CAPLESS MULTIAXIAL SCREW AND SPINAL FIXATION ASSEMBLY AND METHOD
A spinal fixation assembly and capless multi-axial screw system and method are shown. The assembly comprises a receiver having a rotary lock which in one embodiment includes a plurality of channels which urge and lock the elongated member to the screw using a bayonet type connection.
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This application is a continuation of U.S. patent application Ser. No. 13/290, 358, filed Nov. 7, 2011, which is a continuation of U.S. patent application Ser. No. 12/767,100, filed Apr. 26, 2010, now issued as U.S. Pat. No. 8,066,745, which is a continuation of U.S. patent application Ser. No. 11/193,523, filed Jul. 29, 2005, now issued as U.S. Pat. No. 7,717,943, which are incorporated herein by reference and made a part hereof.
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates to a capless multiaxial screw and spinal fixation assembly and method, particularly useful for fixing and/or aligning vertebrae of the spine. The invention permits multiple angular orientations of an elongated member or rod with respect to a screw that is screwed into a vertebra.
2. Description of the Related Art
Various methods of spinal immobilization have been known and used in the past. The preferred treatment for spinal stabilization is immobilization of the joint by surgical fusion or anthrodesis. This method has been known since development in 1911 by Hibbs and Albe. However, in many cases, in particular cases involving fusion across the lumbosacral articulation and where there are many levels involved, pseudorarthrosis is a problem. It was discovered that immediate immobilization was necessary in order to allow a bony union to form. Post operative external immobilization, such as the use of splints and casts, was a favored method of treatment, however, as surgical techniques have become more sophisticated, various methods of internal and external fixation have been developed.
Internal fixation refers to therapeutic methods of stabilization which are wholly internal to the patient and include commonly known devices such as bone plates and pins. External fixation, in contrast, involves at least some portion of stabilization device which is external to the patient's body. Internal fixation is now the favored method of immobilization because the patient is allowed greater freedom with the elimination of the external portion of the device and the possibility of infection, such as a pin tract infection is reduced.
There have been numerous systems and methods developed in the past for correcting and stabilizing and aligning the spine for facilitating, for example, fusion at various levels or areas of the spine, such as those devices are shown in U.S. Pat. Nos. 4,085,744; 4,269,178; 4,805,602; 5,466,237; 5,474,555; 5,891,145; and 6,869,433 B2. Bone screws with a polyaxial head are commonly used in spine surgery today. They are used chiefly in the lumbar spine and screwed into bone (pedicle) posteriorly. The head of the screw is attached to the shaft of the screw by means of a ball and socket. The top of the screw is machined into a ball, and the head contains a socket into which the ball fits. The screw head further contains a receiver for receiving a separate rod. The rod is fastened to the screw head receiver via a threaded cap. The rod is then fastened to screws placed in adjacent vertebrae thus providing stabilization. The polyaxial head allows the rod to be placed in a variety of angles with respect to the screw allowing conformance to local anatomy.
When the threaded cap is tightened upon the rod, a frictional pressure is transmitted from the threaded cap to the rod thence to the top of the ball, thus locking the ball-in-socket and preventing motion after tightening has occurred. This concept is demonstrated in U.S. Pat. Nos. 5,466,237 and 5,474,555, which illustrate this type of screw.
U.S. Pat. No. 5,466,237 to Bird et al. discloses a bone screw having a spherical projection on the top of the bone screw. An externally threaded receiver member supports the bone screw and spinal rod on top of the spherical projection. An outer nut is tightened onto the receiver member to press the spinal rod against the spherical projection to accommodate various angular orientations of the bone screw relative to the rod.
In another approach shown in U.S. Pat. No. 4,946,458 to Harms, a spherical headed bone screw supported within separate halves of a receiving member. The bottom of the halves are held together by a retaining ring. The top of the receiver halves are compressed about the bone screw by nuts threaded onto a threaded spinal rod.
In still another approach taken by Harms et al. in U.S. Pat. No. 5,207,678, a receiver member is flexibly connected about a partially spherical head of a bone screw. Conical nuts on opposite sides of the receiver member threaded onto a threaded rod passing through the receiver. As the conical nuts are threaded toward each other, the receiver member flexibly compresses around the head of the bone screw to clamp the bone screw in its variable angular position. One detriment of the systems in the two Harms et al. patents is that the spinal rod must be threaded in order to accept the compression nuts.
