A Dynamic Model of Hip Joint Biomechanics: The Contributionof Soft Tissues

Before recent advances in computer modeling technology, it has been nearly impossible to define the contribution of soft tissuestructureswhen constructingmodels of the body, and in particular the lower extremity. For almost 100 years, the design and fixationof femoral components for total hip arthroplasty (THA), whether cemented or press fit, have been predicated on the Koch model ofhip biomechanics. A more comprehensive model, which includes the dynamic contribution of soft tissues, has expanded the Koch’sstatic model. This new model has led to a more complete representation of reality and has become the basis for the inclusion of anew stem design element (a lateral flare), a new concept of implant fixation (rest fit), and consequent significant increase in bonepreservation and implant stability.