Radiographic Evaluation of Periprosthetic Metallosis After Total Arthroplasty

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


J South Orthop Assoc. 2002;11(1) 

In This Article

Abstract and Introduction

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.

The pathologic effects of periprosthetic particulate debris have emerged as significant factors in failure of total knee arthroplasties. The term metallosis has been used to describe the intraoperative findings of gross metallic debris and blackening of periprosthetic tissue.[1,2,3] Histologic analysis of the joint fluid and synovial tissue has revealed polyethylene and acrylic cement debris, in addition to metal particles.[4] Local tissue response to particulate debris consists of a foreign-body reaction, with infiltration of macrophages and giant cells.[3] Phagocytosis of the particulate debris stimulates production and release of cytokines.[5] The tissue reaction ultimately results in periprosthetic bone destruction, osteolysis, and granulomatous fibrosis in the surrounding soft tissue.[4,8] The magnitude of the reaction depends on particle type, size, concentration, and duration of exposure.[6,7,8]

Revision total knee arthroplasty in cases with metallosis can be difficult. The surgery frequently requires extensive synovectomy, soft tissue and bone debridement, and replacement of all components. Unfortunately, it is difficult to anticipate the extent of the periprosthetic bone and soft tissue destruction with preoperative physical examination and radiographic assessment. Patients can present with pain, instability, effusion, and edema. Frequently, however, if the components remain well fixed, the symptoms are minimal, and some patients are asymptomatic. If patients are not treated in the early stages, there may be significant risk of massive bone and soft tissue destruction, requiring a complex revision arthroplasty to reconstruct the joint.

Radiographs that suggest complete wear of the tibial polyethylene insert or the polyethylene part of the metal-backed patellar component have been associated with significant metallosis.[3,9] Furthermore, a radiographic sign indicating metallic debris has also been described.[6] We describe preoperative radiographic evaluation, intraoperative findings, and a minimum 4-year follow-up for 71 consecutive cases treated with revision total knee arthroplasty at our institution. A retrospective analysis was performed to examine the relationship between preoperative radiographs and the intraoperative soft tissue and bone condition when gross metallic debris was present. The purpose of this study was to demonstrate the clinical significance of a radiographic sign associated with periprosthetic metallosis.