Prosthetic migration measured by radiostereometric analysis (RSA) within the first 2 years of knee arthroplasty is predictive of long-term aseptic mechanical loosening.1 This makes it a good tool for evaluating the likely performance of new implant designs.1
In this randomised control trial of 75 cemented posterior-stabilised knees implant migration, clinical outcomes, and patient reported outcome measures (PROMs) were reviewed at one week, and then 3, 6, 12, and 24 months post-operatively.1 Maximum total point motion (MTPM), translations and rotations of the tibial components were all measured using RSA.1
No differences in mean MTPM migrations were observed between the groups for either the tibial or femoral components. At two years post-op the mean tibial MTPM was 0.93mm in the anatomic group compared to 1.00mm in the symmetrical group.1 In the femur these values were 1.04mm and 1.14mm, respectively.1 No significant differences were observed for any of the other parameters.1
The authors concluded that the anatomical tibial design demonstrated a comparable component migration pattern to the proven symmetrical design. This suggests that the long-term risk of aseptic loosening is also comparable for the two designs.1
Although this study did not demonstrate any difference in clinical outcomes or PROMS, the authors acknowledge that the study was not powered to compare PROMs results.1
