An in-vitro comparative study of the performance of different commercially available intramedullary femoral plugs during total hip replacement
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In vitro investigation of cement pressure and migration of commercially-available cement plugs during femoral implant fixation
Research team: Dr Rajshree Mootanah, Professor John Dowell, Dr Maarten Kroon
Distal flow of polymethylmethacrylate (PMMA) bone cement during insertion of the femoral implant results in reduced pressure and hence cement-bone interdigitation and long-term fixation. It has long been appreciated that insertion of cement plugs in the intramedullary canal helps overcome this problem.
The aim of this study is design an experimental set-up to compare the performance of the following four designs of cement plugs: (a) REX (A-one Medical B.V.), (b) Hardinge (DePuy International Ltd), (c) Amber Flex (Summit Medical Ltd) and (d) Cemlock (Sulzer). This was done by recording data of proximal and distal pressures and migration of the cement plugs during cement pressurisation and insertion of the femoral prosthesis in prepared Sawbone femurs.
X-ray of a fitted cement plug
Two pressure transducers (Entran 35 bar) were positioned at 40 mm and 150 mm below the medial proximal end of the prepared femur and were connected to an analogue/digital converter (Instrunet 100) to record the cement pressures during the tests. A special jig was used to position the femur and accommodate the linear potentiometric displacement transducer (LPDT - Techni Measure), which was used to measure migration of the cement plugs during testing. The femoral component and prepared femur were fixed to the testing machine. An average number of three tests were carried out for each cement restrictor and average data of intramedullary pressures and migration of cement restrictor were computed.
A typical graph of cement pressures for the different cement plugs
A typical graph for the different stages of one test is shown. Peak pressures in the range of 548 kPa to 1,112 kPa were obtained for the different plugs during insertion of the prosthesis. Migration values in the range of 0.19mm to 3.4mm were recorded when there was no excessive distal cement flow.
This series of investigations shows that Hardinge and REX cement restrictors produce higher distal pressure and AmberFlex and REX produced the least migration.
Publications:
- Kroon, M., Visser, C., Mootanah, R., Schuttevaer, H., & Brand, R. 2006, "Performance of three gelatine-based resorbable cement plugs: results of in vitro study on 15 synthetic femurs and a prospective randomized in vivo study on 103 patients", Acta Orthopaedica; 77(6):893-898
- Pratt D, Mootanah R, Dowell J, 2005, "A Comparison of Pressurisation, Distal Migration and Canal Occlusion In 4 Commonly Available Cement Restrictors Used In Total Hip Arthroplasty", Journal of Bone and Joint Surgery supplement (Br.): The proceedings of the British Hip Society 2004, 87-B (1):49
- Mootanah, R., Allen, E., & Ingle, P. 2004, "Comparison of Performance of Different Cement Restrictors by Finite Element Methods", J. Middleton, M. Jones, & N. Shrive, eds., Computer Methods in Biomechanics & Biomedical Engineering, First Numerics, UK.
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