A rare case of bilateral large osteolysis following cemented and cementless total knee arthroplasties

Abstract

A 66-year old woman (BMI 36) presented for routine follow-up after undergoing total knee arthroplasty (TKA) in the right knee 12 years ago, and TKA in the left knee 4 years ago. The right TKA was a cementless cruciate-retaining prosthesis (Encore Medical Foundation Knee, femoral component porous coated CoCrMb alloy, tibial component Ti-alloy with 4 screws, PE insert 9 mm). The left TKA was a cemented cruciate-retaining prosthesis (Zimmer Natural Knee II, femoral component CoCrMb alloy, tibial baseplate component Ti-alloy, PE insert 9 mm). The patient reported only mild problems (knee score 88 points, function score 60 points). Radiographs and CT scans revealed extensive osteolysis at the proximal medial tibia of both knees (Figures 1 and ​and2).2). There was a mild varus malalignment (4°) of both legs. Rotational alignment measured on the CT scans showed a rotational mismatch between femoral and tibial components of 8° (femoral internal rotation) in the right knee and no mismatch (1° of femoral internal rotation) in the left knee. Figure 1. Anterioposterior and lateral radiograph and CT scans showing osteolysis of the distal right femur and the proximal tibia 12 years after implantation of a cemenless TKA. Figure 2. Anterioposterior and lateral radiograph and CT scans showing osteolysis of the distal left femur and the proximal tibia 4 years after implantation of a cemented TKA. Open biopsy was performed bilaterally to rule out a possible malignancy or infection. Microscopic histological examination revealed chronic inflammation and hisitocytic infiltrates in both knees. Polyethylene particles were observed within the cytoplasma of the histiocytes. There was no evidence of metal debris. All microbiological cultures were negative. During revision, both tibial baseplates were manually assessed as being well fixed to the lateral tibial bone stock, providing no evidence that baseplate loosening was the cause of the osteolysis. However, upon removal of the baseplates, the cortical bone at the proximal medial tibia was observed to be very thin and completely missing in some regions, as already revealed on the CT scans. Osteolytic defects were filled with autologous cancellous bone and augmented with bone cement, and both knees were implanted with a modular constrained TKA prosthesis.