The combined use of simulation and navigation to demonstrate hip kinematics.

Computer navigation of total hip arthroplasty and computer simulation of hip motions based on collision detection were both introduced more than ten years ago. Neither of these promising technologies has achieved its full potential to improve patient outcomes. Combining these two technologies allows the individual strengths of each to more easily demonstrate hip kinematics in a clinically useful way. All normal and pathologic combined hip motions must be clearly and accurately reported to fully evaluate the kinematics involved in total hip arthroplasty, femoroacetabular impingement syndrome, and other hip disorders. The use of three-dimensional data graphs allows for a rapid and thorough evaluation of the very large data sets that are required for the purpose of making a complete report of all combined hip motions. Data can be obtained from simulations made with use of high-resolution computed tomographic scans and computer-aided implant-design files or from clinically obtained motion analysis on fresh cadavers or normal subjects. The use of these methods and graphics allows for the thorough evaluation of the geometries of current implant designs and will help improve future implant designs. The pathologic structures in hips with femoroacetabular impingement can be modeled in three dimensions, and surgical treatment plans can be developed to provide impingement-free normal hip motion without excessive osseous resection. The combination of these technologies provides hope for the improved surgical placement of total hip implants by providing the basis for a kinematic, impingement-based total hip navigation system.