Implant/Construct Interactions in the Biomechanics of Total Hip Dislocation

描述（由申请人提供）：脱位是全髋关节置换术（THA）失败的第二大原因，仅次于无菌性松动。为了补充临床登记或实验室实验研究提供的有限机制研究能力，已经开发了一个解剖学和动力学上真实的三维非线性有限元（FE） THA脱位模型。该配方建立在之前大量的FE工作基础上，现在还包括植入物与周围解剖骨表面和髋关节囊的相互作用。预处理序列的结构是为了有效地改变单个种植体设计参数和部件的手术定位。胶囊在物质上以非均质超弹性连续鞘表示，其解剖和机械性能取自早期的尸体测试。输入运动学和动力学序列取自（未植入tha的）受试者进行易脱臼挑战动作的早期运动研究。采用伺服液压加载系统和一种新的经骨盆THA植入方案进行的证实性试点实验再现了撞击/脱位行为的计算结果，包括胶囊妥协效应，具有可比的定量量级。试点计算表明，稳定的运动范围和抵抗脱位的力矩在很大程度上取决于(1)包膜机械退化的总体程度，(2)内部包膜物质连续性的局部缺陷（例如，切口）或外部附着体完整性的局部缺陷（例如，骨插入物的脱离），以及(3)手术修复的技术细节。四个假设，具有相应的特定目的，被构建为一个分析框架，用于参数化研究包膜完整性、脱位运动挑战、种植体设计和部件手术放置之间的相互作用。相关性：THA脱位率变化约一个数量级（约1%至10%），这取决于手术入路、植入物设计、组件放置/方向和囊的机械能力。这个问题在翻修手术中尤其令人烦恼（“8%的发生率”），这在许多外科医生的手术中所占的比例越来越大，而且在翻修手术中，胶囊受损是司空见惯的事情。近年来，外科医生对这一领域的认识和兴趣大大增加，各种胶囊修复/加固程序显示出希望，并且在植入物设计和组件放置控制方面出现了许多新的选择。现实的有限元分析是一种理想的工具，用于系统地评估影响位错倾向的许多因素之间的复杂相互作用，以减少这一麻烦的复杂性。

DESCRIPTION (provided by applicant): Dislocation remains second only to aseptic loosing as a leading cause of failure in total hip arthroplasty (THA). To complement the limited capabilities for mechanistic investigation afforded by clinical registries or by laboratory experimental studies, an anatomically and kinetically realistic three-dimensional nonlinear finite element (FE) model of THA dislocation has been developed. The formulation builds on substantial previous FE work, to now also include implant interaction(s) with the surrounding anatomic bony surfaces and with the hip joint capsule. The pre-processing sequence is structured for efficient parametric variation of individual implant design parameters and of surgical positioning of the components. The capsule is materially represented in terms of a heterogeneous hyperelastic continuum sheath whose anatomy and mechanical properties are taken from earlier cadaver testing. Input kinematic and kinetic sequences are taken from earlier motion studies of (non-THA-implanted) subjects performing dislocation-prone challenge maneuvers. Corroborative pilot work experimentally with a servo-hydraulic loading system and a novel trans-pelvic THA implantation protocol has reproduced the computations in terms of impingement/dislocation behavior, including capsule compromise effects, of comparable quantitative magnitude. Pilot work computationally has shown that the stable range of motion and the moment developed to resist dislocation depend strongly upon (1) the overall degree of capsule mechanical degradation, (2) focal defects either of internal capsule substance continuity (e.g., incisions) or of external attachment integrity (e.g., detachment from bony insertions), and (3) technical specifics of surgical repair. Four hypotheses, with corresponding specific aims, are structured as an analytical framework for parametric study of the interactions between capsular integrity, dislocation motion challenge, implant design, and component surgical placement. Relevance: THA dislocation rates vary by about an order of magnitude (approximately 1% to 10%), depending on surgical approach, implant design, component placement/orientation, and mechanical competence of the capsule. The problem is particularly vexing for revision surgery (" 8% incidence), a growing proportion of many surgeons' practices and in which capsule compromise is commonplace. Surgeon awareness and interest in this area has increased greatly in recent years, with various capsule repair/reinforcement procedures showing promise, and with many new options arising in terms of implant design and control of component placement. Realistic finite element analysis is an ideal vehicle for systematically assessing the complex interactions of the many factors influencing dislocation propensity, toward the goal of reducing this troublesome complication.