Patient-reported outcome 1 to 4 years after periprosthetic knee fracture: a nationwide cross-sectional matched study

Background and purpose — Periprosthetic knee fractures (PPKFs) can be a serious complication after total knee arthroplasty (TKA). We aimed to compare patient-reported outcome (PRO) scores reported between 1 and 4 years after PPKF with a matched uncomplicated TKA control group. Methods — This nationwide cross-sectional matched cohort study included 372 TKA patients with a PPKF occur-ring from 2019 to 2022 and a control group of 878 uncomplicated TKA patients matched by age, time since TKA, and sex. The study population was derived from the Danish National Patient Register. The patients received questionnaires regarding knee function, quality of life, pain and satisfaction in 2023. The questionnaires included Oxford Knee Score (OKS), the Forgotten Joint Score (FJS), and the EQ-5D-5L Index. Results — The response rate was 48%. Mean OKS was 7 (confidence interval [CI] 5–9) points lower after a PPKF with a score of 30 (standard deviation [SD] 11) in the PPKF group vs 37 (SD 11) in the control group. The FJS was 13 (CI 7–19) points lower after a PPKF with a score of 50 (SD 30) in the PPKF group vs 63 (SD 30) in the control group. Mean EQ-5D-5L Index scores were 0.17 (CI 0.12–0.22) lower after a PPKF with a score of 0.68 (SD 0.25) in the PPKF group vs 0.85 (SD 0.25) in the control group. Additional analysis of patients who completed PROMs 1–2 years compared with 3–4 years after PPKF showed better PRO scores after 3–4 years with an OKS of 32 (SD 12) vs 27 (SD 12), FJS 55 (SD 32) vs 43 (SD 32), and EQ-5D-5L Index of 0.74 (SD 0.34) vs 0.60 (SD 0.34). Conclusion — Following PPKF, patients reported worse knee function, more pain, lower satisfaction, and poorer quality of life than those with uncomplicated TKAs.