Aseptic loosening of cemented femoral stems results from migration of wear particles along the bone-cement interface, producing a foreign body reaction. After cement insertion, blood back pressure can disrupt the bone-cement interface, enabling this spread of wear particles. Our study investigates whether altering timing and speed of stem insertion can reduce this risk. We inserted mock “C-Stem” femoral components (De Puy-Synthes), using Smartset HV cement (De Puy-Synthes) into artificial femora, fitted with proximal and distal pressure transducers. Cement insertion began two, three or four minutes after mixing. Cement pressures were then allowed to settle for one minute and the stems were then inserted over durations of 25, 60 or 90 seconds.Background
Methods
Joint aspiration is a useful tool during preoperative workup in suspected periprosthetic infection. The aim of this study was to review efficacy of joint aspiration in our unit and compare results with the published literature. We undertook a retrospective review of 153 consecutive patients who underwent joint aspirations for suspected periprosthetic infection between 03/2011 and 10/2012 who were identified from the hospital electronic database. As per protocol, joint fluid was sent in an EDTA tube for cell count, Paediatric blood culture bottle and the remainder in a specimen pot. 105 (69%) were TKRs and 48 (31%) were THRs. Intraoperative samples were sent as per protocol in only 40 (26%) cases. The hit rate of positive cultures was 11/153 (7%) and specimens sent in paediatric culture bottles identified more positives than if it was omitted (10.5 Vs 5.5%). In conclusion, the hit rate of positive cultures is low in this study compared to the literature (7% Vs 33%) and this is likely due to blanket aspiration of all patients who are undergoing revision. In addition, specimens sent in paediatric culture bottles seem to identify more positives. We recommend cases are selected for aspiration according to AAOS guidelines.
