Numerical Evaluations of an Uncemented Acetabular Component in Total Hip Arthroplasty: Effects of Loading and Interface Conditions.

Using finite element (FE) models of intact and implanted hemipelvises, the study aimed to investigate the influences of musculoskeletal loading and implant-bone interface conditions on preclinical analysis of an uncemented acetabular component after total hip arthroplasty (THA). A new musculoskeletal loading dataset, corresponding to daily activities of sitting up-down, stairs up-down and normal walking, for a pelvic bone was generated based on previously validated Gait2392 model. Three implant-bone interface conditions, fully bonded and debonded having two rim press-fits (1 mm and 2 mm), were analyzed. High tensile (2000-2415 μϵ) and compressive strains (900-1035 μϵ) were predicted for 2 mm press-fit, which might evoke microdamage in pelvic cortex. Strain shielding in periprosthetic cancellous bone was higher for bonded condition during sitting up activity, compared to other combinations of interface and loading conditions. Only the nodes around acetabular rim (less than 6%) were susceptible to interfacial debonding. Although maximum micromotion increased with increase in press-fit, postoperatively for all load cases, these were within a favorable range (52-143 μm) for bone ingrowth. Micromotions reduced (39-105 μm) with bone remodeling, indicating lesser chances of implant migration. Bone apposition was predominant around acetabular rim, compared to dome, for all interface conditions. Periprosthetic bone resorption of 10-20% and bone apposition of 10-15% were predicted for bonded condition. Whereas for press-fit (1 mm and 2 mm), predominant bone apposition of 200-300% was observed. This study highlights the importance of variations in loading and interface conditions on in silico evaluations of an uncemented acetabular component.