Abstract: An anchoring system for a spinal support rod. The anchoring system includes a self-tapping orthopedic fastener that is bored through the ilium via a lateral incision and a mounting receiver that is positioned to receive the orthopedic fastener via a posterior incision. The orthopedic fastener may be implanted from a lateral approach or a posterolateral approach. The mounting receiver may be implanted from a posterior or superior posterior approach.

Abstract: A transpedicular anchoring screw including a screw body having a first helical thread having:includes a proximal portion, having notched portions inscribed within notched angular sectors and separated by separation portions inscribed within separation angular sectors, where, over a screw pitch, a ratio between the sum of the measurements of the separation angular sectors and the sum of the measurements of the notched angular sectors is between 50% and 150%. The anchoring screw also includes a distal portion, having notched portions inscribed within notched angular sectors and separated by separation distal portions inscribed within separation angular sectors, where, over a screw pitch, a ratio between the sum of the measurements of the separation angular sectors and the sum of the measurements of the notched angular sectors is between 0% and 10%.

Abstract: A system for reducing deformities of the vertebrae in the spine includes a first reduction assembly, a second reduction assembly, and a reduction drive assembly. The first reduction assembly is configured for attachment to a first reduction tower that attaches to a first vertebra. The second reduction assembly is configured for attachment to a second reduction tower that attaches to a second vertebra. The reduction drive assembly includes an arcuate rack gear operably coupling the first reduction assembly to the second reduction assembly to translate the first reduction assembly relative to the second reduction assembly along an arcuate path in a first plane.

Abstract: A system includes a screw tower, an instrument, and a housing. The instrument includes a driver shaft extendable longitudinally through the screw tower, and a threaded sleeve mounted on a proximal portion of the driver shaft. The housing includes one or more retention members coupleable to the screw tower, and a threaded button threadably coupleable to the threaded sleeve. The threaded sleeve is rotatable about a longitudinal axis to urge the driver shaft longitudinally relative to the screw tower.

Abstract: A low-profile offset-type spinal fusion device includes a first screw, a connection base, a nut and a compression part. The first screw has an external thread and a flange. The connection base includes a penetration part and a connection part disposed no higher than the penetration part, and can sleeve the first screw through a first hole of the penetration part to contact the flange with opposite ends of the first screw protruding out of the first hole. The nut, used to engage the first screw, has a bottom surface to contact against the penetration part. When the first screw is installed by penetrating the first hole, the nut and the flange are located to opposite ends of the first hole. The compression part is to screw into a cavity of the connection part for depressing a connecting bar tightly in the cavity.

Abstract: This invention relates to devices and methods for the electrochemical removal of unwanted deposits in humans and animals, or for prevention of bone loss following implantation of metal and other surgical materials in the body. A selected voltage is applied using direct current and an electrode to discourage growth or remove deposits, including bone spurs, and may be applied using microneedles in skin contact with a human or animal.

Abstract: An ultrasonically assisted clamping system and method for extending a spinal support rod system to additional vertebrae of the spine. A clamp assembly and a receptacle assembly securely couple an additional extension rod to an existing spinal support rod. Various embodiments further include an ultrasonic assist for cutting through tissue that may be present in the vicinity of the existing spinal support rods. In some embodiments, the clamp assembly is configured to augment the ultrasonic aspect of the system. The system cuts through and locally removes tissue from and proximate to the spinal support rods where the clamp assembly is to be mounted, without the need for a separate surgical procedure for removing the tissue prior to implantation, thereby providing a secure clamping of the newly implanted extension rod to the existing base spinal support rod.

Abstract: A bone fixation assembly may include an elongate fixation member and a flexible tensioning element. The elongate fixation member may include a central longitudinal axis, a distal portion couplable to a first bone fragment of a bone, and a proximal portion couplable to a second bone fragment of the bone to provide fixation of the second bone fragment relative to the first bone fragment. The flexible tensioning element may be couplable to the proximal and distal portions of the elongate fixation member to secure the elongate fixation member to the bone. The flexible tensioning element may be configured to span a bone fracture intermediate the first bone fragment and the second bone fragment to preload the bone fracture in compression to resist tensile force imparted across the bone fracture, thereby maintaining fixation of the first bone fragment relative to the second bone fragment.

