Migration in large femoral head ceramic-on-ceramic monoblock acetabular component compared with modular ceramic-on-polyethylene acetabular component in total hip arthroplasty using radiostereometric analysis with 5 years’ follow-up: a randomized cont

BACKGROUND AND PURPOSE: An uncemented ceramic-on-ceramic (CoC) monoblock cup is an acetabular component designed for younger and more active patients. We compared migration, revision rates, and clinical results of this uncemented CoC monoblock acetabular component with a commonly used uncemented ceramic-on-polyethylene (CoPE) modular cup. METHODS: In this prospective randomized controlled trial we used radiostereometric analysis (RSA) to study primary THAs that were performed after being allocated 1:1 to uncemented CoC monoblock acetabular component or to uncemented ceramic-on-polyethylene (CoPE) modular cup. Radiographs were obtained directly postoperatively, and at 1.5, 3, 6, 12, 24, and 60 months postoperatively. Migration of both cups was calculated using model-based RSA (mbRSA) in terms of translations and rotations. Revision rates and patient-reported outcome measures (PROMs) (Harris Hip Score, Oxford Hip Score, EQ-5D-5L) were also registered. RESULTS: We included 50 patients. The monoblock cup shows a statistically significant higher total translation compared with the modular cup (mean difference -0.71 mm, 95% confidence interval 0.10-1.31) at 5 years' follow-up. Both cups show an increased translation along the x- and y-axes over time, which stabilized after 3 months. No statistically significant differences were found in the rotation patterns of the cups. However, both cups show an increased rotation about the z-axis over time, which decreased between 2 and 5 years' follow-up. All PROMs improved after surgery and remained stable. CONCLUSION: Although the CoC monoblock cup showed a higher translation than the CoPE modular cup, the revision rates and clinical outcomes in both groups were similar. The CoC monoblock cup showed acceptable mid-term outcomes comparable with the CoPE modular cup.