Metallosis in an apparently well fixed total knee replacement

One of the findings of prosthetic failure seen either on pre operative radiograph or at surgery is metallosis. To our knowledge, this has not been described in an apparently well-fixed noninfected prosthetic joint. Metallosis can be due to polyethylene bearing wear resulting in metal on metal wear and has been seen with macro motion of prosthesis against underlying cement or bone1. CASE REPORT An 80-year-old female presented with knee discomfort shortly after total knee replacement on same side. At two years, this discomfort deteriorated following a fall. On examination, the right knee had tenderness over the distal femoral bone/ prosthesis interface and patello-femoral crepitus was noted. Blood tests did not show any signs of infection. Radiograph of the knee replacement was reported to be within normal limits2. A bone scan was reported as normal3. Because of ongoing pain, the decision to explore the total joint replacement with possibility of revision was made. At exploration of the total knee replacement signs of metallosis were found adjacent to both the femoral and tibial components (Fig.1 & 2). Figure 1 Figure 1 Metallosis in an apparently well fixed total knee replacement 2 of 3 Figure 2 Figure 2 There were no obvious signs of loosening (bubble test was negative). Although the components appear well fixed the polyethylene was considered compromised by the metal debris and revision was undertaken. The extraction of the prosthesis was very easy and there was deficient cementation in a quadrant on each component allowing macro motion and with metallosis formed in these areas, we interpreted this as indicating the joint replacement was loose. The tissue samples taken for microbiology did not grow any micro organisms. The histological examinations of the tissue samples did show signs of metal in the synovium but no polymorphs were seen4. Following the revision surgery patient did well and symptom of pain has completely settled. DISCUSSION Metallosis is usually not seen in a well fixed knee replacement but in a loose knee replacement1. Finding of metallosis in an apparently well fixed knee replacement without poly ethylene wear should alert the surgeon to the possibilities that the component(s) is (are) loose. Further we believe that metallosis is an indication for revision as it is the sign of a failing or failed knee replacement. CORRESPONDENCE TOMr. P Mukherjee MRCS Senior SHO Trauma andOrthopaedics Torbay Hospital South Devon Healthcare NHSTrust Torquay UK TQ2 7AA Phone: 00-44-7886080203Email: [email protected] References1. Hart R, Janeck M, Bucek B. Case report of extensivemetallosis in extra articular tissues after unicompartmentalknee joint replacement. Acta Chir Orthop Traumatol Cech.2003; 70(1): 47-50.2. McGovern TF, Moskal JT. Radiographic evaluation ofperiprosthetic metallosis after total knee replacement. JSouth Orthop Assoc. 2002 Spring; 11(1):18-24.3. Worland RL, Arrendondo J, Angles F, Jessup DE.Scintigraphic evaluation in total knee failure secondary tosevere metallosis. J Arthroplasty. 1998 Jan; 13(1):116-9.4. Della Valle CJ, Bogner E, Desai P, Lonner JH, Adler E,Zuckerman JD, Di Cesare PE. Analysis of frozen sections ofintraoperative specimens obtained at the time of reoperationafter hip or knee resection arthroplasty for the treatment ofinfection. J Bone Joint Surg Am. 1999 May; 81(5):684-9. Metallosis in an apparently well fixed total knee replacement 3 of 3Author InformationPavel Mukherjee, MRCSDepartment of Orthopaedic Surgery, South Devon Healthcare NHS Trust, Torbay Hospital Mark J. Ashworth, FRCS (Orth)Department of Orthopaedic Surgery, South Devon Healthcare NHS Trust, Torbay Hospital