Implant stability and clinical performance of a bicruciate-retaining total knee arthroplasty: A radiostereometric analysis up to 7.5 years follow-up.

Background: A previous randomized controlled trial showed higher tibial migration and more device-related complications in bicruciate-retaining compared to cruciate-retaining total knee arthroplasty, raising concerns about long-term implant stability and prompting this follow-up study to assess migration patterns and clinical outcomes up to 7.5 years postoperatively.

Methods: In this follow-up study, the bicruciate-retaining group from an initial single-centre randomized controlled trial was monitored at 5 and 7.5 years postoperatively. Implant migration was measured through model-based radiostereometric analysis and reported as total translation and rotation for femoral and tibial components. Clinical outcomes, including multiple patient-reported outcomes and functional assessments, were also evaluated.

Findings: A total of 13 bicruciate-retaining patients participated in this follow-up study, with 12 completing the 7.5-year follow-up. At 5 and 7.5 years postoperatively, the median(interquartile range) total translation and total rotation for the tibial components were 0.24 mm (0.18-0.48) and 0.59° (0.46-1.10) and 0.30 mm (0.18-0.81) and 0.73° (0.50-1.39), respectively. For the femoral components, total translation and total rotation were 0.46 mm (0.34-0.64) and 0.43° (0.25-0.69) at 5 years, and 0.43 mm (0.24-0.74) and 0.36° (0.30-0.83) at 7.5 years. Clinical and functional outcome scores, on average, were high but one patient reported mediolateral instability.

Interpretation: Migration patterns for both bicruciate-retaining components generally stabilized from 2 to 7.5 years postoperatively, although some outliers show migration of >0.2 mm. Given the high frequency of device-related adverse events and potential healthy survivor bias, these findings do not support the routine clinical use of this implant.