Trunnion design and femoral head diameter increase corrosion at the taper interface in retrieved large-diameter metal-on-metal total hip arthroplasty

Abstract

s / International Journal of Surgery 10 (2012) S53–S109 S55 ABSTRACTS 0128: TRUNNION DESIGN AND FEMORAL HEAD DIAMETER INCREASE CORROSION AT THE TAPER INTERFACE IN RETRIEVED LARGEDIAMETER METAL-ON-METAL TOTAL HIP ARTHROPLASTY Adam Hexter , Anna Panagiotidou , Gordon Blunn , John Skinner , Alister Hart . 1 London Implant Retrieval Centre, Imperial College London, London, UK; Royal National Orthopaedic Hospital, London, UK Aim: To characterise corrosion at the taper interface in large diameter metal-on-metal total hip arthroplasty and the effect of femoral head diameter. Method: Corrosion was qualitatively assessed using a peer-reviewed grading system for 111 components from three different manufacturers (ASR, BHR, Durom). Unexpectedly a ridged appearance was commonly observed on the female taper surfaces, which corresponded exactly with the ridges of the trunnion surface. A new grading system was created to measure this imprinting phenomenon. Results: 92% of the components experienced corrosion, with at least moderate corrosion seen in 61%. The manufacturer did not influence corrosion both for head components (p1⁄40.52) and trunnions (p1⁄40.20). A strong positive correlation (r1⁄40.776, p1⁄40.01) was observed between the imprinting scores and corrosion scores. Larger head diameters showed higher corrosion (r1⁄40.241, p1⁄40.02). Conclusions: Corrosion affects all manufacturers and is associated with the presence of ridges on the female taper surface. It appears that the rough surface of the trunnion causes extensive mechanical damage at the female taper surface and creates a hostile corrosive environment. Femoral head diameter correlates with corrosion, which is clinically significant considering the increasing use of larger head sizes. Future work must now clarify the optimum trunnion design and femoral head diameter. 0129: WEAR AND CORROSION AT THE TAPER INTERFACE IN RETRIEVED ASR XL METAL-ON-METAL TOTAL HIP ARTHROPLASTY Adam Hexter , Anna Panagiotidou , Gordon Blunn , Johann Henckel , John Skinner , Alister Hart . 1 London Implant Retrieval Centre, London, UK; Royal National Orthopaedic Hospital, London, UK Aim: To quantify wear at the ASR XL taper interface and determine the relationship between taper corrosion and blood metal ions. Method: Corrosion was qualitatively assessed using a peer-reviewed grading system for 52 ASR XL femoral head components. Blood metal ion levels in hips showing at least moderate corrosion was compared with those without moderate corrosion. Profilometry was performed in hips (n1⁄412) that failed due to debris-induced synovitis in the presence of low bearing surface wear (<10mm/year combined head/ cup). Results: 98% of the components were corroded, with at least moderate corrosion observed in 66%. Corrosion did not influence the levels of blood cobalt (p1⁄40.16) and chromium (p1⁄40.12) ions. The median volumetric loss was 3.08mm3 (range: 0.61-9.44) and the maximum wear depth ranged from 14-85mm. Conclusions: Metal debris is implicated in the formation of soft-tissue reactions and we show that taper wear and corrosion is substantial. Currently there is no other culprit that could account for the higher failure rate of the ASR XL when compared to resurfacing. Greater corrosion did not equate to increased metal ion levels. Future work must determine the relative contributions of the bearing surface and taper interface tomaterial loss and blood metal ions. 0157 WINNER OF ORTHOPAEDIC RESEARCH UK PRIZE: ACCURACY OF DIGITAL TEMPLATING IN TOTAL HIP REPLACEMENT AND POSTOPERATIVE LEG LENGTH INEQUALITY John Kyle , Anthony McWilliams , Richard Grogan . 1 James Cook University Hospital, Middlesbrough, UK; Bradford Royal Infirmary,