The painful metal-on-metal hip resurfacing 2009
A. J. Hart, FRCSG(Orth), Clinical Senior Lecturer & Honorary Consultant Orthopaedic Surgeon1; S. Sabah, BSc, Medical Student1; J. Henckel, MRCS, Clinical Research Fellow & Specialist Registrar in Orthopaedics1; A. Lewis, FRCS(Orth), Consultant Orthopaedic Surgeon1; J. Cobb, FRCS, Professor of Orthopaedic Surgery1; B. Sampson, MRSC, CChem, Director of Supraregional Trace Element Laboratory1; A. Mitchell, FRCR, Consultant Musculoskeletal Radiologist1; and J. A. Skinner, FRCS(Orth), Consultant Orthopaedic Surgeon2 1 Department of Radiology Imperial College, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK. 2 Department of Orthopaedics Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK.We carried out metal artefact-reduction MRI, three-dimensional CT measurement of the position of the component and inductively-coupled plasma mass spectrometry analysis of cobalt and chromium levels in whole blood on 26 patients with unexplained pain following metal-on-metal resurfacing arthroplasty. MRI showed periprosthetic lesions around 16 hips, with 14 collections of fluid and two soft-tissue masses. The lesions were seen in both men and women and in symptomatic and asymptomatic hips. Using three-dimensional CT, the median inclination of the acetabular component was found to be 55° and its positioning was outside the Lewinnek safe zone in 13 of 16 cases. Using inductively-coupled plasma mass spectrometry, the levels of blood metal ions tended to be higher in painful compared with well-functioning metal-on-metal hips. These three clinically useful investigations can help to determine the cause of failure of the implant, predict the need for future revision and aid the choice of revision prostheses.