Bone screw
A bone fixation system with variable z-axis translation is provided. The bone fixation system includes an outer tulip coupled to a bone fastener. An inner tulip, which provides a seat for an elongate fixation rod, is located inside the outer tulip. The inner tulip together with a seated rod is permitted to translate along the z-axis in an unlocked position. Also in the unlocked position, the bone fastener is free to angulate relative to the outer tulip. The bone fixation system includes a locked position in which the z-axis position of the inner tulip and rod relative to the outer tulip is fixed. Also in the locked position, the bone fastener is locked with respect to the outer tulip. The system may be adjusted between the locked and unlocked positions by way of a set screw or independently by rotation of the inner tulip relative to the outer tulip.
This application is a continuation of U.S. patent application Ser. No. 15/230,190 filed on Aug. 5, 2016 entitled “Bone screw” which is a continuation of U.S. patent application Ser. No. 14/175,058 filed on Feb. 7, 2014 entitled “Bone screw” now U.S. Pat. No. 9,451,991 which claims priority to and benefit of U.S. Provisional Patent Application Ser. No. 61/762,854 entitled “Threaded bone screw with variable Z-axis translation” filed on Feb. 9, 2013, U.S. patent application Ser. No. 15/230,190 filed on Aug. 5, 2016 entitled “Bone screw” is also a continuation of U.S. patent application Ser. No. 14/175,065 filed on Feb. 7, 2014 entitled “Bone screw” now U.S. Pat. No. 9,463,047 which claims priority to and benefit of U.S. Provisional Patent Application Ser. No. 61/762,854 entitled “Threaded bone screw with variable Z-axis translation” filed on Feb. 9, 2013, all of which are incorporated by reference in their entirety herein.
FIELD OF THE INVENTIONThe present invention is directed to surgical devices and methods, and in particular, to bone fixation devices used in spinal surgery.
BACKGROUND OF THE INVENTIONSpinal fusion is a common surgical procedure used to correct numerous disease states including degenerative disorders, trauma, instability, and deformity. A frequent method of fusion entails the use of bone screws placed through various sections of the vertebral body including the body, pedicle, facets, lamina, lateral masses, and/or transverse processes. These screws are then linked rigidly with a rod, plate or other fixation device to immobilize the vertebral segments.
Due to the variation in a patient's anatomy and differences in screw placement technique, screws are often not perfectly aligned which makes securement of a fixation device more difficult. To solve this, many screws that have a threaded shank portion incorporate an articulating tulip or receiver connected to the proximal end of the shank portion, such as in a polyaxial or multi-axial bone screw. Polyaxial bone screws allow for a variation in the angulation of the tulip/receiver relative to the shank portion in order to allow the tulip/receiver to more closely align for receiving a fixation device such as a fixation rod within the tulip/receiver. Some bone screws allow for the lateral translation of the tulip/receiver relative to its point of fixation. Further alignment may be accomplished by contouring of the fixation device itself to compensate for any remaining misalignment. For example, if a fixation rod is employed, the rod is bent to conform to the patient anatomy and location of the tulip/receiver to securely attach thereto.
A body in three-dimensional space has six degrees of freedom, namely, translation through the perpendicular x, y, and z planes, combined with the rotation through the three perpendicular axes (pitch, yaw, and roll). Typical articulating polyaxial screws allow three dimensional rotations (pitch, yaw, and roll). Some designs also incorporate lateral x-plane translation. Longitudinal translation (y-plane), generally along the cephalad-caudal direction or axis of the fixating rod or plate, is usually accomplished by fixing the tulip/receiver to different positions along the rod or plate.
Anterior/posterior translation (along the z-plane) is typically accomplished by persuading the vertebral body itself, using instruments to raise or lower the vertebral body until the tulip/receiver is properly aligned with the rod or plate. Frequently, however, this anterior/posterior translation may not be desirable as it may produce suboptimal alignment of the vertebral bodies or even cause fractures of the bone or pullout of the shank portion of the screw from the bone due to the stresses placed on it during the persuading process. The other option for adjustment along the z-axis employed is to partially back out the screw, leaving it proud. This, however, reduces the bone-screw interface thereby weakening the overall strength of the construct. Some designs, such as the one illustrated in U.S. Pat. No. 7,588,593, allow for vertical adjustment but require manual assembly of the screw and head construct during surgery. Hence, there is a need for modular bone screw assemblies that can provide variable angle orientation together with z-axis translation which are easy to assemble.
SUMMARY OF THE INVENTIONAccording to one aspect of the invention, a bone fixation system is provided. The bone fixation system includes a bone fastener having a bone engaging portion and a head connected to the bone engaging portion. The system includes an outer receiver having a proximal end, a distal end and a longitudinal axis. The outer receiver includes a sidewall extending between the proximal end and the distal end and having an inner surface and an outer surface. An inner bore extends through the outer receiver between a top opening at the proximal end and a bottom opening at the distal end. The bone fastener is connected to the outer receiver such that the bone engaging portion extends through the bottom opening. The outer receiver includes two oppositely disposed arms that are defined by the sidewall and at least one rod channel that is defined between the two arms. The at least one rod channel is interconnected with the top opening and the inner bore. The inner surface of each arm has a longitudinally extending interlocking surface adjacent to a longitudinally extending smooth surface. The interlocking surface of one arm is opposite from the interlocking surface of the other arm and the smooth surface of one arm is opposite from the smooth surface of the other arm. The outer receiver further includes an interlocking inner surface at the distal end. The bone fixation system further includes a first locking cap located inside the inner bore of the outer receiver. The first locking cap has an interlocking outer surface configured to interlock with the interlocking inner surface at the distal end of the outer receiver. The first locking cap has at least one upwardly extending tab. The bone fixation system further includes an inner receiver that is sized to fit inside the outer receiver. The inner receiver includes a base and two oppositely disposed arms extending upwardly from the base. The inner receiver includes at least one channel defined between the arms. Each arm has an interlocking inner surface and an interlocking outer surface. The interlocking outer surface of each arm of the inner receiver is configured to engage the interlocking surfaces on the arms of the outer receiver. The inner receiver is coupled to the first locking cap by the at least one tab. A second locking cap is removably located between the arms of the inner receiver and has an interlocking outer surface configured to interlock with the interlocking inner surface of the arms of the inner receiver. The bone fixation system includes an unlocked position in which the bone fastener angulates with respect to the outer receiver and the inner receiver is free to translate longitudinally with respect to the outer receiver; and a locked position in which the bone fastener and inner receiver are fixed with respect to the outer receiver.