U.S. Pat. No. 6,869,433 discloses the use of a pedicle screw assembly that comprises a screw having a head with a convex portion and a receiver that receives the head. The receiver also receives an elongated member, such as a spinal fixation rod. The receiver has a concave portion which has a radius of curvature which is less than the radius of curvature of the convex portion of the head whereby to create an interference fit between the convex portion of the head and the concave portion of the receiver. The device also includes an internal nut and external nut that compresses the rod against a pressure disc which in turn compresses the head convex portion of the screw into the receiver concave portion and locks the angular position of the receiver with respect to the screw.
One of the problems with the prior art devices is the number of parts and components, especially those components that utilize a threaded cap screw to secure the rod to the anchoring screw, whether internal or external, to fix the rod relative to the screw. Problems with the threaded fastener, that is, threaded cap or set screw, are numerous and include risk of cap loosening, loss of cap intra-operatively, cross threading, thread failure, failure of the cap in driving instrument and limitations upon torque application.
What is needed, therefore, is a system and method that provide a lock or connection between the rod and screw without the use of external nuts, screws, caps or threads of the type shown in the prior art.
These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.
SUMMARY OF THE INVENTIONThe present invention improves the spinal fixation and the locking between an elongated member or rod and a screw.
One object of the invention is to provide a system and method that reduces or eliminates the need for external or internal caps or screws to lock the relative position of a rod to a screw.
Another object of the invention is to provide a simple bayonet-type connection that eliminates the fixation systems of the past and/or simplifies the spinal fixation procedure.
In one aspect, this invention discloses a capless multiaxial screw comprising a screw having a threaded portion and a screw head, a receiver having a bore for receiving the threaded portion and a receiving channel for receiving an elongated member, the channel further comprising a locking channel in communication with the channel, a compression member for situating in the bore, the compression member comprising a second receiving channel having a first end and a second end and further associated with a first end, and a receiving area associated with the second end for receiving and engaging the screw head, the elongated member cooperating with the compression member to lock the elongated member to the screw when the elongated member is received in the first and second receiving channels and the receiver is rotated from an unlocked position to a locked position.
In another aspect, this invention discloses a spinal fixation assembly comprising a receiver having a bore for receiving a screw having a screw head that is larger than a diameter of the bore, and a compression member dimensioned to be received in the bore and having a first end for receiving an elongated member and a second end for engaging the screw head, the receiver comprising a receiving channel for receiving the elongated member and a locking channel for locking the elongated member to the screw when the receiver is rotated from an unlocked to a locked position.
In yet another aspect, this invention relates to a spinal fixation assembly comprising a receiver having a bore for receiving a screw having a screw head that is larger than a diameter of the bore and a receiving channel for receiving an elongated member, and a compression member dimensioned to be received in the bore and having a first end for engaging the elongated member and a second end for engaging the screw head, the receiver comprising a rotary lock for locking the elongated member to the screw.
In still another aspect, this invention relates to a spinal fixation assembly comprising a receiver having a bore for receiving a screw having a screw head, and a compression member dimensioned to be received in the bore and having a first end for engagement with an elongated member and a second end for engagement with the screw head, the receiver comprising a locking channel and a receiving channel coupling the locking channels, the receiving channel receiving the elongated member and the locking channels cooperating to secure the elongated member to the screw when the receiver is rotated.
In another aspect, this invention discloses a receiver for use with a polyaxial screw comprising a body having a bore and a connection channel for receiving an elongated member and for locking it to the screw when the receiver is rotated.
In another aspect, this invention discloses a spinal fixation assembly comprising a receiver having a bore for receiving a screw having a screw head, and a compression member dimensioned to be received in the bore and having a first end and a second end, the receiver comprising an integral rotary lock for locking the elongated member to the screw when the receiver is rotated.
In another aspect, this invention relates to a method for securing an elongated member to a spinal column, comprising the steps of screwing a screw into a spinal bone, the screw having a head that is received in a seat of a receiver having a bore through which threads of the screw may pass, situating the rod into the receiver, and rotating the receiver to fasten the rod onto the screw.
