Abstract
Uncemented porous coated femoral implants rely on bone in growth to achieve stable, long lasting fixation. The loss of proximal femoral bone mass around hip stems has been traditionally termed ‘stress shielding’ and has been linked to the transfer of loads to the diaphysis and the relative unloading of the proximal femur. Proximally loading devices should then minimize or avert stress shielding altogether. We prospectively evaluated the changes in the periprosthetic bone mass density after insertion of an off-the-shelf non-cemented stem designed to engage both cortices at the metaphyseal level.
A total of 10 total hip arthroplasties with a proximally coated lateral flare device were evaluated with dual-energy x-ray absorptiometry and qualitative radiographic changes 3 weeks after surgery and at 12, 24 and 52 weeks thereafter. The regions of interest (ROI) used in this study corresponded to the zones described by Gruen.
All hips were radiologically stable. The DEXA measurements revealed an overall increase in the BMD at 52 weeks of 4%. Greater gains were observed at or below the lateral flare of the stem in the metaphyseal femur.
The use of an extended proximally loading device proved to have a beneficial effect in the periprosthetic bone mass density due to its geometry and inherent primary stability evidenced by the DEXA and subsidence values.
Correspondence should be addressed to Richard Komistek, PhD, International Society for Technology in Arthroplasty, PO Box 6564, Auburn, CA 95604, USA. E-mail: ista@pacbell.net
