Fatigue fractures which originate at stress-concentrating voids located at the implant-cement interface are a potential cause of septic loosening of cemented femoral components. Heating of the component to 44 degrees C is known to reduce the porosity of the cement-prosthesis interface. The temperature of the cement-bone interface was recorded intra-operatively as 32.3 degrees C. A simulated femoral model was devised to study the effect of heating of the component on the implant-cement interface. Heating of the implant and vacuum mixing have a synergistic effect on the porosity of the implant-cement interface, and heating also reverses the gradients of microhardness in the mantle. Heating of the implant also reduces porosity at the interface depending on the temperature. A minimum difference in temperature between the implant and the bone of 3 degrees C was required to produce this effect. The optimal difference was 7 degrees C, representing a balance between maximal reduction of porosity and an increased risk of thermal injury. Using contemporary cementing techniques, heating the implant to 40 degrees C is recommended to produce an optimum effect.

This study shows evidence that previously unappreciated variations in manufacturing processes may have a major impact on the clinical outcomes of patients.

No abstract

Peer reviewed articleirborne contamination has been shown to be a significant source of wound contamination in orthopaedic surgery. This is the first reported study looking at the efficacy of ActivTek 300, a portable UV/TiO2-based air purifier unit to reduce airborne contamination in a clinical setting. In this randomised study the investigator was blinded as to whether the unit had been on or off for the previous seven days.Air contamination was measured weekly using a validated technique in ward treatment rooms using a Mini Air Sampler (MAS-100) and agar plates, over a period of 12 weeks. The agar plates were then incubated for 24 hours and the results were expressed as number of colony forming units per plate (cfu). The biomedical scientist who manually counted the number of cfus was blinded as to whether the unit was on or off. Measurements were duplicated to improve the accuracy of the study, and in addition to this an identical experiment was set up in a second treatment room on a separate randomisation schedule. Analysis of the data demonstrated median colony count was significantly lower with the unit on (Median = 43 interquartile range (IQR) 30 to 83) than when it was off (median = 95 IQR 44 to 143) (p < 0.01). This represents a 55% mean reduction in the colony count. This study suggests that the portable UV/TiO2-based air purifier unit is efficacious in reducing airborne contamination in the clinical environment and may have a promising role in reducing overall infection rates in surgical patients. AbstractA 252