In another aspect, this invention discloses a capless multiaxial screw comprising a screw having a threaded portion and a screw head and a receiver having a bore for receiving the threaded portion and a receiving channel for receiving an elongated member, the receiving channel further comprising a locking channel in communication with the receiving channel, the receiver locking the elongated member to the screw when the elongated member is received in the receiving channel and the receiver is rotated from an unlocked position to a locked position.
The above mentioned aspects and the embodiments shown and described herein could be used alone or together and/or in combination with one or more of the features covered by one or more of the claims set forth herein, including but not limited to one or more of the following features or steps:
The capless multiaxial screw fixation assembly wherein the receiver comprises a plurality of channels that capture the elongated member.
The capless multiaxial screw fixation assembly wherein each of the plurality of channels defines an intermediate area for capturing the elongated member to facilitate adjusting a position of the elongated member before it is locked in the receiver.
The capless multiaxial screw fixation assembly wherein the plurality of channels are defined by a first surface and a second surface, each of the plurality of channels having an intermediate step for defining the intermediate area.
The capless multiaxial screw fixation assembly wherein the screw, receiver and compression member are preassembled.
The capless multiaxial screw fixation assembly wherein the locking channel is a helical channel defined by at least one surface of the receiver.
The capless multiaxial screw fixation assembly wherein the seat area is generally concave, the screw head having a curvature that generally complements the concave receiving area.
The capless multiaxial screw fixation assembly wherein the receiving channel comprises a first axis and the second receiving channel comprises a second axis, the second axis and the first axis being generally parallel when the receiver is in the unlocked position and generally perpendicular when the receiver is actuated to the locked position.
The capless multiaxial screw fixation assembly wherein when the receiver is rotated, the receiver moves from a first position to a second position in response thereto, such that when the receiver is in the second position, the elongated member is closer to the screw head than when the elongated member is in the first position.
The capless multiaxial screw fixation assembly wherein the first position corresponds to the unlocked position and the second position corresponds to the locked position.
The capless multiaxial screw fixation assembly wherein the receiving channel is generally perpendicular to an elongated member axis of the elongated member when the receiver is in the locked position.
The capless multiaxial screw fixation assembly wherein the locking channel provides a bayonet connection between the elongated member and the screw.
The capless multiaxial screw fixation assembly wherein the receiving channel is generally parallel along an axis of the receiver and the locking channel spirals about the axis of the receiver when moving in an axial direction.
The capless multiaxial screw fixation assembly wherein the receiving channel extends from an end of the receiver in a direction that is generally parallel to an axis of the receiver and the locking channel extends in a direction that is generally not parallel to the axis of the receiver.
The capless multiaxial screw fixation assembly wherein when the compression member is received in the bore and the first channel becomes generally aligned with the second channel, the locking channel becomes situated at least partially around the compression member.
The capless multiaxial screw fixation assembly wherein the receiver comprises at least one camming surface that cooperates with an opposing surface for defining the locking channel, the at least one camming surface facilitates camming the elongated member urges the compression member to apply a compressive force against the compression member which, in turn, urges the compression member to apply a compressive force against the screw head in response thereto.
The capless multiaxial screw fixation assembly wherein the receiver comprises a plurality of camming surfaces that cooperate with a plurality of opposing surfaces, respectively, to define the locking channel, the plurality of camming surfaces camming against the elongated member to force the elongated member against the compression member which, in turn, applies a compressive force against the screw head when the receiver is rotated.
The capless multiaxial screw fixation assembly wherein the locking channel comprises a first locking channel area and a second locking channel area, the receiver comprises a first camming surface generally opposed to a first opposing surface to define the first locking channel area and a second camming surface generally opposed to a second opposing surface to define the second locking channel area, the first and second camming surfaces camming against the elongated member to force the elongated member against the compression member which, in turn, applies a compressive force against the screw head when the receiver is rotated.
The capless multiaxial screw fixation assembly wherein the locking channel comprises a lock member associated therewith for facilitating retaining the receiver in a locked position.
The capless multiaxial screw fixation assembly wherein the lock member comprises a detent in the receiver and associated with the locking channel.
