A biomechanical study of the effect of weight loading conditions on the mechanical environment of the hip joint endoprosthesis

Abstract Background Total hip arthroplasty is one of the most successful orthopedic surgical procedures aiming to eliminate pain related to several types of hip arthritis and restore mobility. Obesity has been associated with an increased risk of complications after a total hip arthroplasty such as poor wound healing, periprosthetic joint infection, instability, and aseptic loosening. Methods This paper presents an in-vitro study on composite femoral models to investigate the impact of different weight loading conditions on the mechanical environment of the hip joint endoprosthesis considering normal-weight and overweight individuals from 70 to 110 kg. The micro strains on the femur during single-leg stance of gait were measured on critical stress points based on the Gruen femoral zones. Findings The micro strains increase as the weight increases implying that the displacement in the hip joint endoprosthesis is higher for overweight subjects enhancing the risk of failure. The highest increase was measured in Gruen zone 1 by 5.60% indicating that the great trochanter is subjected to higher stress shielding with increasing the weight. Also, the statistically significant increase of the micro strain values with increasing the weight in Gruen Zones 3 (2.91%), 5 (1.56%), and 11 (1.75%) may enhance the risk for a periprosthetic fracture at the lower region of the prosthesis. Interpretation This is the first biomechanical study which quantifies the effect of increasing weight loading conditions on the mechanical environment of the hip joint endoprosthesis considering different positions of evaluation.