A reliable and representative simulation study to investigate the risk of impingement in total hip replacement (THR) patients.

Objectives The objective of this doctoral thesis is to construct a reliable and representative, three-dimensional experimental model for the systematic evaluation of the range of motion in Total Hip Replacement (THR), through the integration of specific maneuvers at high-risk of dislocation, and contingent upon variable parameters of pelvic version. A secondary aim is to explicate the underlying mechanisms contributing to impingement phenomena. Materials and methods We designed a tridimensional model in a free and open-source simulation environment. Different scenarios were simulated, and the range of motion of the prosthetic hip was assessed. Movements at particular risk of dislocation were assessed, and a study was conducted considering the range of motion of the femur allowed until contact (impingement) between geometries (discriminating bone-to-bone contact, implant-on-implant contact, and implant-on-bone contact). Furthermore, different pelvic version angles were evaluated to assess potential differences. Results The anteverted pelvis registered impingement in a greater number of movements (6 out of 9) and presented an overall reduced range of motion until geometries contact, in particular related to posterior dislocation prone movement. Conversely, the pelvic orientation with the average higher range of motion in different simulation scenarios was the neutral pelvis. The type of impingement that first occurred for most dislocation movements was the implant-on-bone contact. In contrast, the impingement that occurred at higher angles was the implant-on-implant type, which had a relevance only in pure hip extension movements. Conclusions The current thesis offers a methodologically rigorous and replicable experimental framework marked by both robustness and high fidelity to average anatomical and biomechanical realities. The reported findings not only substantiate the importance of pelvic version in THR, defining higher risk for the anteverted pelvis, but also, they highlight the prominent role of implant-on-bone impingement in instability and dislocation.