The capless multiaxial screw fixation assembly wherein the lock member cooperates with an end wall of the locking channel to define a locking area at which the elongated member is locked when it is in the locked position.
The capless multiaxial screw fixation assembly wherein the receiving channel lies in a first plane that is generally planar and the locking channel lies in a second plane that is non-planar.
The capless multiaxial screw fixation assembly wherein the second plane spirals about an axis of the retainer.
The capless multiaxial screw fixation assembly wherein the locking channel spirals about an axis of the retainer.
The capless multiaxial screw fixation assembly wherein the screw head is generally spherical and the seat area is also generally spherical and dimensioned to receive and complement the screw head.
The spinal fixation assembly wherein the rotary lock comprises at least one engaging surface for engaging the elongated member and for locking the elongated member to the screw when the receiver is rotated to a locked position.
The spinal fixation assembly wherein the receiver is generally cylindrical and the bore extends along an axis of the receiver, the receiver comprising a first locking aperture in communication with the bore and a second locking aperture in communication with the bore; the first and second locking apertures cooperating to define the rotary lock.
The spinal fixation assembly wherein the first locking aperture and the second locking aperture cooperate to define a locking channel for receiving the elongated member.
The spinal fixation assembly wherein the first locking aperture and the second locking aperture cooperate to define a generally s-shaped channel when viewed in cross-section for receiving the elongated member.
The spinal fixation assembly wherein the rotary lock comprises a locking channel in the receiver that is in communication with the receiving channel.
The spinal fixation assembly wherein the locking channel is defined by a first channel in a wall of the receiver and a second channel in the wall of the receiver, the first and second channels being generally opposed.
The spinal fixation assembly wherein the first channel and the second channel extend away from the receiving channel about a receiver axis of the receiver such that rotation of the receiver will move from an unlocked position to a locked position.
The spinal fixation assembly wherein the first channel and the second channel spiral in a common direction about a receiver axis of the receiver.
The spinal fixation assembly wherein the locking channel and the receiving channel cooperate to provide a bayonet connection between the elongated member and the screw.
The spinal fixation assembly wherein the receiving channel lies in a plane that is generally planar and the locking channel lies in a plane that is generally curved.
The spinal fixation assembly wherein the receiver comprises a wall that lies in an arcuate plane about a receiver axis of the receiver and the locking channel also lie in the arcuate plane.
The spinal fixation assembly wherein a starting area of the locking channel is situated at a different radial position and a different axial position relative to the receiver axis when compared to an end position of the locking channel when the elongated member is locked to the screw.
The spinal fixation system wherein the receiver comprises a first engaging surface, the first engaging surface engaging the elongated member and forcing it against the compression member which, in turn, engages the screw head with a compressive force when the receiver is rotated.
The spinal fixation system wherein the locking channels comprise a first camming surface and a second camming surface, respectively, that engages the elongated member and forces it against the compression member until the elongated member becomes fixed relative to the screw.
The spinal fixation system wherein the locking channel lies in a plane that is at predetermined angle relative to the receiving channel.
The spinal fixation system wherein the predetermined angle is approximately 90 degrees.
The spinal fixation system wherein the predetermined angle is an acute angle that extends toward a vertebrae when the screw is screwed into the vertebrae.
The receiver wherein the connection channel defines a bayonet connection channel.
The receiver wherein the connection channel comprises a plurality of channels that cooperate to define the bayonet connection channel.
The receiver wherein the plurality of channels spiral about an axis of the receiver.
The spinal fixation system wherein the integral rotary lock comprises a continuous channel for receiving the elongated member and for urging the elongated member toward the screw head when the receiver is rotated.
The spinal fixation system wherein the integral rotary lock comprises a first channel that extends about a receiver axis in a first direction and a second channel that extends about the receiver axis in a second direction and a receiver channel coupling the first and second channels.
The spinal fixation system wherein the first and second directions extend away from the receiving channel about a receiver axis of the receiver such that rotation of the receiver will move from an unlocked position to a locked position.
The spinal fixation system wherein the receiver channel lies in a plane that generally extends along an axis of the receiver.
The spinal fixation system wherein the first and second channels spiral about the receiver axis.
The spinal fixation system wherein the first and second channels lie in imaginary planes that intersect an axis of the receiver at acute angles.
