LAUSR

Ten years following withdrawal and revision of large diameter metal on metal hips (MOM), there remains an uncertainty in how best to manage asymptomatic patients with abnormal imaging and/or raised blood metal ion levels. This study investigates the trajectories of symptoms, serological metal ion tests and cross-sectional imaging in these patients. 523 patients with 707 acceptable functioning MOM hips (defined as Oxford Hip Score (OHS) >30) on active monitoring were identified. Surveillance at two time intervals included: patient-reported pain and function (OHS), blood metal ion (Cobalt (Col) and Chromium (Chr)) and/or cross-sectional imaging with MRI. Mean serum metal ion levels in parts per billion (ppb) were Co1 4.5 (S.D. 11.5), Co2 4.7 (S.D. 11.6) and Ch1 3.0 (S.D. 4.8) and Ch2 3.2 (S.D. 4.9). Median OHS was 42 (IQR 28–27). OHS was not significantly correlated to serum metal ion levels (Col Pearson correlation = -0.105 P = 0.106, Chr Pearson correlation = -.125 P = 0.054). There was no significant change in Col (-0.48, P = 0.414) and Chr levels (-0.25, P = 0.325) between the two time intervals. 45 patients had metal ion levels >7 ppb, 64.4% had OHS >30. 6 patients had metal ions level greater than 50 ppb, with no significant deterioration of OHS. Our results indicate that there are a subset of patients with high metal ion levels, stable imaging and acceptable function who can safely be actively monitored thereby assisting in joint decision making with this challenging patient group.