SYMPOSIA PAPER Published: 01 May 2013

Low Cobalt and Chromium Levels from a Single Metal-on-Metal Total Hip Arthroplasty Implant


Metal-on-metal (M/M) total hip arthroplasty (THA) was considered an attractive option for young and active patients due to a theoretic reduction in wear and a decreased dislocation rate when using larger femoral head sizes. Recent studies demonstrate an increase in cobalt (Co) and chromium (Cr) ion levels with the use of some M/M THA implants. The purpose of this study was to define the Co/Cr levels in patients who received a specific implant and to evaluate the M/M implant radiographically and clinically. From 2005–2009, 76 patients underwent THA using a single implant. All patients were contacted and 40 (31 males, 9 females, age 57.1 years ± 8.4, ASA 2.5 ± 0.6) of the 76 chose to have Co/Cr levels drawn. There were 45 joints (22 right, 23 left) that received THA with the diagnosis of osteoarthritis (80 %), avascular necrosis (15.6 %), and fracture (4.4 %). The average acetabular cup size was 56.2 mm ± 3.0 (range 50–60) and head size was 49.8 mm ± 3.6 (range 40–54). The average acetabular cup inclination was 40.0° ± 7.2 (range 29–64°). Of the 45 joints, 3 were revised (2 septic revision, 1 aseptic revision). Co/Cr levels were measured 2.3 years ± 1.1 after surgery, with an average cobalt level of 1.1 μg/L ± 0.8 and chromium level of 1.7 μg/L ± 1.3. At 6 months clinical follow-up, 2 patients complained of anterior groin pain (4.4 %) and 6 patients complained of a limp or Trendelenberg gait (13.3 %). The hip society score averaged 85.5 ± 16.3 and WOMAC score averaged 87.2 ± 17.5. There was no correlation between elevated Co/Cr levels and acetabular cup inclination, revision rate, femoral head diameter, and self-assessment scores. The results of this short-term study demonstrate that the Co/Cr levels from the use of this M/M THA implant are slightly elevated, but are within an acceptable range to not cause clinically significant problems (<17 μg/L), and that patients perform well according to standardized questionnaires.

Author Information

Chen, Antonia, F.
Dept. of Orthopaedic Surgery, Univ. of Pittsburgh Medical Center, Pittsburgh, PA, US
Pigott, Matthew, T.
Univ. of Pittsburgh Medical School, Pittsburgh, PA, US
McClain, Edward, J.
UPMC St. Margaret, Pittsburgh, PA, US
Klatt, Brian, A.
Dept. of Orthopaedic Surgery, Univ. of Pittsburgh Medical Center, Pittsburgh, PA, US
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Developed by Committee: F04
Pages: 1–12
DOI: 10.1520/STP156020120028
ISBN-EB: 978-0-8031-7572-3
ISBN-13: 978-0-8031-7546-4