The spinal fixation system wherein the receiver channel lies in a receiver plane, the first channel lies in a first plane and the second channel lies in a second plane, first and second planes intersecting the receiver plane at an acute angle that extends toward a vertebrae when the screw is screwed into the vertebra.
The method wherein the method further comprises the step of situating the elongated member against a compression member which engages the screw head to fasten the elongated member to the screw when the receiver is rotated.
The method wherein the method comprises the step of aligning a receiving channel of the compression member with a receiving channel of the receiver before the situating step.
The method wherein the method comprises the step of providing the compression member and receiver pre-aligned prior to the screwing step.
The method wherein the retainer comprises a receiving channel and a locking channel, the method further comprising the steps of situating the elongated member in the receiving channel and rotating the receiver so that the elongated member becomes situated in the locking channel.
The method wherein the method further comprises the step of aligning the receiver before the rotating step.
The method wherein the method further comprises the steps of screwing a second screw into a second spinal bone, the second screw having a head that is received in a seat of a second receiver having a bore through which threads of the second screw may pass, situating the elongated member into the second receiver and rotating the second receiver to fasten the elongated member onto the second screw after performing the first rotating step, thereby fixing the relative positions of the first and second spinal bones.
The method wherein the method further comprises the step of aligning a first receiving channel of the first receiver with a second receiving channel of the second receiver before the second rotating step.
The method wherein the method further comprises the step of repeating the method using a plurality of screws having a plurality of retainers, respectively, and the elongated member to secure a plurality of vertebrae together in a fixed relationship.
The capless multiaxial screw wherein the receiver comprises a plurality of channels that capture the elongated member.
The capless multiaxial screw wherein each of the plurality of channels defines an intermediate area for capturing the elongated member to facilitate adjusting a position of the elongated member before it is locked in the receiver.
The capless multiaxial screw wherein the plurality of channels are defined by a first surface and a second surface, each of the plurality of channels having an intermediate step for defining the intermediate area.
The capless multiaxial screw wherein at least one of the first and second surfaces is not planar.
The capless multiaxial screw wherein the locking channel is a helical channel defined by at least one surface of the receiver.
The capless multiaxial screw wherein the capless multiaxial screw further comprises a compression member for situating in the bore, the compression member comprising a generally concave seat, the screw head having a curvature that generally complements the generally concave seat.
The capless multiaxial screw wherein the receiving channel comprises a first axis, the elongated member axis of the elongated member being generally parallel to the first axis when the elongated member is in the unlocked position and generally perpendicular when the receiver is actuated to the locked position.
The capless multiaxial screw wherein when the receiver is rotated, the receiver moves the elongated member from a first position to a second position in response thereto, such that when the receiver is in the second position, the elongated member is locked to the screw head.
The capless multiaxial screw wherein when the receiver is rotated, the receiver moves the elongated member from a first position, through an intermediate position, to a second position.
The capless multiaxial screw wherein the first position corresponds to the unlocked position and the second position corresponds to the locked position.
The capless multiaxial screw wherein the receiving channel is generally perpendicular to an elongated member axis of the elongated member when the receiver is in the locked position.
The capless multiaxial screw wherein the locking channel provides a bayonet connection.
The capless multiaxial screw wherein the receiving channel is generally parallel along an axis of the receiver and the locking channel spirals about the axis of the receiver when moving in an axial direction.
The capless multiaxial screw wherein the receiving channel extends from an end of the receiver in a direction that is generally parallel to an axis of the receiver and the locking channel extends in a direction that is generally not parallel to the axis of the receiver.
The capless multiaxial screw wherein the receiver comprises at least one camming surface that cooperates with an opposing surface for defining the locking channel, the at least one camming surface facilitates compressing the elongated member against the screw.
The capless multiaxial screw wherein the receiver comprises a plurality of camming surfaces that cooperate with a plurality of opposing surfaces, respectively, to define the locking channel, the a plurality of camming surfaces for camming against the elongated member to lock the receiver to the screw.
The capless multiaxial screw wherein the locking channel comprises a first locking channel area and a second locking channel area, the receiver comprises a first camming surface generally opposed to a first opposing surface to define the first locking channel area and a second camming surface generally opposed to a second opposing surface to define the second locking channel area, the first and second camming surfaces camming against the elongated member to force the elongated member against the compression member which, in turn, applies a compressive force against the screw head when the receiver is rotated.
