Systems and methods for distraction

1. A system for distraction, comprising:

a housing;

a first distraction rod having a cavity, wherein the first distraction rod is configured for telescopic displacement relative to the housing;

a second distraction rod, wherein the second distraction rod is configured for telescopic displacement from within the cavity; and

a drive system comprising a first lead screw and a second lead screw disposed annularly around the first lead screw, wherein the drive system is configured to rotate the first lead screw to move the second lead screw relative to the first lead screw, and wherein upon displacing the second lead screw relative to the first lead screw, the second lead screw is configured to rotate with the first lead screw to move at least one of the first distraction rod and the second distraction rod relative to the housing.

2. The system of claim 1 , wherein the drive system comprises a driving element that is at least partially located within the housing.

3. The system of claim 2 , wherein the driving element is remotely controllable.

4. The system of claim 3 , wherein the driving element comprises at least one of a permanent magnet, an inductively coupled motor, an ultrasonically actuated motor, a subcutaneous hydraulic pump, a shape memory-driven actuator, and a magnetorestrictive element.

5. The system of claim 3 , wherein the driving element comprises a radially-poled permanent magnet configured for rotation within the housing.

6. The system of claim 5 , wherein the radially-poled permanent magnet is configured to be rotated by application of an externally applied rotating magnetic field.

7. The system of claim 1 , wherein the first distraction rod and the housing are restrained to prevent substantially all axial rotation with respect to each another about the longitudinal axis.

8. The system of claim 1 , wherein the second distraction rod and the first distraction rod are restrained to prevent substantially all rotation with respect to each another about the longitudinal axis.

9. The system of claim 1 , wherein the second distraction rod and the housing are restrained to prevent substantially all rotation with respect to each about the longitudinal axis.

10. The system of claim 1 , wherein the second distraction rod is configured to be substantially fully displaced from within the cavity before the first distraction rod begins to displace from within the housing.

11. The system of claim 10 , further comprising:

a first stop at a proximal end of the second distraction rod; and

a second stop at a distal end of the first distraction rod, wherein the first stop of the second distraction rod is configured to engage the second stop of the first distraction rod when the second distraction rod is substantially fully displaced from within the cavity.

12. The system of claim 1 , wherein the drive system is configured to move the first distraction rod in relation to the housing and move the second distraction rod in relation to the first distraction rod.

13. A method of modifying a limb of a patient, comprising:

providing a distraction device comprising:

a housing;

a first distraction rod having a proximal end, a distal end, and a cavity, wherein the first distraction rod is telescopically displaceable relative to the housing;

a second distraction rod having a proximal end and a distal end, wherein the second distraction rod is telescopically displaceable from within the cavity; and

a drive system comprising a first lead screw and a second lead screw disposed annularly around the first lead screw, wherein the drive system is configured to rotate the first lead screw to move the second lead screw relative to the first lead screw, and wherein upon displacing second lead screw relative to the first lead screw, the second lead screw is configured to rotate with the first lead screw to move at least one of the first distraction rod and the second distraction rod relative to the housing;

decoupling a first portion of a bone within the residual limb from a second portion of the bone;

attaching the housing to one of the first portion and the second portion of the bone within the residual limb; and

attaching the second distraction rod to the other of the first portion and the second portion of the bone within the residual limb, wherein the drive system is configured to be actuated so as to increase at least one of a force and a distance between the first portion and the second portion of the bone.

14. The method of claim 13 , further comprising modifying skin of the residual limb such that an additional internal space is made within the residual limb to facilitate an axial elongation of the bone.

15. The method of claim 13 , wherein the bone comprises a femur.

16. The method of claim 13 , wherein the drive system comprises a driving element at least partially located within the housing.

17. The method of claim 16 , wherein the driving element is non-invasively actuatable.

18. The method of claim 17 , wherein the driving element comprises at least one of a permanent magnet, an inductively coupled motor, an ultrasonically actuated motor, a subcutaneous hydraulic pump, a shape memory-driven actuator, and a magnetorestrictive element.

19. The method of claim 17 , wherein the driving element comprises a radially-poled permanent magnet configured for rotation within the housing.

20. The method of claim 19 , wherein the radially-poled permanent magnet is configured to be rotated by application of an externally applied rotating magnetic field.