Key result
The Echo Bi-Metric stem showed no statistically significant difference in migration (subsidence of 2.7 mm) at 24 months compared to the Bi-Metric stem (2.3 mm, p=0.6).
Why the study?
Although new implants are developed to improve durability, whether minor design changes in the Echo Bi-Metric THA stem improve clinical performance compared with its predecessor, the Bi-Metric stem, was unestablished.
Does the Echo Bi-Metric THA stem reduce migration at 24 months compared to the Bi-Metric THA stem in patients with osteoarthritis?
RCT (n=62)
Single-blind
Block randomization
No
Does the Echo Bi-Metric THA stem reduce migration at 24 months compared to the Bi-Metric THA stem in patients with osteoarthritis?
The Echo Bi-Metric stem demonstrated similar migration patterns and clinical outcomes at 24 months compared to its predecessor, the Bi-Metric stem, suggesting the design modifications did not significantly alter early stability.
EBM and BM stems show equivalent 24-month migration; confirms comparable early stability for the successor design in uncemented THA.
Background and purpose - Despite the good results after total hip arthroplasty (THA), new implants are continuously 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 features of the BM stem, but minor changes in the design might improve the clinical performance. We compared the migration 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 significant 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 respectively), 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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Dyreborg et al. (2020) conducted an RCT in Primary osteoarthritis (n=62). Echo Bi-Metric (EBM) THA stem vs. Bi-Metric (BM) THA stem was evaluated on Y-translation (subsidence) at 24 months (p=0.6). The Echo Bi-Metric stem showed no statistically significant difference in migration (subsidence of 2.7 mm) at 24 months compared to the Bi-Metric stem (2.3 mm, p=0.6).
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