Automated range-of-motion device for total hip arthroplasty prosthesis

Hip simulators are regularly used by researchers to assess total hip arthroplasty (THA) implants, range of motion, stability, and alignment of acetabular cup and stem. Previous papers have described three types of simulators: three-dimensional protractors, biaxial rocking motion (BRM) protractors, and single-axis prosthetic range-of-motion (PROM) devices. We have developed a new hip simulator in which the ROM device is completely automated in three independent axes (elevation, internal/ external rotation, and plane of elevation). Coupled with the simulator, we used a FaroArm Gold Series coordinate measuring machine (CMM) to accurately align the implant components. The results show that the methodology and alignment setup are accurate and repeatable. With this simulator and digitizer, we are able to study the characteristics of numerous THA implants at various orientations of the pelvis, acetabular cup, stem, and femur.