No effect of femoral offset on bone implant micromotion in an experimental model

Abstract

IV, biomechanical study.

Evaluating the primary stability of standard vs lateralised cementless femoral stems – A finite element study using a diverse patient cohort

“…Furthermore, FE predictions indicative of fibrous tissue formation (micromotion) and periprosthetic bone damage (interfacial strains) were within acceptable ranges, for most subjects, suggesting that the standard offset is sufficient to achieve primary stability. This is consistent with a previous insilico study on a single-subject [19], however, the analysis performed on the diverse cohort of femora also…”

“…The study also used a simplified model to represent the musculoskeletal forces, which does not take into account the effect of changing the head centre location (which is a natural result of lateralization) on the musculoskeletal forces. While changes in the head centre location are expected to introduce differences in the muscle and joint contact forces (up to 15%), it is unlikely to induce changes in the peak micromotion and strains large enough to impact the primary stability of the implants [19]. Press-fit interference was not modelled in this study.…”

“…It has been suggested that this may be because lateralised stems tend to be subjected to high torsional loads, which may increase the risk of aseptic loosening of the implant [2]. In contrast, results from a recent in-silico study found that while lateralised stems may influence the muscle forces, the effect on even the peak implant micro-movement, with respect to the host bone is minimal (< 20 µm) to impact the primary stability [19], which is essential for the long-term success of cementless THRs . However, this was based on data for a single subject, which may not be representative of the variation within the THR population.…”

Virtual trial to evaluate the robustness of cementless femoral stems to patient and surgical variation

“…Alteration in the head centre location are expected to induce changes in muscle and joint contact forces (Myers et al, 2018), which are expected to increase the range of variability in the peak interfacial strains, particularly for extremes bounds of the anteversion ranges explored in this study. However, for the range of implant positions considered, the magnitude of change in forces applied to the proximal femur are unlikely to introduce excessive changes to the mean and the overall micromotion/interfacial strain distributions that will significantly impact the primary stability (Amirouche et al, 2016;Heller et al, 2001). The interference due to the press-fit insertion of the implant was not modelled in this study.…”

Femoral Stress Changes after Total Hip Arthroplasty with the Ribbed Prosthesis: A Finite Element Analysis

“…Total hip arthroplasty (THA) is a primary treatment for advanced hip diseases such as severe hip osteoarthritis and avascular necrosis of the femoral head. Each year, over a million patients undergo this operation around the world [1][2][3][4]. Unfortunately, about 10% of patients remain not satisfied with the treatment effect [5][6][7].…”