Bone fixation system

1. A bone fixation system comprising:

an intramedullary nail including a proximal portion defining

a first proximal bore configured to accept a lag screw, and

a second proximal bore configured to accept a portion of an antirotation screw insertion tool, the second proximal bore having a predetermined diameter;

a lag screw configured to extend through the first proximal bore in the proximal portion of the intramedullary nail, the lag screw including

a sheath, and

a rod mounted for sliding movement within the sheath, the rod including a threaded distal end defining an internally threaded diagonal bore having a predetermined diameter; and

an antirotation screw configured to be mounted at the end of the antirotation screw insertion tool and inserted through the second proximal bore, the antirotation screw including

a screw head having a predetermined diameter less than the predetermined diameter of the second proximal bore and greater than the predetermined diameter of the diagonal bore,

a shank having a threaded distal portion configured to achieve good purchase in bone and a threaded proximal portion configured to engage the internally threaded bore of the rod.

2. The bone fixation system according to claim 1 , wherein;

the intramedullary nail has a distal portion of the intramedullary nail having a longitudinal axis;

the first proximal bore extends at an angle in the range of about 120° to about 140° with respect to the longitudinal axis of the distal portion of the intramedullary nail; and

the second proximal bore extends at an angle in the range of about 90° and about 105° with respect to the longitudinal axis of the distal portion of the intramedullary nail.

3. The bone fixation system according to claim 2 , wherein:

the rod has a longitudinal axis; and

the diagonal bore extends at an angle in the range of about 25° to about 55° with respect to the longitudinal axis of the rod.

4. The bone fixation system according to claim 1 , wherein:

the sheath of the lag screw has a predetermined outer diameter; and

the antirotation screw has a predetermined diameter not more than half the predetermined outer diameter of the sheath of the lag screw.

5. The bone fixation system according to claim 1 , wherein:

the lag screw has a predetermined length when fully extended; and

the antirotation screw has a predetermined length no more than ¾ths of the predetermined length of the lag screw.

6. The bone fixation system according to claim 1 , wherein:

the intramedullary nail has a proximal end, a distal portion, and a predetermined length; and

the distal portion of the intramedullary nail defines a targeted screw hole located a predetermined distance from the proximal end of the intramedullary nail, wherein the predetermined distance is between about 44% and about 67% of the predetermined length of the nail.

7. The bone fixation system according to claim 1 , wherein:

the intramedullary nail has a proximal end, a distal portion having a distal tip, and a predetermined length; and

the distal portion of the intramedullary nail defines

a first targeted screw hole located a first predetermined distance away from the proximal end of the intramedullary nail, wherein the first predetermined distance is between about 34% and about 52% of the predetermined length of the intramedullary nail;

a distal locking hole located near the distal tip of the intramedullary nail;

a distal locking slot located in close proximity to the distal locking hole; and

a second targeted screw hole located between the first targeted screw hole and the distal locking hole.

8. A method of repairing a fracture in a femur, the method comprising;

implanting an intramedullary nail in the femur, the intramedullary nail including

a proximal portion defining

a first proximal bore configured to accept a lag screw, and

a second proximal bore configured to accept a portion of an antirotation screw insertion tool, the second proximal bore having a predetermined diameter,

a lag screw configured to extend through the first proximal bore in the proximal portion of the intramedullary nail, the lag screw including

a sheath, and

a rod mounted for sliding movement within the sheath, the rod including a threaded distal end defining an internally threaded diagonal having a predetermined diameter, and

an antirotation screw configured to be mounted at the end of the antirotation screw insertion tool and inserted through the second proximal bore, the antirotation screw including

a screw head,

a shank, and

a locking mechanism configured to lock the antirotation screw within the diagonal bore;

inserting the lag screw through the first proximal bore in the proximal portion of the intramedullary nail;

mounting the antirotation screw on the portion of the antirotation screw insertion tool;

inserting the antirotation screw insertion tool through the second proximal bore in the proximal portion of the intramedullary nail until the screw head abuts the intramedullary nail;

manipulating the antirotation screw insertion tool to lock the antirotation screw within the diagonal bore of the lag screw; and

removing the antirotation screw insertion tool.

9. The bone fixation system according to claim, 8 wherein:

the antirotation screw comprises

a threaded distal end configured to achieve good purchase in bone; and

a threaded proximal end; and

the diagonal bore has an internally threaded end configured to mate with the threaded proximal end of the antirotation screw; and

the locking mechanism comprises the threaded proximal end of the antirotation screw and the internally threaded end of the diagonal bore.

10. The method according to claim 9 , wherein manipulating the antirotation screw insertion tool comprises rotating the antirotation screw until the threaded proximal end of the antirotation screw engages the internally threaded end of the diagonal bore.