Abstract: Surgical instruments, methods, and systems are provided for securing spinal fixation elements to bone. For example, a spinal fixation system is provided that has a receiver with proximal and distal ends. The proximal end of the receiver is configured to receive various fixation members, such as spinal rods and set screws, therein. The distal end of the receiver has a hook member that is operably coupled thereto and has an opening that is configured to receive bone therein. The hook member is configured to be secured to bone without penetrating the bone.

Abstract: A bone hook apparatus is provided that includes a base, a rod receptacle disposed on a proximal side of the base, a first hook distally extending from the base and oriented in a first direction, and a second hook distally extending from the base and oriented in a second direction opposing the first direction, the first hook and second hook together configured to receive the bone. Kits and spinal constructs employing the bone hook apparatus are also described.

Abstract: A spinal implant system (10) includes a superior attachment rod (12) coupled to, and articulating with respect to, a roller housing (17), an inferior cross bar member (20) coupled to the roller housing (17), and an inferior attachment rod (14) coupled to the inferior cross bar member (20). At least one of the superior and inferior attachment rods (12, 14) is supported by a flexure assembly (16). The inferior attachment rod (14) is coupled to the inferior cross bar member (20) with a swivel joint (32) and/or a telescoping portion (20).

Abstract: A spinal fixation construct for aligning vertebral bodies includes a bone screw, a spinal rod, a flexible member, and a fixation member. The spinal rod is disposed within a saddle portion of a housing of the bone screw, and includes an elongated body having a first end and a second end. The spinal rod is formed from a first material having a first modulus of elasticity. The flexible member is coupled to the spinal rod, and includes an elongated body having a first end portion and a second end portion. The flexible member is formed from a second material having a second modulus of elasticity that is different from the first modulus of elasticity. The fixation member includes a threaded body portion and a head portion defining a hole therethrough. A portion of the flexible member extends through the hole of the head portion.

Abstract: Spinal implants and methods of extending pre-existing spinal implant constructs. An extension clamp may be connected to an original spinal implant including an elongated rod attached to a portion of the spine without removal of the original spinal implant. The extension clamp may include a yoke and an extension rod extending from the yoke. The yoke may include a first end and a second end, the first end having first and second rod engaging portions and a channel between the first and second rod engaging portions for encompassing a fastener, and the second end being spaced apart from the first end. The first and second rod engaging portions may be configured and dimensioned to secure the extension clamp to the elongated rod.

Abstract: This present invention utilizes a shape memory alloy (SMA) to improve on prior art in the design of clamps used for shut off, squeeze off, of plastic pipe which transmits gas or fluid under pressure. More particularly, but not exclusively, the present invention incorporates SMAs as actuators to simplify and improve clamp design for squeeze off of plastic pipe that is used in the transmission of pressurized gas and fluid. This invention may be deployed and operated remotely by the user. This present invention relates specifically to the application of trained SMA tubes, rods, bars, and beams as actuators for clamping and squeeze off of plastic pipe and tubing used to transmit gas or fluid.

Abstract: A fixation assembly for bone fixation and a method for joining bones or bone fragments of a single bone and translating uniform compression to the bones. The fixation assembly comprises a post member coupled to a screw member. The post member comprises a head portion connected to an anchoring portion, wherein the head portion is offset from the anchoring portion by a first angle. The head portion may comprise a curved body annularly extending from a first end to a second end, wherein the first end is separated from the second end by a slot, and wherein the curved body defines a tapered annular bore therein. The anchoring portion comprises a first leg extending from the first end of the curved body and a second leg extending from the second end of the curved body. The screw member comprises a tapered bulbous portion connected to a threaded elongated portion.

Abstract: A patient-specific navigational guide (1, 1?) for use in spinal surgery, comprises two tubular guiding member (2) extending from a proximal opening (2a) and a distal opening (2b) for guiding a surgical operation on a patient's vertebra (100, 100?). The two tubular guiding members are integral with a bearing frame (3) comprising at least five contact members (11, 15, 16) designed to match with a corresponding plurality of contact areas on the patient's vertebra (100, 100?) in order to define a unique coupling configuration of the patient-specific navigational guide (1, 1?) on the patient's vertebra (100, 100?).

