Can blood metal ion levels be used to identify patients with bilateral Birmingham Hip Resurfacings who are at risk of adverse reactions to metal debris?
OBJECTIVE
We investigated whether blood metal ion levels could effectively identify patients with bilateral Birmingham Hip Resurfacing (BHR) implants who have adverse reactions to metal debris (ARMD).


METHODS
Metal ion levels in whole blood were measured in 185 patients with bilateral BHRs. Patients were divided into those with ARMD who either had undergone a revision for ARMD or had ARMD on imaging (n = 30), and those without ARMD (n = 155). Receiver operating characteristic analysis was used to determine the optimal thresholds of blood metal ion levels for identifying patients with ARMD.


RESULTS
The maximum level of cobalt or chromium ions in the blood was the parameter which produced the highest area under the curve (91.0%). The optimal threshold for distinguishing between patients with and without ARMD was 5.5 µg/l (83.3% sensitivity, 88.4% specificity, 58.1% positive and 96.5% negative predictive values). Similar results were obtained in a subgroup of 111 patients who all underwent cross-sectional imaging. Between 3.2% and 4.3% of patients with ARMD were missed if United Kingdom (7 µg/l) and United States (10 µg/l) authority thresholds were used respectively, compared with 2.7% if our implant specific threshold was used, though these differences did not reach statistical significance (p ≥ 0.248).


CONCLUSIONS
Patients with bilateral BHRs who have blood metal ion levels below our implant specific threshold were at low-risk of having ARMD. Cite this article: Bone Joint J 2016;98-B:1455-62.
The Royal Orthopaedic Hospital, Birmingham B31 2AP, UK and Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford OX3 7LD, UK.
G S
GS
Matharu
The Royal Orthopaedic Hospital, Birmingham B31 2AP, UK.
F
F
Berryman
The Royal Orthopaedic Hospital, Birmingham B31 2AP, UK.
L
L
Brash
University of Birmingham, Birmingham B15 2TT, UK.
P B
PB
Pynsent
The Royal Orthopaedic Hospital, Birmingham B31 2AP, UK.
D J
DJ
Dunlop
The Royal Orthopaedic Hospital, Birmingham B31 2AP, UK.
R B C
RB
Treacy
D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D015415:Biomarkers / Q000097:blood; D002857:Chromium / Q000097:blood*; D003035:Cobalt / Q000097:blood*; D005260:Female; D005547:Foreign Bodies / Q000097:blood* / Q000209:etiology; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure / Q000209:etiology; D012372:ROC Curve; D012086:Reoperation; D012680:Sensitivity and Specificity
D015415:Biomarkers; D002857:Chromium; D003035:Cobalt
Adverse reactions to metal debris; Blood metal ions; Hip resurfacing; Metal-on-metal