A compression fastener may include a shaft and a helical thread disposed about the shaft. The shaft may include a proximal end, a distal end, a proximal shaft portion, and a distal shaft portion. The helical thread may include at least one concave undercut surface and a plurality of pitches that may include at least one first pitch along the proximal shaft portion and at least one second pitch along the distal shaft portion. The at least one concave undercut surface may be angled towards one of the proximal end and the distal end of the shaft, and the at least one first pitch and the at least one second pitch may not be equal to each other.

A spine alignment system is disclosed. The spine alignment system includes a pedicle screw having a longitudinal axis, the pedicle screw having a screw head. The screw head includes a slot having a longitudinal axis that is substantially perpendicular to the longitudinal axis of the pedicle screw. An extension shaft is secured to the pedicle screw, such that a longitudinal axis of the extension shaft is substantially coaxial with the longitudinal axis of the pedicle screw. The spine alignment system also includes a cap having a slot that forms a substantially cylindrical passage with the slot of the pedicle screw head. The substantially cylindrical passage is configured to receive an alignment rod such that alignment of the spine occurs as the rod is translated along the extension shaft to the pedicle screw.

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 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.

An anchoring system for implanting in bone, the system comprising a first coupling assembly having a first clamp and a first coupling body that receives and holds a first stabilization element; a second coupling assembly that receives and holds a second stabilization element; and a plate that attaches to the first coupling assembly and the second coupling assembly, wherein the first coupling assembly attaches to a bone fastener, and wherein the first coupling body includes a cap retainer that receives a locking cap that applies a directional force to force the first coupling body toward the plate, and applies another directional force to force the first clamp toward the plate, thereby fixedly securing the first coupling body and the first clamp to the plate.

Modular devices, assemblies, and methods for coupling one or more fixation elements, such as bone fasteners and/or elongate rods. The device includes at least one coupling element having a body portion for receiving a bone fastener and an extension portion extending transversely from the body portion. A locking assembly is received in the coupling element and includes a locking member, a clamp portion, and a ring portion, wherein the locking member is configured to contact an upper portion of the clamp portion and the ring portion is configured to at least partially surround a lower portion of the clamp portion. When unlocked, the bone fastener is moveable within the clamp portion to allow for polyaxial movement of bone fastener relative to the coupling element, and when locked, the bone fastener is fixed relative to the coupling element.

A spinal fixation device for securing two stabilizing rods to bone has a threaded shaft for fastening to bone, a primary rod coupling head and a secondary rod coupling head. The first rod coupling head is connected to the threaded shaft and has a side wall and a cavity for receiving a rod, the cavity being open toward a top of the first rod coupling head. In a neutral position of the first rod coupling head, the first rod coupling head extends symmetrically around the longitudinal axis of the threaded shaft. The second rod coupling head is rotatably connected to the first rod coupling head, around an axis of rotation that is disposed at an angle that is not perpendicular to the longitudinal axis of the threaded shaft when the first rod coupling head is in the neutral position.

A method of preventing bone blowout may include forming a hole in a bone, the hole having a bone hole diameter, and inserting a bone fastener into the hole. The bone fastener may include a shaft having a minor diameter and a helical thread. The helical thread may be disposed about the shaft and may include a first undercut surface and a second undercut surface. The first undercut surface may be angled toward one of the proximal end and the distal end of the shaft, and the second undercut surface may be angled toward the other one of the proximal end and the distal end of the shaft. The minor diameter of the shaft may not be greater than 5% larger the bone hole diameter.

A pedicle bone fastener may include a shaft, a helical thread, and an integrated attachment feature. The shaft may include a proximal end, a distal end, and a longitudinal axis. The helical thread may be disposed about the shaft along the longitudinal axis between the proximal and distal ends of the shaft. The helical thread may include a first undercut surface and a second undercut surface. The first undercut surface may be angled toward one of the proximal end and the distal end of the shaft and the second undercut surface may be angled toward the other one of the proximal end and the distal end of the shaft. The integrated attachment feature may be disposed at the proximal end of the shaft and configured to be adjustably secured to a spinal stabilization implement.

A percutaneous access device includes an inner tube and an outer tube disposed about at least a portion of the inner tube. The outer tube may be sized to span from a skin incision in a patient to a site proximate the spine of the patient. The distal end of the outer tube may be adapted to releasably engage a bone anchor. The inner tube may be adjustable relative to the outer tube between a first position and a second position in which the distal end of the inner tube contacts the bone anchor. A bone anchor assembly includes a bone anchor having a distal bone engaging portion and a receiving member having a recess for receiving a spinal fixation element. The proximal end of the receiving member may have an arcuate groove formed on an exterior surface thereof to facilitate connection of an instrument to the receiving member.