Abstract: An apparatus for coupling with a fixation rod to allow spinal compression, distraction, and fixation along an antero-lateral aspect of a spine includes an elongated plate, first and second fixation screws, and a first arm. The elongated plate includes a first aperture at a superior end and a second aperture at an inferior end. The first fixation screw is received by the first aperture and engages a first body portion of a first vertebra. The second fixation screw is received by the second aperture and engages a second body portion of a second vertebra. The first arm extends transversely from a first base portion on the elongated plate and includes a first hook to couple with a first portion of the fixation rod.

Abstract: A bone hook having a displaceable jaw is provided. The hook includes a rod receiving portion and main body with a jaw defining a slot for receiving a bone, and an actuator configured to vary the dimension of the slot. The actuator is configured to translate a rotation into an adjustment of a height of the slot thereby gripping or clamping a pedicle, lamina, or transverse process bone between the jaw and main body.

Abstract: A spinal implant for immobilizing the C1 vertebra with respect to the C2 vertebra of the spine provides controlled coupling between the C1 and C2 vertebrae, and includes a C1 component attachable to the C1 vertebra, two C2 components attachable to the C2 vertebra, and a transverse element. The C1 component has two wings each of which retains a rod holder that rotates and translate for capturing a C2 component rod. Each C2 component has a hook for connection with a side of the C2 vertebra lamina and a rod for attachment to one of the rod holders of the C1 component. Each C2 component receives and secures the transverse connector which holds position of the C2 components relative to one another. Each C2 component may include a plate configured for compression against the C2 vertebra spinous process, with each plate including spikes to aid in preventing construct migration.

Abstract: A spinal fixation system includes a rod and anchor devices that include a bone engaging fastener having a head defining a spherical socket. A ball insert is placed within the socket and rotated so that the ball insert is juxtaposed with the socket. The anchor device further includes a yoke defining a yoke channel for receiving the rod and a stem engaged to the ball insert captured within the socket. A sleeve disposed between the yoke channel and the fastener head supports the rod. A set screw is operable to clamp the rod against the sleeve and draw the insert into engagement within the socket. A releasable detent defined between the yoke and the fastener head is configured to releasably retain the yoke in at least one discrete position relative to the fastener. Portions of the releasable detent may also exert a frictional retention force against the fastener head.

Abstract: The present invention relates to a fixation device for a correction bar used in the operation of pectus excavatum, and more particularly, to a fixation device for securing the correction bar inserted into a thoracic cavity to a rib in an operation of correcting pectus excavatum, which a sort of thoracic malformation. The fixation device of a correction bar used in the operation of pectus excavatum includes a plurality of rib fixation units fastened to the correction bar and each having a rib support portion and a fastening portion formed at both ends thereof, the rib support portion being formed of a hook portion bent in such a manner as to be hooked and secured to a rib, and the fastening portion being formed of a rectangular through-hole or a slot; and a fastening screw unit adapted to fasten the plurality of rib fixation units hooked and secured to upper and lower ribs to the correction bar through the respective fastening portions of the plurality of rib fixation units.

Abstract: A receiving part for connecting a shank of a bone anchoring element to a rod. The receiving part has a first end, a second end and a recess having a substantially U-shaped cross section. The recess extends from the first end in a direction of the second end forming two legs open at the first end. The recess defines a channel to receive the rod. The channel has a longitudinal axis. The legs have an inner thread to receive a securing element having an outer thread cooperating with the inner thread. The legs are provided with stiffening structures. In one embodiment, the stiffening structures are formed by the wall thickness of the outer edges of the legs being larger than the wall thickness of the legs at a location closest to the central axis of the receiving part.

Abstract: The present invention provides a pedicle screw for spinal fixation having a bone fastener portion a permanent rod coupling, a breakaway portion connected to the permanent rod coupling and a temporary rod coupling. A permanent rod can be positioned in the permanent rod coupling and a temporary rod can be positioned in the temporary rod coupling and when the temporary rod is not needed the temporary rod coupling can be removed by separation at a breakaway portion.

Abstract: The present invention includes a pedicle screw made with a bone fastener and a rod coupling head, the rod coupling head comprising an upper rod coupling: the lower rod coupling having a lateral rod opening adapted to receive a permanent rod; an angled bore extends into the lateral rod opening; and a permanent rod fastener in the angled bore to engage a permanent rod in the lateral rod opening; and a upper rod coupling having an upper rod opening adapted to receive a temporary rod, wherein the upper rod opening is formed to receive a temporary rod fastener; wherein the upper rod coupling is detachable from the lower rod coupling at a transition and a temporary rod is temporarily affixed into the upper rod opening during a bone realignment and a permanent rod is positioned in the lateral rod opening and engaged by the permanent rod fastener upon final bone alignment.