According to another aspect of the invention, a bone fixation system is provided. The bone fixation system includes a bone fastener having a bone engaging portion and a head integrally connected to the bone engaging portion. The system includes an outer receiver having a proximal end, a distal end and a longitudinal axis. The outer receiver has a sidewall extending between the proximal end and the distal end and an inner surface and an outer surface. The outer receiver includes an inner bore extending between a top opening at the proximal end and a bottom opening at the distal end. The bone fastener is connected to the outer receiver such that the bone engaging portion extends through the bottom opening. The outer receiver includes two oppositely disposed arms defined by the sidewall and at least one rod channel defined between the two arms. The at least one rod channel is interconnected with the top opening and the inner bore. The inner surface of each arm of the outer receiver has a longitudinally extending interlocking inner surface adjacent to a longitudinally extending smooth surface. The interlocking inner surface of one arm is opposite from the interlocking inner surface of the other arm and the smooth surface of one arm is opposite from the smooth surface of the other arm. The outer receiver includes an interlocking inner surface at the distal end. The bone fixation system further includes a first locking cap located inside the inner bore of the outer receiver. The first locking cap has an interlocking outer surface configured to interlock with the interlocking inner surface at the distal end. The outer surface of the first locking cap is interconnected by a top surface and a bottom surface. The first locking cap includes two tab-engaging surfaces. The bone fixation system further includes an inner receiver sized to fit inside the outer receiver. The inner receiver includes a base and two oppositely disposed arms extending upwardly from the base. The inner receiver includes at least one channel defined between the arms and each arm has an interlocking inner surface and an interlocking outer surface. The interlocking outer surface of each arm of the inner receiver is configured to engage the interlocking inner surfaces on the arms of the outer receiver. The inner receiver further includes two oppositely disposed tabs extending downwardly from the base. The two tabs are configured for engagement with the two tab-engaging surfaces on the first locking cap. The inner receiver is coupled to the first locking cap by the two tabs engaging the tab-engaging surfaces. The bone fixation system further includes a second locking cap removably located between the arms of the inner receiver and having an interlocking outer surface configured to interlock with the interlocking inner surface of the arms of the inner receiver. The bone fixation system includes an unlocked position in which the bone fastener angulates with respect to the outer receiver and the inner receiver is free to translate longitudinally with respect to the outer receiver and a locked position in which the bone fastener and inner receiver are fixed with respect to the outer receiver.
According to another aspect of the invention, a bone fixation system is provided. The bone fixation system includes an outer receiver having an inner bore and an open proximal end and an inner receiver having an inner bore and an open proximal end. The inner receiver is located inside an outer receiver. The inner receiver is movable along a longitudinal axis relative to the outer receiver in an unlocked position and the inner receiver is longitudinally fixed relative to the outer receiver in a locked position. Converting between the locked and unlocked positions is achieved by rotation of the inner receiver relative to the outer receiver.
According to another aspect of the invention, a bone fixation system is provided. The bone fixation system includes an outer receiver having a sidewall that defines an inner bore and an open proximal end. The sidewall has an inner surface and an outer surface that defines at least one channel opening to the inner bore and the open proximal end. The outer receiver includes an interlocking inner surface formed on the inner surface. The bone fixation system further includes an inner receiver including a sidewall that defines an interior, an open proximal end, and an inner base at a distal end. The sidewall has an inner surface and an outer surface that defines at least one channel opening to the interior and the open proximal end. The inner receiver includes an interlocking inner surface formed on the inner surface and an interlocking outer surface formed on the outer surface. The inner receiver is located inside the outer receiver such that the at least one channel of the inner receiver is substantially aligned with the at least one channel of the outer receiver. The inner receiver is movable along a longitudinal axis relative to the outer receiver in an unlocked position. A rod is disposed inside the at least one channel of the inner receiver. The bone fixation system further includes a first locking cap having an interlocking outer surface. The first locking cap is located in the inner receiver such that the interlocking outer surface of the first locking cap is interlocked with the interlocking inner surface of the inner receiver in a first locked position. The rod is located between the inner base and the first locking cap and the inner receiver is free to translate longitudinally in the first locked position.
