Acetabular Cup Seating Impact Sensing for Press-Fit Acetabular Cup Fixation

Total Hip Arthroplasty (THA) is an excellent and reliable pain relieving operation which improves the function and quality of life for patients disabled by osteoarthritis [1]. Non-cemented hemispherical acetabular cup implants are now popular and accepted by surgeons world-wide [2]. In surgery, the acetabular cup is impacted into the native acetabulum with a cup impactor and hand-held mallets. Surgeons rely on multiple impacts to achieve the satisfactory stability and fully seat the implant [3]. The impacts on cup impactors greatly affect the quality of the surgery. Quantifying the load-transfer at the bone-implant interface and the understanding of the distribution pattern [2] is essential to determine the optimal force range that can satisfactorily seat the hemispherical acetabular cup to achieve mechanical stability without causing potential damage to surrounding tissue. This paper presents a novel acetabular cup seating impact capturing system that quantifies and records the dynamic impacts applied on an acetabular cup by surgeons using a cup impactor with different sized mallets. The system is an integrated mechatronics system. It consists of three modules: microcontroller-based sensing, wireless communication and PC-based data acquisition. The system is designed as an add-on unit to the cup impactor. Laboratory-based preliminary testing was performed on the system by surgeons using synthetic polyurethane left hemipelvis saw bones. Dynamic impacts applied on a non-cemented hemispherical acetabular cup were captured, recorded and wirelessly transferred to a computer in real time.