CATASTROPHIC OSTEOLYSIS IN TOTAL KNEE REPLACEMENT - A REPORT OF 17 CASES

One hundred eighty-five total knee revisions were done by the 2 senior authors from 1988 to 1994. Of these, 17 patients were identified as h aving severe osteolysis. The average age was 62.7 years, and the avera ge weight was 90.8 g. All patients had osteoarthritis. Preoperative as piration was negative in all patients. Eight patients had a metal-back ed patella, 8 had a cementless implant, 4 had a cemented implant, and 5 had a hybrid implant. The average time interval from the index surge ry to radiographic evidence of lysis was 56 months. Radiographic revie w showed gross polyethylene wear in 10 patients, loose tibial implants in 8, fractured baseplates in 2, and evidence of a metallic synovitis in 2. Retrieved polyethylene liners had a average thickness of 7 mm, and none were conforming. Osteolytic defects were defined and classifi ed according to Engh's criteria. The histology showed a foreign body r eaction with intracellular refractile polyethylene particles. Four cas es had metallic debris. The exposure at the time of revision required a rectus snip in 4, V-Y-quadricepsplasty in 2, and tibial tubercle ost eotomy in 1. Posterior stabilized implants were used in 65% and a cons trained implant in 30%. Lytic defects were reconstructed with cement o nly in 47% of knees, allograft in 30%, and metallic wedges in 35%. Bas ed on this report, the authors conclude that younger, overweight patie nts seem to be at higher risk of implant failure and that osteolysis i s not restricted to cementless implants. Furthermore, because review o f the radiographs leads to a constant underestimation of the lytic def ect, the surgeon must be prepared to deal with complex revisions.