Optimized medial unicompartmental knee arthroplasty outcome: learning from 20 years of propensity score matched registry data

Mette Mikkelsen; Andrew Price; Alma Becic Pedersen; Kirill Gromov; Anders Troelsen

doi:10.2340/17453674.2022.2265

Authors

Mette Mikkelsen Department of Orthopaedic Surgery, Clinical Orthopaedic Research Hvidovre (CORH), Copenhagen University Hospital Hvidovre, Copenhagen, Denmark https://orcid.org/0000-0002-1189-1633
Andrew Price Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Science, University of Oxford, Oxford, UK
Alma Becic Pedersen Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark https://orcid.org/0000-0002-3288-9401
Kirill Gromov Department of Orthopaedic Surgery, Clinical Orthopaedic Research Hvidovre (CORH), Copenhagen University Hospital Hvidovre, Copenhagen, Denmark https://orcid.org/0000-0002-8114-5193
Anders Troelsen Department of Orthopaedic Surgery, Clinical Orthopaedic Research Hvidovre (CORH), Copenhagen University Hospital Hvidovre, Copenhagen, Denmark https://orcid.org/0000-0003-0132-8182

DOI:

https://doi.org/10.2340/17453674.2022.2265

Keywords:

Arthroplasty, Knee, Osteoarthrosis, Revision, Unicompartmental knee arthroplasty

Abstract

Background and purpose: Unicompartmental knee arthroplasty (UKA) has increased in use. We investigated changes to UKA revision risk over the last 20 years compared with total knee arthroplasty (TKA), examined external and patient factors for correlation to UKA revision risk, and described the survival probability for current UKA and TKA practice.

Patients and methods: All knee arthroplasties reported to the Danish Knee Arthroplasty Register from 1997 to 2017 were linked to the National Patient Register and the Civil Registration System for comorbidity, emigration, and mortality information. All primary UKA and TKA patients with primary osteoarthritis were included and propensity score matched 4 TKAs to 1 UKA. Revision and mortality were analyzed using competing risk cox regression with a shared gamma frailty component.

Results: The matched cohort included 48,195 primary knee arthroplasties (9,639 UKAs). From 1997–2001 to 2012–2017 the 3-year hazard ratio decreased from 5.5 (95% CI 2.7–11) to 1.5 (CI 1.2–1.8) due to increased UKA survival. Cementless fixation, a high percentage usage of UKA, and increased surgical volume decreased UKA revision risk, and increased in occurrence parallel to the decreasing revision risks. Current UKA practice using cementless fixation at a high usage unit has a 3-year implant survival of 96% (CI
97–95), 1.1% lower than current TKA practice.

Interpretation: UKA revision risk has decreased over the last 20 years, nearing that of TKA surgery. High usage rates, surgical volume, and the use of cementless fixation have increased during the study and were associated with decreased UKA revision risks.