A new Approach to the Fixation of a Metacarpophalangeal Joint Prosthesis

A significant problem with rigid prosthetic stems applied in the finger bones, as well as in other bones of the upper and lower extremity, is resorption of bone at the interface. An investigation was carried out using a plastic plug which would more evenly distribute the stresses to the bone, with fine ridges to produce enhanced fixation by bony ingrowth. A total knee prosthesis in the cat was used as the model, radiographic and histological studies being made at up to one year. A finite element analysis identified areas of high interface and material stresses. With a finely grooved plug, bone ingrowth occurred in all regions except for the region near the bone entry, where the finite element analysis showed the highest interface shear stresses and bone material stresses to occur.