PATTERN OF PERIPROSTHETIC BONE REMODELLING AROUND STABLE UNCEMENTED TITANIUM TAPERED HIP STEMS – A PROSPECTIVE 7-YEAR FOLLOWUP STUDY AND A 13 YEAR CROSS SECTIONAL STUDY WITH DEXA

Abstract

We analysed periprosthetic bone mineral density (BMD) by dual-energy X-ray absorptiometry (DEXA) in patients after uncemented total hip arthroplasty (THA) (press-fit CLS Spotorno stem). Only patients with good clinical outcome (Merle d‘ Aubigne score > 12) were included to obtain normative data for regular bone response.

Two separate studies were performed: A prospective longitudinal study over a time period of 7 years (group A) (n = 26 patients: 12 women, 14 men) and an additional cross-sectional study, mean follow-up13 years (10 to 15 years) (group B) (n = 35 patients: 18 women, 17 men). Regions of interest were defined according to Gruen (ROI 1–7) and as netto average ROI (NETAVG) for the periprosthetic femoral bone. After the initial remodelling process, BMD at 1 year was compared to the 7-year (longitidinal) and to the 13-year (cross-sectional) follow-up values of the affected limb to determine long term periprosthetic changes of bone mineral density.

The longitudinal study (group A) showed BMD values of 91.1% and 92.8% after 1 year, 91.2% and 90.2% after 7 years compared to the initial post-operative values for women and men, respectively. ROIs around the proximal stem (ROI 1 and 7) showed the lowest absolute values and decreased most during follow-up (ROI 1: 80.7% and 84.5%, ROI 7: 71.1% and 75.5% after 7 years, for women and men respectively). In the cross-sectional study (group B) BMD was determined 89.1% and 87.8% after 13 years compared to the initial values of group A for women and men. Distribution of BMD in ROIs 1-7 (group B) showed no significant changes compared to the 1 year and 7 year results of group A. The results reflect normative long term changes in the periprosthetic bone after implantation of THA in defined ROIs of a well functioning tapered corundum-blasted titanium stem.