Biomechanical comparison of newly designed stemless prosthesis and conventional hip prosthesis – An experimental study

Abstract

Local bone loss after implantation of traditional stem‐type prostheses remains an unsolved problem during the long‐term application of total hip replacement. The stress shielding effect and osteolysis were thought to be the two main factors that result in local bone loss after prosthesis implantation. A newly designed stemless cervico‐trochanteric (C‐T) prosthesis was thus developed to reduce stress shielding and osteolysis caused by the implantation of conventional stem‐type prosthesis. Eight synthetic femora were implanted with C‐T and porous coated anatomic (PCA) prostheses. Under 2,000‐Newton load, the surface strains of proximal femora were compared between the intact, PCA press‐fit femora and the C‐T implanted femora with three different fixation modes: two‐screw fixation, three‐screw fixation, and three‐screw combined with cement fixation. The results revealed that stress shielding in the C‐T implanted femora was significantly eliminated compared to that of the PCA implanted femora (p<0.01). No statistical difference in strain magnitude was found for the C‐T implanted femora among the three different fixation modes (p>0.1). The C‐T implanted femur has more physiological strain distribution. Moreover, from the C‐T prosthetic characteristic design, the localized osteolysis would be also reduced due to the overall coverage of neck‐trochanteric area. The newly designed C‐T prosthesis may be a useful alternative to the traditional stem‐type prosthesis in the future.