Early periprosthetic bone remodelling around cemented and uncemented custom-made femoral components and their uncemented acetabular cups.

INTRODUCTION: Periprosthetic bone remodelling after total hip replacement may contribute to aseptic loosening of the prosthesis. The selection between cemented and uncemented fixation of the stem is mainly determined by patient's age, general constitution and CT scan-estimated bone quality; intra-operative observation may ultimately influence the choice of the fixation method. The influence of cemented versus uncemented stem fixation on periprosthetic bone remodelling around the uncemented cup has, to our knowledge, never been studied until now.

METHODS: A total of 75 patients received intra-operatively manufactured stem prostheses and a standard hydroxy apatite-coated pinnacle cup. The pre-operative CT scans provides guidance for the bone quality and hence the type of stem fixation: cemented or uncemented. The influence of either type of stem fixation on periprosthetic bone remodelling around the cup and the stem was measured by bone mineral density at 6 weeks, and 3, 6 and 12 months after surgery.

RESULTS: Early changes in bone mineral density were noted. The type of stem fixation had an influence on the bone remodelling of the femur and also of the pelvis. The caudal part of the acetabulum was subject to a greater loss in BMD at 12 months in the group with cemented stem fixation. Changes at 12 months correlated with the changes measured at any time point.

CONCLUSIONS: The selection of the stem implant and its type of fixation in the femoral cavity (cemented or uncemented fixation) seems to have an impact on the bone mineral density of the acetabulum. Long-term clinical follow-up is required to draw conclusions regarding the influence on prosthesis survival.