STABILIZING BONES USING SCREWS AND RODS

An orthopedic fixation device for affixing the screw head of a polyaxial pedicle screw has a tulip, a saddle, and a ring. The tulip has an interior cavity and two opposed threaded arms and a lower ledge. The saddle is inserted into the tulip body, and has a U shaped groove for receiving a spinal fixation rod. The ring has a diameter that is smaller than the widest diameter of the screw head, and is formable into a diameter larger than the widest diameter of the screw head when the screw head is pushed into the ring. The ring has a connection portion that mates with a connection portion of the saddle. The screw head is clamped within the tulip body between the saddle and the ring when a cap is threaded between the tulip arms.

FIELD OF THE DISCLOSURE

This disclosure relates to stabilizing bones using screws and rods, and more particularly to screws with multiple threads and attaching modular fixation heads (“tulips”) after screw insertion.

BACKGROUND OF THE DISCLOSURE

Many types of spinal irregularities cause pain, limit range of motion, or injure the nervous system within the spinal column. These irregularities may result from, without limitations, trauma, tumor, disc degeneration, and disease. Often, these irregularities are treated by immobilizing a portion of the spine. This treatment typically involves affixing a bone screw to one or more vertebrae and connecting the bone screws to an elongate spinal rod that stabilizes members of the spine.

The screw may be a pedicle screw having a tulip head for coupling the screw to the elongate spinal rod. There exists a need for improved designs of the screws, instruments for implantation, and enhanced methods for placement and assembly of the devices.

SUMMARY OF THE DISCLOSURE

In an embodiment of the disclosure, an orthopedic fixation device for affixing the screw head of a polyaxial pedicle screw, includes a tulip defining a distal and proximal end and forming a tulip body forming an interior cavity, two opposed arms extending away from a proximal end of the body, cooperating threads disposed on mutually facing sides of each arm, and a ledge positioned at a distal end of the tulip body at an entrance to the cavity; a saddle defining a distal and proximal end, the saddle sized and dimensioned to be insertable into the tulip body, forming a U shaped groove on the saddle proximal end sized to receive a spinal fixation rod inserted between the tulip arms, and forming a curved surface on the saddle distal end sized and dimensioned to conformingly receive the screw head; and a ring for engaging the screw head, the ring positionable to form a first diameter smaller than the widest diameter of the screw head, positionable to form a second diameter larger than the widest diameter of the screw head when the screw head is passed into the ring, and positioned upon a proximal side of the tulip ledge; the screw head clampable within the tulip body interior cavity in a position between the saddle and the ring when the saddle is urged in a distal direction towards the tulip ledge.

In a variation thereof, the saddle is insertable into a distal end of the tulip body.

In another variation thereof, the device further includes a retaining ring positionable upon a proximal side of the tulip ledge, having a diameter larger than the diameter of the tulip ledge, and forming a ring engaging profile having a diameter smaller than a diameter of the tulip ledge; whereby the ring presses against the profile when the saddle is urged in a distal direction, to thereby prevent the ring from moving out of the cavity.

In a further variation thereof, the retaining ring has a gap formed therethrough, the retaining ring thereby insertable past the tulip ledge by winding the retaining ring past the tulip ledge; the tulip additionally forms a detent portion positioned distal to the threads upon an interior surface of the cavity, and the saddle additionally forms a detent portion mateable with the detent portion of the tulip to mutually releaseably connect the tulip and the saddle.

In a still further variation thereof, the saddle further includes a plurality of distally extending arms, the ring including at least two segments positionable mutually apart to form the second diameter when the screw head is passed therebetween, and the at least two segments being urged mutually together by the plurality of distally extending arms to position the at least two segments into the first diameter when the saddle is urged in a distal direction; and/or the tulip interior cavity includes tulip detent portions, and each of the at least two segments include clip detent portions mateable with the tulip detent portions to releasably retain the at least two segments apart to facilitate insertion of the screw head.

In further variations thereof, the ring is a torsion ring having cam lobes which engage the screw head to twist the ring and deflect the cam lobes to expand a diameter of the ring as the screw head is passed through the ring; the ring is integrally formed with the saddle, the saddle rotatable to form the second diameter to admit passage of the screw head into the saddle; the tulip ledge is formed as two intersecting openings having relatively different diameters; a set screw blocks rotation of the saddle after the saddle has been rotated to form the first diameter to engage the screw head; and/or wherein the ring is sheared as the screw head is passed through the ring to thereby expanded a diameter of the ring.

In another variation thereof, the ring: forms a peripheral axially extending profile forming a plurality of peripheral kerfs extending partially along the length of the of the axially extending profile, forms a ledge peripherally extending radially about, and extending inwards towards, an axial center of the ring, and includes a plurality of kerfs extending through the ledge enabling the ledge to form the second diameter.

In another variation, the device further includes a retaining ring: positionable upon a proximal side of the tulip ledge, having a diameter larger than the diameter of the tulip ledge, and forming a ring engaging profile having a diameter smaller than the diameter of the tulip ledge and dimensioned to receive the ring ledge and prevent the ring ledge from forming the second diameter.

In a further variation, the tulip: includes a second detent portion within the cavity, distal to the detent positioned distal to the threads; and the ring: forms a peripheral axially extending profile forming a plurality of peripheral kerfs extending partially along the length of the of the axially extending profile, forms a ledge peripherally extending radially about, and extending inwards towards, an axial center of the ring, includes a plurality of kerfs extending through the ledge enabling the ledge to form the first diameter and the second diameter, and forms a detent peripherally disposed about a proximal end of the ring, mateable with the second detent portion of the tulip.

In other variations thereof, the ring forms one or more axially extending kerfs; the tulip including at least one radially extending pin, the pin extending into a kerf of the ring as the ring is moved axially, the pin thereby guiding movement of the ring and blocking movement of the ring beyond an axially extending length of the kerf; and/or at least one kerf extending from a proximal surface of the ring and extending axially to a length less than an axial length of the ring, and at least one kerf extending from a distal surface of the ring and extending axially to a length less than an axial length of the ring, the ring thereby compressible about a proximal periphery and compressible about a distal periphery.

In yet further variations thereof, the ring includes a plurality of serrations on an exterior surface cooperative with an interior surface of the tulip cavity to reduce movement of the ring when a screw head is clamped; the plurality of serrations are disposed at an angle that is offset with respect to a central axis of the ring; the ring includes a radially extending flange, the tulip including a radially extending flange, the flange of the ring and the flange of the tulip engageable as the ring is moved axially to define an extent of axial movement of the ring; and/or the radially extending flange of the ring formed as a plurality of flexible digits each having at a free end a flange portion.

In another variation thereof, the ring forming one or more axially extending kerfs, the one or more kerfs enabling expansion of a distal peripheral end of the ring, the retaining ring including an internal profile shaped to contain the distal peripheral end of the ring and block expansion of the distal peripheral end of the ring when the distal peripheral end of the ring is seated within the internal profile; the ring engaging profile is disposed distally to the tulip ledge when the retaining ring is positioned upon the tulip ledge.

