Intramedullary device assembly and associated method

Abstract

An intramedullary device for repairing defects of a bone is provided. The intramedullary device is configured to be inserted into the medullary canal of a bone and includes a stud protruding from the end. The stud includes a portion that is tapered from a first cross-sectional area to a second cross-sectional where the second cross-sectional area is smaller than that of the first cross-sectional area and the second cross-sectional area defines a region of concentrated stress. The stud also includes a portion configured to engage the internal threads of a fastener retained within an intramedullary device assembly, such as a guide member adapter. The external threads of the stud engage the internal threads of the fastener to secure the intramedullary device to the intramedullary assembly when a first torque is applied to the fastener.

1 . An intramedullary device for repairing a defect of a bone, comprising:
 an elongate body including a proximal end and a distal end; and   a stud protruding from the proximal end of the elongate body configured to be removably attached to a guide adapter, the stud comprising;
 a distal portion attached to the proximal end of the elongate body; and 
 a proximal portion opposite the distal portion; 
 wherein at least the proximal portion of the stud comprises a threaded portion; 
 wherein the distal portion defines a first cross sectional area and a second cross-sectional area wherein the second cross-sectional area is smaller than the first cross-sectional area and wherein the stud is broken at the second cross-sectional area when a threshold amount of force is applied to the threaded portion. 
   
     
     
         2 . The intramedullary device of  claim 1 , wherein the distal portion of the stud is tapered from the first cross-sectional area proximate the proximal portion of the stud to the second cross-sectional area proximate the proximal end of the elongate body. 
     
     
         3 . The intramedullary device of  claim 1  further comprising a medial portion of the stud disposed between the distal portion and the proximal portion, wherein the medial portion of the stud comprises at least one flat facet. 
     
     
         4 . The intramedullary device of  claim 1 , wherein the distal portion of the stud is tapered. 
     
     
         5 . The intramedullary device of  claim 1 , further comprising a nub between the stud and the proximal portion of the elongate body. 
     
     
         6 . The intramedullary device of  claim 1 , wherein the threads of the breakaway stud of the intramedullary device are configured to engage a threaded fastener within a guide adapter. 
     
     
         7 . The intramedullary device of  claim 6 , wherein the intramedullary device is configured to be secured to the guide adapter by applying a first torque to the threaded fastener. 
     
     
         8 . The intramedullary device of  claim 7 , wherein the intramedullary device is configured to be separated from the guide adapter when the breakaway stud is broken away from the intramedullary device by a second torque applied to the threaded fastener wherein the second torque is greater than the first torque. 
     
     
         9 . The intramedullary device of  claim 8 , wherein the threaded fastener comprises a fastener head that engages a shoulder within the guide adapter to retain the threaded fastener within the guide adapter. 
     
     
         10 . The intramedullary device of  claim 6 , further comprising a recess configured to engage a tab defined by the guide adapter to prevent relative rotation between the intramedullary device and the guide adapter. 
     
     
         11 . The intramedullary device of  claim 1 , further comprising an undercut proximate the second cross sectional area. 
     
     
         12 . An intramedullary device for repairing a defect of a bone, comprising:
 an elongate body including a proximal end, a distal end; and   a stud protruding from the proximal end of the elongate body configured to be removably attached to a guide adapter, the stud comprising;
 a distal portion attached to the proximal end of the elongate body wherein the distal portion defines a region configured for the concentration of stress; and 
 a proximal portion opposite the distal portion; 
   wherein the stud is separated from the elongate body proximate the region configured for the concentration of stress in response to a threshold force being applied to the proximal portion of the stud.   
     
     
         13 . The intramedullary device of  claim 12 , wherein the threshold force comprises a pulling force in response to the stud being drawn into the guide adapter. 
     
     
         14 . The intramedullary device of  claim 12 , wherein the proximal portion comprises a threaded portion. 
     
     
         15 . The intramedullary device of  claim 12 , wherein the proximal portion of the stud is engaged by a fastener within the guide adapter. 
     
     
         16 . The intramedullary device of  claim 15 , wherein the fastener is configured to secure the elongate body to the guide adapter in response to a first force being applied to the fastener. 
     
     
         17 . The intramedullary device of  claim 16 , wherein in response to a second force being applied to the fastener, the threshold force is applied to the proximal portion of the stud. 
     
     
         18 . A method comprising:
 applying a first torque to a fastener within a guide adapter to engage a stud of an elongate body of an intramedullary device;   applying a second torque to the fastener within the guide adapter to cause the stud of the elongate member to be separated from the elongate member;   wherein the stud is separated from the elongate body proximate a region configured for the concentration of stress.   
     
     
         19 . The method of  claim 18 , wherein the region configured for the concentration of stress comprises a portion of the stud with the smallest cross-sectional area.