Abstract: A bone fixation assembly includes a plurality of bone fixation elements that each include a bone anchor configured to be implanted into underlying bone, such as a vertebra. Each bone anchor is received in an anchor seat, and the anchor seats are joined by a fixation rod so as to operatively couple and fix the position and orientation of the vertebrae relative to each other. The bone anchor is free to rotate relative to the anchor seat, and is also free to pivot in a desired direction relative to the anchor seat.

Abstract: A polyaxial bone anchor has a locking element shaped and configured to allow an anchoring member (e.g., a screw or hook) to polyaxially rotate at large angles about a central axis of the bone anchor before compression locking the anchoring member within an anchor head.

Abstract: Connector assemblies, systems, and methods thereof. An articulating connector has a first end that clamps to a first rod in an existing construct and a second end having a second end that clamps to a second rod in a new construct or such that the new construct can be extended from the existing construct. In the case of different sized constructs used in different areas of the spine, an articulating connector has a first end that clamps to a first rod in a new construct having rods of a first size and a second end having a second end that clamps to a second rod in a new construct having rods of a second size. The clamping portions are capable of translating and rotating with respect to each other.

Abstract: A medical implant assembly including a receiver and a fastener. The receiver having helically wound thread extending up to a top surface thereof. The fastener having an axis of rotation and a continuously helically wound thread form. The continuously helically wound thread form having a start structure and an upper loading surface extending between a root and a crest of the continuously helically wound thread form. The start structure having a leading face extending below the upper loading surface. The leading face including a partial curvate surface extending between the root and the crest. The start structure being configured as a single lead start structure and a dual lead start structure.

Abstract: A pedicle screw implant construct kit, comprising at least one pedicle screw, at least one collar comprising a recess for receiving a rod, the collar configured to be coupled to a head of the pedicle screw, an elongated rod for connecting the collar to one more additional collars to couple between the pedicle screw and one or more additional screws, and a locking ring sized to be positioned over at least a distal portion of the collar to restrain relative movement of the screw head and rod by exerting radial compression force onto the collar. In some embodiments, the components of the kit are comprised of carbon reinforced composite material, optionally with no radiation blocking material. In some exemplary embodiments of the invention, the kit includes two locking rings on a collar, optionally both below the rod.

Abstract: Fiber-reinforced polymer matrix composite material bone screws having threads surfaced with a metallic layer are described. In some embodiments, the metallic layer comprises a plurality of anchors placed to engage with the composite material and resist shearing when the bone screw is inserted or removed.

Abstract: A vertebral body replacement device, dimensioned for implantation between a first and second vertebral bone is described. The vertebral body replacement device includes a superior endcap, an inferior endcap and a central core between the superior and inferior endcaps. The vertebral body replacement device further includes a fusion aperture extending through the superior and inferior endcaps and central core. The vertebral body replacement device is made of radiolucent material and can be implanted from a lateral or anterior approach to the spine.

Abstract: Disclosed herein are a spinal fixation assembly and method to provide adequate rigidity and support for a vertebral column without requiring additional pedicle screws and spinal rods. The spinal fixation assembly includes a spinal rod loop with multiple sides configured to be attached to a vertebral body with two or more pedicle screws. Each pedicle screw is adapted to fit at various locations along the spinal rod loop.

Abstract: A spinal screw assembly includes a bone screw having a head with a rounded outer surface and an anchor portion for fixation to the bone. The assembly also includes a body member defining an internal cavity communicating with a bottom surface of the body member through a lower opening, with an interior surface adjacent the lower opening configured to engage the rounded outer surface of the head of the screw, and an upper portion defining a channel for receiving a fixation rod. The screw head is configured for uploading into the cavity of the body member through the bottom opening until the rounded outer surface enters into pivotal engagement with the interior surface of the internal cavity, with the screw extending downwardly through the lower opening, so as to allow for variable angular movement of the bone screw relative to the body member prior to locking the spinal screw assembly with a closure.

Abstract: A modular head polyaxial pedicle screw assembly has a pedicle bone screw, a tulip, a split locking ring and a saddle. The screw has a head and a threaded shank. The split locking ring has a split ring body with one or more positioning tabs extending from a first surface of the split ring body. The split ring locking ring is configured to be placed internal of the tulip positioned in a recess, groove or undercut of an inner surface of the tulip. Upon assembly of the pedicle screw into the tulip, at least a maximum diameter of the head is positioned above the recess, groove or undercut allowing the split locking ring to be inserted into the recess or groove thereby securing the pedicle screw inside the tulip wherein the head of the pedicle screw abuts the one or more positioning tabs.

