1. Institute of Functional Surfaces, Mechanical Engineering, University of Leeds, Leeds LS2 9JT, Yorkshire, U.K.
2. School of Engineering College of Engineering and Physical Sciences, University of Birmingham, Birmingham B15 2TT, West
Midlands, U.K.
3. Leeds Institute of Rheumatic and Musculoskeletal Medicine, Chapel Allerton Hospital, Chapeltown Road, Leeds LS7 4SA, Yorkshire, U.K.