The capless multiaxial screw wherein the locking channel comprises a lock member associated therewith for facilitating retaining the receiver in a locked position.
The capless multiaxial screw wherein the lock member comprises a detent in the receiver and associated with the locking channel.
The capless multiaxial screw wherein the lock member cooperates with an end wall of the locking channel to define a locking area at which the receiving member is locked when it is in the locked position.
The capless multiaxial screw wherein the receiving channel lies in a first plane that is generally planar and the locking channel lies in a second plane that is non-planar.
The capless multiaxial screw wherein the second plane spirals about an axis of the retainer.
The capless multiaxial screw wherein the locking channel spirals about an axis of the retainer.
The capless multiaxial screw wherein the receiver comprises a seat, the screw head is being generally spherical and the seat is also generally spherical and dimensioned to receive and complement the screw head.
These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.
Referring now to
As illustrated in
The spinal fixation assembly 10 comprises a retainer or receiver 20 having a generally cylindrical receiver wall 20c (
As shown in FIGS. 3 and 11-13, the bore 22 receives the threaded portion 12a of the screw 12 until the screw head 12b is received in the seat 20d (as illustrated in
Note that the receiver 20 comprises a receiving channel 26 (
In one embodiment, the lock 28 cooperates and is in communication with the receiving channel 26 to provide a continuous channel 30 for receiving the elongated member or rod 24. The lock 28 cooperates with the receiving channel 26 and urges rod 24 toward the screw head 12b and vertebra, such as one of the vertebra 14-18 in
Note that the lock 28 comprises the first channel 32 and a second channel 34 (
As illustrated in
The channels 32 and 34 generally lay in planes P1 and P2 that are at the angles C (
As illustrated in
The spinal fixation assembly 10 may further comprise a compression member 40 (
The compression member 40 comprises a length D6 (
During operation, the compression member 40 is urged downward (as shown in
Note that the compression member 40 (
Referring back to
As shown in
An operation or method regarding this illustration will now be described. As illustrated in
The channel 26 of receiver 20 and second channel 42 of compression member 40 are provided or arranged in a common plane P3, as shown in
Note that the rod 24 is supported by and between the arcuate or curved wall portions 50 and 52, which causes the rod 24 to be situated above the bottom surface 40c of the second channel 42 of compression member 40, as illustrated in
The camming or bayonet type action of the rotary lock 28 on receiver 20 forces the rod 24 in an axial direction parallel with axis A of receiver 20 when the receiver 20 is turned or rotated with a tool, such as a screwdriver (not shown), placed in channel 26, as illustrated in
It should be appreciated that when the rod 24 is in the locked position shown in
Thus, as illustrated in
If the compression member 40 is being used, compression member 40 is located in each bore 22 of each receiver 20 and generally aligns the channels 42 and 26, as illustrated in
At this point in the procedure, the surgeon aligns the rod 24 in the receiver 20 to the desired position relative to the spine, vertebrae and other receivers 20 that are being used. He positions the rod 24 and polyaxial or angular position of each receiver(s) 20 relative thereto. It should be understood that the screws and position of the vertebrae, such as vertebrae 14-18, relative to each other may also be adjusted. Once the bones 14-18 are adjusted and angular or polyaxial position of each receiver 20 is adjusted, the surgeon locks each receiver 20 to rod 24 by rotating or turning the receiver 20 with a tool, such as a screwdriver (not shown), placed in channel 26. This causes the receivers 20 to become fixed or locked onto their respective screws 12 and the spinal bones or vertebrae 14-18 (
It should be understood that before the rod 24 is placed in the receiving channel 26 and the receiver 20 is rotated, the surgeon may tighten one or more screws 12 to a tighter or fixed seated position by situating the tool, such as a hex wrench (not shown), through the aperture 43 (
As mentioned, the surgeon rotates the receiver 20 about its axis, as illustrated in
Thus, when it is desired to lock the receiver 20 and the screw 12 to the rod 24, the surgeon rotates the receiver 20 in the clockwise direction, as illustrated in
Thus, it should be understood that when receiver 20 is rotated, the walls 20e and 20h provide the camming force necessary to cam and urge the rod 24 against the compression member 40. This, in turn, causes the surface or wall 40b of compression member 40 to compress and lock against the end portion 12b2 (
As illustrated in
It should be appreciated from the foregoing that the receiving channel 26 is in communication with the channels 32 and 34 of lock 28 and that the lock 28 cooperates with the rod 24 to not only lock the rod 24 to the screw 12, but also to fix a position of the vertebrae 14, 16 and 18.
