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

Reference:

Bartlett, G. E., Beard, D. J., Murray, D. W. and Gill, H. S., 2008. The femoral stem pump in cemented hip arthroplasty: an in vitro model. Medical Engineering & Physics, 30 (8), pp. 1042-1048.

Related documents:

Official URL:

http://dx.doi.org/10.1016/j.medengphy.2007.12.011

Related URLs:

• http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18280197

Abstract

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.

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