Abstract: A surgical hook insertion device includes an elongate body defining a lumen therethrough and an actuation assembly. The elongate body has a retaining portion configured and dimensioned to releasably retain a laminar hook therein. The actuation assembly includes an actuation rod and an actuator member. The actuation rod is slidably disposed within the lumen of the elongate body. The actuator member is operatively coupled with the actuation rod and is slidably mounted on the elongate body, wherein the actuation assembly is transitionable between a first position in which a portion of the actuation rod engages the laminar hook releasably disposed in the retaining portion and a second position in which the actuation rod disengages the laminar hook.

Abstract: A polyaxial screw assembly includes an internal load dampening mechanism for sharing and dampening loads between at least one screw member and at least one rod member interconnected by the assembly. A method of interconnecting the orthopedic screw with the rod includes dampening with a body member interconnecting the screw to the rod.

Abstract: An axial spinal rod connector includes a central connector and first and second portions. The first and second portions are each integrally formed with the central connector to define a longitudinal axis. Each of the first and second portions includes an outer end portion and a set screw. The outer end portion defines a passage about the longitudinal axis and defines a blind hole orthogonal to the longitudinal axis. The blind hole extends into the passage. The passage is sized and configured to slidably receive a spinal rod. The set screw is sized and configured to engage the blind hole. The set screw at lease partially interfering with the passage when engaged with the blind hole to fix a spinal rod relative to the spinal rod connector.

Abstract: A tool set for implanting a rod in a human spine in conjunction with bone screws. The tool set includes a pair of end guide tools that receive opposite ends of the rod in channels and under manipulation by a surgeon facilitate transport of the rod toward the bone screws attached to the guide tools. Intermediate guide tools having guiding pass through slots are utilized to guide intermediate locations along the rod toward associated bone screws. An attachment structure operably connects the guide tools to the bone screws. The guide tools each include a lower guide and advancement structure to allow a closure top with mating structure to be rotated and driven downward against the rod and to cooperate with similar structure in the bone screw to seat and lock the rod therein. A method utilizing the tool set allows a surgeon to percutaneously implant the rod in the patient.

Abstract: A surgical system and method for fusionless correction of a spine disorder are provided. The method comprising the steps of: providing access to a spine; providing a longitudinal element extending between a first end including a first fixation element and a second end including a second fixation element; engaging the first fixation element with a first costovertebral surface and engaging the second fixation element with a second costovertebral surface such that the longitudinal element is disposed in a costotransverse orientation along a selected section of the spine; and preventing growth of the selected section of the spine with the longitudinal element.

Abstract: A stabilization system for the spine that includes an elongated member, preferably an elastic cord, and a plurality of attachment mechanisms, preferably lamina hooks. The stabilization system is configured to extend across a plurality of spinal motion segments to dynamically couple the motion segments in a manner that places the system in tension to apply a compression force to the posterior of the spine. The system and method may have particular application after a laminectomy or laminoplasty procedure.

Abstract: Apparatus and devices for percutaneously extending an existing spinal construct ipsilaterally with an additional spinal construct in a patient are disclosed. The additional spinal construct comprises a rod connector that includes an elongate additional rod integrally attached thereto. The additional rod is placed through an access port in a first orientation generally parallel to the longitudinal axis of the access port and rotated to a different second orientation generally transverse to the longitudinal axis of the access port. During such rotation the additional rod is moved subcutaneously beneath the skin of the patient from the existing spinal rod to an additional bone engaging implant. In another arrangement, the extension of an existing spinal construct in a minimally invasive procedure comprises a rod connector having an offset support for receiving an additional spinal rod that may be placed laterally interiorly or exteriorly of the existing spinal construct.

Abstract: Embodiments of the present invention are directed toward a system of apparatuses to correct spinal deformities along with associated surgical techniques. The apparatuses comprise passages or channels in which spinal rods of differing diameters may be secured to allow a surgeon to vary the diameter of rods used along the length of the spine. Additionally, embodiments of the present invention are directed toward instrumentation for reduction of spinal rods into spinal pedicle screws.