When it is desired to unlock the rod 24 from the screw 12, the surgeon simply rotates the receiver 20 in a counterclockwise direction in the illustration and reverses the procedure.
Referring now to
Note in the embodiment in
It should be appreciated that the intermediate holding area 60b in the channels 32′ and 34′ enable an intermediate step between initial rod 24′ insertion and final rod 24′ locking. In other words, this is a rod 24′ capturing step during which the rod 24′ is loosely captured in the receiver 20′, but it is not rigidly locked into place against screw 12′ yet. This allows the surgeon greater ease and flexibility when he adjusts the screws 12′ position with respect to the rod 24′ while the rod 24′ is in place. For example, the surgeon may move the screws 12′ closer together (compression) or In the illustration being described, the intermediate capturing step is accomplished by rotating the receiver 20′ partially, such as approximately 30 degrees in the illustration as shown in
The introduction area comprises an associated dimension D13 (
In the illustration shown in
The channels 32′ and 34′ are configured such that they comprise or define the introduction area 60a for receiving the rod 24′ in the receiver 20′, as illustrated in
During a surgical procedure, the surgeon may make the desired adjustments of the rod 24′ relative to the screws 12′ and vertebrae 14′-18′ while the rod 24′ is loosely captured in the intermediate holding area 60b. The surgeon then uses the tool, such as a screwdriver (not shown), to rotate the receiver 20′ to the locked position shown in
Advantageously, this system and method facilitates providing a locking receiver 20 that reduces or eliminates the need for threading, internally or externally.
Advantageously, the immediate holding areas 60b of channels 32′ and 34′ of the second embodiment are dimensioned and configured to facilitate locking the rod 24′ onto the screws 12′ while permitting ease of adjustment between the receiver 20′ and the rod 24′ when the rod 24′ and receiver 20′ are situated in the intermediate holding area 60b′, as illustrated in
In the embodiments being described, the rod 24, screw 12, receiver 20 and compression member 40 are all made of titanium alloy. Other materials may be used such as metals, metal alloys, carbon fibers, composites, plastics or hybrid materials.
For example, the screw 12 may have a length D11 (
Advantageously, this system and method provide a capless multiaxial screw which eliminates the need for caps or screws or threads of the type used in the prior art. This system and method combine a very simplified yet effective means for locking an elongated member or rod 24 to a screw 12 and spinal bone in the manner described and shown herein.
While the apparatus, system and method herein described, and the form of apparatus for carrying this method into effect, constitute several illustrative embodiments of this invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made in either without departing from the scope of the inventions, which is defined in the appended claims.
Claims
1. A spinal fixation assembly comprising:
- a receiver having a bore for receiving a screw having a screw head that is larger received in said bore; and
- a compression member dimensioned to be received in said bore and having a first end for receiving an elongated member and a second end for engaging said screw head;
- said receiver comprising a receiving channel for receiving said elongated member and a locking channel for locking said elongated member to said screw when said receiver is rotated from an unlocked to a locked position.
2. The spiral fixation assembly as recited in claim 1 wherein said locking channel spirals about an axis of said receiver.
3. The spiral fixation assembly as recited in claim 1 wherein said locking channel and said receiving channel cooperate to provide a bayonet connection between said elongated member and said screw.
4. The spiral fixation assembly as recited in claim 1 wherein said bore comprises a generally rounded or tapered seat associated with a coupling end of said receiver, said screw head comprising a rounded profile and received in said rounded seat to permit said receiver to move polyaxially relative to said screw after said screw is mounted into a vertebra.
5. The spiral fixation assembly as recited in claim 1 wherein said bore comprises a diameter that is greater than a cross-sectional dimension of said receiving channel and said compression member comprises a diameter that is received in said bore.
