A bone implant may include a shaft having a proximal end, a distal end, a longitudinal axis, a proximal shaft portion, and a distal shaft portion. The proximal shaft portion may include a first minor diameter, and a first helical thread disposed about the proximal shaft portion defining a first major diameter. The first helical thread may include a first concave undercut surface. The distal shaft portion may include a second minor diameter, and a second helical thread disposed about the distal shaft portion defining a second major diameter. The second helical thread may include a second concave undercut surface. The first and second concave undercut surfaces may be angled towards the distal end of the shaft. The second minor diameter may be smaller than the first minor diameter and the second major diameter may be smaller than the first major diameter.

A coupling assembly for use in surgical constructs includes a first body and a second body. One of the first body and the second body includes a male member and another of the first body and the second body includes a female member. The male member is sized and shaped to be received within the female member and the female member has an internal bore sized and shaped to receive the male member therein. One of the male member or the female member includes one or more engagement features formed therewith or attached thereto. The engagement features are operable to provide a gripping interface between the male member and the female member to couple the male member and the female member one to another.

A coupling device for coupling a rod to a bone anchor includes a receiving part having a central axis, a coaxial passage, and an engagement recess extending laterally into the passage, and a pressure member having an expandable portion to clamp the head, a radially outwardly facing surface, and an engagement surface extending from the radially outwardly facing surface. The engagement surface of the pressure member is recessed from an outer surface of the receiving part. The pressure member is movable axially from a first position towards a second position where the receiving part directly engages the pressure member to increase a compression force on the expandable portion for clamping an inserted head. The engagement surface of the pressure member is engageable through the engagement recess of the receiving part by the instrument to move the pressure member axially from the second position back towards the first position.

A bone attachment assembly may include an attachment head, a set screw configured to attach to the attachment head, and a rod surface with a first raised portion and a second raised portion that define a lowered portion positioned between the first raised portion and the second raised portion. The first raised portion, the second raised portion, and the set screw may be configured to directly contact a rod in order to retain the rod within the attachment head.