Abstract
The longevity of cemented femoral components has been shown to be related to the cement used. The reason for this difference between the available commercial preparations is unclear. One mode of failure of the stem is thought to be cracking within the cement mantle. This may be secondary to residual stress resulting from shrinkage of the cement on curing. It was hypothesised that there was a difference in shrinkage on curing between the different polymethylmethacrylate cements used commonly in hip arthroplasty.
Under standardised conditions, a fixed volume of Palacos-R, Palacos-LV, Simplex, CMW1 Radio-opaque, CMW2 and CMW Endurance was mixed under vacuum and allowed to cure in a measuring cylinder of fixed volume. The cylinder was then split open 24 hours later and the block of cement removed. The final volume of cement was then determined by measuring the volume it occupied in a container filled with water using Archimedes principle.
Our results indicate that, under standardised conditions, the degree of shrinkage for each commercial preparation was Palacos-R 6.9%, CMW1 5.2%, CMW2 5.4%, CMW Endurance 5.3%, Simplex 5.8% and Palacos-LV 7.2%.
There is a difference in the amount of shrinkage on curing between the different types of bone cements in use commercially and this may account for their differences in long term outcome.
Editoral Secretary Mr Peter Howard. Correspondence should be addressed to BHS at the Royal College of Surgeons, 35 - 43 Lincoln’s Inn Fields, London WC2A 3PN.
