Pseudotumour secondary to metallosis following total wrist arthroplasty

Metallosis is a recognized complication of arthroplasty, due to abnormal deposition of metal debris within soft tissues. It has been reported in hip, knee and shoulder replacement; however, there remains limited literature on metallosis in total wrist arthroplasty (TWA). Previous case reports have documented complications, including carpal tunnel syndrome secondary to metallosis, however we report the first case of pseudotumour secondary to metallosis following TWA. A 54-year-old right-hand-dominant male underwent an uncemented left total wrist arthroplasty, for psoriatic arthropathy, using a Universal 2 (KMI Medical Inc., Carlsbad, United States) prosthesis and Herbert (KLS Martin, Tuttlingen, Germany) ulnar head component. Six years following the index procedure he presented with a 6-month history of persistent swelling to the radial aspect of his wrist and intermittent pain. There was no history of injury or trauma and inflammatory markers were unremarkable. Radiological imaging showed a large, lucent lesion on the radial aspect of the distal radius with associated soft tissue swelling. The prosthesis remained in a satisfactory position. Magnetic resonance imaging confirmed an expansile mass in the distal radius, with a thick rim of enhancement after injection of contrast (Figure 1). Histology showed a core of fibrinous material with focal deposition of pigmented histiocytes and metallic debris. Foreign-body giant-cell reaction was seen with no evidence of inflammation or neoplasia. The patient underwent revision left wrist arthroplasty. The radial component was well fixed despite a large adjacent bone defect. The carpal component was loose and the polyethylene liner had failed, resulting in articulation between the two metallic surfaces causing the metal debris. The pseudotumour was resected to healthy tissue, the bone defect grafted with Bioset putty and the carpal and radial component revised using larger implants. Cement was not used at either initial or revision surgery. Follow-up at six months demonstrated a good range of motion with no evidence of recurrent problems. The aetiology of metallosis is abnormal contact between metallic surfaces that results in shedding of metallic particles (Chang et al., 2005). These metallic fragments become engulfed by histiocytes releasing inflammatory mediators, which in turn activate osteoclasts, resulting in bone resorption. In addition, polyethylene wear and the generation of wear particles also lead to cytokine induction and osteoclastic resorption, thus potentiating this inflammatory response. Unconsolidated polyethylene particles, known as fusion defects, may also be responsible for increased polyethylene wear. Though polyethylene wear has long been accepted as a major cause of osteolysis in total hip arthroplasty, a recent study addressing this issue in TWA showed no correlation between polyethylene debris and the degree of periprosthetic osteolysis (Boeckstyns et al., 2014). Pseudotumours are focal solid or semiliquid masses around the prosthesis, mimicking neoplasia or infection in the absence of either of these (Daniel et al., 2012). With respect to conventional joint replacements, periprosthetic granulomatous masses or pseudotumours have been reported for over 30 years. A recent systematic review of pseudotumour following hip and knee arthroplasty reported an incidence of 0.1% to 3% for symptomatic pseudotumours (Daniel et al., 2012). Radmer et al. (2003) found evidence of severe titanium wear in 39 of 40 patients with TWA, all of whom required revision surgery, though they did not report any cases of pseudotumour. The exact cause of pseudotumours is unclear. The consistent factor among patients is increased wear, either due to wear-prone bearing surfaces or suboptimal component positioning, although this is not universal. Radmer et al. (2003) concluded that even in a non-weight-bearing joint, such as the wrist, titanium Letters to the Editor Short Report Letters 594110 JHS0010.1177/1753193415594110Journal of Hand Surgery (European Volume)Short report letters research-article2015