1 This is an author-produced version of the article published by Elsevier as: Joyce, J.T. Prediction of lubrication regimes in two-piece metacarpophalangeal prostheses. Medical Engineering & Physics 2007, 29(1), 87-92. doi:10.1016/j.medengphy.2006.02.004 Prediction of Lubrication Regimes in Two-Piece Metacarpophalangeal Prostheses Thomas J Joyce Centre for Rehabilitation and Engineering Studies (CREST) School of Mechanical and Systems Engineering Stephenson Building University of Newcastle upon Tyne Claremont Road Newcastle upon Tyne NE1 7RU UK Abstract Various designs of two-piece finger prosthesis with conforming spherical surfaces have been proposed. These were compared by calculating the lubrication regime for the material combinations and operating conditions expected at the metacarpophalangeal joints of the fingers. Consideration was given to a range of loads from 2 to 50N, a range of entraining velocities from 0mm/s to 30mm/s, and a range of prosthesis radii from 3mm to 10mm. This theoretical lubrication analysis indicated that the optimum material combination of those available for two- piece metacarpophalangeal prostheses is in the order: ceramic-on-ceramic; metal-on-metal; pyrocarbon-on-pyrocarbon; and metal-on-polymer. However it should be recognised that other