Convened under the auspicious of esteemed endorsers - ISTA

A novel process has been developed to “stitch in” ionic silver into the upper surface of titaniumalloy (Ti6Al4V). The process produces a modification by anodisation of the titanium alloy indilute phosphoric acid, followed by absorption of silver from an aqueous solution. Theengineered surface modification is therefore integral with the substrate and loaded with silver byan ion exchange reaction. Using this technique the maximum inventory of silver for typical amega-prosthesis is 6mg and this is greater than 300 times lower than the No ObservableAdverse Affects Level (NOAEL). Scanning electron microscopy revealed that the silver wasconcentrated in pits and forming reservoirs of ionic silver exposed to the body tissues.Laboratory-based studies focusing on the safety and efficacy of silver as a bactericidal agenthave included investigation into cytotoxicity using fibroblast and osteoblast cell lines, theimpact of silver in reducing corrosion and laboratory testing to establish if the modified surfacehas an effect on the wear and mechanical characteristics. A range of fatigue, static, tensile pulloff tests were performed. The silver elution profiles for both silver loaded and HA coated over asilver loaded surface have been examined. Histological studies were also performed to examinethe impact of the silver on osseointegration.The in vitro results confirm that silver is an effective antimicrobial agent. The mechanicalcharacterization studies have identified that the surface treatment has no or minimal impact onthe implant surface. Early results of the elution studies are encouraging showing that the HAcoating of a silver loaded surface does not “seal” in the silver.To date (May 10) 147 silver treated mega-prostheses have been implanted since March 2006.The majority of implants were distal femoral (29%), proximal tibial (23%) or hemiplevic (10%).The most common indication was revision of a failed limb salvage reconstruction (58%), withthe dominant cause of failure being infection. The next most common indication was bonetumour (31%) and the large majority were used in the high risk skeletal locations of the tibia(44%) and the pelvis (27%). Early clinical results are encouraging indicating a significantreduction in the incidence of infection.Three implants have been retrieved. An analysis of a proximal humeral replacement that hadbeen in situ for 6 mths identified that there was 10-20% remaining on the implant surface.This novel process of “stitching-in” silver appears to be a safe and effective surface treatmentin helping to control infections of mega-prostheses. This technology has the potential to betransferred to other arthroplasty joints.Saturday, October 9, 2010, 14:50-15:20Session A22: Tribology and Biomechanics in ArthroplastyMobile-Bearing Total Knee Arthroplasty for Knee OsteoarthritisComplicated With Permanent Patellar Subluxation*Risa Utsunomiya - Tokushima Municipal Hospital - Tokushima City, JapanShunji Nakano - Tokushima Municipal Hospital - Tokushima-City, JapanMasaru Nakamura - Tokushima Municipal Hospital - Tokushima, JapanTakashi Chikawa - Tokushima Municipal Hospital - Tokushima, Japanfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]