Abstract: An osteosynthesis device for the treatment of the spine is disclosed having a fork head which is U-shaped in a side view, and which fork head, in the proximal direction, has two fork legs with an internal thread and in which a connecting rod can be received, and a grub screw is passed through the internal thread, and the fork head is detachably connected to a bone anchor. The bone anchor is pivotably mounted in the ball seat of the fork head, wherein the fork head in the ball seat area has slots open towards the distal side and thereby at least one deflectable leg is formed.

Abstract: A construct may include a connector having a first body portion and a second body portion rotatably coupled to another. A first implant cavity may be defined, at least partly, by at least two threaded arm portions defining a first axis between the at least two threaded arm portions. The first implant cavity may include a first receiving cavity configured to adjustably orient a first rod in a plane substantially perpendicular to the first axis, and the second implant cavity may include a second receiving cavity configured to orient a second rod. In some embodiments, the threaded arm portions are configured to receive a first set screw such that when the first set screw is fully tightened along the first axis the first rod is fixed relative to the first body portion in a direction extending substantially parallel with the plane.

Abstract: A bone anchoring device includes a receiving part having a first end with an end surface, a second end, a recess at the first end for receiving a rod, and a flexible head receiving portion at the second end for pivotably holding a head of a bone anchoring element, and a clamping ring positionable around the head receiving portion and movable from a first position where the head is pivotable relative to the receiving part, to a second position where the clamping ring exerts a radial force onto the head receiving portion to lock the head. The receiving part further includes a first engagement structure at or adjacent the end surface extending radially outwardly from an outer surface of the receiving part, such that a width of the receiving part including the first engagement structure is at least as wide as a maximum width of the clamping ring.

Abstract: Treatment of spinal irregularities, including, in one or more embodiments, derotation apparatus and systems that can be used to reduce the rotation of vertebral bodies. Derotation apparatus that may comprise a tube assembly comprising an inner sleeve and an outer sleeve disposed over the inner sleeve. The inner sleeve may have a distal end for attachment to an implant. The tube assembly may further comprise a handle assembly. The tube assembly may further comprise a ball joint assembly disposed between the tube assembly and the handle assembly. The ball joint assembly may comprise a ball joint configured for attachment to a coupling rod. The ball joint assembly further may comprise a reducing extension below the ball joint, the reducing extension being sized to fit in a central bore of the inner sleeve. Orthopedic fixation devices comprising a ball joint are also disclosed.

Abstract: A polyaxial bone screw assembly includes a receiver having an axial bore with a pair of opposed downward-facing shoulder surfaces pre-formed therein between a discontinuous guide and advancement structure and a bottom opening, a shank having a capture portion configured for positioning into the axial bore with the shank extending downward through the bottom opening, and a pressure insert having upward-facing contact surfaces. The pressure insert is configured for positioning into the axial bore of the receiver into a first position and for subsequent rotation about a longitudinal axis by a tool into a second position that locates the upward-facing contact surfaces at least partially under the downward-facing shoulder surfaces to inhibit the pressure insert from moving upwardly within the axial bore.

Abstract: Systems and methods for reducing the risk of PJK, PJF, and other conditions are disclosed herein. In some embodiments, a longitudinal extension can be added to a primary fixation construct to extend the construct to one or more additional vertebral levels. The extension can be attached to a first attachment point, such as a bone anchor implanted in a vertebra that is superior to the primary construct. The extension can also be attached to a second attachment point, such as a component of the primary construct or an anatomical structure disposed inferior to the first attachment point. The extension can be more flexible than the primary construct and/or can limit motion to a lesser degree than the primary construct, thereby providing a more-gradual transition from the instrumented vertebrae to the natural patient anatomy adjacent thereto. The extension can be placed with little or no soft tissue disruption.

Abstract: The present invention relates to a connector for simultaneously fixing a screw head and a rod, wherein the connector can be firmly fixed to a screw head and a rod, which have been surgically inserted, without requiring disassembly of the screw head and the rod, thus minimizing damage to the affected region. The connector may comprise: a connecting block in which a head accommodation hole portion is formed on one side thereof to be able to accommodate at least a portion of a screw head installed in a vertebral body, and a rod accommodation groove portion is formed on the other side thereof to be able to accommodate at least a portion of a rod that extends from the screw head; a connecting rod formed in a shape extending from the connecting block; and a fixing device that fixes the connecting block to the screw head.

