Abstract:
Total hip arthroplasty (THA) is highly successful but still exhibits an annual revision rate near 5%, now most often driven by implant dislocation and hard-on-hard bearing complications. To elucidate the underlying biomechanical failure modes, a novel anatomically grounded three-dimensional finite element (FE) model of the hip—including bone, hardware, and a fiber-reinforced capsule—was developed and rigorously validated against cadaver-based sit-to-stand dislocation tests. The model was then applied to four principal failure scenarios: (1) dislocation mechanics under posterior capsule defects and varying soft-tissue repair techniques, including the effects of obesity and implant geometry on subluxation resistance; (2) detailed contact mechanics of impingement, contrasting bone-on-bone versus hardware edge-loading stress fields; (3) linear elastic fracture mechanics and extended FE (XFEM) analyses of ceramic liner fracture initiation and propagation as functions of cup position, edge radius, and high-body-weight loading during stooping and squatting; and (4) metal-on-metal (MoM) implant wear and trunnionosis, exploring edge-loading sensitivity to cup lip geometry, large-head stability, and micromotion-driven wear under gait and rise-to-stand kinematics. Key findings include the critical role of posterior capsule integrity in resisting dislocation, the predominance of egress-site stresses in impingement, cup orientation thresholds beyond which ceramic fracture is likely, and the exponential increase in trunnion wear with head diameters above 40 mm. By integrating detailed capsule mechanics, contact behavior, fracture criteria, and wear processes, this work provides a unifying biomechanical framework to guide implant design, surgical technique, and patient-specific optimization in THA.
