Active compression apparatus, methods of assembly and methods of use

1. An active compression bone screw apparatus for generating active compression of bone segments comprising:

a distal bone engagement portion;

a proximal bone engagement portion;

a central portion configured to promote axial elongation and radial rotation of the apparatus during rotation of said apparatus into said bone segments;

said central portion interposed between the proximal bone engagement portion and the distal bone engagement portion and having a perforation formed through a side wall of the central portion;

a limiting feature formed by opposing sides of the perforation that constrains the axial elongation and the radial rotation of the apparatus;

said limiting feature comprised of an asymmetric receiving portion and an asymmetric protruding portion.

2. The apparatus of claim 1 wherein the apparatus has a unitary contiguous structure.

3. The apparatus of claim 1 wherein the apparatus is cannulated.

4. The apparatus of claim 1 wherein the proximal bone engagement portion comprises threads having a pitch that are distinct from a pitch of threads of the distal bone engagement portion.

5. The apparatus of claim 1 wherein the distal bone engagement portion comprises threads.

6. The apparatus of claim 1 wherein the limiting feature also limits a change in a circumference of the apparatus.

7. The apparatus of claim 1 wherein the perforation comprises a helical form that defines a continuous helical strut.

8. The apparatus of claim 1 wherein the limiting feature has a stepped shape.

9. The apparatus of claim 1 wherein the perforation is formed through the sidewall perpendicular to a longitudinal central axis of a shaft of said apparatus and parallel to a radial direction of said shaft.

10. The apparatus of claim 1 wherein the active compression comprises active compression over a period of greater than 12 hours.

11. An active compression bone screw apparatus for generating active compression of bone segments comprising:

a cannulated body having a compression preload feature;

a perforation formed through a sidewall of the cannulated body; and

said cannulated body configured to promote axial elongation and radial rotation upon deformation of the perforation through an activation of the compression preload feature during rotation of said cannulated body into said bone segments,

the axial elongation and the radial rotation constrained by corresponding change limiting features formed in opposing sides of the perforation;

said change limiting features comprised of a receiving portion having an asymmetric shape and a protruding portion having an asymmetric shape.

12. The apparatus of claim 11 wherein an exterior of the sidewall of the cannulated body comprises threads.

13. The apparatus of claim 11 wherein the compression preload feature comprises a plurality of threads having different pitches formed on an exterior of the sidewall of the cannulated body.

14. The apparatus of claim 11 wherein the activation of the compression preload feature comprises a rotation of the apparatus.