The impact of subject weight and activity level on over-inserted cemented acetabular cups after Total HIP...

In cemented Total Hip Arthroplasty (THA), several risk factors have been identified with the failure of the acetabular component, including body mass index (BMI), exercise, femoral head size, cup placement, and cement mantle integrity. Elevated BMI and larger femoral heads increase bone and cement stresses, accelerating wear and predisposing to aseptic loosening. This study evaluates the effect of over-inserted acetabular cups on cement mantle interfaces and pelvic bone stresses using two femoral head sizes (28 mm and 36 mm), four body weights (normal, overweight, obese, and morbidly obese), and three activities (one-leg stand, stair descent, and stumbling). Results show that von Mises stresses rise with increasing body weight, activity intensity, and femoral head size, with the highest values observed in the superior periacetabular region of the pelvic bone for the morbidly obese subject during stumbling with the 36 mm head. Stresses at the bone-cement interface exceeded those at the cement-cup interface, particularly in the superior quadrant of over-inserted cups. Our findings suggest that morbidly obese subjects are at a higher risk of aseptic loosening due to the stresses induced in the bone-cement interface during physical activities, resulting in higher peak hip reaction forces. This risk is increased in the case of over-insertion of the acetabular cup, leading to a thinner cement layer. These findings highlight the combined influence of implant design, patient characteristics, and surgical technique on long-term THA performance.