Similar fixation of total knee arthroplasty components with medial congruent and cruciate retaining polyethylene inserts. A randomised double-blinded controlled radiostereometry trial with 24 months of follow-up.

Abstract

To assess the influence of a higher constraint medial congruent (MC) versus a cruciate retaining (CR) (gold standard) polyethylene insert on the migration of cemented tibial and femoral components of the Persona Total Knee System. High-constraint inserts may increase forces on components and potentially affect implant migration and long-term fixation. A cohort of 66 patients with primary knee osteoarthritis received a cemented Persona total knee arthroplasty and were randomised to either an MC or a CR polyethylene insert. Tibial and femoral component migration was assessed using static radiostereometric analysis, with the first stereo-radiograph taken supine on the first postoperative day (baseline) and again at 3-, 12-, and 24-month follow-up. Tibial and femoral component migration was evaluated in six degrees of freedom and as maximum total point motion (MTPM). At the 12-month follow-up, the mean difference in tibial component MTPM was 0.04 mm (95% confidence interval [CI]: -0.21 to 0.28). The mean MTPM was 0.81 mm (95% CI: 0.64-0.99) in the MC group and 0.85 mm (95% CI: 0.68-1.03) in the CR group. Signed migrations were similar for the MC and the CR group throughout 24 months of follow-up (p > 0.09). At the 12-month follow-up, the mean difference in femoral component MTPM was 0.18 mm (95% CI: -0.17 to 0.53). The mean MTPM was 1.08 mm (95% CI: 0.83-1.32) in the MC group and 1.26 mm (95% CI: 1.01-1.51) in the CR group. The femoral components with MC insert had 0.18 mm (95% CI: 0.03-0.32) and 0.20 mm (95% CI: 0.01-0.39) more lateral migration at 3- and 12-month follow-up, respectively. At the 24-month follow-up, there was no statistically significant differences in migration for either translations, rotations or MTPM. Both tibial and femoral components had similar and acceptable fixation regardless of the type of polyethylene insert. Level I.