A prosthesis for replacing a joint between a first bone and a second bone in a human hand or foot includes first and second rigid blocks (110, 120) interconnected by a flexible bridging structure (130). In certain embodiments, the flexible bridging structure employs a helical spring oriented with its central axis aligned with a central axis of a bone anchor portion of the first rigid block. One or more shear-limiting element (101, 140) is deployed within an internal volume of the helical spring (130) to limit an extent of shear deformation applied to the helical spring. Other aspects of the invention relate to adjustable bone-abutment flanges, an alternative bridging structure employing a helically-twisted leaf spring, and a structure and method for bridging between the first metacarpal and the scaphoid in case of removal of the trapezium from the hand.