SIGNIFICANCE AND REPRODUCIBILITY OF BONE- DENSITOMETRIC DEXA-MEASUREMENTS AFTER IMPLANTATION OF TOTAL HIP-ARTHROPLASTY

For the determination of reproducibility of bone densitometric measure ments we performed a measurement according to the DEXA- method. 35 pat ients after implantation of total hip replacement were examined with a Lunar DPX-L. We received a maximum reproduction error of 1.2% accordi ng to the GRUEM-analysis. The operated hip of 17 patients showed an in crease in bone density between 5 and 18% by the implantation of an art hroplasty compared to the preoperative values. The non-operated prosth esis-corrected hip showed a reproduction error of 3.8% in ROI 1 in 17 patients, otherwise a maximum of 1.3%. Considering an interfemoral dif ference in bone density of up to 20%, differences in periprosthetic bo ne density of up to 40% compared to the contralateral side can be with in the normal range in a retrospective measurement. Therefore retrospe ctive determination of bone density after cementless hip arthroplasty only is of limited value. Only prospective analysis can provide reliab le information about the actual loss of bone density.