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The clinical implications of elevated blood metal ion concentrations in asymptomatic patients with MoM hip resurfacings: a cohort study.

ABSTRACT: To determine whether elevated blood cobalt (Co) concentrations are associated with early failure of metal-on-metal (MoM) hip resurfacings secondary to adverse reaction to metal debris (ARMD).Cohort study.Single centre orthopaedic unit.Following the identification of complications potentially related to metal wear debris, a blood metal ion screening programme was instigated at our unit in 2007 for all patients with Articular Surface Replacement (ASR) and Birmingham MoM hip resurfacings. Patients were followed annually unless symptoms presented earlier. Symptomatic patients were investigated with ultrasound scan and joint aspiration. The clinical course of all 278 patients with 'no pain' or 'slight/occasional' pain and a Harris Hip Score greater than or equal to 95 at the time of venesection were documented. A retrospective analysis was subsequently conducted using mixed effect modelling to investigate the temporal pattern of blood Co levels in the patients and survival analysis to investigate the potential role of case demographics and blood Co levels as risk factors for subsequent failure secondary to ARMD.Blood Co concentration was a positive and significant risk factor (z=8.44, p=2×10(-16)) for joint failure, as was the device, where the Birmingham Hip Resurfacing posed a significantly reduced risk for revision by 89% (z=-3.445, p=0.00005 (95% CI on risk 62 to 97)). Analysis using Cox-proportional hazards models indicated that men had a 66% lower risk of joint failure than women (z=-2.29419, p=0.0218, (95% CI on risk reduction 23 to 89)).The results suggest that elevated blood metal ion concentrations are associated with early failure of MoM devices secondary to adverse reactions to metal debris. Co concentrations greater than 20 µg/l are frequently associated with metal staining of tissues and the development of osteolysis. Development of soft tissue damage appears to be more complex with females and patients with ASR devices seemingly more at risk when exposed to equivalent doses of metal debris.

SUBMITTER: Langton DJ

PROVIDER: S-EPMC3612810 | biostudies-other | 2013

REPOSITORIES: biostudies-other

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The clinical implications of elevated blood metal ion concentrations in asymptomatic patients with MoM hip resurfacings: a cohort study.

Langton David J DJ Sidaginamale Raghavendra P RP Joyce Thomas J TJ Natu Shonali S Blain Peter P Jefferson Robert Drysdale RD Rushton Stephen S Nargol Antoni V F AV

BMJ open 20130312 3

<h4>Objective</h4>To determine whether elevated blood cobalt (Co) concentrations are associated with early failure of metal-on-metal (MoM) hip resurfacings secondary to adverse reaction to metal debris (ARMD).<h4>Design</h4>Cohort study.<h4>Setting</h4>Single centre orthopaedic unit.<h4>Participants</h4>Following the identification of complications potentially related to metal wear debris, a blood metal ion screening programme was instigated at our unit in 2007 for all patients with Articular Su ...[more]

PMID: 23482990

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Project description:BACKGROUND: Modern metal-on-metal hip resurfacing was introduced as a bone-preserving method of joint reconstruction for young and active patients; however, the large diameter of the bearing surfaces is of concern for potentially increased metal ion release. PATIENTS AND METHODS: 71 patients (< 65 years old) were randomly assigned to receive either a resurfacing (R) hip arthroplasty (n = 38) or a conventional metal-on-metal (C) hip arthroplasty (n = 33). Functional outcomes were assessed preoperatively and at 6, 12, and 24 months. Cobalt and chromium blood levels were analyzed preoperatively and at 3, 6, 12, and 24 months. RESULTS: All functional outcome scores improved for both groups. At 12 and 24 months, the median UCLA activity score was 8 in the R patients and 7 in the C patients (p < 0.05). At 24 months, OHS was median 16 in C patients and 13 in R patients (p < 0.05). However, in spite of randomization, UCLA scores also appeared to be higher in R patients at baseline. Satisfaction was similar in both groups at 24 months. Cobalt concentrations were statistically significantly higher for R patients only at 3 and 6 months. Chromium levels remained significantly higher for R patients until 24 months. No pseudotumors were encountered in either group. One R patient was revised for early aseptic loosening and in 2 C patients a cup insert was exchanged for recurrent dislocation. INTERPRETATION: R patients scored higher on UCLA, OHS, and satisfaction at some time points; however, as for the UCLA, preoperative levels were already in favor of R. The differences, although statistically significant, were of minor clinical importance. Chromium blood levels were statistically significantly higher for R patients at all follow-up measurements, whereas for cobalt this was only observed up to 6 months. The true value of resurfacing hip arthroplasty over conventional metal-on-metal hip arthroplasty will be determined by longer follow-up and a possible shift of balance between their respective (dis)advantages.

Dataset Information

The clinical implications of elevated blood metal ion concentrations in asymptomatic patients with MoM hip resurfacings: a cohort study.

Publications

The clinical implications of elevated blood metal ion concentrations in asymptomatic patients with MoM hip resurfacings: a cohort study.

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