Migration of the uncemented Echo Bi-Metric and Bi-Metric THA stems: a randomized controlled RSA study involving 62 patients with 24-month follow-up
Background and purpose — Despite the good results after total hip arthroplasty (THA), new implants are continu- ously being developed to improve durability. The Echo Bi- Metric (EBM) THA stem is the successor to the Bi-Metric (BM) THA stem. The EBM stem includes many of the fea- tures of the BM stem, but minor changes in the design might improve the clinical performance. We compared the migra- tion behavior with radiostereometric analysis (RSA) of the EBM stem and the BM stem at 24 months and evaluated the clinical outcome.
Patients and methods — We randomized 62 patients with osteoarthritis (mean age 64 years, female/male 28/34) scheduled for an uncemented THA to receive either an EBM or a BM THA stem. We performed RSA within 1 week after surgery and at 3, 6, 12, and 24 months. The clinical outcome was evaluated using Harris Hip Score (HHS) and Oxford Hip Score (OHS).
Results — At 24 months, we found no statistically sig- nificant differences in migration between the two implants. During the first 3 months both the EBM and the BM stems showed visible subsidence (2.5 mm and 2.2 mm respec- tively), and retroversion (2.5° and 2.2° respectively), but after 3 months this stabilized. The expected increase in HHS and OHS was similar between the groups.
Interpretation — The EBM stem showed a migration at 24 months not different from the BM stem, and both stems display satisfying clinical results.
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Copyright (c) 2020 Karen Dyreborg, Mikkel R Andersen , Nikolaj Winther, Søren Solgaard, Gunnar Flivik, Michael M Petersen
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