Nail-based compliant hip fixation system
System, including methods, devices, and kits, for hip fixation. The system may comprise an intramedullary nail configured to be placed longitudinally into a proximal femur. The system also may comprise a fixation element configured to be placed transversely through the nail, such that the fixation element is slideable along its long axis in the nail and extends out of the nail to a head of the proximal femur and is anchored in the head. A compliant member may be located in the nail and configured to deform reversibly in response to a load applied to the head of the proximal femur after placement of the fixation element, to reversibly change an angular orientation of the fixation element with respect to the nail.
1. A system for hip fixation, comprising:
an intramedullary nail configured to be placed longitudinally into a proximal femur of a subject;
a sleeve disposed in the nail;
a fixation element configured to be placed into the proximal femur and through the sleeve, such that the fixation element is slideable along its long axis in the sleeve and extends out of the nail to a head of the proximal femur and is anchored in the head; and
a compliant member located in the nail and configured to deform reversibly in response to a load applied to the head of the proximal femur by the subject after the nail and the fixation member have been implanted in the proximal femur of the subject, to reversibly change an angular orientation of the fixation element with respect to the nail;
wherein the angular orientation is defined as an angle formed between a long axis of the nail and the long axis of the fixation element.
2. The system of claim 1 , wherein the compliant member includes an elastomer.
3. The system of claim 2 , wherein the elastomer is viscoelastic.
4. The system of claim 1 , wherein the sleeve and the nail are formed separately from one another.
5. The system of claim 4 , wherein the sleeve and the compliant member are formed of different materials relative to one another.
6. The system of claim 5 , wherein the sleeve is formed of metal and the compliant member includes a polymer.
7. The system of claim 4 , wherein the compliant member is formed in situ between the nail and the sleeve.
8. The system of claim 4 , wherein the compliant member and the sleeve have complementary surface features that restrict movement of the compliant member and the sleeve relative to one another.
9. The system of claim 1 , wherein the nail defines an aperture, and wherein at least a portion of the compliant member is disposed between the sleeve and a wall of the aperture.
10. The system of claim 1 , wherein the nail defines an aperture in which the compliant member is mounted.
11. The system of claim 10 , wherein the compliant member and a wall of the aperture have complementary surface features that restrict removal of the compliant member from the aperture.
12. The system of claim 1 , wherein the compliant member includes a pair of deformable elements that are formed separately from one another.
13. The system of claim 1 , wherein the compliant member includes a spring.
14. The system of claim 1 , wherein at least a portion of the compliant member is continuous with the nail.
15. The system of claim 1 , wherein the fixation element has an external thread to anchor the fixation element in the head of the femur.
16. A method of hip fixation, the method comprising, in any order:
placing an intramedullary nail longitudinally in a proximal femur of a subject, the nail containing a sleeve; and
placing a fixation element into the proximal femur and through the sleeve, such that the fixation element is slideable along its long axis in the sleeve and extends out of the nail to a head of the proximal femur and is anchored in the head;
wherein a compliant member is located in the nail and is configured to deform reversibly in response to a load applied to the head of the proximal femur by the subject, to reversibly change an angular orientation of the fixation element with respect to the nail, and
wherein the angular orientation is defined as an angle formed between a long axis of the nail and the long axis of the fixation element.
17. The method of claim 16 , further comprising a step of selecting the compliant member based on one or more characteristics of the subject, wherein the compliant member is selected from a set of two or more compliant members having different deformabilities relative to one another.
18. The method of claim 17 , wherein the set of two or more different compliant members are provided by a set of two or more nails each containing one of the two or more different compliant members.
19. A system for hip fixation, comprising:
an intramedullary nail configured to be placed longitudinally into a proximal femur of a subject;
a fixation element configured to be placed into the proximal femur and transversely through the nail, such that the fixation element is slideable along its long axis in the nail and extends out of the nail to a head of the proximal femur and is anchored in the head; and
a compliant member located in the nail and configured to deform reversibly in response to a load applied to the head of the proximal femur by the subject after the nail and the fixation member have been implanted in the proximal femur of the subject, to reversibly change an angular orientation of the fixation element with respect to the nail;
wherein the angular orientation is defined as an angle formed between a long axis of the nail and the long axis of the fixation element, and
wherein the compliant member is formed of material selected from the group consisting of (a) metal and (b) a composite including a polymer matrix containing carbon fibers.