According to another aspect of the invention, a bone fixation system is provided. The bone fixation system includes a bone fastener having a bone engaging portion and a head integrally connected to the bone engaging portion. The bone fixation system further includes an outer receiver having a proximal end, a distal end and a longitudinal axis. The outer receiver has a sidewall extending between the proximal end and the distal end and an inner surface and an outer surface. An inner bore extends between a top opening at the proximal end and a bottom opening at the distal end of the outer receiver. The bone fixation system further includes a bone fastener connected to the outer receiver such that the bone engaging portion extends through the bottom opening. Two oppositely disposed arms are defined by the sidewall of the outer receiver and at least one rod channel is defined between the two arms. The at least one rod channel is interconnected with the top opening and the inner bore. The inner surface of each arm has a longitudinally extending interlocking inner surface adjacent to a longitudinally extending smooth surface. The interlocking inner surface of one arm is opposite from the interlocking inner surface of the other arm and the smooth surface of one arm is opposite from the smooth surface of the other arm. The outer receiver further includes an interlocking inner surface at the distal end. The bone fixation system further includes a first locking cap located inside the inner bore of the outer receiver. The first locking cap has an interlocking outer surface configured to interlock with the interlocking inner surface at the distal end of the outer receiver. The bone fixation system further includes an inner receiver sized to fit inside the outer receiver. The inner receiver includes a base and two oppositely disposed arms extending upwardly from the base. The inner receiver includes at least one channel between the arms. Each arm has an interlocking inner surface. The inner receiver is located inside the inner bore of outer receiver such that the oppositely disposed arms of the inner receiver are disposed in the location of the smooth surfaces and the interlocking inner surface of each arm is flush with the adjacent interlocking surfaces of the outer receiver. The bone fixation system further includes a second locking cap located between the arms of the inner receiver. The second locking cap has an interlocking outer surface configured to interlock with both the interlocking inner surface of the arms of the inner receiver and the adjacent interlocking inner surface of the arms of the outer receiver. The inner receiver includes an unlocked position in which the inner receiver is free to translate longitudinally with respect to the outer receiver and a locked position in which the inner receiver is fixed with respect to the outer receiver. The locked position is achieved by the interlocking outer surface of the second locking cap engaging both the interlocking inner surface of the outer receiver and the interlocking inner surface of the inner receiver.
According to another aspect of the invention, a bone fixation system is provided. The bone fixation system includes an outer receiver. The outer receiver has a sidewall that defines an inner bore and an open proximal end. The sidewall has an inner surface and an outer surface that defines at least one channel opening to the inner bore and the open proximal end. The outer receiver includes an interlocking inner surface formed on the inner surface. The bone fixation system further includes an inner receiver. The inner receiver has a sidewall that defines an interior, an open proximal end, and an inner base at a distal end. The sidewall of the inner receiver has an inner surface and an outer surface that defines at least one channel opening to the interior and the open proximal end. The inner receiver includes an interlocking inner surface formed on the inner surface. The inner receiver is located inside the outer receiver such that the at least one channel of the inner receiver is substantially aligned with the at least one channel of the outer receiver. The inner receiver is movable along a longitudinal axis relative to the outer receiver in an unlocked position. The bone fixation system further includes a locking cap having an interlocking outer surface. The locking cap is located in the inner receiver and interlocked with the interlocking inner surface of the outer receiver and the interlocking inner surface of the inner receiver in a locked position wherein longitudinal translation of the inner receiver is fixed relative to the outer receiver.
According to another aspect of the invention, a bone fixation system is provided. The bone fixation system includes an outer receiver. The outer receiver has a sidewall that defines an inner bore and an open proximal end. The sidewall has an inner surface and an outer surface that defines at least one channel opening to the inner bore and the open proximal end. The outer receiver includes an interlocking outer surface formed on the outer surface. The bone fixation system further includes an inner receiver. The inner receiver has a sidewall that defines an interior, an open proximal end, and an inner base at a distal end. The sidewall has an inner surface and an outer surface that defines at least one channel opening to the interior and the open proximal end. The inner receiver includes an interlocking inner surface formed on the inner surface. The inner receiver is located inside the outer receiver such that the at least one channel of the inner receiver is substantially aligned with the at least one channel of the outer receiver. The inner receiver is movable along a longitudinal axis relative to the outer receiver in an unlocked position. The bone fixation system includes a locking cap. The locking cap has an interlocking outwardly-facing surface and an interlocking inwardly-facing surface. The interlocking outwardly-facing surface is movable independently and relative to the interlocking inwardly-facing surface. The interlocking outwardly-facing surface is located in the inner receiver and interlocked with the interlocking inner surface of the inner receiver in a first locked position. The interlocking inwardly-facing surface is interlocked with the interlocking outer surface of the outer receiver in a second locked position. The second locked position prevents the longitudinal translation of the inner receiver relative to the outer receiver.
