NACCT Platform Abstracts 2012 - The American Academy of Clinical ...

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OUTPATIENT EXPERIENCE OF HIP ARTHROPLASTY METAL ION EVALUATIONS
Jerrold Leikin 1 , Patrick M Whiteley 2 , Brandon K Wills 3 , Kirk L Cumpston 3
1 NorthShore University HealthSystem - OMEGA, Glenview IL USA
2 Kaiser Hosptial, San Jose CA USA
3 Virginia Commonwealth University Medical Center, Richmond VA USA
OUTPATIENT EXPERIENCE OF HIP ARTHROPLASTY METAL ION EVALUATIONS
Background: Last year, we presented our outpatient clinic experience of the first twenty of patient evaluations for elevated
blood metal ion levels from metal-on-metal (MoM) hip arthroplasties. We now present additional data for 26 months involving
32 patients.
Methods: This was a consecutive series of patients presenting to two outpatient medical toxicology clinics from January 1,
2010-March 1, 2012 with history of having undergone total hip arthroplasty. Presenting signs, symptoms, and interventions
were reviewed. Available cobalt and chromium levels were summarized as median concentration with Interquartile Range
(IQR).
Results: A total of 32 patients were analyzed. The average age was 55.2 years (range 28 to 86 years). There were 10 males
and 22 females. Ten patients exhibited no symptoms and sought evaluation for gsymptom (n=7) while 2 other patients had
been previously diagnosed with fibromyalgia. Twenty-five (78%) had pain described as hip or thigh pain, clicking sound with
ambulation and/ or grinding with activity. Two (7%) patients had ataxia and later diagnosed with demyelination neuropathy with
one patient demonstrating marked improvement after revision. Patients with MoM arthroplasties generally exhibit a tenfold
increase in metal ion levels than traditional arthroplasties (Cobalt level 22.1 mg/mL IQR .9-59 in MoM vs. 1.25 ng/mL IQR
0.9 to 2.6 in non-MoM). Finally, 17 (58.6%) patients had replacement or revision of their hip implant. Of these patients, 10
(34.5%) had pre- and post-procedure cobalt and chromium concentrations. The median pre- and post-procedure cobalt
concentrations were 44ng/mL (IQR 5-80) and 2.65ng/mL (IQR 1.2-4.1) respectively. The median pre- and post- procedure
chromium concentrations were 31ng/mL (IQR 3.8-91) and 3.45ng/mL (IQR 1-8) respectively. No patients underwent
chelation.
Discussion: A significant number of individuals who seek toxicology consultation will either have minimal symptoms (fatigue,
muscle aches) or be essentially asymptomatic (n=19 or 59%). Ion levels alone are not diagnostic for systemic toxicity.
Documented neurotoxicity is extremely uncommon and, does not appear to be a dose-related phenomenon. The decision for
hip revision solely for toxicologic reasons is exceptionally rare and usually involves a multidisciplinary approach. This series
suggests that MoM arthroplasty can result in elevated cobalt and chromium concentrations. Most patients seeking toxicologic
referral may be minimally symptomatic and seek guidance regarding elevated blood/serum metal ions; however, toxicologic
based interventions are unusual.