Patent Description:
Many people contend with orthopedic issues as a result of age, disease, and trauma, as well as congenital and acquired complications and conditions. While some of these issues can be alleviated without surgery, other issues respond better to surgery. In some cases, surgery may include the insertion of an orthopedic implant. Orthopedic spine assemblies and constructs such as spine plates, bone screw assemblies for spinal rods and other devices (spinal components) have made a profound contribution to the correction of spinal deformities, accidents and other problems in the cervical as well as thoracic, lumbar and sacral spine. These and other spinal devices are typically fixed to vertebrae using vertebral bone screws. Vertebral bone screws are specially designed and manufactured bone screws that are placed into the bone of a vertebra. Vertebral bone screws placed in the vertebra offer superior strength and pull-out resistance as compared to other forms of fixation in spine surgery. The ability to achieve vertebral fixation has allowed surgeons to obtain more secure fixation of the spinal components involved, which permits more powerful correction of spine problems and reported better clinical outcomes.

In addition to other uses, bone screws provide a solid foundation for the attachment of spinal rods. Spine rods are used for the fixation of a plurality of vertebrae for various situations. A spine rod is held relative to the vertebrae by a spine rod bone screw assembly. Various types of spine rod bone screw assemblies are known such as those that allow for inter-operative adjustments in the coronal, transverse and sagittal planes - generally known as poly-axial spine rod bone screw assemblies. Certain spine rod bone screw assemblies allow for various degrees of freedom of attachment of a spine rod thereto from any direction, angle, and height. In all cases, however, the spine rod bone screw assemblies hold a spine rod and are fixed to a vertebra. The poly-axial spine rod bone screw assembly thus permits spine rods to be rigidly locked into a variety of positions along with other types of implant components. This allows a surgeon to tailor-make each construct.

One type of poly-axial spine rod bone screw assembly is known as a poly-axial tulip head spine rod holder. The poly-axial tulip head spine rod holder consists of a poly-axial bone screw, a poly-axial head that is shaped like a tulip (poly-axial tulip head), and an insert within the poly-axial tulip head. The poly-axial tulip head is situated about the poly-axial bone screw head while the insert is situated within the poly-axial tulip head, the insert that interacts with the bone screw head and the tulip head. Downward pressure exerted against the insert during installation of a spine rod and set screw in the poly-axial tulip head causes the insert to bind against the poly-axial bone screw head and between the poly-axial tulip head such that the orientation of the tulip head is fixed relative to the bone screw. While current poly-axial tulip head spine rod holders are adequate, there is room for improvement.

Thus, there is a need for an improved poly-axial tulip head spine rod bone screw assembly.

A modular polyaxial bone screw assembly with the features as defined in the preamble of claims <NUM> and <NUM> is known from <CIT>.

The present invention is defined in claims <NUM> and <NUM> while preferred embodiments are set forth in the dependent claims.

A modular poly-axial bone screw/screw assembly has three components, a poly-axial bone screw, a poly-axial tulip head, and an insert forming a collet disposed within the tulip head, the collet interacting with the tulip head to lock axial orientation of the collet within the tulip head and to provide a frictional interference fit with the bone screw head in order to lock orientation of the tulip head on and relative to the bone screw.

The tulip head has an inner configuration that interacts with the outer configuration of the collet to lock axial and/or rotational position of the collet within and relative to the tulip head, and thus about the bone screw head. The collet also has a resilient, tapered base with a plurality of slots in and about its end that allow the end to elastically splay outwardly over and upon the head of the bone screw to create a snap or frictional interference fit between the splayed collet and the bone screw head when a spine rod is fixed in the tulip head. An increase in spherical coverage created by the present configuration increases the amount of surface contact of the collet with the bone screw head. This allows for more controlled, uniform and secure orientation of the tulip head with respect to the bone screw.

According to the present invention, the inner configuration of the tulip head comprises a plurality of projections protruding radially inwardly and spaced about the inner circumferential wall of the tulip head, while the outer configuration of the collet comprises a like plurality of depressions formed into its outer circumferential wall to receive the plurality of projections. Elastic deformation snap fits the collet within the tulip head. In another form, the plurality of projections are situated on the collet, and the plurality of depressions are situated in the inner circumferential wall of the tulip head, while the plurality of projections are situated on the outer conferential wall of the collet.