Abstract: The present invention is generally directed to orthopedic fixation devices that comprise a pre-assembled double headed tulip assembly, having two tulip elements to receive rods, wherein the assembly may be configured to receive a bone fastener in at least one of the tulip elements. At least one of the tulip elements may comprise a saddle and a ring to attach the double headed tulip to a bone fastener.

Abstract: A ratcheted spinal device including a variable-length member including a ratchet mechanism that has an operative configuration that allows a change in length of the variable-length member in one direction and prevents a change in length of the variable-length member in an opposite direction, wherein the variable-length member includes polyaxial-joint attachment members for attachment to bone, which permit pivoting movement of the attachment members about more than one pivoting axis.

Abstract: The present invention provides a sacral-iliac plate having an iliac portion with a first screw hole for receiving a first fastener to secure the iliac portion to the iliac bone. A sacral portion integrated monolithically with the iliac portion is also provided with a second and third screw holes for receiving second and third fasteners to secure the sacral portion to the sacral bone. The sacral portion also includes a tulip for receiving and securing a spinal rod.

Abstract: A polyaxial bone anchoring device is provided including a bone anchoring element (1) comprising a head (3) and a shank (2); a receiving part (4, 4?) for receiving a rod (100) for coupling the rod to the bone anchoring element, the receiving part comprising a first end (4a), an opposite second end (4b) and a central axis (C) extending through the first end and the second end, and a channel (9) for receiving the rod and an accommodation space (11) for receiving the head; a pressure element (6, 6?) arranged in the receiving part and configured to exert pressure onto the head; wherein the pressure element (6) comprises flexible sections (66a, 66b) facing away from the head (3), characterized in that the flexible sections (66a, 66b) comprise a free end portion (69a, 69b) with respect to the central axis (C) that cooperates with an inclined surface portion (15a, 15b) of the receiving part (4) such as to hold the pressure element (6) in a position in which it exerts a pre-load onto the head before the head is lo

Abstract: A connection assembly configured to securely connect a spinal implant to a bone anchor. In particular, a variable angle connection assembly that is able to securely connect the spinal implant to the anchors even when there is a variance in the angle and position of the anchors with respect to the spinal implant. Furthermore, a connection assembly that will not inadvertently lock the components of the connection assembly preventing the relative movement of the components.

Abstract: This disclosure describes example embodiments of rod reduction instrumentation and other rod and vertebrae manipulation instruments. The rod reducers can be used during the installation of a rod based surgical fixation system to help urge the rod into the fixation anchors. The reducers described provide various configurations delivering large reduction distance capabilities, strong controlled reduction coupled with an ability to quickly advance the reducer if desired, and reduction of bulk through the surgical corridor.

Abstract: A pivotal bone anchor assembly providing an adjustable securement of a fixation rod across at least two vertebrae. The assembly includes a pedicle screw having a spherical head portion, a threaded shaft portion, and a tool engagement surface in the head portion for use in driving the screw into a vertebra. The head portion of the screw is positioned in a body member adjacent an interior surface disposed about a bottom opening of the body member such that the shaft portion of the screw extends therethrough and the head portion engages the interior surface so as to provide for pivotal motion between the body member and the pedicle screw. The bone anchor also includes a bushing insertable into the body member and having an outwardly projecting structure that snaps under a downward facing abutment surface to maintain the bushing within the body member.

Abstract: Apparatus and methods for distracting and/or compressing bone. An exemplary apparatus may comprise a rod having a thread. The apparatus also may comprise a first assembly and a second assembly each coupled, or configured to be coupled, to the rod and each configured to be attached to a respective pin extending into bone. The apparatus further may comprise a nut engaged, or configured to be engaged, with the thread and configured to be turned to drive the second assembly along the rod. In some embodiments, at least one of the assemblies may have at least two degrees of rotational freedom that can be eliminated by manipulating a single graspable member. In some embodiments, the rod and the second assembly may have anti-rotation features configured to interact with one another to permit travel of the second assembly along the rod while preventing rotation of the second assembly about the rod.

