Orthopedic fixation device with lag screw and compression screw

Inventors

Rakes, Jordan • Watanabe, Kohsuke • Ricci, William M. • Chan, Daniel S.

Assignees

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

Abstract

An orthopedic fixation device (e.g., an intramedullary (“IM”) nail or bone plate) including a lag screw and a compression screw, the compression screw being nested with the lag screw. In accordance with one or more features of the present disclosure, the compression screw may include a partially non-threaded medial segment, an enlarged diameter, and/or a cannulated bore. In addition, and/or alternatively, the lag screw may be provided as an integrated assembly including a lag screw and an outer sleeve to enable the lag screw to telescope or slide relative to the outer sleeve and IM nail.

Core Innovation

The invention relates to an orthopedic fixation device in the form of an intramedullary ("IM") nail and/or a bone plate that includes a nested arrangement of a lag screw and a compression screw. The IM nail body includes an opening formed therethrough, and both the lag screw and the compression screw are positioned within the opening. The lag screw includes a plurality of teeth on a first segment and a tip, while the compression screw includes a driven end, a first threaded segment, a second non-threaded segment, and a tip so that the compression screw is partially threaded.

The core interaction causes compression by cooperation between the compression screw and the lag screw, where the first threaded segment of the compression screw is arranged to interact with the plurality of teeth formed on the lag screw. Rotation of the compression screw causes the lag screw to move, thereby moving the lag screw toward the body of the IM nail and compressing across the fracture. The partial threading and the nested configuration provide a mechanism that manages how the lag screw advances and how compression is generated.

The invention further includes compression control using a step/reduced-diameter portion on the medial wall or reduced-diameter inner portion that contacts the compression screw and stops further advancement, forcing a specific tooth/rack or tooth-thread engagement behavior that moves the lag screw laterally to compress the fracture. In addition, a telescopic or integrated lag screw assembly is described, including an outer sleeve/barrel coupled within the IM nail, an assembly screw and an inner-bore stop that control lag screw sliding/telescoping to maintain contact and compression while reducing lateral prominence.

Claims Coverage

The independent claim set includes 2 independent inventive structures, each centered on an IM nail body with a lag screw and a partially threaded compression screw whose rotation drives lag screw movement via engineered tooth-thread interaction. Across the independent claims, the coverage is refined by adding a cannulated bore, specific medial/lateral wall geometry, partially non-threaded segments, and telescopic lag screw assembly components with defined retention and stopping features.

Overall, the claim coverage is directed to an IM nail where a partially threaded compression screw drives lag screw movement via interaction between teeth on the lag screw and threads on the compression screw, with further limitation in one branch using telescopic lag screw assembly behavior that allows the lag screw to move toward the IM nail body.

Stated Advantages

Documented Applications