Medial unicompartmental knee arthroplasties: Radiographic findings associated with conversion to total knee...

Identify radiographic findings after Unicompartmental Knee Arthroplasty (UKA) that might lead to conversion to Total Knee Arthroplasty (TKA) in comparison to an asymptomatic control group without the need to conversion to TKA.

Radiographs of patients with UKA before aseptic conversion to TKA were compared to an asymptomatic control group without conversion. Radiographic findings like osteolytic rim, osteolysis, material integrity and positioning, periprosthetic fractures, and osteoarthritis (OA) were evaluated.

A total of 99 patients were included (male/female, 60/39; mean age, 67 ± 9.7 years), 42 in the conversion group and 57 in the control group. In the conversion group, an osteolytic rim with a sclerotic line was observed at the femoral component in 16.7 % and at the tibial component in 54.8 %, while it was observed in 10.5 % and 30.7 % in the control group (femoral, p = 0.676; tibial, p = 0.014, respectively). Osteolysis was present in the conversion group at the femoral component in 1.2 % and at the tibial component in 8.3 %, while no femoral or tibial component osteolysis was present in the control group (femoral, p = 0.32; tibial, p = 0.008, respectively). OA was more advanced in the conversion group compared to the control group in the lateral femorotibial compartment (p < 0.001) and the patellofemoral compartment (p = 0.008). The femoral material integrity was more often intact in the conversion group (p = 0.045), and the femorotibial ratio was higher in the control group (p = 0.040).

Features commonly present in patients needing a conversion from UKA to TKA were tibial osteolytic rim and osteolysis. Additionally, OA was more advanced in the conversion group at the lateral femorotibial compartment and patellofemoral compartment compared to the asymptomatic control group.