According to another aspect of the invention, a bone fixation system is provided. The bone fixation system includes a bone fastener having a bone-engaging portion and a head integrally connected to the bone-engaging portion. The bone fixation system further includes an outer receiver having a proximal end, a distal end and a longitudinal axis. The outer receiver includes a sidewall extending between the proximal end and the distal end. The outer receiver has an inner surface and an outer surface and an inner bore extending between a top opening at the proximal end. The outer receiver includes a bottom opening at the distal end. The bone fastener is connected to the outer receiver such that the bone-engaging portion extends through the bottom opening. The outer receiver includes two oppositely disposed arms defined by the sidewall and at least one rod channel defined between the two arms. The at least one rod channel is interconnected with the top opening and the inner bore. The outer surface of each arm has a longitudinally extending interlocking outer surface adjacent to a longitudinally extending smooth surface. The interlocking outer surface of one arm is opposite from the interlocking outer surface of the other arm and the smooth surface of one arm is opposite from the smooth surface of the other arm. The outer receiver includes an interlocking inner surface at the distal end. The bone fixation system includes a first locking cap located inside the inner bore of the outer receiver. The first locking cap has an interlocking outer surface configured to interlock with the interlocking inner surface at the distal end of the outer receiver. The bone fixation system further includes inner receiver that includes a base and two oppositely disposed arms extending upwardly from the base. At least one channel is defined between the arms. Each arm has an interlocking inner surface. The inner receiver is located inside the inner bore of the outer receiver. The bone fixation system includes a second locking cap having an outer surface and inner surface interconnected by a top surface and a bottom surface. The second locking cap has two oppositely disposed, downwardly extending legs; each leg has an interlocking inner surface configured to engage the longitudinally extending interlocking outer surface of each arm of the outer receiver. The second locking cap includes a cylinder configured to rotate relative to the legs. The cylinder includes an interlocking outer surface that is configured to engage with the interlocking inner surface of the inner receiver. The cylinder is connected to the inner receiver by engagement of the threaded outer surface of the cylinder with the threaded inner surface of the inner receiver. The inner receiver includes an unlocked position in which the inner receiver is free to translate longitudinally with respect to the outer receiver and a locked position in which the inner receiver is fixed with respect to the outer receiver. The bone fastener includes an unlocked position in which the bone fastener angulates with respect to the outer receiver and a locked position in which the bone fastener is fixed with respect to the outer receiver. The first locking cap is rotated into interlocking engagement with the interlocking surface of the interlocking inner surface at the distal end and downwardly within the inner bore of the outer receiver against the head of the bone fastener into the locked position to fix the position of the bone fastener relative to the outer receiver. The top surface of the second locking cap includes slots for engaging a tool to rotate the legs of the second locking cap between the unlocked and locked positions. The bone fixation system further includes a cover having a circular top and a plurality of downwardly extending, circumferentially located legs. The top has at least one slot configured to access the slots of the second locking cap. The bone fixation system further includes an elongate fixation rod located between the arms of the inner receiver. Rotation of the cylinder of the second locking cap downwardly onto the rod fixes the position of the rod relative to the inner receiver. In the locked position, the legs of the second locking cap are interlocked with the outer receiver.
The invention is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to-scale. On the contrary the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:
Before the subject devices, systems and methods are described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a spinal segment” may include a plurality of such spinal segments and reference to “the screw” includes reference to one or more screws and equivalents thereof known to those skilled in the art, and so forth.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.
All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.
It should also be understood that the term “system”, when referring to a system of the present invention, most typically refers to a set of components which includes multiple bone stabilization components such as a superior or cephalad component configured for implantation into a superior vertebra of a vertebral motion segment and an inferior or caudal (towards the feet) component configured for implantation into an inferior vertebra of a vertebral motion segment. A pair of such component sets may include one set of components configured for implantation into and stabilization of the left side of a vertebral segment and another set configured for the implantation into and stabilization of the right side of a vertebral segment. Where multiple bone segments such as spinal segments or units are being treated, the term “system” may refer to two or more pairs of component sets, i.e., two or more left sets and/or two or more right sets of components. Such a multilevel system involves stacking of component sets in which each set includes a superior component, an inferior component, and one or more medial components therebetween.
The superior and inferior components (and any medial components therebetween), when operatively implanted, may be engaged or interface with each other in a manner that enables the treated spinal motion segment to mimic the function and movement of a healthy segment, or may simply fuse the segments such as to eliminate pain and/or promote or enhance healing. The interconnecting or interface means include one or more structures or members that enables, limits and/or otherwise selectively controls spinal or other body motion. The structures may perform such functions by exerting various forces on the system components, and thus on the target vertebrae. The manner of coupling, interfacing, engagement or interconnection between the subject system components may involve compression, distraction, rotation or torsion, or a combination thereof. In certain embodiments, the extent or degree of these forces or motions between the components may be intra-operatively selected and/or adjusted to address the condition being treated, to accommodate the particular spinal anatomy into which the system is implanted, and to achieve the desired therapeutic result.
In certain embodiments, the multiple components, such as superior and inferior spinal components, are mechanically coupled to each other by one or more interconnecting or interfacing means or fixation devices such as elongate fixation members, rods and plates but are not limited thereto. In other embodiments, components interface, in a manner that constrains their relative movement and enables the treated segment to mimic the function or partial function and/or movement or partial movement of a healthy segment. Typically, spinal interconnecting means is a dorsally positioned component, i.e., positioned posterior of the superior and inferior components, or may be a laterally positioned component, i.e., positioned to the outer side of the posterior and inferior components. The structures may include one or more struts and/or joints that provide for stabilized spinal motion. The various system embodiments may further include a band, interchangeably referred to as a ligament, which provides a tensioned relationship between the superior and inferior components and helps to maintain the proper relationship between the components.
Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In addition, each of the inventive embodiments described herein may be employed in a percutaneous, minimally invasive surgical procedure, a mini-open procedure or an open procedure. Utilization of minimally invasive techniques can shorten the procedure's time and speed recovery by the patient. The application of these inventions in a minimally invasive manner is not a requirement. Also, the invention is not limited to the spine and may be employed in other areas where fixation to bone is useful either in human or animal applications.
