Abstract
Purpose: The ABG Total Hip Joint Replacement is a cementless, hydroxyapatite coated prosthesis designed to be metaphyseal loading. The aim of our study was to analyze the changes in proximal femoral bone mineral density (BMD) following implantation of this prosthesis.
Method: Dual energy x-ray absorptiometry (DEXA) scanning has been shown to be an accurate and reliable method of assessing BMD following total hip arthroplasty. 14 patients undergoing primary ABG Total Hip Joint Replacement were recruited into the study following informed consent. BMD was determined for each of the seven periprosthetic zones of Gruen from DEXA scans, which were performed serially at preoperative,, 3 months, 6 months, 1 year and 2 years.
Results: 8 patients have now completed their scans. The most dramatic change in BMD was found in zone 7 which is the femoral calcar. In this region there was a progressive decrease in average BMD to 75% of the preoperative value at 2 years. In zones 2 and 3 representing the femoral cortex lateral to the prosthesis there was an increase in BMD to approximately 114.5% at 3 months and this was maintained at 2 years. In the remaining zones BMD was reasonably stable between 97.5 and 101%.
Conclusion: We have found that in the 2 years following ABG hip arthroplasty there is a dramatic decrease in BMD to 75% within the region of the femoral calcar. Further scans are required to determine if this is progressive. In the remaining regions BMD is either increased or relatively well preserved.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
