DEXA analysis of Antega total hip prosthesis

Periprosthetic bone remodeling can be studied using dual-energy absorptiometry X-ray analysis (DEXA), the most precise and effective method for analyzing bone mineral density (BMD). However, in order to show significant differences in BMD using DEXA, it is necessary to use high resolution equipment, to demonstrate reproducibility of the examination, and to adopt statistical rigor in data analysis. We performed a longitudinal study using DEXA on a consecutive and homogeneous series of 40 patients (20 males and 20 females) who underwent total hip replacement. The patients received a cementless Antega prosthesis, of titanium alloy with a plasma spray covering. DEXA exams were performed 1, 4, 7, 12 and 24 months after surgery, and the images were analyzed in the areas of Gruen. Globally, BMD was significantly reduced at month 4 in reference to baseline (exam at month 1). At subsequent exams, BMD did not further decrease but was followed by a progressive recovery over the 2-year study. The recovery at 2 years (with respect to the 4-month exam) was statistically significant for female patients but not for males. No statistical differences in BMD were found between patients (60 years and > 60 years, nor for patients with different sized stems. For the individual zones of Gruen, the mineralometric behaviors for zones 2, 3, 5 and 6 were similar while that for zones 1 and 7 showed a particular behavior. The trend in variations of periprosthetic BMD observed in our population differs from that in the majority of studies published in the literature. Our longitudinal densitometric study has all the requisites to be considered reliable; a longer follow-up will strengthen our results which, already in the short term, are valid and support the use of the Antega stem in hip replacement surgery. Received: 14 January 2000/Accepted: 18 February 2000