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The sidewall 40 of the outer receiver 24 forms two upstanding, oppositely disposed arms 50. The arms 50 are spaced apart from each other to define at least one channel 52 in the sidewall 40. In one variation, the channels 52 comprise two oppositely disposed, substantially U-shaped spaces that interconnect with the proximal opening 42 and the inner bore of the outer receiver 24. The channels 52 are shaped to receive an elongate fixation member 32 such as a spinal fixation rod or other elongate member to be connected to the outer receiver 24 by placement of the elongate fixation member 32 into the channels 52. The outer receiver 24 includes a rod-receiving location 54. The rod-receiving location 54 is generally located above the bone fastener receiving location 46. In the rod-receiving location 50 of the outer receiver 24, the inner surface defines at least two oppositely disposed threaded portions or inner interlocking surfaces 56. These threaded portions 56 extend longitudinally vertically in the rod-receiving location 54 and are configured to threadingly engage threads or other complimentary interlocking features formed on the outer surface of the rod locking cap 30. Adjacent to the threaded portions 56 are two oppositely disposed smooth surfaces 58 that also run longitudinally vertically in the rod-receiving location 54. The smooth surfaces 58 provide the inner receiver 28 with a channel or location for unimpeded longitudinal, vertical translation of the inner receiver 28 relative to the outer receiver 24. The smooth surfaces 58 may appear as vertical notches or recessed portions formed into the inner surface of the outer receiver 24. Hence, the inner surface of the outer receiver 24 includes both recessed regions 58 and non-recessed regions 56. The non-recessed regions 56 include threads 60. The recessed regions 58 are recessed with respect to the non-recessed regions 56. The recessed regions 58 are smooth surfaces that extend longitudinally vertically adjacent to the longitudinally extending non-recessed threaded regions 56 in the rod receiving location 54. The recessed regions 58 are configured to receive the arms of the inner receiver 28 such that the inner receiver 28 may translate vertically relative to the outer receiver 24 within the recessed regions 58. With the inner receiver 28 positioned within the recessed regions 58, the inner surface of the arms of the inner receiver 28 are flush with the non-recessed regions 56 of the inner surface of the outer receiver 24 as are their respectively interlocking surfaces/threads to provide a smooth transition between them for unimpeded locking engagement. The outer surface of the outer receiver 24 may include two small holes (not shown) oppositely disposed in the arms 50 for permitting a reduction instrument or other instrument to grasp onto the outer receiver 24.
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The bone fixation system 20 is assembled by passing the shank portion 36 of the bone fastener 22 through the proximal opening 42 and into the distal opening 44 in the outer receiver 24 with the head 34 coming to rest in the seat of the bone fastener receiving location 46 of the outer receiver 24. An additional retainer (not shown) may be employed if the distal opening 44 is too large to retain the head 34 of the bone fastener 22. The retainer forms an additional seating location for the bone fastener 22 permitting it to be retained inside the outer receiver 24. The fastener locking cap 26 is inserted into inner bore of the outer receiver 24 and into the bone fastener receiving location 46 where the threads 70 of the bone fastener locking cap 26 are engaged with threads 48 in the bone fastener receiving location 46 in a manner that permits angulation of the fastener 22 or not as desired. At least one optional spring 95 is disposed in spring-receiving areas and the inner receiver 28 is inserted into the inner bore of the outer receiver 24 such that the arms 88 of the inner receiver 28 slide within the recessed portions 58. An elongate fixation member 32 is located between the arms 88 within the inner receiver 28. The elongate fixation member 32 is permitted to translate along the longitudinal z-axis together with the inner receiver 28 being biased by the at least one spring 95 when in an unlocked position. When the desired position along the z-axis is ascertained, the rod locking cap 30 is inserted into the outer receiver 24 and between the arms 88 of the inner receiver 28 and the threads 91 on the rod locking cap 30 are threadingly engaged with the threads 94 on the inner receiver 28 simultaneously with the threads 60 on the outer receiver 24 to lock the longitudinal translation of the inner receiver 28 relative to the outer receiver 24. Initial threaded engagement of the rod-locking cap 30 may be with the inner receiver 28 or outer receiver 24 before simultaneously threading with both. Continued downward threaded engagement of the rod locking cap 30 results in the rod locking cap 30 bearing down upon the elongate fixation member 32 locking it into position. At any time, the fastener locking cap 26 may be turned by grasping the prongs 74 such that the fastener locking cap 26 translates downwardly and bears down with force onto the head 34 of the bone fastener 22 locking its angulation relative to the outer receiver 24. Prior to insertion of an elongate fixation member 32, a driver is inserted into the inner bore of the outer receiver 24, through the central aperture 86 of the inner receiver 28, through the bore 72 of the fastener locking cap 26 to engage the driver connection feature 38 in the head 34 of the bone fastener 22. The driver is then turned to drive the bone fastener 22 into the bone anatomy. With the shank portion 36 resident in the anatomy, the outer receiver 24 is permitted to angulate relative to the bone fastener 22 until the fastener locking cap 26 is turned to a locked position in which it bears downwardly onto the head 34 of the fastener 22 thereby arresting the angulation of the outer receiver 24 relative to the bone fastener 22. The fastener locking cap 26 may be rotated in an opposite direction to unlock the outer receiver 24 relative to the bone fastener 22 so that the angulation of the outer receiver 24 may be adjusted and relocked as desired. This may be repeated as needed
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The bone fastener 102 is configured to engage the anatomy to couple the bone fixation system 100 to the anatomy. The bone fastener 102 includes a head 116 at a proximal end and an elongate threaded shank portion 118 extending between the head 116 and a distal end along a longitudinal axis. The bone fastener 102 is configured as a typical bone screw; however, the invention is not so limited and any fastener or other-shaped anchor may be employed. The bone fastener 102 may be a self-tapping bone screw having at least one cutting flute. Alternatively, a bone screw that requires a hole to be pre-tapped prior to insertion may be employed. The head 116 can be generally arcuate having a curved or bulbous outer surface and may be spherical or partially spherical in shape. The head 116 can include a driver connection feature 119 at the proximal end for mating with any type of driver such as a hex tool having a hexagonal distal tip to enable the application of torque to drive the bone fastener 102 into the anatomy.
