US Patent 7322983 Self-locking bone screw and implant

An orthopedic implant assembly is presented which has a flange member having a through bore with internal threads and a screw which has a single continuous thread that has a first section and a second section. The cross sectional configuration of the thread in the first section is different than the cross sectional configuration in the second section. The first section defines a cancellous thread while the second section defines a locking .thread which is an asymmetrical buttress thread that has the same pitch and angle along the leading or thrust surface as the cancellous thread and a thicker square spiral edge or face joined to a transverse rear surface.