In another embodiment of the disclosure, an orthopedic fixation device for affixing the screw head of a polyaxial pedicle screw includes a tulip defining a distal and proximal end and forming a tulip body forming an interior cavity, two opposed arms extending away from a proximal end of the body, cooperating threads disposed on mutually facing sides of each arm, and a ramp positioned at a distal end of the tulip body at an entrance to the cavity; a saddle defining a distal and proximal end, the saddle sized and dimensioned to be insertable into the tulip body, forming a U shaped groove on the saddle proximal end sized to receive a spinal fixation rod inserted between the tulip arms, forming a mating connection portion on peripheral surface of a distal end; and a ring for engaging the screw head, the ring having a first diameter smaller than the widest diameter of the screw head, formable into an second diameter larger than the widest diameter of the screw head when the screw head is passed into the ring, including a mating connection portion mateable with the mating connection portion of the saddle, whereby the ring and the saddle are mutually releaseably connectable, and having a ramp cooperative with the ramp of the tulip; the screw head clampable within the tulip body interior cavity in a position between the saddle and the ring when the saddle is urged in a distal direction towards the tulip ledge and the ramp of the ring slides against the ramp of the tulip.

In variations thereof, the saddle is insertable into a distal end of the tulip body; the saddle and connected ring are insertable into a distal end of the tulip body when the saddle and ring are mutually connected; the tulip additionally forming a detent portion positioned distal to the threads upon an interior surface of the cavity, and the saddle forming a detent portion on a proximal end mateable with the detent portion of the tulip to mutually releaseably connect the tulip and the saddle; the ring forms one or more axially extending kerfs; the one or more axially extending kerfs dividing the ring into segments; the tulip includes at least one radially extending pin, the pin extending into a kerf of the ring as the ring is moved axially, the pin thereby guiding movement of the ring and blocking movement of the ring beyond an axially extending length of the kerf; and/or at least one kerf extending from a proximal surface of the ring and extending axially to a length less than an axial length of the ring, and at least one kerf extending from a distal surface of the ring and extending axially to a length less than an axial length of the ring, the ring thereby compressible about a proximal periphery and compressible about a distal periphery.

In other variations thereof, the ring includes a plurality of serrations on an exterior surface cooperative with an interior surface of the tulip cavity to reduce movement of the ring when a screw head is clamped; the plurality of serrations are disposed at an angle that is offset with respect to a central axis of the ring; the ring includes a radially extending flange, the tulip includes a radially extending flange, the flange of the ring and the flange of the tulip are engageable as the ring is moved axially to define an extent of axial movement of the ring; the radially extending flange of the ring is formed as a plurality of flexible digits each having at a free end a flange portion; and/or the mating connecting portion of the ring includes a curved proximal surface.

In another embodiment of the disclosure, an orthopedic fixation device for affixing the screw head of a polyaxial pedicle screw, includes a tulip defining a distal and proximal end and forming a tulip body forming an interior cavity, two opposed arms extending away from a proximal end of the body, cooperating threads disposed on mutually facing sides of each arm, and a ledge positioned at a distal end of the tulip body at an entrance to the cavity; a saddle defining a distal and proximal end, the saddle sized and dimensioned to be insertable into the tulip body, forming a U shaped groove on the saddle proximal end sized to receive a spinal fixation rod inserted between the tulip arms, forming a mating connection portion on peripheral surface of a distal end; and a ring for engaging the screw head, the ring having a first diameter smaller than the widest diameter of the screw head, formable into a second diameter larger than the widest diameter of the screw head when the screw head is passed into the ring, including a mating connection portion mateable with the mating connection portion of the saddle, whereby the ring and the saddle are mutually releaseably connectable, and positioned upon a proximal side of the tulip ledge; the screw head clampable within the tulip body interior cavity in a position between the saddle and the ring when the saddle is urged in a distal direction towards the tulip ledge.

In variations thereof, the saddle is insertable into a distal end of the tulip body; the saddle and connected ring are insertable into a distal end of the tulip body when the saddle and ring are mutually connected; and/or the tulip additionally forms a detent portion positioned distal to the threads upon an interior surface of the cavity, and the saddle forming a detent portion on a proximal end mateable with the detent portion of the tulip to mutually releaseably connect the tulip and the saddle.

In another variation thereof, the device further includes a retaining ring: positionable upon a proximal side of the tulip ledge, having a diameter larger than the diameter of the tulip ledge, and forming a ring engaging profile having a diameter smaller than a diameter of the tulip ledge; whereby the ring presses against the profile when the saddle is urged in a distal direction, to thereby prevent the ring from moving out of the cavity.

In another variation thereof, the retaining ring having a gap formed therethrough, the retaining ring thereby insertable past the tulip ledge by winding the retaining ring past the tulip ledge.

In a still further variation thereof, the ring forms a peripheral axially extending profile forming a plurality of peripheral kerfs extending partially along the length of the of the axially extending profile, forms a ramp peripherally extending radially about, and extending inwards towards, an axial center of the ring, and includes a plurality of kerfs extending through the ramp enabling the ramp to form the first and second diameter.

In other variations thereof, the ring forms one or more axially extending kerfs; the tulip includes at least one radially extending pin, the pin extending into a kerf of the ring as the ring is moved axially, the pin thereby guiding movement of the ring and blocking movement of the ring beyond an axially extending length of the kerf; and/or at least one kerf extends from a proximal surface of the ring and extends axially to a length less than an axial length of the ring, and at least one kerf extends from a distal surface of the ring and extending axially to a length less than an axial length of the ring, the ring thereby compressible about a proximal periphery and compressible about a distal periphery.

In yet further variations thereof, the ring includes a plurality of serrations on an exterior surface cooperative with an interior surface of the tulip cavity to reduce movement of the ring when a screw head is clamped; the plurality of serrations are disposed at an angle that is offset with respect to a central axis of the ring; the one or more kerfs enabling expansion of a distal peripheral end of the ring, the retaining ring including an internal profile shaped to contain the distal peripheral end of the ring and block expansion of the distal peripheral end of the ring when the distal peripheral end of the ring is seated within the internal profile; and/or the ring engaging profile is disposed distally to the tulip ledge when the retaining ring is positioned upon the tulip ledge.

In another embodiment of the disclosure, a pedicle screw comprises a head that has a rounded shape; a tool engagement disposed in an end of the head for engaging a tool for turning the screw; a shaft having a neck end and an insertion end, the head attached at the neck end; a first thread extending along at least a portion of the shaft; and a second thread extending along at least a portion of the shaft having the first thread, whereby the second thread forms a dual lead together with the first thread.

In variations thereof, the screw further includes a third thread forming a triple lead together with the first and second thread; the screw further includes a third thread and a fourth thread forming a quad lead together with the first and second thread; the minor diameter in the region of the quad lead is larger than the minor diameter in the region of only the first thread; the minor diameter in the region of both the first and second thread is larger than the minor diameter in the region of only the first thread; and/or the position of the dual lead along the shaft is determined by a position and extent of cortical bone into which the screw is to be inserted.

In other variations thereof, the position of the dual lead along the shaft is determined by a position of cortical bone of the pedicle into which the screw is to be inserted; the position of the dual lead along the shaft is determined by a position of cortical bone of the pedicle into which the screw is to be inserted, and the first thread extends along the insertion end and enters the cancellous bone of the body of the vertebra when the screw is inserted; the insertion end is pointed; the screw head is grooved; and/or the head forms a polyaxial screw head.

