Devices for controlling the unloading of superelastic and shape memory orthopedic implants
This disclosure provides novel devices for controlling the unloading stress and recoverable strain of Nitinol devices and/or other shape memory material devices. The devices may be used to bring bone fragments into close proximity with each other, generate a compressive load between the bone fragments, and maintain that compressive load between the bone fragments while healing occurs.
1. A method for controlling an unloading stress of an orthopedic implant comprising:
deforming a shape memory material implant to generate a stress level and recoverable strain within the implant;
holding the implant in the deformed state with a retaining mechanism, wherein the retaining mechanism is configured to allow adjustment of stress and recoverable strain of the implant; and
inserting the deformed implant into pre-drilled holes in bone.
2. The method of claim 1 , further comprising adjusting the retaining mechanism to alter the stress level and recoverable strain.
3. The method of claim 1 , wherein the shape memory material is nitinol.
4. The method of claim 3 , wherein the implant is a staple.
5. The method of claim 3 , wherein the implant is a compression screw.
6. The method of claim 3 , wherein the implant is a compression plate.
7. The method of claim 3 , wherein the implant is an intramedullary implant.
8. The method of claim 3 further comprising adjusting the retaining mechanism to control the extent of staple legs opening to or beyond a parallel state.
9. The method of claim 1 , wherein the retaining mechanism comprises an internal retaining pin.
10. The method of claim 1 , wherein at least a portion of the implant is reversibly stretched prior to holding the implant with the retaining mechanism.
11. A method for controlling an unloading stress of an orthopedic implant comprising:
deforming a shape memory material implant to generate a stress level and recoverable strain within the implant;
holding the implant in the deformed state with a retaining mechanism;
adjusting the retaining mechanism to alter the stress level and recoverable strain; and
inserting the deformed implant into pre-drilled holes in bone.
12. The method of claim 11 , wherein the shape memory material is nitinol.
13. The method of claim 11 , wherein the implant is selected from the group consisting of a staple, a compression screw, an intramedullary implant, and a compression plate.