The Utility of metal ion trends in predicting revision in metal on metal total hip Arthroplasty

Abstract Background There is a paucity of data examining metal ion levels over time. Methods We retrospectively reviewed 59 patients (69 hips) with an ASR THA. We reviewed pre-revision cobalt and chromium concentrations over time. Results Seventy-one percent of patients who were revised and had multiple ion measurements (12/17) demonstrated increasing cobalt ion levels or elevated ion levels over time. There was a trend towards an elevated risk of revision for increasing cobalt and chromium levels starting at 12 and 4 ppb, respectively; this was significant for chromium levels above 7 ppb (HR 22.35, p=0.001). Similarly, there was a trend towards an elevated risk of pseudotumor formation for increasing cobalt and chromium levels starting at 5 and 2.5 ppb, respectively; this was significant for cobalt levels above 7 ppb (HR 6.88, p=0.027). Conclusion Patients with increasing ion levels merit close surveillance as these findings are concerning for the development of ARMD.