Tibial migration of a novel cementless total knee arthroplasty

Aims: The search for enhanced fixation and longevity in total knee arthroplasty (TKA) continues. Radiostereometric analysis (RSA) allows early detection of implant migration predictive of future aseptic loosening and is the recommended method for evaluating new implants. This multicentre RSA study evaluated early fixation and migration stability of a novel cementless tibial baseplate used in primary TKA. Methods: A total of 30 patients undergoing primary TKA were enrolled at two academic centres. All patients received a porous cementless tibial baseplate combined with either a cementless or cemented femoral component. The patella was selectively resurfaced based on surgeon preference and was resurfaced using either a cementless onlay or a cemented inset biconvex design. During surgery, RSA beads were inserted into the tibia, femur, and patella. RSA examinations were performed at six weeks (baseline), six months, 12 months, and 24 months postoperatively. The primary outcome was change in maximum total point motion (MTPM) of the tibial baseplate over 24 months. Secondary outcomes included component migration patterns and patient-reported outcome measures (PROMs). Results: In total, 29 patients completed minimum 24-month follow-up. Mean tibial baseplate MTPM was 1.018 mm (SD 0.742) at six months and 1.210 mm (SD 0.571) at 24 months. The change in MTPM between six and 12 months was -0.096 mm (SD 0.551) and between 12 and 24 months was 0.095 mm (SD 0.603), remaining below accepted RSA thresholds associated with increased risk of aseptic loosening. Translational and rotational migration stabilized by six months. Patients reported substantial improvement in functional (Oxford Knee Score, Forgotten Joint Score) and health-related (EuroQol five-dimension questionnaire) PROMs and high satisfaction at 12 and 24 months. Conclusion: This novel cementless tibial baseplate demonstrated early stabilization with no evidence of continuous migration over two years. These RSA findings suggest a low risk of future aseptic loosening, and support the early fixation performance of this implant design.