Abstract: Anchor for attachment to a bony structure, comprising a hook, an anchor body with a distal wall facing the hook, and a fastening system for fastening a connection member to the anchor body. A slot is defined between the hook and the distal wall, for receiving a bony structure such as a vertebra portion. The anchor further comprises a retention member having a distal end with teeth, passing through the distal wall and being movable relative to the anchor body, from a retracted position to a protracted position where the distal end protrudes from the distal wall, inside the slot. The proximal end of the retention member defines a seat for the connection member.

Abstract: A transverse fixation device is disclosed. The device includes one or more connecting bodies disposed substantially between two elongate rods. Each connecting body includes a receptacle that is capable of engaging with the two elongate rods. A c-ring comprising an outer surface having a spherical curvature is also included. A third rod may be inserted into the c-ring. A clamp included in the connecting bodies may then be disposed about the c-ring and third rod to allow the connecting bodies to slidingly engage with the third rod.

Abstract: An adjustable rod for spinal corrective surgery is provided that includes a first elongate member and a second elongate member, each having rod portions couplable to one or more bone connecting elements and expansion portions slidably moveable with respect to one another. A plurality of holes in each expansion portion are alignable with one another to choose the length of the adjustable rod and a locking element is inserted through a pair of aligned holes to couple the first and second elongate members and secure or fix the length of the expandable rod.

Abstract: A spinal fixation system includes a rod and anchor devices that include a bone engaging fastener having a head defining a spherical socket. A ball insert is placed within the socket and rotated so that the ball insert is juxtaposed with the socket. The anchor device further includes a yoke defining a yoke channel for receiving the rod and a stem engaged to the ball insert captured within the socket. A sleeve disposed between the yoke channel and the fastener head supports the rod. A set screw is operable to clamp the rod against the sleeve and draw the insert into engagement within the socket. A friction element in the form of a wave spring is disposed between the yoke and the fastener head is configured to releasably retain the yoke in at least one discrete position relative to the fastener.

Abstract: This equipment comprises at least one anchoring assembly including two antagonistic hooks connected to each other through a rod, a first of these hooks having a body crossed by a hole for letting through the rod and being able to be connected to connection means with which the anchoring assembly may be connected to another part of the equipment; said body has an aperture laid out substantially perpendicularly to the axis of said hole, communicating with this hole, and the anchoring assembly has a tightening member which may be engaged into this aperture until it abuts against the rod engaged in the hole, and tightened in order to immobilize this rod in this hole. Said tightening member is directly connected to a part belonging to said connection means, which allows the mounting of the latter on the body of said first hook.

Abstract: A spine stabilization system including a first anchor, a second anchor and a rod for connecting the first and second anchors together. The first anchor includes an anchor body and a hook. A slot is defined between the hook and a first wall of the anchor body, facing the hook, the slot being configured to receive a bony structure. The first anchor further comprises a flexible member having first and second ends, and an intermediate portion therebetween. The anchor body is provided with an exit passage from which the first and second ends extend, and a loop passage going through the first wall and facing the hook, the intermediate portion extending from the loop passage to form a loop going through the slot and around the bony structure.

Abstract: A spinal construct comprises a longitudinal member extending between a first end and a second end and including an intermediate portion. A construct member includes a first surface and a second surface movable relative to the first surface in a configuration for connection with a first portion of vertebral tissue. The construct member defines an implant cavity configured for disposal of the first end. Systems and methods are disclosed.

Abstract: The present invention provides an implant that can be inserted on top of a previously placed spinal fixation element. The implant includes a bone anchor and a connector body. The bone anchor includes a proximal head and a distal shaft extending along a longitudinal axis configured to engage bone. The connector body is configured to engage the proximal head of bone anchor and engage a spinal fixation element offset from longitudinal axis of the bone anchor shaft. Because, the implant is inserted over the spinal fixation element, direct visualization of the surgical site is available during insertion. In addition, the implant may provide tactile or audible feedback indicating that the spinal fixation element has been engaged by the implant.

Abstract: A spinal hook includes a hook member, an inner collet, and an outer portion. The hook member includes a head portion and a blade portion. The inner collet includes a base portion configured to rotatably engage the head portion and a pair of engaging portions defining a slot configured to receive a connecting rod therein. The outer portion is movable relative to the inner collet between a locked position in which the outer portion causes the pair of engaging portions to move toward each other and an unlocked position in which the outer portion causes the pair of engaging portions to be spread apart to facilitate insertion or removal of the connecting rod.

