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Radiographic Evaluation of Periprosthetic Metallosis After Total Arthroplasty

Thomas F. McGovern, MD, Joseph T. Moskal, MD

Posted: 11/19/2002; J South Orthop Assoc. 2002;11(1) © 2002 Southern Medical Association

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Abstract

This retrospective study examined the clinical significance of a radiographic sign associated with periprosthetic metallosis after total knee arthroplasty. Of 71 knees undergoing revision arthroplasty over an 8-year period, 11 had gross evidence of metal debris identified intraoperatively.

Histologic preparations confirmed the presence of particulate metal debris in all cases. Radiographs in 7 of 11 cases were positive for metallosis. The radiographic sign identified on lateral radiographs was divided into 3 types based on the size of the mass.

The magnitude of soft tissue pathology and the extent of osteolysis correlated with the size of the mass on preoperative radiographs. Replacement of all components was necessary in 71% of cases with radiographs positive for metallosis and 47% of cases with negative radiographs.

Only 1 of the 11 knees with metallosis had a late postoperative infection, for which 2-stage revision arthroplasty was required. All cases with positive radiographs had gross and histologic confirmation of metal and polyethylene debris. These data suggest that careful assessment of radiographs can facilitate preoperative planning.

Discussion

Periprosthetic metallosis is a pathologic diagnosis made at the time of surgery. The metal-on-metal abrasion responsible for the condition releases a tremendous amount of particulate debris. Periprosthetic metallic and polyethylene particles have been shown to induce a foreign-body reaction in failed total-joint arthroplasties.[1,2,3,9] Osteolysis is mediated by prostaglandin E2, collagenase, and interleukin-1 released by local tissue macrophages.[5,10] The extent of bone and soft tissue destruction can be underestimated by routine analysis of preoperative radiographs. This study demonstrated a radiographically evident soft tissue granuloma in 64% of the cases with gross metallic synovitis identified intraoperatively. Metal, polyethylene, and methylmethacrylate particles have all been shown to stimulate periprosthetic soft tissue destruction. The particulate debris responsible for the formation of the extensive granuloma, and bone destruction could not be determined from the data presented in this study; however, all cases with positive radiographs had gross and histologic confirmation of metal and polyethylene debris.

 

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