In an alternative, the inner configuration of the tulip head comprises a radially inwardly projecting lip extending about the inner circumferential wall of the tulip head creating an overhang and an undercut, while the outer configuration of the collet comprises a circumferential ledge. Other means may be used to lock the axial and/or rotational position of the collet in and to the tulip head.

The collet has an elastic/resilient base created at least in part by a plurality of cuts, slots, cutouts or the like that allows the poly-axial bone screw head to snap into the base of the collet thus causing a frictional interference fit. Particularly, the plurality of cuts in the base allows the elastic/resilient base of the collet to splay slightly during reception of the poly-axial bone screw head, then conform about the poly-axial bone screw head once pressure is applied by insertion of a spine rod and set screw into the tulip head, while the tapered end binds around, between and against the bone screw head and the inner wall of the tulip head.

Further advantages of the present invention will become apparent from consideration of the drawings and the following description of forms of the invention. A person skilled in the art will realize that other forms of the invention are possible and that the details of the invention can be modified in a number of respects without departing from the inventive concept. The following drawings and description are to be regarded as illustrative in nature and not restrictive.

The above mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and the invention itself will be better understood by reference to the following description of forms of the invention taken in conjunction with the accompanying drawings, wherein:.

A description of the features, functions and/or configuration of the components depicted in the various figures will now be presented. It should be appreciated that not all of the features of the components of the figures are necessarily described. Some of these non-discussed features as well as discussed features are inherent from the figures. Other non-discussed features may be inherent in component geometry and/or configuration.

Referring to <FIG>, there is depicted a form of modular poly-axial (polyaxial) bone screw/screw assembly ("modular poly-axial bone screw"), generally designated <NUM>, for use in the spine and fashioned as described in the above Summary of the Invention, the modular poly-axial bone screw <NUM> for holding a spine rod (not shown) relative to the spine (not shown). <FIG> shows the three components of the poly-axial bone screw <NUM> in an exploded or pre-assembled view, the assemblage comprising a poly-axial bone screw ("bone screw") <NUM>, a tulip head <NUM>, and an insert/collet ("collet") <NUM>.

The bone screw <NUM> has a generally globular (and therefore poly-axial) head <NUM> with a socket <NUM> in a top of the head <NUM> that is configured to receive a bone screw installation tool (not shown). In one form, the socket <NUM> is hexalobe-shaped and configured to receive a hexalobe bone screw installation tool. Other socket configurations may be used. A circumferential angle, slant, or taper <NUM> is preferably, but not necessarily, provided about the socket <NUM>. A neck <NUM> projects from the head <NUM> opposite the socket <NUM>. A shank <NUM> extends axially from the neck <NUM> and terminates in a tip <NUM>. The shank <NUM> has first external threads/threading <NUM> along a lower portion of its axial length ("lower threading") proximate the tip <NUM>, and second external threads/threading <NUM> along an upper portion of its axial length between the lower threading <NUM> and the neck <NUM>. The shaft preferably, but not necessarily, increases in diameter from the tip <NUM> to the neck <NUM>.

The tulip head <NUM> is defined by a generally tulip shaped body <NUM>, having a bottom <NUM>, a first side or sidewall <NUM> and a second side or sidewall <NUM>, the second sidewall <NUM> opposite the first sidewall <NUM>, the nomenclature first and second being arbitrary here and throughout unless otherwise indicated. The first sidewall <NUM> is generally arc-shaped and includes threads/threading <NUM> on its interior wall/surface. The second sidewall <NUM> is generally arc-shaped and includes threads/threading <NUM> on its interior wall/surface. The internal threading <NUM>, <NUM> accepts a set screw (not shown) for fully seating the spine rod in the tulip head. The first sidewall <NUM> has an arcuate top <NUM> that is preferably, but not necessarily, sloped or slanted radially inwardly, and the second sidewall <NUM> likewise has an arcuate top <NUM> that is preferably, but not necessarily, sloped or slanted radially inwardly. The first sidewall <NUM> has a first flat <NUM> on its exterior surface extending generally from proximate the top <NUM> to the bottom <NUM>. The first sidewall <NUM> further has a first notch <NUM> on one lateral side of the sidewall <NUM> proximate the top <NUM>, and a second notch <NUM> on the other lateral side of the sidewall <NUM> proximate the top <NUM>, the first and second notches permitting receipt of an installation tool (not seen) and otherwise. In like manner, the second sidewall <NUM> has a second flat <NUM> on its exterior surface extending generally from proximate the top <NUM> to the bottom <NUM>. The second sidewall <NUM> further has a third notch <NUM> on one lateral side of the sidewall <NUM> proximate the top <NUM>, and a fourth notch <NUM> on the other lateral side of the sidewall <NUM> proximate the top <NUM>. The lower portion <NUM> of the body <NUM> is generally rounded.

