Intercalary implant

Abstract

An intercalary implant has two stem members and a collar. One stem member includes a stem portion to be received in the intramedullary canal of a native end portion of a long bone and a threaded male portion to be outside of the intramedullary canal. The second stem member also includes a stem portion to be received in the intramedullary canal of the opposite native end portion of the long bone. The second stem member has a spacer portion and a shoulder to be outside of the intramedullary canal. The collar has an annular base portion with an opening and a cylindrical female threaded portion. When assembled, collar connects the first and second stem members and the implant spans a gap in the shaft of the long bone. The parts can be assembled without distracting the native end bone portions in the proximal-distal direction to prevent damage to soft tissue around the native end bone portions.

1 . An intercalary implant for use in replacing a missing portion of the shaft of a long bone, wherein the long bone includes native proximal and distal portions having intramedullary canals, the implant comprising: 
 a first stem member including a stem portion to be received in the intramedullary canal of one of the native portions of the long bone, the first stem member including a threaded male portion to be positioned outside of the intramedullary canal;    a second stem member including a stem portion to be received in the intramedullary canal of the other of the native portions of the long bone, the second stem member further including a spacer portion to be positioned outside of the intramedullary canal and a shoulder to be positioned outside of the intramedullary canal, the spacer portion being between the stem portion and the shoulder; and    a collar including an annular base portion with an opening and a cylindrical portion open at one end, the cylindrical portion having a threaded interior surface to receive and mate with the threaded male portion of the first stem member; wherein:    the collar receives part of the second stem member through the opening in the base portion of the collar, and the collar is movable in a proximal-distal direction along at least part of the length of the spacer portion of the second stem member between an extended position and a retracted position;    in the extended position the annular base portion of the collar is spaced from the stem portion of the second stem member and abuts the shoulder of the second stem member and the cylindrical portion of the collar extends over and beyond the shoulder of the second stem member;    in the retracted position the collar is positioned so that at least part of the shoulder is exposed; and    the shoulder and the opening of the annular base portion of the collar are sized and shaped so that when the collar is threaded onto the threaded male portion of the first stem member the position of the first stem member is fixed with respect to the position of the second stem member;    the shoulder of the second stem member has a radial dimension and an axial dimension;    the opening in the annular base portion of the collar has a radial dimension;    the spacer of the second stem member has a radial dimension and an axial dimension;    the cylindrical portion of the collar has an interior radial dimension and an axial dimension;    the radial dimension of the shoulder of the second stem member is greater than the radial dimension of the opening in the annular base portion of the collar;    the interior radial dimension of the cylindrical portion of the collar is greater than the radial dimension of the spacer of the second stem member;    the interior radial dimension of the cylindrical portion of the collar is greater than the radial dimension of the shoulder of the second stem member; and    the axial dimension of the cylindrical portion of the collar is greater than the axial dimension of the shoulder of the second stem member.    
   
   
       2 . A method of surgically replacing a missing part of the shaft of a long bone comprising: 
 preparing the long bone so that proximal and distal portions of the long bone remain, the proximal and distal portions of the long bone each having an intramedullary canal;    providing a first stem member, a second stem member and a collar, wherein the first stem member includes a stem portion and an integral male threaded portion, the second stem member includes a stem portion, an integral spacer and an integral shoulder, and the collar includes a female threaded portion;    implanting the stem portion of one of the stem members in the intramedullary canal of the proximal portion of the long bone;    implanting the stem portion of the other of the stem members in the intramedullary canal of the distal portion of the long bone;    positioning the male portion of the first stem member against the shoulder of the second stem member without distracting the proximal and distal parts of the bone in the proximal-distal direction; and    assembling the first stem member, second stem member and collar by threading the collar onto the threaded male portion of the second stem member without distracting the proximal and distal parts of the bone in the proximal-distal direction without inserting any portion of the first stem member into any portion of the second stem member and without inserting any portion of the second stem member into any portion of the first stem member.