Evidence for the Applicability of Musculoskeletal Human Models to Improve Outcomes of Total Hip Arthroplasty

Abstract

During the preoperative planning of total hip replacements (THR) the patient’s biomechanical condition is widely neglected. The result can be a suboptimal implant selection and positioning, which may cause muscular dysfunctions, especially for revision THR. Thus, this study provides evidence in the use of musculoskeletal human models (MHM) during preoperative planning to improve postoperative outcomes. Therefore, a patient-specific MHM is placed in the pose of single leg stance. First, gluteus medius muscle activation is simulated in three adapted situations: healthy, after primary THR and after revision THR. In a second step, a parameter study with adjustable implant parameters (neck-shaft angle, femoral offset and antetorsion angle) is executed to investigate the effects on the gluteus medius activation. The gluteus medius activation of all three situations shows a remarkable increase to the status after revision THR, with a high risk of muscular impairments occurring due to muscle weakening. The parameter study demonstrates a considerable influence of the adjustable parameters not only on gluteus medius activation but also on hip joint contact force. Concluding, MHM not only allow the analysis of a patient’s individual biomechanical condition, but also improve biomechanical outcomes by enabling the simulation of different geometrical THR implant parameters during surgery planning to support the surgeon in identifying the optimal implant parameters and positioning from both the muscle function and a kinematical (bony) perspective.