DOS 2018

DOS Kongressen 2018 · 107 The survival of TKAs converted from medial UKA resembles the survival of revision TKAs and not primary TKAs – Results from the Danish Knee Arthroplasty Registry Anders El-Galaly, Andreas Kappel, Poul Torben Nielsen, Steen Lund Jensen Department of Orthopaedic Surgery, Aalborg University Hospital Background: Medial UKA is increasingly popular but may subsequently be con- verted to a TKA. It is debated whether the survival of these conversion TKAs (uTKA) resembles the survival of primary TKAs (pTKA) or TKA to TKA revisions (rTKA). Purpose / Aim of Study: To evaluate the survival of uTKA and compare it with pTKA and rTKA. Materials and Methods: 1.005 uTKAs conducted between 1997 and 2017 were retrieved from the Danish Knee Arthroplasty Registry and compared to 88.713 pTKAs and 3.535 rTKAs. Patients and surgery details were analyzed. Implant survival was estimated by Kaplan Meier analysis and Cox Regression was used to estimate the association between survival and clinical features. Findings / Results: Median time from UKA to TKA was 2.3 years and the most frequent indications for conversion were aseptic loosening (27%), pain (26%) and progressive osteoarthritis (14%). Mean age of uTKA was lower (66 years) than both rTKA (69 years) and pTKA (69 years) (p<0.001). 5- and 10- year implant survival were comparable between uTKA and rTKA (0.90 vs 0.91 and 0.86 vs 0.88, p=0.31) and both were lower than pTKA (0.97 and 0.96, p<0.001). Correspondingly, uTKA and rTKA had a similar adjusted hazard ra- tio (HR) for revision when compared to pTKA (2.82 vs 2.86, p<0.001). Early conversion of UKA (<2.3 years) was associated with an increased risk of revi- sion (HR=1.72, p=0.02). Conversion due to aseptic loosening or pain did not influence the risk of revision, while conversion due to progressive osteoarthritis lowered the risk (HR=0.23, p<0.01). Conclusions: Regarding survival, a TKA converted from a medial UKA behaves like a revision TKA but is inferior to a primary TKA. Early conversion increased the risk of revision whereas conversion due to progressive osteoarthritis low- ered the risk. 48.