Abstract
Aims: Cementing techniques in arthroplasty affect the outcome of the procedure. Pressurisation is used to improve the cement/bone interface, relying on ante-grade pressure against a resisting force. It is known that ultra high molecular weight polyethylene (UHMWPE) leaves particulate debris, which may lead to aseptic loosening, suggesting a biodegradable cement restrictor may be better. We compared cement restrictor migration at insertion between two types of restrictors, to find if they behaved in a similar fashion.
Methods: A prospective, randomised study with 16 patients per group was compared. Each group was allocated either a UHMWPE or a biodegradable restrictor, inserted according to the manufacturer’s instructions. All procedures used the same approach by one of two surgeons using a cemented polished, tapered stem prosthesis. At insertion the restrictor depth was measured from a fixed reference point, prior to cement introduction, which allowed comparison with post-operative standardised EBRA radiographs. By measuring stem lengths we were able to calculate the individual magnification and hence increase the accuracy of restrictor migration measurement.
Results: In each group 15 patients completed the study. The results showed a marked significance, with mean migrations of 3.0cm vs. 0.5cm (biodegradable vs. UHMWPE). Mann-Whitney U test gives a value for p< 0.002. The medians (2.9vs.0.4), standard deviations (1.8 vs.0.4) and ranges (0.6–6.4 vs.0–1.2) were also significant.
Conclusions: In this study, the biodegradable restrictor used was found to allow significantly more migration than the UHMWPE one used. Although there are positive advantages in avoiding the use of UHMWPE restrictors, further advances need to be made before abandoning it completely.
Theses abstracts were prepared by Mr Peter Kay. Correspondence should be address to him at The Hip Centre, Wrightington Hospital, Appley Bridge, Wigan, Lancashire WN6 9EP.
