Abstract
Introduction A wide range of stress-shielding phenomena following THA have been described in the past 20 years. Bone densitometry (DXA) stars as a golden standard in evaluating bone stock and bone density redistribution after total hip replacement.
In this study, DXA scan was employed to evaluate and compare the behaviour of different femoral components including a recently developed stemless implant which features complete stress transfer over the proximal femur.
Methodology A total of 120 patients, operated with six different femoral implants, were included in the present study. Five of these stems are widely commercially available (ABG, CFP, IPS, Mayo, Zweymueller) and present different patterns of stress distribution. The sixth is a custom made implant and features a pronounced lateral flare and complete femoral neck preservation. Rationale of this design is to obtain full load transfer on the proximal femur.
Average interval between the operation and the DXA exam was 3 years, each group included 20 patients. Bone mineral density was measured by DXA in the seven Gruen femoral regions (ROI), using the software metal removal (Hologic QDR 4500 W, MA-USA).
Results Differences in bone density were found in each group as well as between different groups. Significant differences (p< 0.001) were found between the stemless implant and the other five groups in zone I, IV and VII.
CFP, IPS and ABG groups showed decreased bone density in ROI I, while Mayo, IPS, ABG and Zweym-ueller were osteopenic in ROI VII. An increased bone density in ROI IV was found in Zweymueller, Mayo, ABG and IPS groups.
Conclusion Our data suggest that a conservative stemless implant with complete proximal load transfer, produces a homogeneous and more physiologic redistribution of bone density, allowing maintenance of proximal periprosthetic bone stock.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
