A hinged bone screw and tool set is used for implanting such bone screws in a human spine, followed by the implantation of a longitudinal connecting member into the bone screws. The hinged bone screw includes a shank with an upper portion and a receiver with integral arms forming a U-shaped channel. A lower curved seat partially defining the U-shaped channel cooperates with an upper portion of the bone screw shank for hinged movement of the shank with respect to the receiver. The tool set includes an insertion tool, a bone screw driver, a reduction tool and a closure starter. The insertion tool includes a bone screw attachment structure and a laterally opening channel. The insertion tool further includes a threaded portion for cooperation with the reduction tool to provide synchronized placement of a closure structure in the bone screw receiver while reducing and capturing a longitudinal connecting member within the receiver. Further alternative bone screws are hinged, polyaxial or fixed and include lordosing or kyphosing lateral surfaces.

A pivotal bone anchor assembly includes a receiver with an open channel and a central bore having opposed recessed retaining structures with downwardly-facing surfaces located below a closure mating structure, and a shank having an upper capture portion positionable into the central bore and having a partially spherical lower surface that is slidably engageable with a partially spherical seating surface adjacent a bottom opening of the receiver to provide for pivotal motion of the shank with respect to the receiver. The pivotal bone anchor assembly also includes a compression insert disposed within the central bore having an upper rod-seating surface between insert arms and flange structures projecting laterally outward from the insert arms and configured to snap into the recessed retaining structures to inhibit axial rotation and upward movement of the compression insert within the receiver after the upper capture portion of the shank is positioned within the central bore.

A pivotal bone anchor assembly includes a receiver having an axial bore with an internal support surface adjacent a lower opening and a channel configured to receive a fixation rod, as well as a shank having a proximal end portion configured to be pivotally supported by the internal support surface with the shank extending downward through the lower opening. The proximal end portion includes a drive socket engageable by a drive tool, an upwardly-facing planar top surface surrounding and entirely peripheral to the drive socket, and a central bore extending from the drive socket to a distal tip configured to receive a guide wire. The assembly further includes an insert with an upper surface configured to receive the fixation rod and a lower surface configured to transfer a downward force toward the proximal end portion of the shank to lock the assembly, with the planar top surface of the shank remaining spaced apart from the lower surface of the insert so as to not directly receive the downwardly-directed force when the assembly is locked by a closure.

A receiver of a pivotal bone anchor assembly includes a receiver body having a base, a pair of upright arms extending upwardly from the base with opposed interior surfaces defining an open channel for receiving a rod, and an axial bore centered around a longitudinal axis and extending downward through the open channel and the base to a bottom opening in communication with a bottom surface of the base. The receiver also includes an internal non-threaded recess with a downwardly-facing surface formed into internal surfaces of the axial bore and spaced below a guide and advancement structure. The receiver further includes a horizontally elongated tool engaging groove formed into the upper portions of the outwardly-facing exterior surfaces of the each of the upright arms.

Devices and systems can be used to treating spinal conditions. For example, this document describes artificial facet joint systems that can be implanted to treat spinal conditions while facilitating normal stability and motions of the spine. Such systems and methods can be used to treat spinal conditions such as, but not limited to, spondylosis, vertebral fractures, and the like.

A pivotal bone anchor assembly includes a receiver with an open channel and a central bore having opposed recessed retaining structures with downwardly-facing surfaces located below a closure mating structure, and a shank having an upper capture portion positionable into the central bore and having a partially spherical lower surface that is slidably engageable with a partially spherical seating surface adjacent a bottom opening of the receiver to provide for pivotal motion of the shank with respect to the receiver. The pivotal bone anchor assembly also includes a compression insert disposed within the central bore having an upper rod-seating surface between insert arms and flange structures projecting laterally outward from the insert arms and configured to snap into the recessed retaining structures to inhibit axial rotation and upward movement of the compression insert within the receiver after the upper capture portion of the shank is positioned within the central bore.

A pivotal bone anchor assembly includes a receiver defining a channel for receiving an elongate rod and a central bore with an internal engagement surface adjacent a bottom opening, as well as a shank having an anchor portion and a capture structure opposite the anchor portion positionable within the central bore through the bottom opening. The pivotal bone anchor assembly further includes a retainer configured to capture and hold the capture structure within the central bore and having an outer surface with a lower portion that is engageable the internal engagement surface of the receiver, together with a compression insert having an upper surface engageable with the elongate rod and a lower surface in overlapping engagement with an upper portion of the outer surface of the retainer, with the compression insert being spaced apart from the capture structure of the shank upon assembly of the separate components within the receiver.

A system for interconnecting bones includes an implantable member configured to be mechanically coupled to a first bone, configured to be mechanically coupled to a second bone, configured to provide substantially no resistance to compression of the implantable member, configured to support a tensile load within a predetermined range of tensile loads extending from a first load to a second load, configured to have a predetermined elasticity within the range of tensile loads, configured to have a first characteristic at the first load, and configured to have a second characteristic at the second load. The system also includes a means for measuring the first characteristic and the second characteristic. And the system includes a means for calculating a tension between the first bone and the second bone based on the first characteristic and the second characteristic.

A pivotal bone anchor assembly includes a receiver having a central bore with a spherical seating surface adjacent a bottom opening and upright arms defining a channel for receiving a rod. The upright arms include side outer surfaces with horizontal tool engagement grooves spaced below top surfaces and having downwardly-facing upper groove surfaces and upwardly-facing lower groove surfaces that extend to front and back planar surface portions of the upright arms. The upright arms also include vertical tool engagement slots extending into and downward across the side outer surfaces from the top surfaces through to at least the upper groove surfaces of the horizontal tool engagement grooves. The assembly also includes a shank having an anchor portion for attachment to patient bone and a capture portion with a curvate lower surface configured for slidable engagement with the spherical seating surface of the receiver prior to locking the assembly with a closure.

A dynamic fixation medical implant includes a longitudinal connecting member assembly having an elongate coil-like outer member and an inner cylindrical core attached to the outer member at only one end thereof. Some assemblies include a second longitudinal connecting member in the form of a rod that is fixed to the inner core and extends outwardly from the assembly. Certain assemblies include a threaded core or threaded inserts that cooperate with a helical slit of the coil-like outer member. Two or more cooperating bone screw assemblies attach to the connecting member assembly. The bone screw assemblies may include upper and lower compression members for affixing to and cradling the coil-like outer member only, allowing relative movement between the outer member and the inner cylindrical core. Press fit or snap-on features attach one end of the coil-like outer member to one end of the inner cylindrical core.