Bone plate with form-fitting variable-angle locking hole

1. A system comprising:

a bone plate including:

an inner surface configured to face the underlying bone, and an outer surface opposite the inner surface; and

an internal surface that extends from the outer surface to the inner surface so as to define a hole that is oriented along a central hole axis, wherein the internal surface includes 1) a plurality of threaded regions that define respective columns of thread segments, and 2) a plurality of recessed surfaces that are disposed between respective adjacent ones of the thread segments, the recessed surfaces being offset radially outward with respect to the columns of thread segments; and

a variable angle locking screw having a threaded head,

wherein the bone plate is configured to mate with the threaded head of the variable angle locking screw in the hole at an angle within a range of angles, such that the threaded head threadedly purchases with all of the columns of thread segments, and wherein the angle is oblique to the central hole axis, and

wherein the thread angle of the thread segments of the bone plate and the thread angle of the threaded head of the bone screw define a ratio between 1.1:1 and approximately 1.8:1.

2. The system as recited in claim 1 , wherein the recessed surfaces are offset radially outward with respect to the respective threaded regions.

3. The system as recited in claim 1 , wherein the internal surface defines a lead-in surface that is tapered radially inward from the outer surface to the columns.

4. The system as recited in claim 1 , further comprising an undercut surface that is tapered radially outward as it extends from the columns to the inner surface.

5. The system as recited in claim 1 , wherein the outer surface defines a perimeter of an opening to the hole, and the perimeter defines a circle.

6. The system as recited in claim 1 , wherein the internal surface defines a plurality of transition regions between the columns and respective adjacent ones of the recessed surfaces.

7. The system as recited in claim 6 , wherein respective depths of the thread segments taper along the transition regions in a circumferential direction away from the respective columns to the respective recessed surface.

8. The system as recited in claim 7 , wherein the recessed surfaces are smooth.

9. The system as recited in claim 8 , wherein the recessed surfaces are defined by respective radii that also define at least a portion of the transition regions.

10. The system as recited in claim 1 , wherein the recessed surfaces and the columns define respective centerlines that are each oriented at a common angle with respect to the central hole axis.

11. The system as recited in claim 10 , wherein the common angle is between approximately 5 degrees and approximately 30 degrees.

12. The system as recited in claim 1 , wherein no portion of the internal surface extends radially inward of the columns.

13. The system as recited in claim 1 , wherein the range of angles is within a cone that is centered about the central hole axis.

14. The system as recited in claim 1 , wherein the hole is open to a compression hole that is configured to receive a compression screw having an unthreaded head that bears against the interior surface so as to compress the bone plate against the underlying bone.

15. The system as recited in claim 1 , wherein the thread segments of the bone plate define a thread angle, the threaded head of the bone screw defines a thread angle, and the thread angle of the thread segments is greater than the thread angle of the threaded head.

16. The system as recited in claim 15 , wherein the thread angle of the thread segments of the bone plate is approximately 80 degrees, and the thread angle of the threaded head of the bone screw is approximately 60 degrees.

17. The system as recited in claim 1 , wherein the ratio is approximately 4:3.