Investigating the potential advantages of a new design metacarpophalangeal joint

This paper investigates a new metacarpophalangeal joint design aimed at treating patients with moderate to severe forms of arthritis affecting the index, long, ring, and little fingers. Current small joint arthroplasty designs, including those for the metacarpophalangeal joint of the hand, have had limited success owing to mechanical failures and can be divided into two main families: single-piece elastomer implants and surface articulating implants. The design proposed in this study involves combining the principles of a surface weight-bearing articulating implant with those of a spanning elastomeric implant. The design consists of metacarpal and proximal phalangeal articulating housings and a central flexible spanning elastomer rod that maintains the alignment of the metacarpal and proximal phalangeal components. A preliminary finite element analysis was used to investigate the stresses in the design, the wear of the articulating bearing surfaces for different material combinations, and the stresses between the central elastomer rod and the articulating housings. This preliminary analysis shows that the design should withstand the probable loading conditions experienced within the human body and that the wear rates of the articulating surfaces and the central elastomer are acceptable.