Extrusion of metal radiological marker from a total ankle replacement insert: a case report

Total ankle arthroplasty has become an increasingly performed procedure for the treatment of ankle arthritis. Failures related to polyethylene inserts can result from uncorrected deformities or malalignment of the components. We report a case of a 63-year-old man who underwent total ankle arthroplasty for osteoarthritis of the ankle. The talar component was placed in neutral alignment. Initial postoperative recovery and rehabilitation were unremarkable. At 9 months postoperatively, plain radiographs of the ankle showed worsening varus tilt when compared with radiographs taken earlier. There was also radiographic evidence of separation of the posterior metal marker, suggestive of a fracture of the polyethylene insert. Revision surgery to correct the varus tilt and replace the polyethylene insert was performed. At operation, the polyethylene insert was found to be intact with no evidence of fracture. The posterior metal marker of the polyethylene insert was found to be extruded from the insert. Small degrees of ankle prosthesis malalignment can lead to various degrees of polyethylene liner failure, such as metal marker extrusion. This article also shows that these metal markers may not be accurate indicators of the integrity of the polyethylene insert.