Abstract: The present invention discloses a device for stabilization of bone segment and an extending assembly thereof. The device comprises a screw assembly, two supporting members and two extending members. The screw assembly comprises a receiver and an anchoring member. The receiver has a retainer and two opposite arms extending along the longitudinal axis of the device from the positions adjacent to the retainer. The anchoring member is connected to the retainer. The supporting members are connected to the arms respectively and extend along the longitudinal axis. Each one of the extending members has a through hole respectively. The extending members are connected to the arms with the supporting members passing through the through holes respectively.

Abstract: Surgical support instruments are described herein that can couple to, e.g., an implanted anchor and provide a platform for coupling other surgical implements thereto. In one embodiment, an instrument can include an elongate body having opposed projections extending laterally from a distal portion thereof that can at least partially surround a shank of an implantable anchor such that a longitudinal axis of the elongate body is laterally offset from a longitudinal axis of the anchor. The instrument can further include a lock configured to exert a drag force on a head of the anchor to control polyaxial movement of the instrument relative to the anchor. Further, a proximal portion of the elongate body can be configured to receive a retractor assembly including a plurality of tissue manipulating implements and selectively lock the retractor assembly at any of a plurality of positions along a length of the elongate body.

Abstract: A bone fixation system with variable z-axis translation is provided. The bone fixation system includes an outer tulip coupled to a bone fastener. An inner tulip, which provides a seat for an elongate fixation rod, is located inside the outer tulip. The inner tulip together with a seated rod is permitted to translate along the z-axis in an unlocked position. Also in the unlocked position, the bone fastener is free to angulate relative to the outer tulip. The bone fixation system includes a locked position in which the z-axis position of the inner tulip and rod relative to the outer tulip is fixed. Also in the locked position, the bone fastener is locked with respect to the outer tulip. The system may be adjusted between the locked and unlocked positions by way of a set screw or independently by rotation of the inner tulip relative to the outer tulip.

Abstract: Embodiments herein are generally directed to spinal implants for use in orthopedic stabilization assemblies. In some embodiments, these implants may be used in conjunction with laminoplasty or laminectomy procedures.

Abstract: A bone anchor system can comprise a fastener, a rod housing and a first directional component configured for connection to the fastener. The fastener can comprise a shaft having a shaft diameter, an anchoring projection on the shaft, and a head at an end of the shaft. The rod housing can be connected to the head of the fastener. The first directional component can comprise a first body portion having a first outer diameter larger than the shaft diameter, a first bore extending through the first body portion, the first bore sized to receive the shaft diameter, and a first locking component extending from the first body portion configured to engage the rod housing to limit movement of the housing.

Abstract: A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in an integral receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A friction fit compression insert (some with lock and release feature), a planar split retaining ring and a shank upper portion cooperate to provide for pop- or snap-on assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra. The shank and receiver once assembled cannot be disassembled and the receiver and insert may include aligned tool receiving apertures for lock and release of the polyaxial mechanism.

Abstract: A cervical polyaxial bone anchor includes a shank having an integral spherical head and a receiver having an upper channel for receiving a rod and a lower seat near a lower opening for receiving a closed retainer that includes a compressible upper portion engaged with the receiver seat and an expandable lower portion capturing the shank head. An outer sleeve slidable with the receiver prohibits expansion of the retainer lower portion during operation. A compression insert engages the retainer upper portion and is in friction fit with the shank head prior to fixing of an angle of the shank with respect to the receiver.

Abstract: A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in a receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. The upper portion expands a retaining member in the receiver cavity to capture the shank upper portion in the receiver. In some embodiment either the retaining member or an insert provide for a friction fit of the shank upper portion in the receiver resulting in non-floppy placement of the shank with respect to the receiver. Some retainers and inserts have a lock-and-release feature. Final locking of the polyaxial mechanism is provided by frictional engagement between the shank upper portion and the retaining member. A pre-assembled receiver, retaining member and optional insert may be popped-on or snapped-on to the shank upper portion prior to or after implantation of the shank into a vertebra.

Abstract: A spinal screw assembly providing an adjustable securement of a fixation rod across at least two vertebrae. The assembly includes a pedicle screw having a spherical head portion, a threaded shaft portion and a tool engagement surface in the head portion for use in driving the screw into a vertebrae. The head portion of the screw is positioned in a body member adjacent a curvilinear surface disposed about an aperture in the end of the body member such that the shaft portion of the screw extends therethrough and the curvilinear inner surface abuts and mates with the head portion of the screw so as to define a ball joint therewith. The body member additionally defines a pair of opposed parallel slots therein adapted to receive a portion of the fixation rod and a locking cap bears against the fixation rod to releasably secure the rod within the assembly.

