Principles and experimentation of wrist prostheses of the universal joint type.
The till now wrist prosthesis have a poor rotatory stability either they are flexible or rigid; specially the spheric ones, they are unable, from their very conception, to transmit the pronation-supination; the condylar ones have an incomplete stability because of their insufficient embedding. The prono-supination transmission needs a "universal joint" prosthesis, whose sellar surfaces are deeply embedded; so, it is possible to get in the same time firm stability and normal ranges of motion. The articular components, crescent roll shaped, are chained each other in perpendicularly plans and fixed in the radius and in the carpus-metacarpus. This is the mono-articular prosthesis, radio-carpal, type A. With an ulna piece, articulated with the radial one by a spherical pivot, we have a bi-articular prosthesis, type B, including the lower radio-ulnar joint: so we have the true total wrist prosthesis. Experimented on cadaveric specimens, these two prostheses, inserted by dorsal approach, have physiologic ranges of motion and absolute rotatory stability. Further studies may define the best dimensions of the prosthesis according to individual variations and ancillary tools set, before beginning the clinical experimentation.
D001696:Biomechanical Phenomena; D006801:Humans; D007595:Joint Prosthesis; D008722:Methods; D014955:Wrist Joint / Q000503:physiopathology / Q000601:surgery*