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The sidewall 120 of the outer receiver 104 forms two upstanding, oppositely disposed arms 130. The arms 130 are spaced apart from each other to define two oppositely disposed channels 132 formed in the sidewall 120. The channels 132 comprise two oppositely disposed, substantially U-shaped spaces that interconnect with the proximal opening 122 and the inner bore of the outer receiver 104. The channels 132 are shaped to receive an elongate fixation member 112 such as a spinal fixation rod or other elgonate member to be connected to the outer receiver 104 by placement of the elongate fixation member 112 into the channels 132. The outer receiver 104 includes a rod-receiving location 134. The rod-receiving location 134 of the outer receiver 104 is substantially in the location of the two arms 130 and the inner surface of the arms 132 define two oppositely disposed smooth surfaces such that the inner receiver 108 which fits within the arms 130 of the outer receiver 104 may unimpededly translate longitudinally along the z-axis. The arms 130 extend upwardly from the bone fastener receiving location 126 such that the outer surface of the arms 130 is set back from the outer surface of the bone fastener receiving location 126 to create a circumferential ledge surrounding the arms 130. The outer surface of each of the arms 130 includes a smooth surface 136 extending longitudinally that is adjacent to a threaded or interlocking outer surface 138 extending longitudinal along the outer surface of each arm 130. The threaded surface 138 on the outer surface of one arm 130 is oppositely disposed from a threaded surface 138 on the outer surface of the second arm 130. Also, the smooth surface 136 on the outer surface of one arm 130 is oppositely disposed from the smooth surface 136 located on the outer surface of the second arm 130. The outer surface of the outer receiver 104 may include two small holes (not shown) oppositely disposed in the arms 130 for permitting a reduction instrument or other instrument to grasp onto the outer receiver 104.
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The bone fixation system 100 is assembled by inserted the bone fastener 102 into the distal opening 124 of the outer receiver 104. A fastener locking cap 106 is inserted into the inner bore of the outer receiver 104 an into the bone fastener receiving location 126 where the threads 144 on the fastener locking cap 106 are engaged with threads 128 in the bone fastener receiving location. The bone fastener 102 is free to angulate polyaxially relative to the outer receiver 104 in an unlocked position. In a locked position, the fastener locking cap 106 is threaded or turned downwardly to bear upon the head 116 of the bone fastener 102 to lock it into a desired angular relationship. The inner receiver 108 is inserted into the inner bore of the outer receiver 108 such that the arms 156 of the inner receiver 108 are substantially aligned inside the arms 130 of the outer receiver 104. The channels 132 of the outer receiver 104 are also substantially aligned with the channels 162 of the inner receiver 108. The outer surface of the inner receiver 108 is substantially flush with the inner surface of the outer receiver 104 and the inner receiver 108 is free to translate longitudinally along the z-axis inside the outer receiver 104. Prior to the placement of an elongate fixation member 112 into the channels 132, 162, the angular relationship of the outer receiver 104 relative to the bone fastener 102 is fixed or otherwise locked into position by employing a driving tool inserted through the central aperture 154 of the inner receiver 108 to engage the inner bore 145 of the fastener locking cap 106 and rotate it into a locked position. When an elongate fixation member 112 is placed into the channels 132, 162, the elongate fixation member 112 rests on the top surface 152 of the inner receiver 108 and the z-axis or longitudinal position of the elongate fixation member may be adjusted moving both the elongate fixation member and inner receiver into the desired position. The set screw 110 is positioned such that the threaded cylinder 176 is inserted into the inner receiver 108 between the arms 156 of the inner receiver 108. The legs 170 of the set screw 110 slide on the outside of the arms 130 of the outer receiver 104 such that the inner surface of the legs 170 is substantially flush with the outer surface of the arms 130 of the outer receiver 104. With the legs 170 in the location of smooth surfaces 136 of the arms 130, the inner receiver 108 is free to translate relative to the outer receiver 104.
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In use, the bone fixation system 200 is assembled by passing the shank portion 216 of the bone fastener 202 through the proximal opening 220 and into the distal opening 222 in the outer receiver 204 with the bone screw head 214 coming to rest in the seat of the bone fastener receiving location 224 of the outer receiver 204. An additional retainer (not shown) may be employed if the distal opening 222 is too large to retain the bone fastener head 214. The retainer forms an additional seating location for the bone fastener head 214 permitting it to be retained inside the outer receiver 204. The fastener locking cap 206 is coupled to the inner receiver 208 by sliding the tabs 244 into the notches 260 of the inner receiver 208. Both the fastener locking cap 206 and the inner receiver 208 are inserted into the inner bore of the outer receiver 204 such that the arms 254 of the inner receiver 208 are aligned with the smooth surfaces 234 of the outer receiver 204 so that inner receiver 208 and connected fastener locking cap 206 may telescope freely vertically within the inner bore of the outer receiver 204 for adjusting the height of the inner receiver 208, and hence, the height of the elongate fixation member 212 relative to the outer receiver 204. A driver instrument may then be inserted into the proximal opening 220 of the inner bore of the outer receiver 204 and through the central aperture 252 of the inner receiver 208 and through the bore 242 of the fastener locking cap 206 and into the driver connection feature 218 in the bone fastener head 214. The user may then rotate the driver to drive the bone fastener 202 into the anatomy. With the shank portion 216 delivered into bony anatomy, the outer receiver 204 is permitted to angulate with respect to the bone fastener 202. An elongate fixation member 212 is then placed into the channels 228, 261 and between the arms 254 of the inner receiver 208. A set screw 210 is placed into the inner receiver 208 such that its threads 266 engage the threads of the inner surface 258 of the arms 254. The set screw 210 is only slightly advanced into the inner receiver 208 such that the inner receiver 208 may still translate longitudinally relative to the outer receiver 204. Since the inner receiver 208 is advantageously free to translate longitudinally within the inner bore of the outer receiver 204, in particular, free to translate longitudinally within the rod-receiving location of the outer receiver 204, substantial z-axis translation is afforded for precisely locating the elongate fixation member 212 in the desired location custom to the anatomy.
