The Relationship Between Offset And The Hip Stress In The Total Hip Arthroplasty By The Three-dimensional Photoelastic

PremiseThe hip is the foothold between the body weight and the abductor strength. The dynamic balance between them is very important to pelvis'position and normal walk. Because of the center of the femur head is closer to the center of gravity than the consequently abductor lever arm, the abductor is weaker in this balance. Femoral offset is the distance between center of the femur head and the center of the shaft of femur. During the total hip arthroplasty (THA) , rebuild the femoral offset can reablemen the abductor strength. In the whole world the femoral offset was too attention. We made thee three - dimensional photoelastic models of the artificial hip joint to investigate the femoral offset and the hip stress.MethodsPhotoelastic models of human pelvis were made by using light - sensatory material. To rebuild the femoral offset we Let the femoral neck change (25mm. 30mm. 35mm. 40mm) . The weight was put on model and performed froze stress , and the distribution of model stress and morphological change were observed.Use the Spss statistics soft ware to analysis the data. <0. 05 means the data has the statistical significance. Use the AutoCAD to draw the profile curve of the stress.ResultsFrom the result we can see that there is a strong linear regression between Femoral neck length and the femoral offset and the stress area, (r = -0. 926;p <001). Simple regression analysis showed that femoral offset was significantly and positively related to the uniformity of the contact stress of the. ( r =0. 922 , P <0. 01 ) .In these four group of the sheet analysis of variance showed that there is a variance. ( F =3. 210 > F0. 05 (3 ,60);P <0.05) . Simple regression analysis showed that The tatol stress level was related to offset( r = - 0. 565;P < 0.05).Discussion1. the offset and the stability of the artificial hip jointFrom the result we can see that there is a strong linear regression between the offset and the stress area. It means that when the femoral offset is increasing the highest stress area is moving to the center of the hip. It makes the hip more stability.2. The femoral offset and the stress distributeSimple regression analysis showed that femoral offset was significantly and positively related to the uniformity of the contact stress of the . It means that when It means that when the femoral offset is increasing the stress distribute of the pdyethyleness is more uniformity.3. The femoral offset and the stress distributeIn these four groups of the sheet analysis of variance showed that there is a variance. Simple regression analysis showed that the stress level was lower. It means that the acetabulum's total stress level break down. It gets better then short offset.4. The stress distribute and pdyethylenessFrom this experiment we can see that when the offset increasing the stress distribute of the pdyethyleness is more uniformity. According to Maxian theabras of the polyethylene has a positive correlation with stress. The height stress will lead to more abras. So rebuild the femoral offset will increasing the life of the pdyethyleness prosthesis.ConclusionsIt is very important to template both sides of hip preoperatively forrestoring femoral offset in THA Femoral component with more anatomical neck be used with the increase in the femoral neck length.