Early migration following revision total knee arthroplasty with tibial metaphyseal cones: a 2-year prospective RSA cohort study of 25 patients.

BACKGROUND AND PURPOSE: In revision total knee arthroplasty (rTKA), cones can enhance stable fixation in the case of suboptimal metaphyseal bone stock. Combined with stems of sufficient length, cones can offer support and promote osseointegration without graft-related complications. However, their mechanical stability remains underexplored. We aimed to evaluate the stability of tibial rTKA constructs with metaphyseal cones using radiostereometric analysis (RSA) over a 2-year follow-up.

METHODS

25 patients undergoing rTKA with a tibial cone were included. Tantalum markers were placed in the cancellous bone intraoperatively, before placement of the revision construct, to enable migration measurements using model-based RSA (MB-RSA). Tibial component migration was assessed at baseline, 6-week, 3-month, 6-month, 1-year, and 2-year follow-up, with main outcome parameters being total translation (TT) and total rotation (TR) at 2-year follow-up. Clinical outcomes included VAS pain and satisfaction, the Oxford Knee Score, Knee Society Score, KOOS-PS, and adverse events.

RESULTS

At 2-year follow-up the least-squares mean TT was 0.59 mm (95% confidence interval [CI] 0.40-0.78) and TR was 0.76° (CI 0.57-0.96). Migration measures demonstrated substantial inter-individual variability, with heterogeneous early migration patterns across patients. Between 1 and 2 years, median changes in migration were small at group level. At 2 years, 3 of 23 patients had TT > 1 mm and 6 had TR > 1°. Clinical outcome scores generally improved until 6 months to 1 year, followed by a trend towards decline. There was 1 re-revision for aseptic loosening after 1-year follow-up and 1 insert exchange for knee instability.

CONCLUSION

Tibial rTKA constructs with metaphyseal cones demonstrate heterogeneous early migration, followed by limited additional migration at group level between 1 and 2 years. While most constructs showed low migration at 2 years, several patients exhibited increased migration.