The femoral stem pump in cemented hip arthroplasty: an in vitro model.

Journal article

The presence of an intra-articular pump has been proposed as a central mechanism in the process of osteolysis and aseptic loosening of hip arthroplasty. It is not known if this pump exists and its mechanism remains uncharacterised. This study describes a new in vitro model of a cemented femoral stem in which cement/stem interface fluid pressures can be reliably measured under dynamic loads simulating stair climbing. A stem pump mechanism was found that generates both positive and negative clinically significant pressures (mean pressure ranges 5000-17,000 Pa). The timing of pressure peaks on the anterior and posterior aspects of the stem were in anti-phase, giving rise to oscillatory pressure gradients and potentially generating oscillatory fluid flows during the simulated physiological load cycle. The pump mechanism was shown to occur at the interface of a newly implanted polished double-tapered stem and emphasizes the importance of a complete mantle to protect the femoral bone from the raised fluid pressures.

Authors: Bartlett, G; Beard, D; Murray, D; Gill, H

• Publication status: Published
• Journal: Medical engineering and physics
• Volume: 30
• Issue: 8
• Pages: 1042-1048
• Publication date: 2008-10-01
• DOI: 10.1016/j.medengphy.2007.12.011
• EISSN: 1873-4030
• ISSN: 1350-4533
• Language: English
• Keywords: Models, Biological; Humans; Femur; Pressure; Cementation; Arthroplasty, Replacement, Hip