Implant With Improved Surface Properties and Expansion Means

Abstract

This invention relates to and orthopaedic implant having an expansion means adapted to increase the external surface area of the implant, the expansion means positioned to correspond to voids or depressions in the anatomy of a patient. Also described are method for the design and manufacture of such implants.

We claim: 
     
         1 . An orthopaedic femoral shell implant adapted to receive a prosthetic femoral stem, the outer wall of the implant including at least one expansion means adapted to increase the external surface area of the implant at one or more discrete regions on the outer wall of the femoral shell, the expansion means positioned on the outer wall of the femoral shell implant such that, in use, it corresponds with specific, predetermined voids or depressions in the anatomy of a patient. 
     
     
         2 . The implant of  claim 1 , wherein the implant is a patient specific implant, and the location of the expansion means is determined based on patient-specific anatomical information. 
     
     
         3 . The implant of  claim 1 , wherein the external surface of the implant and/or expansion means includes one or more regions of three dimensional lattice. 
     
     
         4 . The implant of  claim 3 , wherein the three dimensional lattice includes one or more rows of three dimensional lattice, wherein the rows of lattice are adjacent, but not connected to each other. 
     
     
         5 . The implant of  claim 4 , wherein the expansion means are located between the rows of three dimensional lattice. 
     
     
         6 . The implant as claimed in  claim 3 , wherein the three dimensional lattice is expandable. 
     
     
         7 . The implant of  claim 6 , wherein the lattice includes bendable struts formed with an area of relative weakness along their length, such that the struts are capable of bending when in a non-expanded position and straightening or partially straightening when in an expanded position. 
     
     
         8 . The implant of  claim 1 , wherein the expansion means is an area of the implant wall adapted to move from a first position to a second expanded position using a press mechanism. 
     
     
         9 . The implant of  claim 1 , wherein the expansion means is an area of the implant wall adapted to move from a first position to a second expanded position using a screw mechanism. 
     
     
         10 . The implant of  claim 1 , wherein the expansion means is an area of the implant wall including folds or bends. 
     
     
         11 . The implant of  claim 10 , wherein the folds or bends are adapted to allow expansion using a concertina mechanism. 
     
     
         12 . The implant of  claim 1 , wherein the expansion means is an area of implant wall corresponding to a defect or void, the area of implant wall being only partially connected to the implant using a hinge mechanism, such that the expansion means can be moved about the hinge from a first insertion position inside the outer surface of the implant to a second expanded position extending outwardly from the implant surface. 
     
     
         13 . The implant of  claim 12 , wherein the implant includes a means to maintain the hinged expansion means in the second expanded position. 
     
     
         14 . A method for the expansion of a patient-specific orthopaedic implant to fill a void or space in a patient's anatomy, the method including the steps of;
 a. locating an implant as described in one or more of the embodiments above in an anatomically correct position in a patient's body as decided by pre-operative planning;   b. actuating the one or more expansion means in the implant wall to extend the outer implant wall to fill the void or pace in the patient's anatomy.