BACKGROUND:The reasonable implantation range of femoral prosthesis in unicompartmental knee arthroplasty in patients with osteoporosis has not been investigated,and previous studies have often been based on unicompartmental knee arthroplasty models in normal bone,with fewer mechanical studies in models with non-normal bone.Complications after unicompartmental knee arthroplasty have been shown to be highly associated with osteoporosis. OBJECTIVE:To analyze the biomechanical effects of the coronal inclination of the Sled fixed platform femoral prosthesis on unicompartmental knee arthroplasty in patients with osteoporosis and to find the correlation between osteoporosis and mid-and long-term complications after unicompartmental knee arthroplasty. METHODS:Based on the digital imaging technology to obtain the data of the knee joint and prosthesis,a normal bone knee model is then created by using specialized software such as Mimics and Geomagic studio.Based on a validated normal bone knee model,an osteoporotic knee model was created by changing the material parameters.Totally 14 unicompartmental knee arthroplasty finite element models were created using Sled fixed platform femoral prosthesis:standard position(0°),varus and valgus angles:3°,6°,9° in the normal bone and osteoporosis groups.Stress changes on the surface of polyethylene liner,cancellous bone under tibial prosthesis,and cortical bone were calculated and analyzed in all unicompartmental knee arthroplasty models. RESULTS AND CONCLUSION:(1)In the osteoporotic models,the high stress values of the polyethylene liner surface and the cancellous bone under the tibial prosthesis increased with the increase of the tilt angle of the femoral prosthesis,and the high stress values of the cortical bone surface under the tibial prosthesis increased with the increase of the prosthesis valgus angles and decreased with the increase of the varus angles.(2)For the polyethylene liner surface as well as the subcortical bone surface of the tibial prosthesis,the high stress values of the models for each inclination angle in the osteoporosis group were greater than those of the corresponding models in the normal bone group.For the surface of the cancellous bone under the tibial prosthesis,the high stress values of the tilt angle models of the osteoporosis groups were smaller than those of the normal bone groups.(3)Osteoporosis may cause biomechanical abnormalities in the internal structures of the knee after unicondylar replacement,increasing the potential risk of postoperative aseptic loosening of the prosthesis and periprosthetic fractures.Varus and valgus of the femoral prosthesis in the coronal plane should be avoided as much as possible when performing medial unicompartmental knee arthroplasty with a Sled fixation platform in osteoporotic knees.