New research suggests that total knee arthroplasty (TKA) converted from medial unicompartmental knee arthroplasty (UKA) has a three-fold higher risk of revision when compared with primary TKA.
For the study, published in the Journal of Bone & Joint Surgery, researchers compared the outcomes of 1,012 TKAs converted from UKAs with 73,819 de novo primary TKAs and 2,572 revision TKA using data from the Danish Knee Arthroplasty Registry from 1997 to 2017. The primary outcome was the risk of revision.
The authors found that for patients who underwent conversion of UKA to TKA, long-term outcomes were similar to those who underwent revision TKA. Both of these groups had an estimated 15-year implant survival rate of 78 per cent. In contrast, the 15-year implant survival rate for primary TKA was 94 per cent. Implant type did not affect outcomes for patients who underwent conversion of UKA to TKA. The main reasons for UKA conversion were implant loosening, unexplained pain and progression of arthritis.
"On the basis of this study, we believe that careful consideration is necessary before using medial UKA as treatment for knee osteoarthritis, as a potential conversion to a TKA decreased implant survival when compared with that following primary TKA,” the authors concluded.