This paper describes the testing of three single-piece silicone NeuFlex metacarpophalan-geal prostheses in a finger function simulator and describes the resulting modes of prosthesis failure. In all cases, failure was due to imminent fracture of the prosthesis across the pivot of the central hinge section. This result is in contrast with previous in-vitro and in-vivo experience with single-piece silicone Swanson and Sutter metacarpophalangeal prostheses, which both tend to fracture at the junction of the distal stem and the hinge. In comparison with earlier in-vitro simulator tests of the Sutter metacarpophalangeal prosthesis, the NeuFlex prostheses showed a greater longevity before fracture. To date, no other reports of fracture of the NeuFlex metacarpophalangeal prosthesis have been reported, either in vitro or in vivo.
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