The manufacture and evaluation of custom acetabular components for total hip replacement

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The Effect of PMMA Thickness on Thermal Bone Necrosis Around Acetabular Sockets

One aim of custom acetabular hip replacement sockets is to achieve fixation through a uniform cement layer of selected thickness. In vitro experiments demonstrate that curing temperatures are determined by cement thickness and position relative to the socket rim. A maximum thickness of 7 mm is indicated by interpretation of curing temperature-time relationships in terms of predicted bone necrosis. It is concluded that the results contribute to the establishment of an optimum cement layer thickness, but other factors require investigation to complement this work to gain further understanding of the problem. </jats:p

Thermal Analysis of the Tibial Cement Interface with Modern Cementing Technique

Background: The major cause of cemented Total Knee Arthroplasty (TKA) failure is aseptic loosening of the tibial component necessitating revision surgery. Recently, multiple techniques have been described to maximize cement penetration depth and density in the proximal tibia during TKA to potentially avoid early loosening. While cement polymerisation is an exothermic reaction, minimal investigation into the proximal tibial thermal safety margin during cement polymerisation has been undertaken. In animal models osseous injury occurs at temperatures greater than 47 °C when applied for one minute. The aim of this study was to investigate the cement bone interface temperatures in TKA using modern tibial cementing techniques with a cadaveric tibial tray model. Methods: Eight adult cadavers were obtained with the proximal tibial surface prepared by a fellowship trained arthroplasty surgeon. Third generation cementation techniques were used and temperatures during cement polymerization on cadaveric knee arthroplasty models were recorded using thermocouples. Results: The results showed that no tibial cement temperature exceeded 44 °C for more than 1 minute. Two of the eight cadaveric tibias recorded maximum temperatures greater than 44 °C for 55 seconds and 33 seconds, just less than the 60 seconds reported to cause thermal injury. Average maximum polymerization temperatures did not correlate with deeper cement penetration or tray material. Maximum mantle temperatures were not statistically different between metal and all polyethylene tibial trays. Conclusion: Our investigation suggests that modern cementing techniques result in maximum mantle temperatures that are less than previously recorded temperatures required to cause thermal osseous injury, although this thermal injury safety margin is quite narrow at an average of 4.95 °C (95% confidence interval ± 4.31).Griffith Health, School of Allied Health SciencesFull Tex