Bone preservation with a conservative metaphyseal loading implant.

Proximal load transfer and the absence of distal fixation of the stem are crucial to obtain the best behaviour of the femoral bone after total hip replacement. In this study, dual energy X-ray absorptiometry (DEXA) was employed to understand and compare the bone density changes and thus the re-distribution of mechanical forces in two different extra short stems. Two cohorts of ten patients were included in this retrospective study. Both implants are custom-made and present a well defined lateral flare. The first model is fully coated and presents a short stem (Group A), the second is an unstemmed metaphyseal implant with a polished tip (Group B). DEXA scans were obtained in all patients at the two-year follow-up. A higher BMD was detected in ROIs 1, 2, 4, 5 in Group B confirming a preservation of the proximal bone mass and thus indirectly a more proximal load transfer. The results obtained confirm the importance of the geometry of the implant on proximal bone density. Loading both medial and lateral proximal femoral flares and the complete absence of the diaphyseal portion of the stem provide the optimal bone remodelling of the femur after total hip replacement.