Inferior patient-reported outcomes after total knee arthroplasty for post-traumatic versus primary osteoarthritis: a registry study.

BACKGROUND: Total knee arthroplasty (TKA) performed after knee fracture osteosynthesis for post-traumatic osteoarthritis (PTOF) is technically demanding and may yield inferior outcomes compared with TKA performed for primary osteoarthritis (OA). Comparing patient-reported outcomes (PROs) between these groups is challenging due to differing patient characteristics. METHODS: This observational matched case–control study used data from the Swedish Arthroplasty Register and the Swedish Fracture Register and included 1293 TKAs performed for PTOF between 2000 and 2021, matched 1:2 with TKAs performed for OA based on sex, age, BMI, ASA classification, and time period. For each PTOF TKA and its matched controls, at least one of the following patient-reported outcome measures (PROMs) was available both preoperatively and 1-year postoperatively: KOOS-12, EQ-5D-3L, Likert pain and satisfaction, resulting in four separate matched PTOF cohorts depending on the available PROM. RESULTS: Both groups demonstrated postoperative improvement. For the primary outcome, the PTOF group had a lower 1-year postoperative KOOS-12 total score than the OA group (56 vs 68, p < 0.001), and inferior scores were observed in all KOOS-12 subscales. Fewer patients in the PTOF group reported “no pain” (25% vs 41%, p = 0.003) or were “very satisfied” (43% vs 54%, p = 0.003) than those in the OA group. In linear regression analyses adjusted for type of articulation and corresponding preoperative PROM scores, PTOF remained associated with worse 1-year KOOS-12 outcomes and a lower EQ-5D-3L index score, whereas the adjusted difference in EQ-VAS was not statistically significant. CONCLUSIONS: Although PROs improved in both groups after TKA, PTOF patients reported inferior outcomes compared with OA patients. This difference is likely due to prior trauma and altered knee biomechanics, indicating that PTOF patients should be appropriately counselled preoperatively. LEVEL OF EVIDENCE: III. TYPE OF STUDY: Registry-based matched case–control study.