A wireless intraoperative joint force sensing system for total hip arthroplasty

A wireless sensor-instrumented femoral head was developed that enables the intraoperative measurement of three force components in a total hip arthroplasty (THA). The design of the head was 32 mm in diameter with a 12/14 taper at the bottom, being compatible with commonly available THA. Inside the femoral head, there are three Hall effect sensors paired with permanent magnets, along with a microprocessor, a Bluetooth wireless module, a noncontact reed switch, and three lithium button batteries, all components were hermetically encapsulated. These components work together to measure and transmit the hip forces applied to the head during surgery. Through bench-top calibration, the system demonstrated a mean measurement error of approximately 8 % for forces up to 800 N. Additionally the practical applications of the prosthesis were tested on three hips from two cadavers undergoing THA. The hip forces were successively measured as the hip was passively moved, revealing insights into the potential for anterior or posterior dislocations with dislocation-prone positions. Understanding these intraoperative hip forces could aid surgeons in making the optimal decisions regarding implant placement and component selection, to minimize the risk of postoperative complications such as dislocation. Overall, this sensor-instrumented prosthesis will be useful for quantifying intraoperative hip forces.