Wear performance study of a spherical shaft designed rotating hinge knee prosthesis

Abstract This study aims to assess the wear performance of the spherical shaft rotating hinge knee (RHK) prosthesis and examine particle release. The wear test was performed for the spherical shaft RHK prosthesis using a knee joint wear simulator for 5 million cycles. The volumetric wear rate, wear patterns, surface roughness, and wear debris were analyzed. After 5 million cycles of in vitro wear simulation, the volumetric wear rates were found to be 6.26±0.99, 0.22±0.28, and 0.13±0.13 mm3/million cycles for the tibial insert, rotation bushing, and bushing lock, respectively. Polishing, adhesion, and scratches were observed on the insert's articular and backside surfaces. The wear debris analysis revealed the presence of granular and flaky debris, indicating that the wear mechanisms of the spherical shaft RHK prostheses primarily involved adhesive wear, abrasive wear, and fatigue wear. The knee implant with a spherical shaft rotating hinge exhibited good wear performance, with the tibial insert being identified as the main source of wear debris rather than the bushings.