Blood Metal Ion Levels After Hip Resurfacing: A Comparison of 2 Different Implants

Background

While hip resurfacing arthroplasty has been shown to be an effective prosthetic solution for end-stage osteoarthritis, prior studies have also reported an increasing concern regarding blood metal ion levels following the use of metal-on-metal articulations. The purpose of this study was to compare early and midterm blood metal ion levels to functional outcomes and implant survivorship for patients treated with the Birmingham Hip Resurfacing (BHR) implant system and the ReCap Magnum.

Methods

A retrospective review identified 104 patients who underwent 134 hip resurfacing arthroplasties using BHR (n = 67) and ReCap (n = 67) at a single institution between 2006 and 2018. ReCap and BHR patients were matched 1:1 by sex, femoral head and acetabular cup sizes, age, and year of surgery. The primary outcome of interest was cobalt (Co) and chromium (Cr) ion levels.

Results

The ReCap cohort had lower median metal ion levels compared to the BHR cohort at 1-2 y (Co: 1.5 vs 1.9 parts per billion [ppb], P = .018; Cr: 1.3 vs 2.8 ppb, P = .008) and 3-5 y (Co: 1.1 vs 1.9 ppb, P = .001; Cr: 1.2 vs 2.2 ppb, P = .003) after surgery. Correlation analysis showed no significant associations between Co and Cr ion levels and pre- and postoperative patient-reported outcomes. Indications for revision differed between groups. Three BHR hips were revised due to adverse reactions to metal debris, whereas 2 ReCap hips required revisions: one for instability and another for periprosthetic fracture.

Conclusions

BHR patients had higher metal ion levels than ReCap patients at 1-2 and 3-5 y after surgery, though these metal levels are still low and in line with prior studies. Indications for revision differed between patients treated with BHR and ReCap. Surgeons should be aware of these outcomes when counseling patients regarding these metal-on-metal articulations.