Abstract: The present teachings provide one or more surgical implements for repairing damaged tissue, such as in the case of a spinal fixation procedure. A bone anchor is provided. The anchor can include a bone fastener. The bone fastener can include a head and a second end adapted to engage an anatomy. The bone fastener can extend along a longitudinal axis. The anchor can also include a coupling arrangement coupled to the head of the bone fastener so that the bone fastener is rotatable about the longitudinal axis to define a first plane of motion. The anchor can further include a saddle, which can be coupled to the coupling arrangement. The saddle can be movable relative to at least one of the bone fastener and the coupling arrangement to define a second plane of motion.

Abstract: Treatment of spinal irregularities, including, in one or more embodiments, derotation apparatus and systems that can be used to reduce the rotation of vertebral bodies. Derotation apparatus that may comprise a tube assembly comprising an inner sleeve and an outer sleeve disposed over the inner sleeve. The inner sleeve may have a distal end for attachment to an implant. The tube assembly may further comprise a handle assembly. The tube assembly may further comprise a ball joint assembly disposed between the tube assembly and the handle assembly. The ball joint assembly may comprise a ball joint configured for attachment to a coupling rod. The ball joint assembly further may comprise a reducing extension below the ball joint, the reducing extension being sized to fit in a central bore of the inner sleeve. Orthopedic fixation devices comprising a ball joint are also disclosed.

Abstract: A laminar fixation clamp has a body that utilizes a clam-shell style pivot controlled by a set screw, to grasp and attach to a spine rod, while receiving a laminar fixation band that can loop around a lamina of a vertebra in order to hold the laminar fixation clamp onto the vertebra. One form comprises a two-piece structure while another form comprises a single-piece structure. In each case, an upper and lower clamping structure situated at a front of the laminar fixation clamp, is received over and onto the spine rod, while a laminar fixation band is received through clamp. The set screw controls the amount of pivoting and thus the clamping force exerted onto the spine rod.

Abstract: A bone fastener comprises a first member defining an implant cavity. A part is connectable with the first member. A second member is configured to penetrate tissue and includes a mating surface engageable with the part. The part is engageable to selectively translate the implant cavity relative to the second member. Implants, spinal constructs, systems, instruments and methods are disclosed.

Abstract: A spinal screw assembly providing an adjustable securement of a fixation rod across at least two vertebrae. The assembly includes a pedicle screw having a spherical head portion, a threaded shaft portion and a tool engagement surface in the head portion for use in driving the screw into a vertebrae. The head portion of the screw is positioned in a body member adjacent a curvilinear surface disposed about an aperture in the end of the body member such that the shaft portion of the screw extends therethrough and the curvilinear inner surface abuts and mates with the head portion of the screw so as to define a ball joint therewith. The body member additionally defines a pair of opposed parallel slots therein adapted to receive a portion of the fixation rod and a locking cap bears against the fixation rod to releasably secure the rod within the assembly.

Abstract: Orthopedic fixation devices and methods of installing the same. The orthopedic fixation device may include a coupling element and a bone fastener, whereby the bone fastener can be loaded into the coupling element through the bottom of a bore in the coupling element.

Abstract: A polyaxial bone anchor has a locking element shaped and configured to allow an anchoring member (e.g., a screw or hook) to polyaxially rotate at large angles about a central axis of the bone anchor before compression locking the anchoring member within an anchor head.

Abstract: A spinal screw assembly providing an adjustable securement of a fixation rod across at least two vertebrae. The assembly includes a pedicle screw having a spherical head portion, a threaded shaft portion and a tool engagement surface in the head portion for use in driving the screw into a vertebrae. The head portion of the screw is positioned in a body member adjacent a curvilinear surface disposed about an aperture in the end of the body member such that the shaft portion of the screw extends therethrough and the curvilinear inner surface abuts and mates with the head portion of the screw so as to define a ball joint therewith. The body member additionally defines a pair of opposed parallel slots therein adapted to receive a portion of the fixation rod and a locking cap bears against the fixation rod to releasably secure the rod within the assembly.