DETAILED DESCRIPTION OF THE DISCLOSURE

This written description uses examples to disclose the embodiments, including the best mode, and also to enable those of ordinary skill in the art to make and use the invention. The patentable scope is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

The description in the present application should not be read as implying that any particular element, step, or function is an essential or critical element that must be included in the claim scope. The scope of patented subject matter is defined only by the allowed claims. Moreover, none of the claims invokes 35 U.S.C. § 112(f) with respect to any of the appended claims or claim elements unless the exact words “means for” or “step for” are explicitly used in the particular claim, followed by a participle phrase identifying a function.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that can cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, sacrosanct or an essential feature of any or all the claims.

After reading the specification, skilled artisans will appreciate that certain features are, for clarity, described herein in the context of separate embodiments, can also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, can also be provided separately or in any subcombination. Further, references to values stated in ranges include each and every value within that range.

As used herein, the term “about” or “approximately” applies to all numeric values, whether or not explicitly indicated. These terms generally refer to a range of numbers that one of skill in the art would consider equivalent to the recited values (i.e., having the same function or result). In many instances these terms may include numbers that are rounded to the nearest significant figure. As used herein, the terms “substantial” and “substantially” means, when comparing various parts to one another, that the parts being compared are equal to or are so close enough in dimension that one skill in the art would consider the same. Substantial and substantially, as used herein, are not limited to a single dimension and specifically include a range of values for those parts being compared. The range of values, both above and below (e.g., “+/−” or greater/lesser or larger/smaller), includes a variance that one skilled in the art would know to be a reasonable tolerance for the parts mentioned.

Headings are provided for the convenience of the reader, and are not intended to be limiting in any way.

Additional aspects, advantages and/or other features of example embodiments of the invention will become apparent in view of the following detailed description. It should be apparent to those skilled in the art that the described embodiments provided herein are merely exemplary and illustrative and not limiting. Numerous embodiments or modifications thereof are contemplated as falling within the scope of this disclosure and equivalents thereto.

Embodiments of the disclosure are generally directed to orthopedic implants, assemblies, systems, instruments, and methods. Specifically, embodiments are directed to modular bone fastener assemblies configured to secure one or more spinal rods, installation instruments, and navigation methods. The modular bone fastener may include a modular screw configured to be inserted into bone with or without navigation and/or robotic assistance. One or more screw extender instruments may provide for secure attachment to and improved maneuverability of the modular screw. After screw installation, a modular head may be deployed and attached to the modular screw with or without navigation and/or robotic assistance. Navigational tracking of the procedure and/or a robotic system may be provided, for example, for accurate placement of the modular screw and/or tulip head, tracking of the vertebral bodies, assembly of the modular head onto the modular screw, and/or intraoperative feedback. These implants and instruments may be used in open and percutaneous approaches to the posterior spine with or without assistance of a navigation or robotic system. Although generally described with reference to the spine, it will be appreciated that the devices and systems described herein may be applied to other orthopedic locations in the body and other medical applications, such as trauma.

Overview

Referring now toFIGS.1-3, an orthopedic fixation device, implant, or bone stabilizing assembly100is shown according to one embodiment. The implant or bone stabilizing assembly100may include a tulip head or modular head120, a bone fastener or modular screw140, and a locking cap160(FIG.1) for securing a spinal rod180in the modular head120. In the case of a polyaxial assembly100, tightening the locking cap160compresses the rod180into the tulip head120, thereby restricting motion of the modular screw140and forming a rigid construct with the bone fastener at a desired angle. The modular screw140may be deployed independently from the modular head120. For example, the modular screw140may be first installed in bone and the modular head120may be later deployed and assembled onto the modular screw140during the surgical procedure. Alternatively, the modular head120and screw140may be pre-assembled prior to installation.

The tulip head120includes a body200and arms220that extend upwardly from the body200. A central bore240may extend through the tulip head120The opposed arms220may define a U-shaped channel, transverse to the bore240, sized and configured to accept the rod180. Each of the arms220has an interior surface defining a threaded portion260for engaging the threaded locking cap160. The outer surface of the tulip head120may define one or more tool engagement216, such as the groove shown, for holding and maneuvering the tulip head120with a suitable tool.

Rod180may be secured in the tulip head120with locking cap160. Locking cap160may define an outer threaded portion280configured to interface with the inner threaded portion260of the tulip head120The locking cap160may be in the form of a set screw with a drive recess300configured to be engaged by a driving instrument, which is able to insert and tighten the locking cap160in the tulip head120. The bottom of locking cap160may be flat or otherwise configured to ensure consistent contact with rod180.

Turning now toFIGS.4-5, bone fastener140may include a bone screw, anchor, clamp, or the like configured to engage bone. In the embodiment shown, bone fastener140is a modular bone screw140, such as a pedicle screw. The modular screw140extends from a proximal end with a screw head132to a distal end configured to engage bone. The modular screw140has a threaded shaft134connected to the screw head132by a neck portion136. It will be appreciated that the threaded shaft134may have a number of different features, such as lead(s), thread pitch, thread angle, shaft diameter to thread diameter, overall shaft shape, and the like, depending, for example, on the particular application, and as detailed herein. The assembly100of the disclosure can be used with a wide variety of such fasteners140as are previously known, hereafter developed, and as detailed in accordance with this disclosure.

Threaded shaft134may terminate at a tip142at the distal end, which may be blunt, pointed, or otherwise configured to engage bone. While the screw head132may have any general shape, in the case of a polyaxial fastener, at least a portion of the screw head132may have a curved or rounded surface in order to allow for rotational movement and/or angular adjustment of the bone fastener140with respect to a clamp within the tulip head120, for example as detailed herein, or as known in the art. For example, at least a portion of the screw head132may be shaped to form a portion of a ball or a sphere, for example as illustrated. The spherical screw head132may define one or more drive and/or engagement138in the head132, such as the surfaces shown, for example, that can be engaged by a screw-driving instrument or other device to turn the screw and drive the screw into body tissue. In one embodiment, the bone screw head132defines a hexalobular drive recess38for driving the screw140into bone. It will be appreciated that any suitably shaped tool drive engagement138may be provided. The screw head132can include grooves to improve grip during compression of the screw head within the tulip.

With further reference toFIGS.4-9, bone screws140include variations140A-140D which have multiple lead threads. InFIGS.4-6, bone screws140A and140B are threaded screws where the number of threads double towards the proximal/head132end of the pedicle screw, forming a ‘dual lead’, ‘two start’, or ‘double thread’ screw. A first thread begins near the distal end, and a second thread, begins at a distance away from the distal end, and can have a start 180 degrees offset from the start of the first thread. Both the first and second threads continue together to terminate near neck136.

FIG.5Adiagrammatically illustrates bone screw140B in a position within a vertebra424, showing the multithreaded portion144located within cortical bone of the pedicle. It should be understood that multithreaded portion144as illustrated is sized to optimize deployment within the pedicle, however depending upon various anatomy within which bone screws of the disclosure may be used, which include bones other than vertebrae, multithreaded portion144may extend over other portions of the screw, or extend along the entire length of the screw.

