing process. However, the stability of the external fixator differs when there is low bone stiffness, which has not been previously investigated. Therefore, this study was conducted to determine the stability of the external fixator to treat pilon fracture associated with osteoporosis and osteoarthritis, particularly to differentiate the stress distribution and micromovement of fracture fragment. Three-dimensional finite element models of the ankle and foot bones were reconstructed based on the computed tomography datasets. The bones consisted of 5 metatarsal, 3 cuneiform, and 1 each of cuboid, navicular, calcaneus, talus, fibula, and tibia bones. They were assigned with linear isotropic behavior. The ankle joint consisted of ligament and cartilage, and they were assigned with the use of linear links and the Mooney-Rivlin model, respectively. During simulation of the gait cycle, 70 N and 350 N were applied axially to the tibia bone to represent the swing and stance phases, respectively. The metatarsal and calcaneus bones were fixed to prevent any movement of the rigid body. The study found that the greatest von Mises stress value was observed at the pin–bone interface for the osteoporosis (108 MPa) model, followed by the osteoarthritis (87 MPa) and normal (44 MPa) models, during the stance phase. For micromovement, the osteoporosis model had the largest value at 0.26 mm, followed by the osteoarthritis (0.09 mm) and normal (0.03 mm) models. In conclusion, the greatest magnitudes of stress and micromovement were observed for the osteoporosis bone and extra care should be taken to treat pilon fracture associated with this pathological condition.     

Characteristic Bone Morphology Change of the Subtalar Joint in Severe Varus Ankle Osteoarthritis

The subtalar joint has a possible compensatory mechanism for supramalleolar deformities; the failure of this mechanism causes the progression of ankle osteoarthritis. However, the reason for this failure has not been fully elucidated. This study aimed to evaluate the characteristics of the morphologic changes in the subtalar joint in varus ankle osteoarthritis using computed tomography. The study included 30 patients with severe osteoarthritis (modified Kellgren-Lawrence classification grade ≥ 3; mean age: 68.5 years) and 30 patients without- or with early osteoarthritis (grade 0-1; mean age: 43.0 years) as the control group. The location of cysts, osteophyte formation in the subtalar joint, and thickness of the subchondral bone plate were evaluated. In the osteoarthritis group, cyst formation was observed on the posterolateral side of the posterior facet of the calcaneus in 6 cases (20%) and of the talus in 7 cases (23.3%). Osteophyte formation was observed in the talus in 21 cases (70.0%) and in the calcaneus in 29 cases (96.6%). Osteophyte formation was observed on the posterior or lateral side of the posterior facet, and osteophyte contact between the talus and calcaneus was observed. The subchondral bone plate of the posterior medial side of the posterior facet of the talus was significantly thicker in the osteoarthritis group. The subtalar joint is less affected in severe varus ankle osteoarthritis containing a thickened subchondral bone plate in the posteromedial aspect of the posterior talar facet.     

Calcaneus fractures with subluxation of the posterior facet. A surgical indication

The charts and radiographs of 118 patients with 126 intraarticular fractures of the calcaneus were reviewed retrospectively. Eleven of 126 (8.7%) calcaneal fractures had injuries consisting of intraarticular calcaneal fracture, lateral subluxation or dislocation of the posterior facet, fracture extension into the calcaneocuboid joint, peroneal tendon subluxation, subluxation of the talus in the ankle mortise, and complete disruption of the anterior talofibular and calcaneal fibular ligaments or fracture of the lateral malleolus. There were six women and five men. The average age was 40 years (range, 17-65 years). The mechanism of injury was a motor vehicle accident in eight and a fall from a height in three. According to the classification of Sanders et al eight fractures were Type II, one was Type III, and two were Type IV. Followup at an average of 26 months (range, 14-38 months) showed that eight of 11 patients (72.7%) had either good or excellent results. When lateral subluxation of the posterior facet of the calcaneus is identified with a preoperative computed tomography scan, operative management is indicated, and the surgeon should search for associated injuries that should be addressed at the time of surgery.