A prosthesis for implantation in an animal or human subject, comprising a first component 6 for attaching to a radius bone, a second component 7 for attaching to an ulna bone, and a linkage 8 for linking the first and second components substantially rigidly with respect to one another when the device is in use. The prosthesis may allow the linkage to move relative to the first and/or second components when the device is being adjusted to fit the patient, but is retained substantially rigidly at a selected position in normal use. The linkage may comprise a shaft 5 which extends from the radial plate 6, and a clevis ring 41 which clamps onto the shaft 5 and either retains a coupling member 42 which in turn has an elongate rod part clamped by cap 51 and bolt 52 (see figure 7)； or retains a coupling member 42â which comprises a rod 61 and a cap 65 which is again clamped by a bolt 52â (see figure 9). A third component 2 may attach to carpal bones via a body part 3 which clamps around the shaft 5.