The tulip head <NUM> has an interior bore <NUM> extending from a top to and through a bottom <NUM> of the body <NUM>. The bore <NUM> receives the bone screw <NUM> and the collet <NUM>. A spine rod reception area is defined in the body, formed as a first pocket, cutout or notch <NUM> between lateral sides of the first sidewall <NUM> and the second sidewall <NUM>, and a second pocket, cutout or notch <NUM> between lateral sides of the first sidewall <NUM> and the second sidewall <NUM>, the first and second pockets are opposite one another. The first and second notches <NUM>, <NUM> are formed to receive a spine rod therein (not shown) and thus are generally arcuate or cup-shaped. The outside of the body <NUM> of the tulip head <NUM> surrounding the first notch <NUM> is a flat <NUM>, while the outside of the body <NUM> of the second notch <NUM> is a flat <NUM>.

The internal threading <NUM>, <NUM> of the first and second sidewalls <NUM>, <NUM>, provide for reception of a set screw or the like (not shown) that is used to "lock up" the tulip head <NUM> on and relative to the bone screw <NUM> via the collet <NUM>.

The inside of the tulip head <NUM> has an inner configuration best discerned in <FIG>. Particularly, the inner configuration comprises a circumferential, radially inwardly projecting lip <NUM> extending about the lower inner circumferential wall of the tulip head, thereby creating an overhang and an undercut <NUM>. Moreover, as discerned in the figure, the annular lower sidewall of the body <NUM> is preferably, but not necessarily, wider at the bottom <NUM>.

The insert/collet <NUM> provides a taper lock and is defined by a generally cylindrical body <NUM> having a base or skirt <NUM> on a lower portion thereof, a first upstanding flange, side or sidewall <NUM>, and a second upstanding flange, side or sidewall <NUM> that define a first pocket, cutout or notch <NUM> between lateral sides of the first and second upstanding flanges <NUM>, <NUM>, and a second pocket, cutout or notch <NUM> between opposite lateral sides of the first and second upstanding flanges <NUM>, <NUM>, the notches <NUM>, <NUM> thus being oppositely disposed. The first and second notches <NUM>, <NUM> are formed to receive a spine rod therein (not shown) and thus are generally arcuate or cup-shaped. An interior bore extends from a top of the body to a bottom <NUM> of the body. The bore allows access to the socket <NUM> of the bone screw head <NUM> of the poly-axial bone screw <NUM>.

A bottom area <NUM> of the collet <NUM> includes a plurality of cuts, cutouts, notches or the like <NUM> that extend axially from the bottom <NUM> towards the upstanding flanges <NUM>, <NUM>. Each cut <NUM> is preferably, but not necessarily, equally circumferentially spaced about the bottom area <NUM> of the body <NUM> and terminates axially in a hole <NUM>. The cuts <NUM> create a collet mechanism that allows the screw head <NUM> to snap into the bottom area <NUM> of the collet <NUM> thus creating a frictional interference fit. It should be appreciated that the number of cuts <NUM> may vary from two (<NUM>) to as many as desired. It is also preferable, but not necessary, that the cuts <NUM> are evenly spaced about the bottom area <NUM>. The cuts <NUM> create a resilient or elastic interference or snap on fit with the polyaxial screw head <NUM> by allowing the bottom area <NUM> to splay slightly then from back around the screw head <NUM>. The spherical coverage of the head <NUM> increases the amount of surface contact between the bottom area <NUM> of the collet <NUM> and the polyaxial screw head <NUM>.

