Ankle replacement system

Abstract

A prosthesis suited for orthopedic implantation possesses a multi-piece stem component that supports an artificial joint surface that can articulate with another artificial joint surface in various ways. The prosthesis can be assembled in a snap fit and/or interlocking fashion that provides positive locking means without the use of screws or other fasteners. The prosthesis can accommodate fitment of a plastic joint surface made, e.g., from ultra high molecular weight polyethylene. The prosthesis is well suited for use in an ankle replacement system that can be installed using minimally invasive intramedullary guidance established with respect to the major axis of the tibia by minimally invasive access through the calcaneus, through an incision in the bottom of the foot. The prosthesis makes possible the installation of a total ankle system using minimally invasive anterior access to the ankle joint for making bony cuts and to install prosthesis components.

What is claimed is: 
     
         1 . A method, comprising:
 coupling a first prosthesis to a first bone, wherein the first prosthesis comprises a stem configured to be disposed in an intramedullary path formed in a first bone and a first artificial joint surface configured to be attached to the stem;   coupling a second prosthesis to a second bone, wherein the second prosthesis comprises a second artificial joint surface; and   coupling the first artificial joint surface to the second artificial joint surface, wherein the first artificial joint surface and the second artificial joint surface form a ball-and-socket joint including mating concave and convex surfaces.   
     
     
         2 . The method of  claim 1 , wherein the first artificial joint surface comprises a concave dome and the second artificial joint surface comprises a convex dome configured to mate with the concave dome. 
     
     
         3 . The method of  claim 1 , wherein the second prosthesis comprises a button-like structure configured to be installed in a reamed-out pocket of the second bone. 
     
     
         4 . The method of  claim 1 , comprising:
 coupling the stem to a platform configured to be coupled to the first artificial joint surface, wherein the platform is fixedly coupled to the stem; and   coupling the first artificial joint surface to the platform.   
     
     
         5 . The method of  claim 4 , wherein coupling the first artificial joint surface to the platform comprises inserting the first artificial joint surface into a cylindrical collar extending away from the stem when the platform is fixedly coupled to the stem, and wherein the cylindrical collar provides a rotational fit between the platform and the first artificial joint surface. 
     
     
         6 . The method of  claim 1 , wherein the first artificial joint surface is coupled to the platform by a loose, non-interference fit. 
     
     
         7 . The method of  claim 6 , wherein coupling the first artificial joint surface to the platform comprises inserting a tab defined by the platform into a hole defined by the first artificial joint surface, wherein the hole has a first diameter and the tab has a second diameter, and wherein the second diameter is less than the first diameter. 
     
     
         8 . The method of  claim 1 , wherein coupling the first prosthesis to the first bone comprises:
 inserting a first stem component including a first external feature into the intramedullary path formed in the first bone;   inserting a second stem component including a second external feature into the intramedullary path formed in the second bone; and   coupling the first stem component to the second stem component rotation of the second stem component relative to the first stem component.   
     
     
         9 . The method of  claim 8 , comprising inserting a tool through an intramedullary path defined by the second bone and into an internally threaded hole defined by the second stem component, wherein the tool is configured to rotate the second stem component relative to the first stem component. 
     
     
         10 . The method of  claim 8 , comprising coupling the first artificial joint surface to the stem in situ. 
     
     
         11 . A prosthesis system, comprising:
 a first prosthesis, comprising:
 a stem sized and configured to be disposed in an intramedullary path formed in a first bone; 
 a first artificial joint surface configured to be attached to the stem; and 
   a second prosthesis, comprising:
 a second artificial joint surface configured to be attached to a second bone and to articulate with the first artificial joint surface, 
   wherein the first artificial joint surface and the second artificial joint surface are each defined by a first arc that is swept along a second arc, wherein the second arc is perpendicular to the first arc.   
     
     
         12 . The prosthesis system of  claim 11 , wherein a trough defined by the first artificial joint surface is configured to nest within a trough defined by the second artificial joint surface. 
     
     
         13 . The prosthesis system of  claim 11 , wherein at least one of the first arc or the second arc has a constant radius. 
     
     
         14 . The prosthesis system of  claim 11 , wherein the stem comprises:
 a first stem component including a first external feature; and   a second stem component including a second external feature, wherein the second stem component is configured to be coupled to the first stem component by rotation of the second stem component relative to the first stem component.   
     
     
         15 . A method, comprising:
 coupling a first prosthesis to a first bone, wherein the first prosthesis comprises
 a stem having a first end and a second end, the first end of the stem including a first engagement feature, the stem having a circular cross-sectional geometry sized and configured to be disposed in an intramedullary path formed in a first bone; 
 a platform having a second engagement feature located on a first side of the platform and a third engagement feature located on a second side of the platform, the second engagement feature of the platform being complementary to the first engagement feature of the stem for coupling the stem to the platform, and 
 a first artificial joint surface coupled to the platform and including a fourth engagement feature, the fourth engagement feature of the first artificial joint surface being complementary to the third engagement feature of the platform for coupling the first artificial joint surface to the platform, wherein the coupling between the first artificial joint surface and the platform is such that the first artificial joint surface may translate relative to the platform when the prosthesis system is implanted in a patient; and 
   a second prosthesis, comprising:
 a second artificial joint surface configured to be attached to a second bone and to articulate with the first artificial joint surface, wherein the first artificial joint surface and the second artificial joint surface include mating concave and convex surfaces, 
   wherein the platform comprises a collar extending away from the stem when the platform is fixedly coupled to the stem, and   wherein the collar is configured to be received in a complementary recess defined by the first artificial joint surface to provide a rotational fit between the platform and the first artificial joint surface;   coupling the second prosthesis to the second bone, wherein the second prosthesis comprises a second artificial joint surface; and   coupling the first artificial joint surface to the second artificial joint surface, wherein the first artificial joint surface and the second artificial joint surface form a ball-and-socket joint including mating concave and convex surfaces.   
     
     
         16 . The method of  claim 15 , wherein the first artificial joint surface comprises a concave dome and the second artificial joint surface comprises a convex dome configured to mate with the concave dome. 
     
     
         17 . The method of  claim 15 , wherein the second prosthesis comprises a button-like structure configured to be installed in a reamed-out pocket of the second bone. 
     
     
         18 . The method of  claim 15 , comprising:
 coupling the stem to a platform configured to be coupled to the first artificial joint surface, wherein the platform is fixedly coupled to the stem; and   coupling the first artificial joint surface to the platform.   
     
     
         19 . The method of  claim 18 , wherein coupling the first artificial joint surface to the platform comprises inserting the first artificial joint surface into a cylindrical collar extending away from the stem when the platform is fixedly coupled to the stem, and wherein the cylindrical collar provides a rotational fit between the platform and the first artificial joint surface.