Changes in BMD in the Proximal Femur after Cementless Total Hip Arthroplasty and Resurfacing Arthroplasty: Prospective, Longitudinal, ComparativeStudy

Yoo, Myung Chul; Cho, Yoon Je; Kim, Kang Il; Chun, Sung Wook; Park, Kyoung Jun; Park, Sung Woo

Abstract

PURPOSE: This study analyzed the differences in bone remodeling and stress shielding between cementless total hip arthroplasty and resurfacing arthroplasty by examining the serial bone mineral density around the prosthesis.
MATERIALS AND METHODS
Fifty total hip arthroplasty procedures and 50 resurfacing arthroplasty procedures, which were performed between July 2002 and June 2003, were examined to this comparative study. The mean age at surgery was 44 years in the THA group and 36 years in the resurfacing arthroplasty group. The bone mineral density was measured by the DEXA at preoperation and 3 months, 6 months, 12 months after surgery in zone I-III of the acetabulum (classified by DeLee & Charnley) and zone I-VII of the femur (classified by Gruen), and the medial and lateral side of the femoral neck in the resurfacing arthroplasty group.
RESULTS
In the acetabulum, zones I and II of both groups showed a significant decrease in the BMD 12 months after surgery but the level of bone loss in the resurfacing arthroplasty group was relatively small compared with those in the THA group. In the proximal femur, the overall amount of bone loss at 3, 6 and 12 months postoperatively were 0.7%, 5%, and 2.6% respectively, and those in zones I and VII at 12 months postoperatively in the THA group were 7.8% and 7.7%, respectively. In the BHR group, the overall bone loss in the proximal femur at 3, 6 and 12 months postoperatively were 5.8%, 4.4%, and 2.9%, respectively. However, those Gruen zones I and VII at 12 months postoperatively were 2.6% and 0.6%, respectively.
CONCLUSION
The level of bone loss in Gruen zones I and VII of the resurfacing arthroplaty group was much lower, which suggests that resurfacing arthroplasty can prevent stress shielding and preserve the proximal bone stock around the femoral stem.