With the set screw 210 in position within the inner receiver 208, a driver instrument 272 of the type depicted in
Furthermore, the inner receiver 208 may include a notch 270 formed in each arm 254 that extends radially from the inner surface 258 of the arms 254. The at least one notch 270 is clearly shown in
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When downward force is exerted onto the elongate fixation member 212, with continued threaded advancement of the set screw 210, z-axis translation will be substantially arrested, as the angular moment or torque of the set screw 210 will turn the inner receiver 208 such that its arms 254 move from the smooth surfaces 234 and into threaded engagement with the threaded portions 232 of the rod-receiving location. Such rotation of the inner receiver 208 relative to the outer receiver 204 will result in locking the z-axis, or vertical or longitudinal position of the elongate fixation member 212 relative to the outer receiver 204. Simultaneously the relative rotation of the inner receiver 208 will also rotate the connected fastener locking cap 206 within the threads 225 of the bone fastener receiving location 224 resulting in the locking down and setting of orientation/angulation of the outer receiver 204 relative to the bone fastener 202. Hence, the present invention permits the set screw 210 to be used to lock down not only the exact position of the rod, but also, the angulation of the outer receiver 204 relative to the bone fastener 202. Furthermore, the fastener locking cap 206 is movable relative to the inner receiver 208 which advantageously allows the distance between the inner receiver 208 and the fastener locking cap 206 to be adjusted. The inner receiver 208 may include a notch 270 formed in the arms 254 such as the top surface of the arms 254 for receiving a tool for rotating the inner receiver 208 relative to the outer receiver 204 without the use of a set screw 210 or prior to the insertion of a set screw 210 to lock down the z-axis distance of the elongate fixation member 212 relative to the outer receiver 204.
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In use, the bone fixation system 300 is assembled by passing the shank portion 316 of the bone fastener 302 through the proximal opening 320 and into the distal opening 322 in the outer receiver 304 with the bone screw head 314 coming to rest in the seat of the bone fastener receiving location 324 of the outer receiver 304. An additional retainer (not shown) may be employed if the distal opening 322 is too large to retain the bone fastener head 314. The retainer forms an additional seating location for the bone fastener head 314 permitting it to be retained inside the outer receiver 304. The fastener locking cap 306 is coupled to the inner receiver 308 by sliding the tabs 344 into the notches 390 of the fastener locking cap 306. The distance between the inner receiver 308 and the fastener locking cap may be adjusted as desired. Both the fastener locking cap 306 and the inner receiver 308 are inserted into the inner bore of the outer receiver 304 such that the arms 354 of the inner receiver 308 are aligned with the smooth surfaces 334 of the outer receiver 304 so that inner receiver 308 and connected fastener locking cap 306 may telescope freely vertically within the inner bore of the outer receiver 304 for adjusting the height of the inner receiver 308, and hence, the height of the elongate fixation member 312 relative to the outer receiver 304. A driver instrument may then be inserted into the proximal opening 320 of the inner bore of the outer receiver 304 and through the central aperture 352 of the inner receiver 308 and through the bore 342 of the fastener locking cap 306 and into the driver connection feature 318 in the bone fastener head 314. The user may then rotate the driver to drive the bone fastener 302 into the anatomy. With the shank portion 316 delivered into bony anatomy, the outer receiver 304 is permitted to angulate with respect to the bone fastener 302. An elongate fixation member 312 is then placed into the channels 328, 361 and between the arms 354 of the inner receiver 308. A set screw 310 is placed into the inner receiver 308 such that its threads 366 engage the threads of the inner surface 358 of the arms 354. The set screw 310 is only slightly advanced into the inner receiver 308 such that the inner receiver 308 may still translate longitudinally relative to the outer receiver 304. Since the inner receiver 308 is advantageously free to translate longitudinally within the inner bore of the outer receiver 304, in particular, free to translate longitudinally within the rod-receiving location 330 of the outer receiver 304, substantial z-axis translation is advantageously afforded for precisely locating the elongate fixation member 312 in the desired location custom to the anatomy while keeping the elongate fixation member connected to the bone fixation system and hence to the anatomy without it popping out of position.
With the set screw 310 in position within the inner receiver 308, a driver instrument 272 of the type depicted in
Furthermore, the inner receiver 308 may include a notch 370 formed in each arm 254 that extends radially from the inner surface 358 of the arms 354. The at least one notch 370 is clearly shown in
Throughout this specification wherever threads, threaded portions or threaded engagements are mentioned, it is to be understood by one skilled in the art that the invention is not so limited and any coupling, locking or interlocking surface or mechanism known to one skilled in the art may be alternatively employed. For example, threaded engagement, twist-lock, snap-fit, friction fit, press-fit, ratcheting mechanism, or any friction locking system is within the scope of the present invention and may be substituted wherever such substitution is possible.
