Similar 1-year tibial implant migration, but higher continuous migration with cementless fixation: a retrospective RSA study of 990 patients with moderate to severe knee osteoarthritis.

BACKGROUND AND PURPOSE: Aseptic loosening is a major cause of revision surgery. The grade of osteoarthritis (OA) may influence tibial implant migration and the risk of aseptic loosening. We aimed to investigate the association between preoperative OA grade and tibial implant migration in cemented and cementless total and unicompartmental knee arthroplasty. METHODS: We performed a retrospective analysis on a prospective clinical cohort of 990 patients (990 knees). Preoperative OA was graded with the Kellgren-Lawrence (KL) scale and categorized as severe (KL 4) or moderate (KL 1-3). Tibial implant migration was measured by radiostereometric analysis (RSA) at 1, 2, and 5 years. The primary outcome was the 1-year mean difference in maximum total point motion (MTPM) between OA groups. The secondary outcome was the difference between groups in the proportion of patients with continuous migration (MTPM > 0.2 mm between years 1 and 2). Analyses were adjusted for age, sex, and body mass index (BMI). RESULTS: 610 patients were classified with severe OA, and 380 patients were classified with moderate OA. Mean 1-year MTPM was similar between OA groups. In the cementless cohort (n = 651), continuous migration occurred in 83/360 (23%) of severe OA cases vs 26/195 (13%) of moderate OA cases. Hence, patients with severe OA and a cementless implant had a mean 73% higher risk of continuous migration. In the cemented cohort (n= 339), comparable results for continuous migration were found. CONCLUSION: Mean 1-year MTPM tibial implant migration values were similar across OA groups. However, patients with severe OA who received cementless implants exhibited a higher risk of continuous migration.