6. The spiral fixation assembly as recited in claim 1 wherein said bore comprises a bore diameter that is greater than a cross-sectional dimension of said receiving channel and said compression member comprising a compression member diameter that is greater than said cross-sectional dimension of said receiving channel, but less than said bore diameter.
7. The spinal fixation assembly as recited in claim 1 wherein said compression member comprises a second receiving channel, wherein said receiving channel comprises a first axis and said second receiving channel comprises a second axis, said second axis and said first axis being generally parallel when said elongated member is in said unlocked position and generally perpendicular when said elongated member is in said locked position.
8. The spinal fixation assembly as recited in claim 1 wherein when said receiver is rotated from said unlocked position to said locked position, said elongated member becomes secured to said screw and situated closer to said screw.
9. The spinal fixation assembly as recited in claim 8 wherein when said receiver is in an unlocked position, said receiving channel becomes generally aligned with a second receiving channel in said compression member.
10. The spinal fixation assembly as recited in claim 1 wherein said receiving channel is generally perpendicular to an elongated member axis of said elongated member when said receiving member is in said locked position.
11. The spinal fixation assembly as recited in claim 1 wherein said locking channel spirals from a first end of said receiver toward a second end of said receiver.
12. The spinal fixation assembly as recited in claim 1 wherein said locking channel defines a helix.
13. The spinal fixation assembly as recited in claim 1 wherein said receiving channel extends from an end of said receiver in a direction that is generally parallel to an axis of said receiver and said locking channel extends at least partially about said axis of said receiver.
14. The spinal fixation assembly as recited in claim 1 wherein said compression member comprises a second receiving channel that becomes generally aligned with said receiving channel when said elongated member is received in said receiver and said first and second receiving channels becoming generally perpendicular when said receiver is rotated to said locked position.
15. The spinal fixation assembly as recited in claim 1 wherein said receiver comprises at least one camming surface that cooperates with an opposing surface for defining said locking channel, said at least one camming surface camming against said elongated member to move said elongated member against said compression member which, in turn, applies a compressive force against said screw head in response thereto.
16. The spinal fixation assembly as recited in claim 1 wherein said receiver comprises a plurality of camming surfaces that cooperate with a plurality of opposing surfaces, respectively, to define said locking channel, said plurality of camming surface camming against said elongated member to force said elongated member against said compression member which, in turn, applies a compressive force against said screw head when said receiver is rotated.
17. The spinal fixation assembly as recited in claim 1 wherein said locking channel comprises a first locking channel area and a second locking channel;
- said receiver comprises a first camming surface generally opposed to a first opposing surface to define said first locking channel area and a second camming surface generally opposed to a second opposing surface to define said second locking channel area, said first and second camming surfaces camming against said elongated member to force said elongated member against said compression member which, in turn, applies a compressive force against said screw head when said receiver is rotated.
18. The spinal fixation assembly as recited in claim 17 wherein said locking channel comprises a lock member associated therewith for facilitating retaining said receiver in a locked position.
19. The spinal fixation assembly as recited in claim 18 wherein said lock member comprises a detent or protrusion or a plurality of detents or protrusions in said receiver and associated with said locking channel.
20. The spinal fixation assembly as recited in claim 18 wherein said lock member cooperates with an end wall of said locking channel to define a locking area at which said elongated member is locked when it is in said locked position.
21. The spinal fixation assembly as recited in claim 1 wherein said receiving channel lies in a first plane that is generally planar and said locking channel lies in a second plane that is non-planar.
22. The spinal fixation assembly as recited in claim 1 wherein said second plane spirals about an axis of said receiver.
23. The spinal fixation assembly as recited in claim 1 wherein said locking channel extends in a direction that is non-axial relative to an axis of said receiver.
24. The spinal fixation assembly as recited in claim 1 wherein said screw head is generally spherical and said compression member comprises a seat that is also generally spherical and dimensioned to receive said screw head.
Type: Application
Filed: Feb 6, 2013
Publication Date: Jun 13, 2013
Applicant: X-spine Systems, Inc. (Miamisburg, OH)
Inventor: David Louis Kirschman (Dayton, OH)
Application Number: 13/760,332
International Classification: A61B 17/70 (20060101);