Abstract: Disclosed herein are a hook with rotating saddle and a rotatable mono axial pedicle screw. In an embodiment, the disclosed hook may include at least one body comprising a hook member and a saddle member. The hook member and saddle member may be rotatably mounted to one another so as to rotate with respect to each other only about a common axis, and the saddle member may be configured for connection to an end of a connecting member. A surgical screw system may include receiver and screw members engagable with one another such that when engaged, only rotation of the receiving member about the longitudinal axis of the screw member and restrain against substantially all other translational or rotational movement.

Abstract: A vertebral stabilization device operable for stabilizing and/or decompressing a portion of the spine, including: a first frame member; a second frame member; a first connector member engaged to the first frame member for securing the first frame member to a first structure of the spine; and a second connector member engaged to the second frame member for securing the second frame member to a second structure of the spine; wherein the first frame member and the second frame member are in a telescoping relationship with each other. The first and second structures of the spine may include spinous processes, laminae, sacral structures, or any other suitable structures. Preferably, the first connector member and the second connector member are substantially arcuate in shape, and may face towards each other, away from each other, or in the same direction.

Abstract: A connector assembly for translateral linking of bilateral spinal fixation rods includes first and second components. The first component has an elongated body having first and second ends, and the first end of the first component is configured to connect to a first spinal fixation rod. The second component has an elongated body having first and second ends, and the first end of the second component is configured to connect to a second spinal fixation rod. The second end of the first component is configured to be slidably connected to the second end of the second component.

Abstract: One exemplary device includes a main body including a shaft having a longitudinal axis; a first clamping mechanism having first and second jaws configured to clamp a spinous process of a first vertebra, and a second clamping mechanism having third and fourth jaws configured to clamp a spinous process of a second vertebra. The first, second, third and fourth jaws extend transversely from the shaft and at least two of two of the jaws are releasably mounted to the shaft and are mountable to and removable from the shaft by relative movement between the respective jaw and the shaft in a direction normal to a longitudinal axis of the shaft.

Abstract: A spinal correction system includes at least one longitudinal element extending between a first portion and a second portion. At least one fixation element includes a first end and a second end that is configured for penetrating tissue. A coupling member is configured for disposal about the at least one longitudinal element. The coupling member includes a first part and a second part being movable relative to the first part between a first orientation and a second orientation such that an inner surface of the parts are fixed with the at least one longitudinal element. The parts include an outer surface such that in the second orientation, the coupling member is configured for a snap fit engagement with the at least one fixation element such that the parts are fixed with the first end. Methods of use are disclosed.

Abstract: A transverse fixation device is disclosed. The device includes one or more connecting bodies disposed substantially between two elongate rods. Each connecting body includes a receptacle that is capable of engaging with the two elongate rods. A c-ring comprising an outer surface having a spherical curvature is also included. A third rod may be inserted into the c-ring. A clamp included in the connecting bodies may then be disposed about the c-ring and third rod to allow the connecting bodies to slidingly engage with the third rod.

Abstract: A hook for attaching a surgical rod to a vertebra includes a rod-receiving portion, a base portion, and a tip portion. The rod-receiving portion includes a pair of side walls that form a channel for receiving the surgical rod. The base portion extends distally from the rod-receiving portion and includes a first flow path extending therethrough. The tip portion extends away from the rod-receiving portion to form a hook portion for attaching to the vertebrae. In other features, the hook includes a second flow path extending through the tip portion.

Abstract: A determination oxygen storage amount used to determine whether a catalyst is degraded is a value obtained by applying a correction amount for removing error caused by response delay time of an output signal of an oxygen sensor to an oxygen storage amount calculated every short time. The correction amount is a value that is calculated using slopes stored in memory, i.e., the slopes for the number of storage cycles (>the short time) corresponding to the response delay time, or the like, and becomes more accurate as a value corresponding to the error as the storage cycle becomes relatively shorter with respect to the response delay time and the number of the slopes stored in the memory increases. The necessary storage capacity of the memory is inhibited from increasing excessively even if the number of the slopes stored in the memory is large.

Abstract: A device useful for spinous process decompression includes a pair of prongs which can be moved apart from each other by rotation of a gear which mates with a threaded rod.