FIGS.7-8are similar toFIGS.4-5, except that a quad lead thread is started after an initial length of dual lead thread. Cross-sections after the start of multiple threads are shown inFIGS.6and9, reflecting the embodiments ofFIGS.5and8, respectively. Two threads A and B are visible inFIG.6, and four threads A-D are visible inFIG.9. Providing multiple threads positions more threads within the most sturdy and high density bone structure, improving engagement, and resulting in increasing strength and resistance to toggling and pull-out. It should be understood that a triple threaded shaft can be formed in a like manner, or other multiple lead threads.

FIGS.5and8have a minor diameter (at base of the threads) in the multithreaded region that is larger than the minor diameter in the single threaded region, which the inventors have found increases the pullout/toggle strength. InFIGS.4and7, the minor diameter remains the same throughout both the single and multithreaded regions.

As the pitch throughout the single and double threaded regions are a ratio of each other, the entire threaded region advances into the body at the same rate, as screw140is turned. With multiple threads, the rate of insertion increases with additional threads, as the lead increases with each additional thread. For example, the dual threaded embodiment ofFIGS.4-5will be inserted with half as many turns as a single threaded screw, and the quad threaded embodiment ofFIGS.7-8will be inserted with one quarter as many turns as a single threaded screw.

The multi-threaded region144is sized and located along shaft134in order to correspond to an anticipated extent of cortical bone where screw140A/B/C/D is to be installed/implanted. The single threaded region is provided to facilitate insertion and/or to be disposed within more fragile cancellous bone once installed.

With further reference toFIG.3, and additional reference toFIGS.10-13, a bone stabilizing assembly100of the disclosure enables assembly of a screw140either before or after the screw has been installed. More particularly, screw140is retained when the saddle150is deployed to a down position interlocking saddle150and clip170, and is further clamped when locking cap160is tightened. Clip170is formed as two half-clips172. A distal ledge242retains clip170axially within tulip body200A, while half-clips172are each movable to translate radially towards an axial centerline of tulip body200A to form a contracted diameter and away from an axial centerline to form an expanded diameter. When saddle150is in the position shown inFIGS.10and13, a contracted diameter is formed. In this manner, as head132is pushed between half-clips172inFIG.11, half-clips172are forced apart by head132to form the expanded diameter, each half-clip172moving radially away from the axial centerline sufficiently to allow the widest portion of head132to pass into tulip body200A.

A spinal fixation rod180is placed into tulip bore240to rest within a rod-shaped portion152of saddle150, which provides consistent deformation and frictional contact with the rod for locking. Saddle150is disposed within an elliptical recess which aligns saddle150to receive the rod, and which prevents rotation of saddle150. Locking cap160is then threaded along arms220to drive rod180into portion152to thereby drive saddle150downwards towards the body into a locked position, as shown inFIG.13. After all components thus connected are positioned as therapeutically needed, cap160is securely tightened to thereafter retain a mutual relationship of the components.

More particularly, saddle150can be maintained in an unlocked position, as shown inFIGS.10A and12, by a detent154formed by saddle detent portion154B in saddle150and a mating tulip detent portion154A formed in tulip body200. Detent154is formed about part or all of a periphery of the saddle and tulip body. In the figures, detent154B (FIG.10/10A) is formed as a protrusion of saddle150and tulip detent154A as a recess, although these elements can be reversed, or another form of detent can be provided, for example a spring loaded ball or other movable part, as is known.

In an embodiment, detent154can provide an additional feature of maintaining a desired position of tulip body200once manually adjusted, for example to facilitate assembly of components into the tulip intraoperatively. More particularly, with reference toFIGS.10and13as examples, a detent slope154C is provided below tulip detent portion154A, which cooperates with saddle detent portion154B to compressively interfere with saddle detent portion154B to urge saddle detent portion154B downwards (as viewed) towards a locking position of saddle150and fastener140. An extent of force exerted and thus a stiffness of a connection between tulip body200and fastener140can be adjusted based upon an extent of interference between slope154C and saddle detent portion154B, and the angle of slope154C, each of which can be chosen to achieve stability of tulip body200in engagement with fastener140, while allowing for ready manual movement of tulip body200. This feature can be provided with other embodiments with detents described herein.

Saddle150is provided with locking prongs158which move to a position interposed between half-clips172and the tulip body when saddle150is moved to the locked position. As can be seen inFIG.10, in particular, prongs158can stop at ledge242, or as shown descend distally through a gap426in ledge242. Mating ramps or chamfers174and176on locking prongs158and half-clips172, respectively, guide the half-clips to translate radially inwards towards the central axis of tulip body200, to block screw head132from leaving tulip body200. Prongs158remain between half-clips172and tulip body200A when in the locked position, to prevent screw head132from being released.

Half-clips172are each provided with an inner screw head contacting surface178which is shaped to mate with screw head132to increase a contact area therebetween. For the same reason, a screw head contacting portion166of saddle150is shaped to mate with screw head132.

With reference toFIGS.11A-11B, which is a cross-section through half-clips172, it may be seen that half-clips172are each provided with two opposed detent portions168which each mate with a detent portion156C of tulip body200A, which detent portions cooperate to retain each half-clip in a radially outwards position to facilitate entry of screw head132. These mating surfaces further ensure an alignment of chamfers174and176as half-clips172translate radially inwards.FIG.11Adepicts the detent portions156C and168engaged with half-clips172translated radially inwards, blocking exit of screw head132.FIG.11Bdepicts detent portions156C and168engaged to retain half-clips in the radially outward position.

To release screw head132, saddle150is pushed or pulled away from screw head150, for example using a suitable tool, to allow half-clips172to once again translate perpendicularly with respect to the central axis, moving out of contact with screw head132and forming an expanded diameter allowing sufficient clearance for the widest portion of screw head132to pass out of tulip body200A.

With reference toFIGS.14-19, in an embodiment of the disclosure, a torsion ring320is provided with a peripheral cam surface328disposed upon cam lobe segments322, and a division324through the ring at a peripheral location. Ring320is disposed within a ring shaped chamber340positioned within tulip body200B at a distal or bottom end (as viewed) thereof. Chamber340is isolated and enlarged inFIG.15for clarity, in which it may be seen that chamber340is likewise provided with a cam surface342. A chamfer344is provided within an upper portion of chamber340to provide relief space for movement of cams lobe segments322. Ring320can be made of any biocompatible material of sufficient strength, flexibility, and durability, and which has a high elasticity. Examples include titanium or nitinol.

Division324of ring320can be provided to facilitate insertion of ring320into tulip body200B. More particularly, one end of ring320at division324can be passed into the interior cavity of tulip body200B, and the remainder of ring320can subsequently be threaded/wound into the interior.

In use, tulip body200B is pressed onto head132of screw140before or after screw140is installed within the body (FIG.17). As tulip body200B and head132are joined, screw head132contacts a distal or lower side (as viewed) of cam328causing distortion of torsion ring320due to pressure from head132(FIG.18). The distortion can have the form of torsional flexing or twisting. Insertion of head132through ring320can be facilitated by the narrowed diameter326adjacent to cam328, and the flexibility of the materials chosen for ring320.

