Self-countersinking bone fastener and method for countersinking a bone fastener used in connection with an orthopedic implant

Inventors

Janna, Sied • Faber, Henry B. • Grusin, Nathaniel Kelley • Bennett, Charles R.

Assignees

Smith and Nephew Orthopaedics AG • Smith and Nephew Asia Pacific Pte Ltd • Smith and Nephew Inc

Abstract

Disclosed herein is a self-countersinking bone screw and a system and a method for countersinking a bone screw or fastener used in connection with an orthopedic implant such as, for example, an intramedullary nail. The bone screw includes one or more cutting features configured to self-countersink the head of the screw. The system and method utilize instrumentation including a plurality of markings or indicia configured to indicate a position of the head of the screw relative to an outer surface of the patient's bone. In use, the method enables a surgeon to quickly and easily countersink one or more bone screws used to couple an IM nail to a patient's bone without requiring additional instrumentation to form a countersunk hole in the patient's bone.

Core Innovation

A self-countersinking bone screw includes a distal end portion, an intermediate shaft portion, a neck portion, an enlarged head portion, an external thread, and one or more cutting flutes extending from the enlarged head portion towards the distal end portion. The enlarged head portion includes a distal end, a proximal end, and a concave outer surface extending from the distal end toward the proximal end. The neck portion provides a transition from the shaft portion to the distal end of the enlarged head portion and includes a minor outer diameter that tapers from the minor outer diameter of the shaft portion toward the enlarged head portion.

The one or more cutting flutes include a distal end and a proximal end, where the distal end of the cutting flute is positioned closer to the distal end portion of the bone screw than the distal end of the neck portion so that, in use, the distal end of the one or more cutting flutes contacts a patient's bone prior to the distal end of the neck portion. The neck portion includes an enlarged diameter thread, as measured from the minor outer diameter of an outer surface of the bone screw to a major diameter of the enlarged diameter thread, such that a height of the external thread in the neck portion is greater than a height of the external thread in the shaft portion.

A method for countersinking a bone fastener to secure an intramedullary (“IM”) nail includes implanting the IM nail within an intramedullary canal, targeting a first screw opening formed in the implanted IM nail, predrilling a first screw hole in the patient's bone, and inserting a first bone screw into the first screw hole and into the first screw opening. In inserting the first bone screw, rotating a head portion of the first bone screw until the head portion is inserted to a depth sufficient such that an uppermost surface of the head portion is countersunk, and not including pre-drilling a countersunk hole.

The method further defines countersinking through the self-countersinking structure of the bone screw, including the concave enlarged head portion and cutting flutes positioned to contact bone prior to the distal end of the neck portion. Additional refinements include using a guide and sleeve coupled to an IM nail and driving the screw with a screwdriver having markings or indicia indicating position relative to the outer surface, including markings corresponding to approaching the outer surface, contacting the outer surface, and being countersunk or at penetration depth flush with the outer surface of the patient's bone.

Claims Coverage

The document includes two independent claims that cover a self-countersinking bone screw and a method of countersinking a bone fastener for securing an IM nail. Across the independent claims, the main inventive features are the concave enlarged head with cutting flutes and their flute placement relative to the neck, and a neck thread geometry constraint where the external thread height in the neck is greater than in the shaft.

Overall claim coverage emphasizes countersinking using a self-countersinking bone screw whose concave enlarged head and cutting flutes extend toward the distal end portion, whose flute distal end is positioned to contact bone prior to the distal end of the neck portion, and whose neck portion includes an enlarged diameter thread such that the external thread height in the neck portion is greater than the external thread height in the shaft portion. For the IM-nail context, the method enables countersinking by rotating the screw head to a countersunk depth without pre-drilling a countersunk hole.

Stated Advantages

Documented Applications