Intramedullary implants for replacing lost bone

Abstract

A bone transport system includes a nail having a proximal end and a distal end, the proximal end configured for securing to a first portion of bone, the distal end configured for securing to a second portion of bone. The system includes a housing having a wall with a longitudinal opening extending a length along a portion thereof. The system further includes a transport sled having a length that is shorter than the length of the longitudinal opening, the transport sled configured for securing to a third portion of bone, the transport sled further configured to be moveable along the longitudinal opening. The system further includes a magnetic assembly disposed within the nail and configured to be non-invasively actuated by a moving magnetic field, wherein actuation of the magnetic assembly moves the transport sled along the longitudinal opening. The system further includes a ribbon extending on opposing sides of the transport sled and substantially covering the longitudinal opening.

What is claimed is: 
     
       1. An implantable dynamic apparatus comprising:
 a nail having a first portion and a second portion, the first portion of the nail configured for securing to a first portion of bone, the second portion of the nail configured for securing to a second portion of bone;   the second portion of the nail configured to be longitudinally moveable with respect to the first portion of the nail, wherein the second portion of the nail includes an internally threaded feature;   a magnetic assembly configured to be non-invasively actuated by a moving magnetic field;   a lead screw having an externally threaded portion, the lead screw coupled to the magnetic assembly, wherein the externally threaded portion of the lead screw engages the internally threaded feature of the second portion of the nail;   wherein actuation of the magnetic assembly turns the lead screw, which in turn changes the longitudinal displacement between the first portion of the nail and the second portion of the nail;   a first abutment surface coupled to the lead screw;   a second abutment surface coupled to the second portion of the nail; and   wherein the turning of the lead screw in a first direction causes the first abutment surface to contact the second abutment surface, stopping the motion of the lead screw with respect to the second portion of the nail, and wherein subsequent turning of the nail in a second direction is not impeded by any jamming between the internally threaded feature and the externally threaded portion.   
     
     
       2. A method for performing a bone transport procedure, the method comprising:
 preparing the medullary canal of a bone for placement of an implantable dynamic apparatus configured to change its configuration at least partially from a moving magnetic field supplied by an external adjustment device, the change in configuration comprising the longitudinal movement of a transport sled;   placing the implantable dynamic apparatus within the medullary canal of the bone;   securing a first end of a nail to a first portion of the bone;   securing a second end of a nail to a second portion of the bone; and   storing information in the external adjustment device, the information comprising an orientation of the nail within the bone and a direction of planned movement of the transport sled.    
     
     
       3. The method of claim 2, wherein the implantable dynamic apparatus further comprises:
 a housing having a wall with a longitudinal opening extending a length along a portion thereof;   the transport sled disposed in the longitudinal opening and configured to move along the longitudinal opening;   a magnetic assembly disposed within the nail and configured to be non-invasively actuated by the moving magnetic field;   a lead screw coupled to the magnetic assembly;   a first abutment coupled to the lead screw; and   a second abutment coupled to the second end of the nail,   
       and wherein the method further comprises:
 securing a third portion of the bone to the transport sled; and 
 applying the moving magnetic field to the magnetic assembly, thereby actuating the magnetic assembly and causing the lead screw to rotate and the transport sled to move along the longitudinal opening, 
 wherein a rotation of the lead screw in a first direction causes the first abutment to contact the second abutment and stops the motion of the lead screw with respect to the nail.  
 
     
     
       4. The method of claim 3, wherein an externally threaded portion of the lead screw and an internally threaded feature of the nail are configured to allow turning of the nail in a second direction, opposite the first direction subsequent to the applying step.  
     
     
       5. The method of claim 3, further comprising:
 by applying the moving magnetic field to the magnetic assembly, causing an externally threaded portion of the lead screw to engage with an internally threaded feature of the nail.    
     
     
       6. The method of claim 3, wherein the transport sled has a length that is shorter than the length of the longitudinal opening.  
     
     
       7. The method of claim 3, wherein the lead screw comprises an externally threaded surface having a coating thereon.  
     
     
       8. The method of claim 3, wherein the applying of the moving magnetic field further comprises using the external adjustment device to rotate at least one rotatable magnet.  
     
