Mobile prosthesis for interpositional location between bone joint articular surfaces and method of use

A method of modification of an orthopaedic joint joining a first bone member to a second bone member within a mammalian body to provide a resultant modified joint:

• the first bone member having a contiguous outer surface which engages with a contiguous outer surface of the second bone member in normal movement of the joint,
• the method comprising coupling a spacer member to the first bone member to overlie the contiguous outer surface of the first bone member conforming to the shape of the first bone member with the spacer member disposed in between the contiguous outer surface of the first bone member and the contiguous outer surface of the second bone member the spacer member consisting of a thin sheet member having an inner surface and an outer surface and a thickness between the inner surface and the outer surface in the range of 0.001 inches to 0.01 inches,
• the sheet member selected from a sheet of metal and a sheet member comprising a composite of plastic or polymer materials with metal providing the inner and outer surfaces as metal, wherein the joint is a diarthrodial joint in which the contiguous outer surfaces comprise contiguous bony surfaces on each of the first bone member and second bone member which are each covered with articular cartilage forming the respective contiguous outer surface of the first bone member and second bone member, and wherein the contiguous bony surfaces on each of the first and second bone members are surfaces which are in contact during normal movement of the joint,
• the method comprising placing the sheet member to overlie an outer surface of the articular cartilage of the first bone member conforming to the shape of the outer surface of the articular cartilage of the first bone member, wherein in the resultant modified joint during normal movement of the joint:
• (a) the inner surface of the sheet member overlies the outer surface of the articular cartilage of the first bone member in engagement therewith and substantially corresponding in shape to the outer surface of the articular cartilage of the first bone member, and (b) the outer surface of the sheet member facing the outer surface of the articular cartilage of the second bone member and in engagement with the outer surface of the articular cartilage of the second bone member;
• wherein the inner surface of the sheet member has a coefficient of friction sufficiently low to facilitate relative movement of the inner surface of the sheet member and the articular cartilage forming the contiguous outer surface of the first bone member in engagement with the inner surface of the sheet member, and wherein the outer surface of the sheet member has a coefficient of friction sufficiently low to facilitate relative movement of the outer surface of the sheet member and the articular cartilage forming the contiguous outer surface of the second bone member in engagement with the outer surface of the sheet member,
• the first bone member having an adjacent outer surface adjacent to the contiguous outer surface of the first bone member which adjacent outer surface is not normally in contact with the second bone member during movement of the joint, the method including coupling the sheet member to the first bone member with the inner surface of the sheet member to overlie both the contiguous outer surface of the first bone member and the adjacent outer surface of the first bone member with a portion of the sheet member disposed in between the outer surface of the articular cartilage of the first bone member and the outer surface of the articular cartilage of the second bone member,
• wherein the contiguous outer surface of the first bone member forms a convexly rounded outer surface over a bulbous end of the first bone member joined to the first bone member by a neck of a reduced circumference than a larger circumference of a portion of the bulbous end, the neck comprising the adjacent outer surface, the sheet member overlying the bulbous end and its larger circumference portion and extending circumferentially about the neck,
• the method including securing the sheet member about the neck with a circumferential ligature which extends circumferentially around the neck about the sheet member where the sheet member extends circumferentially about the neck, wherein the circumferential ligature is selected from the group consisting of a string member, a strap member and a wire member,
• the sheet member having a cap-like member with an opening defined within an edge of the sheet member, the method comprising passing the bulbous end of the first bone member through the opening of the cap-like member to locate the cap-like member over the bulbous end with the edge disposed circumferentially around the neck, and reducing a circumferential extent of the opening proximate the edge about the neck and maintaining the circumferential extent of the opening reduced with the circumferential ligature,
• the method including securing a fastener member to the adjacent outer surface of the first bone member and coupling the circumferential ligature to the fastener member to limit relative rotation of the opening of the cap-like member about the neck yet permit marginal movement of the sheet member relative the outer surface of the articular cartilage of the first bone member without displacement from engagement with the outer surface of the articular cartilage of the first bone member.