The stress shielding in the proximal femur after total hip arthroplasty with biological fixation C2 stem

Objective In order to understand the relationship between bone absorption and the design of metal implants,we evaluated the influence of biological fixation C2 femoral stem on stress-shielding in proximal femur.Methods BMD of 31 cases in the regions of proximal femur adjacent to metal cementless femoral implants 2 years after the cementless THA using C2 femoral stem were determined and compared by means of DEXA.These cases also were examined by radiography and HHS.Results According HHS,excellent outcomes were in 22 patients,good in 8 patients and fair in one patient.All stems were judged stable by X-ray 2 years after THA.Radiographically,no significant bone mineral density changes were note in perioprosthetic regions.There was a mean reduction by 6.67%(range of 2.42%～27.4%) in the value of the BMD for the ROIs(Gruen zones) on the operated compared with the non-operated side.The BMD decrease in Gruen 4 and 7 was significant in statistics by test(t was -5.52 and -7.08 respectively,P0.01).Conclusions Stems of all cases were stable and no bone absorption was observed by X-ray 2 years after THA,but the bone loss was observed by DEXA,especially in femoral calcar,so X-ray is not as sensitive as DEXA to evaluate the bone loss after THA.No significant stress shielding was observed in all cases,and it maybe relate with the design of C2 femoral stem.