Cobalt determination in the hair of patients after metal-on-metal hip implants by instrumental neutron activation analysis

Abstract

In these years, following the alert of possible problems of toxicity issued by national medicine authorities, thousands of patients with hip implants are recalled for a set of analysis, including cobalt determinations in blood and urine. In this framework, additional measurements of cobalt in hair are recommended to monitor the release of metals in the body after surgery. Aiming at a clinical application, the standardization of the hair washing protocol used to remove possible external contamination is essential. To this aim, a method suggested by the International Atomic Energy Agency and based on repeated washings with acetone and deionized water was tested. Specifically, hair samples of two healthy subjects and three patients were measured at different steps of the washing sequence to observe the decrease in the level of cobalt to the plateau corresponding to the bound component. The data confirmed the suitability of the washing method and proved high levels of bound cobalt in hair of two patients requiring revision hip surgery. Moreover, the cobalt bound component was not affected by the neutron exposure of hair. As a result, use of Instrumental Neutron Activation Analysis might be advantageous compared to other analytical techniques.

Correlation Between Co Levels in Hair and Blood of Patients Who Underwent Metal-on-metal Hip Arthroplasty

“…[ 13 ] and in agreement with the results we previously obtained with the same person, that is, the control subject C2 reported by D’Agostino et al. [ 11 ]. Conversely, the 4.3 mg kg -1 preoperation Co mass fraction mean value reported by Fu-Cun et al.…”

“…The quality and metrological traceability of hair analysis carried out in this study are supported by the use of the IAEA washing method, demonstrated to be suitable to remove the unbound Co component [ 11 ], and the agreement between the LTCS and INRIM intercomparison results plotted in Figure 2 . In addition, particular attention was paid to the exclusion of hair samples with insufficient mass and results below the measurement detection limit.…”

“…A fit-for-purpose primary ratio method described by D’Agostino et al. [ 11 ] and based on the instrumental neutron activation analysis (INAA) was applied by the INRIM to establish direct traceability of the results.…”

“…Aiming at filling in the current lack of knowledge on hair analysis as a diagnostic tool in MoM patients’ assessment, we carried out a further study to investigate the existence of a correlation between metal levels in hair and in blood. We selected Co as a target element because we have previously proved that the hair washing protocol proposed by the International Atomic Energy Agency (IAEA) is suitable for Co determinations in hair [ 11 ].…”