A bone lag screw that can provide continuous dynamic compression across the fracture while accommodating resorption as the bone heals.

 Bone fractures are frequently repaired by securing screws across the fractured part of the bone. Ideally, the screws secure the bone fragments together tightly while the bone heals. Frequently, the edges of the fracture will resorb during revascularization, resulting in reduction or elimination of the initial compression provided by the screw. A UNMC researcher has created a bone lag screw that could provide continuous dynamic compression across the fracture while accommodating resorption as the bone heals thus providing improved long-term stabilization until revascularization is completed. The typical screw includes a spring section that could be damaged during insertion because the torque applied to the head of the screw passes through the spring section. This torque results in torsional deformation of the spring section during insertion, which could create stress risers within the spring, possibly leading to early mechanical failure. Furthermore, during the process of removal, the spring could distort and fail mechanically, requiring more destructive extraction methods. The UNMC researcher has also created a drive tool with two spaced-apart drivers. One of the drivers engages the distal drive surface while the other driver engages the proximal drive surface. The two drivers apply torque simultaneously to the screw on opposite ends of the spring section to assure that the spring section does not undergo torsion during deployment.

U.S. Patent Publication No. 20050277940

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