The outside of the collet <NUM> has an outer configuration best discerned in <FIG>. Particularly, the outer configuration comprises a ledge <NUM> extending circumferentially about the body <NUM> proximate the bottom area <NUM>. Because of the elastic nature of the collet <NUM>, the projecting lip <NUM> of the tulip head <NUM> is captured by/on the ledge <NUM>.

Referring to <FIG>, there is depicted another form of a modular poly-axial (polyaxial) bone screw/screw assembly ("modular poly-axial bone screw"), generally designated <NUM>, for use in the spine and fashioned as described in the above Summary of the Invention, the modular poly-axial bone screw <NUM> for holding a spine rod (not shown) relative to the spine (not shown). In like form as the modular poly-axial bone screw <NUM> of <FIG>, the modular poly-axial bone screw <NUM> has three components, namely the poly-axial bone screw ("bone screw") <NUM> as described above, a tulip head <NUM>, and an insert/collet ("collet") <NUM>.

The inside of the tulip head <NUM> has an inner configuration best discerned in <FIG>. Particularly, the inner configuration comprises a plurality of radially inwardly projecting protuberances <NUM> extending about the lower inner circumferential wall of the tulip head. While four (<NUM>) protuberances <NUM> are shown, any number may be used. Moreover, the configuration of the protuberances may be changed as necessary. The annular lower sidewall of the body <NUM> is preferably, but not necessarily, wider at the bottom <NUM>.

The outside of the collet <NUM> has an outer configuration best discerned in <FIG>. Particularly, the outer configuration comprises a plurality of depression, cutouts or the like <NUM> extending about the lower outer circumferential wall of the collet. The number of depressions <NUM> correspond in number to the plurality of protuberances <NUM> of the tulip head <NUM>. While four (<NUM>) depressions <NUM> are shown, any number may be used. Moreover, the configuration of the depressions may be changed as necessary.

The various components of the modular poly-axial bone screws <NUM>, <NUM> are made from a bio-compatible material such as, but not limited to, PEEK, other polymers/plastics, titanium, stainless steel, and alloys of same. Other bio-compatible materials, or course, may be used.

Claim 1:
A modular polyaxial bone screw assembly for holding a spine rod in a fixed spatial orientation relative to vertebral bone, the modular polyaxial bone screw assembly comprising:
a polyaxial bone screw (<NUM>) having a threaded shank and a globular head (<NUM>);
a tulip head (<NUM>) disposed on the globular head (<NUM>) of the polyaxial bone screw (<NUM>) and configured to swivel about the globular head (<NUM>) of the polyaxial bone screw before the tulip head is fixed in spatial orientation relative to the polyaxial bone screw, and to receive and hold a spine rod as the spatial orientation of the tulip head is fixed, the tulip head having a bore (<NUM>) extending from a first end of the tulip head to a second end of the tulip head and defining a generally cylindrical interior with an upper cylindrical portion defining an upper inner cylindrical wall coinciding with and within the first end of the tulip head, inner threading on the upper inner cylindrical wall for threaded receipt of a set screw, and a lower generally cylindrical portion defining a lower inner generally cylindrical wall coinciding with and within the second end of the tulip head and sized to receive the globular head of the polyaxial bone screw; and
a collet (<NUM>) disposed in the interior of the tulip head (<NUM>), the collet having a base section (<NUM>) with a first end resting about the globular head of the polyaxial bone screw and configured to splay on the globular head of the polyaxial bone screw and fix a spatial orientation of the tulip head relative to the polyaxial bone screw through interference between the first end, the globular head of the polyaxial bone screw, and the tulip head when a spine rod is received in and affixed to the tulip head by the set screw, characterised in that the tulip head has an inner configuration on the lower inner generally cylindrical wall, the inner configuration consisting of a lip (<NUM>) extending radially inward from the lower inner generally cylindrical wall, and the collet has an outer configuration comprising a ledge (<NUM>) extending circumferentially about the body proximate the base section (<NUM>) on an outer wall that cooperates with the inner configuration comprising the lip (<NUM>) of the tulip head to fix axial and rotational position of the collet relative to the tulip head.