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

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.