A Study On The Geometrical Morphological Dimensions Of Knee Joint Prostheses For Chinese

There are no significant changes in the main shapes and design directions in the development of knee joint prostheses over the two decades. Most factories are trying to provide more dimensions and more dimension ratio to gain the maximal cover of the cut surface to reconstruct the knee joint. The majority of the knee joint prostheses used in China are designed by and according to the Europeans and Americans. And it is a paucity of data concerning the measuring dimension result of the distal part of the femur, the proximal part of the tibia and the patella during the TKA (total knee arthroplasty). So we made the experiments whose objective were to measure the exact parameters of the Chinese distal part of the femur, the proximal part of the tibia and the patella during the TKA and provide anatomic data for the design of the knee joint prostheses.Experiment 1: Measurement of knee joint and construction of database for Chinese. The morphologic dimensions data of the distal part of the femur, the proximal part of the tibia of the cut surface and the patella were collected during 105 knees (77 patients) TKA. We figured out the mean, standard divisions, aspect ratio and regression equation of the above parameters by using SPSS 12.0 Software. The statistics shows that there is close correlation among parameters of the femoral condyles, tibia plate and patellar (P<0.05) . We consider that not only the measuring methods(the condition of the cut bone, the depth of the cut bone, the slope of the tibia) race, gender, BMI (Body Mass Index) and other individual differences but also the morphologic change of the abnormal knee joint should be taken into consideration in the study on the geometrical morphological dimensions.Experiment 2: Contrasting study on correlated parameters of the tibia plate cut surface of the normal Chinese cadaver We carried 20 knee joints experiments on 10 normal Chinese adult cadavers and cut different thickness of tibia plate on the same cadaver in order to analyze the factors affecting the dimensions of the knee joint prostheses. Comparing the abnormal group and ofnormal cadaver group. The result shows that the differences between the anterior-posterior (A/P) of the medial-lateral (M/L) tibia plates decrease gradually with the increase of the cut thickness of them. The shape of the tibia plate changes from oval to roundness. There are significant difference between abnormal group and normal cadacer group in dimensions of the A/P of medial tibia plate and medial-lateral (M/L) tibia plates ( P<0.05 ). It shows that the main factor cause the difference is the bone morphological change led by the morbidity degree of the knee joint.Experiment 3: Contrasting study on the dimensions of knee joint prostheses. We collected 5 current prosthetic systems (import and joint venture) used in China and contrasted with the dimensions in clinic. The result shows that the dimensions and ratio of the parameters of knee joint prostheses designed by foreign countries are different from our Chinese. The import prostheses have the following problems: the ratio of AP/ ML of the femoral condyle tend to be too large;the AP/ ML ratio range of tibia plate is overconcentrated;the overcoving rate is not very good;the lateral plate overhangs sometimes. So we declared that the import prostheses are not fit for Chinese in all aspects.The study through exactly measured the geometrical dimensions of the abnormal Chinese knee joint and established correlated parameters data base and provide scientific data for the design of the knee joint prostheses which are much fitter for Chinese.