Massive metallosis due to metal-on-metal impingement in substitutive long-stemmed knee prosthesis

Metallosis is a combined chemical and toxic reaction which, if the contact surface of a metal implant is large, may cause extensive damage to the surrounding tissue.1 The importance and the effects of particles generated by wear and corrosion of joint replacement prostheses have been seldom described. This case is of interest because of: (1) prosthetic loosening with massive metallosis; (2) the length of bone loss replaced by the prosthesis (180 mm); (3) a modified Guepar-type prosthesis abundantly cemented; and (4) the history of the patient. A 30-year-old white female patient presented with a 2-year history of localized swelling in the medial aspect of the proximal tibia, and knee discomfort exacerbated by walking. The patient had had a left total 180-mm femur and knee replacement 15 years earlier. A needle biopsy of a subcutaneous mass at the level of the proximal tibia eroding the underlying bone showed metallic debris granuloma with metallosis. The condition was treated by multiple revisions of the prosthesis, consisting of debridement and prosthesis axle replacement in the attempt to block the hinge. Severe black staining due to metallic wear debris and extensive corrosion and metallosis of the surrounding tissues and periprosthetic residual bone were noted.