Prosthesis survival after revision knee arthroplasty for “pain without loosening” versus “aseptic loosening”: a Danish nationwide study

BACKGROUND AND PURPOSE: Patients having a knee arthroplasty revision for the indication “pain without loosening” may have a higher risk of re-revisions than patients revised for other indications. The primary aim of this study was to compare the survival of knee arthroplasties revised for “pain without loosening” compared with “aseptic loosening.” The second was to investigate the prosthesis survival rates in 3 surgical subgroups (total knee arthroplasty (TKA)–TKA; partial revision (revision of tibial or femoral component); unicompartmental knee arthroplasty–TKA) and to compare the prosthesis survival rates for 1997–2009 and 2010–2018. PATIENTS AND METHODS: 4,299 revisions were identified in the period 1997–2018 from the Danish Knee Arthroplasty Register. Of these, 1,111 (26%) were performed due to “pain without loosening” without any other indications, 674 (16%) due to “pain without loosening” combined with other indications, and 2,514 (59%) due to “aseptic loosening”. Survival analysis was performed by a Cox multivariate analysis and Kaplan–Meier curves were presented. RESULTS: The cumulated proportions of re-revision after 2, 5, and 20 years were 12% (95% CI 10–14), 18% (CI 16–20), and 23% (CI 20–25) for “pain without loosening” versus 11% (CI 9.3–12), 16% (CI 14–17), and 19% (CI 18–21) for “aseptic loosening.” There were no statistically significant differences between the 2 indications in repeated analyses for each of the surgical subgroups. The hazard ratio for re-revision comparing “pain without loosening” with “aseptic loosening” was 1.03 (CI 0.87–1.2). The 8-year risk of re-revision for “pain without loosening” was 22% (CI 19–26) versus 22% (CI 20–25) for “aseptic loosening” in the period from 1997–2009, and 18% (CI 15–22) versus 14% (CI 13–16) in the period from 2010–2018. INTERPRETATION: The risk of re-revision was similar for patients having a knee arthroplasty revision for the indication “pain without loosening” compared with “aseptic loosening.” However, we observed a slight improvement of prosthesis survival rates after revisions for both indications from 1997–2009 to 2010–2018. We cannot recommend for or against revision in cases with “pain without loosening” based on these data alone.