After screw140has been inserted into tulip body200B, ring320can resume the ring resting shape as shown inFIG.17prior to screw head132insertion. In an embodiment, the resting state (FIG.17) is approximately halfway between up (FIG.18) and down (FIG.19) positions to minimize deformation of ring320from its neutral state and to minimize stresses. Further, the resting state provides a slanted contact surface which is more easily pushed aside as screw head132is inserted. Screw head132can then become secured in a desired position as described with respect to Embodiment 1, above, with the exception that locking prongs158are not needed.

More particularly, as saddle150is urged against head132by rotation of cap160, head132will eventually exert pressure against an upper surface of cam328, in an opposite direction of movement relative to insertion. As can be seen inFIG.19, when cam328rest against chamber cam surface342, ring320is twisted in a reversed or opposite direction with respect to twisting during insertion, until cams328contact chamber cam surface342, whereby cams328are pinched between head132and cam surface342, and no further twisting of torsion ring320is possible. As such, screw head132is prevented from moving any further in a direction out of tulip body200B.

Removal can be accomplished by unscrewing screw140, by inserting sleeve segments of a tool between screw head132and cam lobe segments322, or by using a suitable tool to pull tulip body200B relative to head132with sufficient force to overcome a force imparted by ring320and chamber cam surface132.

Cams328are shown separated into cam lobe segments322to provide additional flexibility. In an embodiment, cams328are disposed upon a continuously formed peripheral cam lobe that has the same cross-sectional shape as cam lobe segments322and which functions in the same manner, but is not divided into separated cam lobe segments by narrowed diameters326.

With reference toFIGS.20-25, bone stabilizing assembly100A includes a tulip body200C which includes a bottom (as viewed) or distal end244with two intersecting openings. With reference in particular toFIG.21, a first opening246is large enough for screw head132to pass into tulip body200C, and a second opening248is large enough for screw shaft134to pass, and to toggle at various angles, but which is too small for screw head132to pass. The intersection between the first and second openings is large enough to enable passage of screw shaft134therebetween.

In this manner, screw140can be loaded into tulip body200C, before or after screw140is installed in the body, by passing screw head132into first opening246, and translating screw140laterally to position screw head above second opening248. Screw head132can thereafter be prevented from again moving laterally over first opening246by being blocked, thereby locking screw head132within tulip body200C. Blocking is carried out by a saddle150A (FIG.25) which includes a lateral clamping face182positioned on a lateral extension184, which cooperates with a set screw186threadably retained in tulip body200C.

InFIG.22, saddle150A is rotated to align screw head contacting portion166of saddle150A with lateral portion166A pivoted away from first opening246. This forms an expanded diameter of saddle150A which admits passage of screw head132. This can be accomplished by pushing screw head132against saddle150A during insertion, or positioning saddle150A in advance. As screw140is translated laterally, screw140pushes against the screw head contacting portion166to cause lateral portion166A to rotate downwards towards first opening246to form a contracted diameter, and to cause screw head132to become fully seated within saddle150A. In this manner, saddle150A includes both a rod saddle and a ring248having an expanded and contracted diameter depending on a rotational position thereof

Additionally, screw head132contacts tulip ledge242, which has a peripheral diameter at opening248that is smaller than screw head132. This results in saddle clamping face182becoming aligned for contact with laterally approaching set screw186. As set screw186is tightened, saddle150urges screw head132against ledge242to lock spherical ball joint motion of screw head132within tulip body200, while also blocking translation of screw head132laterally towards opening246. Subsequently, as detailed elsewhere herein, as cap160is threaded to push rod180into saddle150A, screw head132is further urged against ledge242to further secure an orientation of screw head132.

The set screw is positioned at an angle with respect to a central axis of the tulip central bore240(the rod slot) to avoid central bore240and locking cap threads260, and to allow the medical practitioner to drive set screw186through a working corridor available in open surgical procedures. A set screw flange188prevents accidental disassembly of set screw186from tulip150A.

It should be understood that the aforedescribed features enable bottom-loading of screw140(a) after installation of screw140within the body, or (b) before installation of screw140within the body, whereby a screw140is loaded through bore240and is then installed within bone, after which screw head132is secured within tulip body200as described above.

As shown inFIG.24, first opening246provides relief for disposing screw140at a greater angle (hypermobility) with respect to an axis through bore240than would be possible with other designs. More particularly, screw shaft134can pass through the area of opening246which would otherwise be blocked by ledge242. Accordingly, tulip body200C can be positioned to exploit this feature where therapeutically beneficial.

Bone stabilizing assembly100A enables separation of screw140and tulip body200C by loosening set screw186and translating screw140laterally to opening246. Additionally, screw140can be affixed in position by either set screw186or locking cap160, or both.

With reference toFIGS.26-44, compression clamps350cooperate with saddle150A to provide a controlled clamping of screw140. Clamps350provide alternatives to the fixation devices. Such clamps improve the locking efficiency and strength of an orthopedic fixation device, particularly in terms of head pull-off and stiffness of a modular or preassembled screw and shank assembly. A specific and known amount of torque can be applied to the locking cap to reliably lock a position of all aspects of the tulip and rod interconnection. The locking cap torque is the only energy that is required to cause this locking.

If an excess amount of torque is applied to cap160, the tulip arms220can become distorted or splayed, which can result in suboptimal performance. Locking cap efficiency can be increased but splay can also increase as load is transferred radially into the threads260. Where clamping efficiency is improved, lower torque can be applied to the locking cap, and forces which could give rise to distortion are reduced. Clamps350enable application of a reduced locking cap torque while maintaining or improving rod and screw head clamping strength.

InFIGS.26-27, a saddle150A forms a detent engagement with tulip body200D, in a manner similar to that ofFIGS.12-13. However, a separate compression clamp350A is movably attached to saddle150A by a dovetail or tongue and groove connection formed between saddle150A and clamp350A, as detailed in the cited reference. A screw head132is inserted into clamp350A when the clamp is in the up/disengaged/release position shown inFIG.26. Clamp350A forms an expanded diameter due to expansion of kerf360to enable screw head132to pass into clamp350A. Clamp350A moves to a down/engaged/clamped position through force imparted by locking cap160which bears upon rod180which in turn bears upon saddle150A (to overcome the resistive force of detent154), which in turn bears upon clamp350A through saddle/clamp clip connection352which in the embodiment shown forms a tongue and groove connection.

As clamp350A is moved to the clamped position, external peripheral ramp354of clamp350A slides along internal peripheral ramp356of tulip200D. Tulip ramp356forms a decreasing diameter in the direction of downward movement of clamp350A, thereby pressing clamp ramp354inwards towards a central axis of clamp350A, thereby causing a diminution or contraction of the diameter of clamp350A, resulting in compression and fixation of screw head132. The diameter of clamp350A can be reduced due to kerf360, which provides room for inwards movement of portions of clamp350A.

More particularly, with reference toFIGS.29-30, clamping strength and reliability are improved at least by the following modifications; an internal radius of clamp350A is extended at a lower periphery358to extend further under screw head132; the width of kerf split360, and the diameter of internal grooves362, are reduced, resulting in greater contact with screw head132; and external peripheral ramp354is elongated, resulting in a greater contact area with tulip internal peripheral ramp356.