Abstract: Various devices and methods are provided for spinal augmentation. In particular, the device can includes a connector element having a superior portion and an inferior portion that is adapted to support adjacent superior and inferior vertebrae and a first superior seating member and a second superior seating member associated with the connector element. The first seating member can be adapted to receive a portion of a lamina of the superior vertebra and the second seating member can be adapted to receive a portion of the lamina of the inferior vertebra. The device can have a variety of configurations, including the connector element and the first and second seating members being unitary and the first and second seating members being separately secured to the connector element.

Abstract: A spinal rod cross connector assembly for connection to adjacent spinal rods provides polyaxial positioning of polyaxial heads of the cross connector assembly relative to each spinal rod and which allows adjustment and fixation of the span of a cross connector or arm of the cross connector assembly between the two polyaxial heads through movement of the cross member relative to only one polyaxial head. Each polyaxial head has a clamp that provides attachment to the respective spinal rod and which allows the body of the polyaxial head to rotate relative thereto. Fixation of the orientation of a polyaxial head is achieved through placement and interaction of a set screw in the polyaxial head. The arm is preferably integral with and extends from a lateral side of one of the polyaxial heads. The second one of the polyaxial heads receives the arm and allows length adjustment relative thereto.

Abstract: A spinal implant provides support for desired parts of the spine. The implant can provide support in fusion situations. The spinal implant includes a pair of longitudinal rods and a transverse rod. A pair of variable cross-link devices couple the transverse rod, respectively, to the first and second longitudinal rods. Each variable cross-link device includes a body, having a curved member, a plug, and a rod engaging member. Fastening the plug into the body of the respective variable cross-link device causes application of force that couples the plug and the rod engaging member to the respective longitudinal rod. Fastening the plug also causes application of force that couples the rod engaging member to the transverse rod. Furthermore, fastening the plug causes application of force that couples the respective longitudinal rod to couple to the variable cross-link device. The surgical procedure may use minimally invasive surgery or non-minimally invasive surgery, as desired.

Abstract: This equipment (1) comprises vertebral anchoring members (2), at least one rigid bar (3) for supporting the vertebrae, parts (4) of this(these) bar(s) (3) for connection to these anchoring members (2), and at least one assembly (10) with two antagonistic hooks (15, 16) connected to each other through a linking rod (17), a first one of these hooks (15) comprising a member (11) for its connection to a supporting bar (3). According to the invention:—the second hook (16) of said assembly (10) comprises a connecting member (11) for connecting to said supporting bar (3), and—this supporting bar (3) has a length such that it extends, after assembly on said vertebral anchoring members (2), along the connecting members (11) of both hooks (15, 16) of said assembly (10), and such that it can be connected to these connecting members (11).

Abstract: An occipital clamping hook assembly includes a hook for engaging a first side of an occipital bone and a compressor movable relative to the hook for applying a compressive force to the occipital bone from a second side of the occipital bone. The occipital clamping assembly further includes a rod-receiving portion coupled to the hook for coupling a rod to the occipital bone engaged by the hook.

Abstract: An implant has a first hook and a second hook. A connector is coupled to the first and second hooks. The implant is adapted in a preferred embodiment to hook and look onto a spine.

Abstract: A connector for a spinal alignment system includes a base, a hook, a guide aperture, and a locking portion. The base includes a channel extending therethrough to receive a fixation rod. The hook extends from the base. The guide aperture is adapted to receive a bone fastener and the locking portion is adapted to engage the bone fastener. The guide aperture extends through one of the base and the hook and the locking portion is located in the other of the base and the hook. The locking portion is coaxial with the guide aperture such that the guide aperture guides a shaft of the bone fastener into alignment with the locking portion when the bone fastener is received by the guide aperture. The bone fastener cooperates with the base and hook to form a tension band construct that resists opposing forces acting on the construct. A rod locking fastener engages the channel and the fixation rod to secure the fixation rod in the channel.

Abstract: A prosthesis assembly replaces a cephalad portion of a left natural facet joint on a vertebral body and a cephalad portion of a right natural facet joint on a vertebral body. The prosthesis assembly has a left prosthesis body accommodating fixation to the vertebral body at or near a left pedicle and without support by a lamina. An artificial left facet joint structure carried by the left prosthesis body and is adapted and configured to replace a cephalad portion of the left natural facet joint. The prosthesis assembly further has a right prosthesis body accommodating fixation to the vertebral body at or near a left pedicle and without support by a lamina. An artificial right facet joint structure is carried by the right prosthesis body and is adapted and configured to replace a cephalad portion of the right natural facet joint.