Factors influencing initial cup stability in total hip arthroplasty.

Background: One of the main goals in total hip replacement is to preserve the integrity of the hip kinematics, by well positioning the cup and to make sure its initial stability is congruent and attained. Achieving the latter is not trivial.

Methods: A finite element model of the cup-bone interface simulating a realistic insertion and analysis of different scenarios of cup penetration, insertion, under-reaming and loading is investigated to determine certain measurable factors sensitivity to stress-strain outcome.

Finite element analysis of resurfacing depth and obliquity on patella stress and stability in TKA.

Patella resurfacing in total knee arthroplasty (TKA) reduces postoperative complications and revisions; however, the optimal cutting depth and angle that minimize patellar strain and fracture remain unclear. We performed three-dimensional finite element analysis (FEA) of resurfacing cutting depth and obliquity to assess the stresses in each component of the knee joint, and fatigue testing to determine cyclic loading conditions over the expected life span of the implant. Maximum stress on the patella increased as cutting depth increased up to 8mm; peak stresses on the idealized button further increased at 10-mm depth.