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

Abstract

ObjectiveTo 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).DesignCohort study.SettingSingle centre orthopaedic unit.ParticipantsFollowing 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.ResultsBlood 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)).ConclusionsThe 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.

Are Females at Greater Risk for Revision Surgery After Hip Resurfacing Arthroplasty With the Articular Surface Replacement Prosthesis?

“…In patients who had bilateral arthroplasties, only HHS and cobalt levels remained significant predictors of revision surgery. These findings are partly consistent with those of some studies which have found elevated blood cobalt concentrations to be a risk factor for joint failure [10,17]. Our findings, however, deviate from those of the aforementioned studies identifying female sex as an independent predictor of revision surgery.…”

Do Complication Rates Differ by Gender After Metal-on-metal Hip Resurfacing Arthroplasty? A Systematic Review

“…When specifically evaluating rates of ALTR between genders, our data demonstrated an increased rate of complication in women; however, a paucity of data specifically evaluating this finding exists [4,5,11,23]. With the available evidence, conclusions are limited as to the cause of our observed findings.…”

Trunnionosis: A pain in the neck

“…Another change in modern trunnion design in that most tend to have a ridge surface machined into the material to accommodate ceramic heads. As shown by Langton et al [4] and Hexter et al [18] , these grooves leave imprints on the majority of tapers and thus increase wear rate and material loss. This could also lead to increased corrosion.…”

“…The term adverse reaction to metal debris (ARMD) is an umbrella term that has been used to describe the effects of metal ion deposition within soft tissues in the body. Patients who become symptomatic and develop ARMD frequently need revision of their prostheses [3] , whilst those who are asymptomatic but suffer with high serum metal ion levels represent a more controversial group to treat [4] .…”