Referring now toFIG.31, clamp350B can include serrations364on an external surface engaged with tulip body200, for example spaced serrations364A peripherally disposed about external peripheral ramp354, which reduce sliding friction between external peripheral ramp354clamp350and tulip internal peripheral ramp356. Other orientations of serrations364can be provided, for example serrations364B as shown upon example clamp350A inFIG.32, which are skewed from vertical. Serrations364A-B are shown at a lower peripheral edge of clamp350A, however they may be placed at other locations along external peripheral ramp354. In addition or alternatively, serrations360may be formed on tulip internal peripheral ramp356. Serrations364may work by forming a shallow piercing of a mating surface to thereby increase sliding friction between the mating surfaces.

With reference toFIGS.26-27and33, a pin368can be fastened to and extend from an internal surface of tulip body200(any variant), positioned to aligned with kerf split360which forms a pin guiding channel. When clamp350is moved distally or downwards (as viewed), pin368enters kerf split360, and thereafter prevents radial rotation of clamp350with respect to tulip body200. Additionally, a maximum downward projection of clamp350relative to tulip body200can be defined by a length of a segment of kerf360that is vertically aligned with pin368, as shown inFIG.27, enabling increased control of an extent of clamping forces, defining a limit of vertical movement, and blocking screw head132and clamp350from being pulled out of tulip body200. Pins368can be press-fit into tulip200, or can be attached by any other suitable means, such as threading, welding, or adhesive, as examples. In an embodiment, pins368are 0.45 mm wide by 1.8 mm long, although the size is dependent upon the size of tulip200, clamp350, kerf360, and the forces to be withstood, and the type of metal or other material from which the respective components are fabricated.

With reference toFIG.34, kerfs360A, which divide clamp350A in two portions, is provided with a narrower width “A”, near the region of the saddle/clamp clip connection352, and a wider width “B” along the remaining portion of kerf360A. Width “A” can be sized to close completely first during compression, thereby defining a limit of compression of kerf360A, and further limiting mechanical distortion, for example bowing, of clamp350A and distortion of tulip body200.

With reference toFIGS.34-35, an additional relief cut or kerf360B is formed in each clamp half of clamp350, for example clamp350A as shown, which enables further reduction of distortion, and particularly bowing, of clamp350and/or splaying of tulip arms220, and enables better conformance to screw head132. Kerfs360B do not extend a complete height of clamp350, thereby not separating clamp350into additional segments. Kerfs360B can be formed in other orientations than the vertical orientation illustrated, for example at an angle from vertical, and can be longer or shorter, as determined for example by measured performance under various use conditions. Likewise additional or fewer kerfs360B can be formed, as can be seen inFIG.35, which contains additional kerfs360C which begin at an upper periphery of clamp350and extend downwards, in contrast to kerfs360B shown inFIG.34, which extend upwards. By combining kerfs360B which alternate in direction, in particular, additional flexibility is imparted to clamp350, enabling better clamping strength due to greater conformity to screw head132.

In an embodiment, there are only a plurality of kerfs360B and no kerfs360C, and in another embodiment there are only a plurality of kerfs360C and no kerfs360B. Similarly, kerfs360A, which divide clamp350into segments, can be formed in the Z-shape shown inFIG.30, or can have other shapes, or can be linear but extend at an angle with respect to an axial centerline of clamp350. Kerfs360A-C further facilitate forming an expanded clamp diameter as screw head132is passed into a clamp, and a contracted diameter as the clamp is engaged and compressed against screw head132.

With further reference toFIG.35, and additional reference toFIGS.36-37, clamp350B includes a peripheral flange372extending from external peripheral ramp354, which engages a mating flange374in tulip body200E. As the overall diameter of clamp350B is enlarged or expanded due to peripheral flange372, clamp350B is compressed to form a contracted diameter during installation and insertion into tulip body200C, and thereafter rebounds to an uncontracted diameter, to thereby align flanges372,374for engagement during clamping, as can be seen inFIG.37.

When flanges372and374are engaged during clamping, clamp350is prevented from being pulled from within tulip body200E. In the embodiment shown inFIGS.35-37, increased pulling force does not result in a substantially increased clamping force, as flanges372and374are not ramped with respect to each other, but mutually engage on flat surfaces. Alternatively, flange372A (shown diagrammatically) and flange374A within tulip body200F can be ramped to cause further compression, as shown inFIG.38. InFIG.38A, flanges372B and374B are illustrated diagrammatically and ramp in a reverse direction to that ofFIG.38, whereby flanges372B and374B form mutually engaging hooks or wedges. As with the flat ramps ofFIG.37, the embodiment ofFIG.38Adoes not cause further compression as a force pulls screw head132in a direction away from engagement with tulip body200G, while providing an increased level of pull-out resistance.

An external surface of clamp300and/or an internal surface of tulip200can be anodized, polished, or otherwise be provided with a low friction coating to facilitate assembly and internal movement, while still maintaining a high dissociation load due to mechanical clamping. Similarly, and with further reference toFIG.37, it may be seen that clamp clip portion352B forms a curved upper surface that tangentially contacts saddle clip portion352A (FIG.37). This can serve to reduce a force needed to move flange352B laterally during clamping, by decreasing friction from micro lateral motion and angulation between the surfaces of the saddle150and clamp300. Further, the curved upper surface of clamp clip portion352B forms a ramp which facilitates entry of clamp clip portion352B into saddle clip portion clip portion352A.

With reference toFIGS.39-40, clamp350C forms a clamp flange372C, which can have any profile, including that of any variant of flange372herein, which cooperates with a mating tulip flange374, as described forFIGS.35-38A. However, flange372C is formed from a free end380of a plurality of flexible digits376, each attached at a fixed end378to the main body of the clamp350C. A projection382extends inwards from free end380towards a central axis of clamp350C. When screw head132enters clamp350C, a peripheral surface of screw head132pushes projection382, causing free end380to move away from the central axis, causing clamp flange372C to project over tulip flange374(any corresponding variant), in a position as shown inFIGS.35-38A. Flexible digits376thus configured are distributed about a periphery of clamp372C to provide an even distribution of force. As shown inFIGS.39-40, digits376can be cut from, or formed with, material of clamp350, avoiding a need to attach additional material.

InFIG.41, clamp350can be provided with a series of discrete peripheral projections382extending from clamp external peripheral ramp354, and which collectively form a clamp flange372D. Each has a profile of any of the types described for flanges372herein, and can be used with a tulip body200having a correspondingly shaped tulip flange374.

With reference toFIGS.42-49, a screw head132is retained within tulip body200G between a saddle150B having an internal surface408shaped to complement an upper portion of screw head132, and a shear ring390which engages a lower portion of screw head132. A retaining ring394supports shear ring390and prevents shear ring390from moving out of an interior of tulip body200G.

Shear ring390has a diameter which is less than the largest diameter of screw head132, and less than the diameter of an opening formed by tulip distal ledge242. In an embodiment, shear ring390can have a tapering interior profile400that corresponds to a shape of a lower portion of screw head132. Shear ring390has a weakened area392that is solid but is more easily broken than a remainder of the ring.

