The effect of component size and orientation on the
concentrations of metal ions after resurfacing arthroplasty of the hip 2008

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D. J. Langton, MRCS,
Orthopaedic Research Register1; S. S. Jameson, MRCS, Specialist Registrar,
Trauma and Orthopaedics1; T. J. Joyce, MSc, PhD, MA, BEng, Lecturer in
Bioengineering2; J. Webb, MRCS, Specialist Registrar, Trauma and Orthopaedics1;
and A. V. F. Nargol, FRCS(Tr & Orth), Consultant Orthopaedic Surgeon1
1 Joint Replacement Unit, University Hospital of North Tees, Hardwick,
Stockton-on-Tees TS19 8PE, UK.
2 Newcastle University, Claremont Road, Newcastle upon Tyne NE1 7RU, UK.

Increased concentrations of metal ions after metal-on-metal resurfacing
arthroplasty of the hip remain a concern. Although there has been no proven link
to long-term health problems or early prosthetic failure, variables associated
with high metal ion concentrations should be identified and, if possible,
corrected. Our study provides data on metal ion levels from a series of 76
consecutive patients (76 hips) after resurfacing arthroplasty with the Articular
Surface Replacement. Chromium and cobalt ion concentrations in the whole blood
of patients with smaller ( 51 mm) femoral components were significantly higher
than in those with the larger ( 53 mm) components (p < 0.01). Ion concentrations
in the former group were significantly related to the inclination (p = 0.01) and
anteversion (p = 0.01) of the acetabular component. The same relationships were
not significant in the patients with larger femoral components (p = 0.61 and p =
0.49, respectively). Accurate positioning of the acetabular component
intra-operatively is essential in order to reduce the concentration of metal
ions in the blood after hip resurfacing arthroplasty with the Articular Surface
Replacement implant.