     
       9. A method for performing a bone transport procedure, the method comprising:
 placing an implantable dynamic apparatus within a medullary canal of a bone, the implantable dynamic apparatus comprising:
 a nail having a proximal end and a distal end; 
 a housing having a wall with a longitudinal opening extending a length along a portion thereof; 
 a transport sled disposed in the longitudinal opening and configured to move along the longitudinal opening, the transport sled including a first contact surface; 
 a magnetic assembly disposed within the nail and configured to be non-invasively actuated by a moving magnetic field; 
 a lead screw coupled to the magnetic assembly; 
   securing the proximal end of the nail to a first portion of the bone;   securing the distal end of the nail to a second portion of the bone;   securing a third portion of the bone to the transport sled;   applying the moving magnetic field to the magnetic assembly to actuate the magnetic assembly and cause the lead screw to rotate and the transport sled to move along the longitudinal opening; and   securing a stop having a second contact surface to the lead screw, wherein in response to the rotation of the lead screw, the stop radially expands and prevents additional rotation of the lead screw.    
     
     
       10. The method of claim 9, wherein the magnetic assembly comprises a cylindrical permanent magnet configured to be turned by the moving magnetic field.  
     
     
       11. The method of claim 10, wherein the cylindrical permanent magnet is held by a magnet holder rotationally coupled to the magnetic assembly.  
     
     
       12. The method of claim 9, wherein the applying comprises applying the moving magnetic field by using an external adjustment device to rotate at least one rotatable magnet.  
     
     
       13. The method of claim 12, further comprising: storing information in the external adjustment device, the information comprising an orientation of the nail within the bone and a direction of planned movement of the transport sled.  
     
     
       14. A method for performing a bone transport procedure, the method comprising:
 placing an implantable dynamic apparatus within a medullary canal of a bone, the implantable dynamic apparatus comprising:
 a nail having a proximal end and a distal end, 
 a housing having a wall with a longitudinal opening extending a length along a portion thereof, 
 a transport sled disposed in the longitudinal opening and configured to move along the longitudinal opening, 
 a magnetic assembly disposed within the nail and configured to be non-invasively actuated by a moving magnetic field, wherein the magnetic assembly comprises a cylindrical permanent magnet configured to be turned by the moving magnetic field and to be held by a magnet holder rotationally coupled to the magnetic assembly, and 
 a lead screw coupled to the magnetic assembly; 
   securing the proximal end of the nail to a first portion of the bone;   securing the distal end of the nail to a second portion of the bone;   securing a third portion of the bone to the transport sled; and   applying the moving magnetic field to the magnetic assembly, thereby actuating the magnetic assembly,
 wherein the actuating causes the lead screw to rotate and the transport sled to move along the longitudinal opening.  
   
     
     
       15. The method of claim 14, further comprising coupling the magnet holder to the cylindrical permanent magnet.  
     
     
       16. The method of claim 15, wherein the coupling further comprises:
 applying a static frictional torque to the cylindrical permanent magnet,   wherein:   when the moving magnetic field couples to the cylindrical permanent magnet at a torque below the static frictional torque, the cylindrical permanent magnet and the magnet holder turn in unison, and   when the moving magnetic field couples to the cylindrical permanent magnet at a torque above the static frictional torque, the cylindrical permanent magnet turns while the magnet holder remains rotationally stationary.    
     
     
       17. The method of claim 16, further comprising adjusting the static friction torque over a range of static frictional torques.  
     
     
       18. The method of claim 14, wherein the magnetic assembly comprises a magnetic housing containing the cylindrical permanent magnet therein and a biasing member interposed between the magnetic housing and the cylindrical permanent magnet, wherein the magnetic housing and the cylindrical permanent magnet are rotationally locked by the biasing member up to a threshold torque value.  
     
     
       19. The method of claim 14, further comprising:
 coupling the lead screw to a nut moveable along a length of the lead screw in response to rotation thereof; and   securing a ribbon to the nut at one end and to the transport sled at an opposing end and passing the ribbon over at least one pulley, wherein movement of the nut in a first direction translates into movement of the transport sled in a second, opposing direction.    
     
     
       20. The method of claim 14, further comprising:
 coupling the lead screw to a nut moveable along a length of the lead screw in response to rotation thereof, the nut containing at least one nut pulley affixed thereto;   disposing at least one exit pulley within the implantable dynamic apparatus at the proximal end;   fixing at least one tension line relative to the proximal end and passing the at least one tension line over both the at least one nut pulley and the at least one exit pulley; and   securing the at least one tension line to the third portion of bone.    
     
     
       21. The method of claim 14, wherein the applying comprises applying the moving magnetic field by using an external adjustment device comprising at least one rotatable magnet, and the method further comprises storing information in the external adjustment device, the information comprising an orientation of the nail within the bone and a direction of planned movement of the transport sled.