Retaining ring394has a larger diameter than the largest diameter of screw head132, and has a larger diameter than tulip distal ledge242. Retaining ring can have an interior profile402corresponding to a shape of a lower surface of shear ring390. Retaining ring394has a weakened point396which can be broken prior to assembly into tulip200, or can be provided with a break along the periphery thereof, or retaining ring394can be provided in the form of a split ring (a spiral that visually appears as an integral ring).

With reference toFIGS.46-49, a bone stabilizing assembly100including the foregoing parts is assembled, first, by bottom loading (as viewed) saddle150B into tulip body200G, and engaging saddle150B at saddle detent portion154B. Next, shear ring390is passed through distal ledge242and positioned within a lower ring chamber398of tulip200G.

Retaining ring394can be assembled next by breaking weakened area396to form a free end, or otherwise passing a broken or free end of retaining ring394into ring chamber398, and then threading/winding the remaining portion of retaining ring394into ring chamber398. Shear ring390and retaining ring394are advantageously formed from a material that retains its original shape after bending, for example a shape memory alloy such as Nitinol, Cobalt Chromium (CoCr), or a titanium/aluminum/vanadium alloy (TAV), or other sufficiently durable and biocompatible metal.

In an alternative embodiment, retaining ring394is fabricated from a high density polymer or highly flexible metal, and is assembled as described above, or is alternatively distorted to be assembled into tulip body200.

Retaining ring394has a larger diameter than tulip distal ledge242and is therefore retained within tulip body200G. After assembly, shear ring390rests within a periphery defined by retaining ring interior profile402, and is thereby likewise retained within tulip body200G.

To engage screw140, with reference toFIG.48, a screw head is pushed into tulip body200G in such a manner as to pass through retaining ring394to engage unbroken shear ring390. As screw head132has a larger diameter than shear ring390, a sufficient pressure exerted upon shear ring390breaks shear ring390at weakened area392, enabling broken ring390to distort to allow screw head132to pass therethrough. Shear ring390is prevented from moving away from screw head132by an upper profile406of tulip ring chamber398. Once screw head132has passed, shear ring390reforms a diameter smaller than screw head132, and rests within retaining ring interior profile402. Shear ring390is formed from a material selected for sufficient durability and flexibility to function as described.

Vertical wall portion404of ring interior profile402laterally engages shear ring390and prevents distortion of shear ring390, particularly when screw head132is driven downwards in a direction of shear ring390and retaining ring394(FIG.49), when locking cap is tightened, as described elsewhere herein. As shear ring390has reformed a diameter smaller than screw head132, and as shear ring390is prevented from further distortion by retaining ring390, screw head132is retained within tulip body200G.

Turning toFIGS.50-56, a screw head132is retained within tulip body200H between saddle150B, described above and shown inFIG.43, and spring ring410which engages a lower portion of screw head132. A retaining ring394A supports spring ring410and prevents spring ring410from moving out of an interior of tulip body200H.

Spring ring410has a lower flange412which has a diameter which is less than the largest diameter of screw head132. Retaining ring394A can have a larger diameter than the largest diameter of screw head132and has a larger diameter than tulip distal ledge242. Retaining ring394A has an interior profile402corresponding to a shape of a lower surface of Spring ring410. Spring ring410includes kerfs360C which extend downwards (as viewed) along a portion of a height of spring ring410, and kerfs360B which extend upwards.

With reference toFIGS.53-56, a bone stabilizing assembly100including the foregoing parts is assembled, first, by distal or bottom loading (as viewed) saddle150B into tulip body200H, and engaging saddle150B at saddle detent portion154B. Next, Spring ring410is passed through distal ledge242. Lastly, retaining ring394A is passed into tulip body200H by placing free end414into tulip body200H first, followed by threading/winding the remaining portion (FIG.53). Retaining ring394A has a larger diameter than tulip distal ledge242and is therefore retained within tulip body200H. A lower end of spring ring410rests within a periphery defined by retaining ring interior profile402A and is thereby likewise retained within tulip body200H.

InFIG.54, a screw head is pushed into tulip body200H in such a manner as to pass through retaining ring394to engage spring ring410. As screw head132has a larger diameter than spring ring lower flange412, a pressure is exerted upon spring ring410to expand a diameter of spring ring410at lower flange412, by expanding kerfs360B. Concomitantly, kerfs306C may be contracted, facilitating distortion of spring ring410to enable screw head132to pass above lower flange412and enter into an interior of spring ring410(FIG.55).

Once screw head132has passed into spring ring410, spring ring410resumes a former unexpanded or contracted diameter, and rests within retaining ring interior profile402A. Spring ring410is formed from a material selected for sufficient durability and an ability to substantially resume a former shape after distortion due to passage of screw head132.

A vertical wall portion404of ring interior profile402A surrounds spring ring lower flange412and prevents re-expansion of spring ring lower flange412, particularly when screw head132is driven downwards in a direction of spring ring410and retaining ring394A (FIG.56), when locking cap is tightened, as described elsewhere herein. As spring ring lower flange412has a diameter smaller than screw head132, and as a diameter of spring ring410can no longer expand, screw head132is retained within tulip body200H.

Embodiment 11—Retained Spring Clip

Referring now toFIGS.57-63, a screw head132is retained within tulip body200J between saddle150B, described above, and spring ring410A which engages a lower portion of screw head132. A retaining ring394A supports spring ring410A and prevents spring ring410A from moving out of an interior of tulip body200H. Spring ring410A is maintained in a deployment position by a ring detent156formed from a ring detent portion156A and a second tulip detent156B, which are otherwise as described with respect to detent154, above. Ring detent is formed about some or all of a periphery of the tulip body and ring.

More particularly, spring ring410A, which otherwise functions as described with respect to spring ring410, above, forms a detent engagement between detent portions156A and156B, whereby spring ring410A is maintained in a position at a proximal or upper end (as viewed) of an interior of tulip body200J, while saddle150B is likewise retained by detent154as described elsewhere herein. As such, an opening is maintained, and components are aligned, for insertion of screw head132.

Spring ring410A has a lower flange412which has a diameter which is less than the largest diameter of screw head132. Retaining ring394B can have a larger diameter than the largest diameter of screw head132, and has a larger diameter than tulip distal ledge242. Retaining ring394B has an interior profile402corresponding to a shape of a lower surface of Spring ring410A. Spring ring410A includes kerfs360C which extend downwards (as viewed) along a portion of a height of spring ring410, and kerfs360B which extend upwards.

With reference toFIGS.60-61, a bone stabilizing assembly100including the foregoing parts is assembled, first, by bottom loading (as viewed) saddle150B into tulip body200J, and engaging saddle150B at saddle detent portion154B. Next, Spring ring410A is passed through distal ledge242. An internal ramp416is formed in an interior of tulip body200J, upon which spring ring detent portion156A slides and deflects inwards, which facilitates engagement of spring ring detent portions156A with second tulip detent portion156B. In this manner, a correct alignment of saddle150B and spring ring410A can be established prior to use, and can be reliably retained until insertion of screw head132.

