Implant/Construct Interactions in the Biomechanics of Total Hip Dislocation

描述（由申请人提供）：脱位仍然是仅次于无菌性松动的全髋关节置换术（THA）失败的主要原因。为了补充临床登记或实验室实验研究提供的有限的机制研究能力，已经开发了THA脱位的解剖学和运动学上真实的三维非线性有限元（FE）模型。该公式建立在之前大量FE工作的基础上，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。预处理序列被构造用于单个植入物设计参数和部件的手术定位的有效参数变化。该关节囊在材料上由异质超弹性连续鞘管代表，其解剖结构和机械性能取自早期尸体试验。输入运动学和动力学序列取自（非THA植入）受试者进行脱位倾向挑战动作的早期运动研究。采用伺服液压加载系统和新型经骨盆THA植入方案进行的确证性试验工作再现了撞击/脱位行为方面的计算结果，包括胶囊损害效应，具有可比的定量幅度。初步计算表明，稳定的运动范围和抵抗脱位的力矩强烈依赖于（1）胶囊机械降解的总体程度，（2）内部胶囊物质连续性的局部缺陷（例如，切口）或外部附着完整性（例如，从骨插入物脱离），和（3）手术修复的技术细节。四个假设，相应的具体目标，被构造为一个分析框架，参数研究之间的相互作用的囊完整性，脱位运动的挑战，植入物设计，和组件的手术放置。相关性：THA脱位率变化约一个数量级（约1%-10%），取决于手术入路、植入物设计、部件放置/定向和关节囊的机械能力。这个问题对于翻修手术（“8%的发生率”）尤其令人烦恼，翻修手术在许多外科医生的实践中所占的比例越来越大，并且其中胶囊受损是常见的。近年来，外科医生对这一领域的认识和兴趣大大增加，各种关节囊修复/加固手术显示出前景，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个理想的工具，系统地评估复杂的相互作用的许多因素影响位错倾向，朝着减少这种麻烦的并发症的目标。

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.