An intervertebral implant may include a shaft having a proximal end, a distal end, a longitudinal axis, a minor diameter, and a helical thread disposed about the shaft along the longitudinal axis between the proximal end and the distal end of the shaft. The helical thread may include a major diameter and a concave undercut surface angled towards one of the proximal end and the distal end of the shaft. The intervertebral implant may be implanted within an intervertebral space between a superior vertebral body and an inferior vertebral body. A ratio of the major diameter to the minor diameter may be less than 1.50. The concave undercut surface may engage the superior vertebral body and the inferior vertebral body and may be shaped to resist at least one force transmitted between the superior vertebral body and the inferior vertebral body to stabilize the intervertebral space.

A bone disunion fastener may include a fastener shaft, a helical thread, and a bone staple. The helical thread may include a concave undercut surface oriented towards one end of the fastener shaft. The bone staple may include a first bone-engaging feature, a second bone-engaging feature, and a middle portion with an opening. The bone disunion fastener may be implanted along a disunion between a first bone portion and a second bone portion. The concave undercut surface may be shaped to resist at least one force transmitted between the first bone portion and the second bone portion to stabilize the disunion. The first bone-engaging feature may engage the first bone portion and the second bone-engaging feature may engage the second bone portion to couple the bone staple to the bone portions and resist at least one force transmitted between the bone portions to stabilize the disunion.

A bone fixation system comprises a first fastener configured to anchor into a first vertebrae, a second fastener configured to anchor into a second vertebrae, and a set screw to retain the second fastener to the first fastener. The first fastener includes a shaft extending along a longitudinal axis and a head. The shaft includes a first cylindrical body. The head of the first fastener includes a second cylindrical body defining a passageway having an interior surface. The passageway defines a longitudinal axis that is different than the longitudinal axis of the shaft. The first cylindrical body of the shaft and the second cylindrical body of the head are angled relative to each other. A head of the second fastener is configured to engage the interior surface of the passageway of the head of the first fastener. The set screw retains the head of the second fastener in the passageway.

A bone screw comprising a shaft having a wall, the wall including a minor diameter and at least one thread having an external thread form. The thread form including a first portion comprising a crest of the thread form and a second portion extends between a minor diameter of the thread form and the first portion. The first portion having a solid configuration relative to the second portion. In some embodiments, systems, spinal constructs, surgical instruments and methods are disclosed.

An anchor for anchoring tensile members to bone includes: a housing extending along a central axis, with a hollow interior; a collet in the hollow interior having a central bore for accepting tensile members and an exterior surface, the collet being configured to swage around and against tensile members; a sleeve having a peripheral wall defining interior and exterior surfaces, the sleeve disposed in the housing's hollow interior axially adjacent to the collet, and movable parallel to the central axis between first and second positions; and wherein at least one of the collet exterior surface and the sleeve interior surface is tapered and the sleeve and the collet are arranged so movement of the sleeve from the first position to the second position causes the sleeve interior surface to bear against the collet exterior surface, causing the collet to swage radially inwards around and against one or more tensile members.

Assemblies and methods for fixation of bone or bone fragments using an orthopedic plate, a modular peg, and a compression screw. The modular peg is screwed into one of the apertures of the orthopedic plate. The modular peg may include an aperture having screw threads designed to receive the threads of the compression screw and serve as an anchor for the compression screw. By rotating the compression screw in relation to the modular peg, the compression screw may advance through the aperture of the modular peg, drawing the head of the screw toward the modular peg, and compressing the bone or bone fragments.

A compression device made of a superelastic material having a peripheral portion with an upper surface, a lower surface, and a central opening extending therethrough is provided. One or more resilient teeth project inward of the peripheral portion into the central opening and are configured to exert a biasing force in an axial direction when deformed in a direction opposite the axial direction.

Surgical tissue retraction systems and methods are described herein. Such systems and methods can be employed in some embodiments to provide medial-lateral tissue retraction to increase access to a surgical site. In one embodiment, a surgical instrument can include a body configured to couple to an implantable anchor, a first tissue manipulating implement coupled to the body and capable of polyaxial movement relative thereto, and a second tissue manipulating implement coupled to the body and capable of polyaxial movement relative thereto. Further, the first and second tissue manipulating implements can be opposed to one another such that they can move any of toward and away from one another.

An anchor assembly can be couplable to a bone and can include an anchor and a housing. The anchor can include a shank securable to bone and a head coupled to a proximal portion of the shank.

The invention relates to a bone anchor for triangular iliosacral osteosynthesis. The bone anchor includes an ilium screw having a first longitudinal direction and an iliosacral screw having a second longitudinal direction. The ilium screw, in a thread-free portion, has a preferably elongated-hole-like through-opening transversely to the first longitudinal direction, and the iliosacral screw has such a smaller outer diameter in relation to the ilium screw that the iliosacral screw can be guided through the through-opening and can be screwed proceeding from the ilium into the sacrum, through the ilium screw.