Lastly, retaining ring394B is passed into tulip body200J by placing free end414into tulip body200J first, followed by threading/winding the remaining portion. Retaining ring394B has a larger diameter than tulip distal ledge242and is therefore retained within tulip body200J. A lower end of spring ring410A is sized and dimensioned to rest within a periphery defined by retaining ring interior profile402, when spring ring410B is released from detent156during engagement of rod180by cap160, as described elsewhere herein, after which spring ring410A is thus captured by retaining ring394B and cannot pass out of an interior of tulip body200J.

Retaining ring394B can now be contrasted with retaining ring394A ofFIGS.50-56. More particularly, retaining ring vertical wall portion404of retaining ring394A is taller than retaining ring vertical wall portion404A of retaining ring394B. This is achieved by lowering a portion of retaining ring394A past tulip distal ledge242. As such, by selecting a profile of retaining ring404, a position of fastener140with respect to tulip body200can be adjusted, as best meets space and other therapeutic requirements. Variants394,394A or394B can be substituted in the various embodiments herein where therapeutically beneficial.

As described with respect toFIG.54, above, a screw head132is pushed into tulip body200J in such a manner as to pass through retaining ring394B to engage spring ring410A. As tulip head132has a larger diameter than spring ring lower flange412(FIG.58), a pressure is exerted upon spring ring410A to expand a diameter of spring ring410A at lower flange412, by expanding/contracting kerfs360B,360C respectively. In addition, expansion of lower flange412and the distortion of spring ring410A causes at least partial disengagement of detent156, facilitating clamping via cap160.

Once screw head132has passed into spring ring410A, spring ring410A resumes a former unexpanded or contracted diameter, and rests within retaining ring interior profile402A. As can be seen in the figures, spring ring410and410A have a lower ramped surface418which facilitates alignment with retaining ring394A,394B, respectively. FIGS. Spring ring410A is formed from a material selected for sufficient durability and an ability to substantially resume a former shape after distortion due to passage of screw head132.

Vertical wall portion404A of ring interior profile402A surrounds spring ring lower flange412(FIG.58) and prevents re-expansion of spring ring lower flange412, particularly when screw head132is driven downwards in a direction of spring ring410A and retaining ring394B (FIG.63), when locking cap160is tightened, as described elsewhere herein. As spring ring lower flange412has a diameter smaller than screw head132, and as a diameter of spring ring410A can no longer expand, screw head132is retained within tulip body200J.

Referring now toFIGS.64-70, a screw head132is retained within tulip body200K between saddle150B, described above, and spring ring410B which engages a lower portion of screw head132. A retaining ring394A supports spring ring410B and prevents spring ring410B from moving out of an interior of tulip body200K. Spring ring410B is maintained in a deployment position by a saddle/clamp clip connection352.

More particularly, spring ring410B includes ascending and descending kerfs360B and360C, enabling flexure in a manner similar to that described for spring rings410and410B. Further spring ring410B forms a clamp clip portion352B having a ramped upper surface, similar to that of clip portion352B ofFIG.37, and in contrast to that ofFIG.36. However, the various profiles of clamp clip portions352A herein can be substituted.

Saddle150A includes a ramped lower surface422which cooperates with the ramped upper surface of clip portion352B to facilitate mutual engagement of spring ring410B and saddle150A. In the embodiment ofFIGS.64-70, ramped lower surface422is curved, and in the embodiment ofFIG.36ramped lower surface422is flat, although these can be substituted, or another ramped profile can be provided.

By maintaining spring ring410B in contact with saddle150A, the latter maintained in position by saddle detent154, an opening is maintained, and components are aligned, for insertion of screw head132.

Spring ring410B has an internally disposed lower profile420which has a diameter which is less than the largest diameter of screw head132. Retaining ring394A can have a larger diameter than the largest diameter of screw head132, and has a larger diameter than tulip distal ledge242. Retaining ring394A has an interior profile402corresponding to a shape of a lower surface of Spring ring410B.

With reference toFIG.67, a bone stabilizing assembly100including the foregoing parts is assembled, first, by assembling spring ring410B onto saddle150A by engaging saddle/clip connection352, then bottom loading (as viewed) the combination into tulip body200K, and engaging saddle150A with tulip detent portion154A at saddle detent portion154B. Alternatively, saddle150A can be bottom loaded and engaged at saddle detent portion154B first, followed by bottom loading spring ring410B and then engaging saddle/clip connection342.

Next, Spring ring410B is passed through distal ledge242, and the ramped upper surface of clamp clip portion352B slides against ramped lower surface422of saddle150A, resulting in engagement of saddle/clamp clip connection352. In this manner, a correct alignment of saddle150A and spring ring410B can be established prior to use, and can be reliably retained until insertion of screw head132.

Lastly, retaining ring394A is passed into tulip body200K by placing free end414into tulip body200K first, followed by threading/winding the remaining portion. Retaining ring394A has a larger diameter than tulip distal ledge242and is therefore retained within tulip body200K. A lower end of spring ring410B is sized and dimensioned to rest within a periphery defined by retaining ring interior profile402, when saddle150A is released from detent154, together with attached spring ring410B, during engagement of rod180by cap160, as described elsewhere herein, after which spring ring410B is thus captured by retaining ring394A and cannot pass out of an interior of tulip body200K.

As described with respect toFIG.54, above, a screw head132is pushed into tulip body200K in such a manner as to pass through retaining ring394A to engage spring ring410B. As tulip head132has a larger diameter than spring ring lower interior profile420, a pressure is exerted upon spring ring410B to expand a diameter of spring ring410B at lower internal profile420, by expanding/contracting kerfs360B,360C respectively.

Once screw head132has passed into spring ring410B, spring ring410B resumes a former unexpanded or contracted diameter, and rests within retaining ring interior profile402A. Spring ring410B is formed from a material selected for sufficient durability and an ability to substantially resume a former shape after distortion due to passage of screw head132.

Vertical wall portion404of ring interior profile402A surrounds a lower portion of spring ring410B and prevents re-expansion of spring ring410B, particularly when screw head132is driven downwards in a direction of spring ring410B and retaining ring394A (FIG.70), when locking cap160is tightened, as described elsewhere herein. As spring ring410B has a diameter smaller than screw head132at lower profile422at rest, and as a diameter of spring ring410B at lower profile422can no longer expand due to engagement with retaining ring394A, screw head132is retained within tulip body200K.

Disassembly can be carried out by reversing the foregoing process. More particularly, cap160can be loosened, followed by pushing saddle150A into saddle detent154by pushing tulip body200K downwards onto screw head132, followed by withdrawal of screw head132once the lower end of spring ring410B is raised free of retaining ring394A.

The bone stabilizing assemblies100of the disclosure allow for assembly of a modular head onto a pedicle screw after placement of the screw in the body, reducing implant prominence and improving ease of access to anatomy for discectomy, interbody placement, and osteotomy. The modular design also allows for multiple types of screw heads to be assembled to screws with varying functionality to increase versatility.

All references cited herein are expressly incorporated by reference in their entirety. There are many different features of the present disclosure and it is contemplated that these features may be used together or separately. Unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Thus, the disclosure should not be limited to any particular combination of features or to a particular application of the disclosure. Further, it should be understood that variations and modifications within scope of the disclosure might occur to those skilled in the art to which the disclosure pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope of the present disclosure are to be included as further embodiments of the present disclosure.