The ability to longitudinally translate the elongate fixation member relative to the outer receiver along the z-axis provides for a variation in the z-axis relation between the elongate fixation member and the bone fastener head. This advantageously allows for easier and more accurate placement of the elongate fixation member or rod, minimizing the amount of rod contouring required, while also minimizing the need for translating the vertebral body itself. Also, the system provides the surgeon with an easy way to simultaneously or independently, as needed, lock down the angulation of the tulip and the longitudinal and lateral position of the rod. These variable lockdown options afford the surgeon with greater flexibility, greater accuracy and greater ease in spinal fixation procedures.
The use of inner and outer receivers that move relative to each other, including multiple inner telescoping receivers, allow for translation when needed within the same confines of a traditional bone fixation assembly while at the same time permitting them to collapse to substantially the same height as a non-translating traditional bone fixation assembly when the translation is unnecessary. In this fashion, the amount that the screw head and rod construct protrudes above the bone surface is minimized leading to less injury to the soft tissues overlying the bone such as muscle and subcutaneous layers and resulting in less pain for the patient.
While z-axis translation can be achieved in some systems, those systems require partial manual assembly of the bone fixation assembly during surgery. Such a system requires increased operative time and increased steps of assembly. The present invention advantageously allows for pre-assembled screw heads, which simplifies the use of the system.
The present invention also advantageously provides the ability to lock the rod at multiple points along the z-axis using the same screw system. While z-axis translation can be achieved in some systems by using different screws with different head designs that secure the rod at different fixed points along the z-axis, such a system requires the surgeon to pre-plan and pre-select which screws will require exactly what amount of z-axis distance between the rod and screw and then to place the screws at the exact height that was pre-determined leaving the surgeon with fewer options for greater accuracy in-situ. The present invention allows for placement of screws of the same design in all vertebral bodies followed by adjustment of the z-axis translation as required at the time of securing the rod to the screw, rather than at the time of placing the screw into the bone.
The present invention also provides for the ability to lock the screw head and rod without transmitting force to the underlying vertebral body. Some systems lock the rod, head assembly, and screw with a locking mechanism that transmits force and/or torque to the underlying vertebral body. This force can be undesirable clinically as it can lead to fracturing of the bone, pullout of the screw, or deformation of the anatomy, among other outcomes. The present invention allows for the securing of all components while minimizing the force and/or torque transmitted to the underlying vertebral body.
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In use, the rod reduction instrument 400 is manipulated so that the prongs 420 extend beyond the distal end of the first cylinder 402. The rod reduction instrument 400 is then brought into proximity above a target bone fixation assembly of the like described above and connected thereto by inserting the nibs 422 of the prongs 420 into holes such as the holes 235, 335. The elongate fixation member 212 that is associated with the target bone fixation assembly 200 is placed within the rod receiving channels 412 of the first cylinder 402. The second cylinder 404 is rotated from a position shown in
It will be understood that many modifications can be made to the various disclosed embodiments without departing from the spirit and scope of the concept. For example, various sizes of the surgical devices are contemplated as well as various types of constructions and materials. It will also be apparent that many modifications can be made to the configuration of parts as well as their interaction. For these reasons, the above description should not be construed as limiting the invention, but should be interpreted as merely exemplary of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present invention.
Claims
1. A bone fixation system, comprising:
- a bone fastener including: a bone engaging portion; and a head integrally connected to the bone engaging portion;
- an outer receiver having a proximal end, a distal end and a longitudinal axis; the outer receiver including: a sidewall extending between the proximal end and the distal end and having an inner surface and an outer surface; an inner bore extending between a top opening at the proximal end and a bottom opening at the distal end; the bone fastener being connected to the outer receiver such that the bone engaging portion extends through the bottom opening; two oppositely disposed arms defined by the sidewall and at least one rod channel defined between the two arms; the at least one rod channel being interconnected with the top opening and the inner bore; the inner surface of each arm having a longitudinally extending interlocking inner surface adjacent to a longitudinally extending smooth surface; an interlocking inner surface at the distal end;
- a first locking cap located inside the inner bore of the outer receiver; the first locking cap having an interlocking outer surface configured to interlock with the interlocking inner surface at the distal end; the outer surface of the first locking cap is interconnected by a top surface and a bottom surface; the first locking cap includes two tab-engaging surfaces;
- an inner receiver sized to fit inside the outer receiver; the inner receiver including a base and two oppositely disposed arms extending upwardly from the base; the inner receiver includes at least one channel defined between the arms; each arm has an interlocking inner surface and an interlocking outer surface; the interlocking outer surface of each arm of the inner receiver being configured to engage the interlocking inner surfaces on the arms of the outer receiver; the inner receiver further including two oppositely disposed tabs extending downwardly from the base; the two tabs are configured for engagement with the two tab-engaging surfaces on the first locking cap; wherein the inner receiver is coupled to the first locking cap by the two tabs engaging the tab-engaging surfaces;
- a second locking cap removably located between the arms of the inner receiver and having an interlocking outer surface configured to interlock with the interlocking inner surface of the arms of the inner receiver;
- wherein the bone fixation system includes an unlocked position in which the bone fastener angulates with respect to the outer receiver and the inner receiver is free to translate longitudinally with respect to the outer receiver and a locked position in which the bone fastener and inner receiver are fixed with respect to the outer receiver.
2. The bone fixation system of claim 1 wherein the locked position is achieved by rotation of the inner receiver from being adjacent to the smooth surfaces on the outer receiver to being adjacent to the interlocking surfaces of the outer receiver to interlock the interlocking surfaces of the outer receiver with the interlocking outer surface of the inner receiver.
3. The bone fixation system of claim 1 wherein rotation of the inner receiver rotates the first locking cap into interlocking engagement with the interlocking surface of at the distal end and downwardly within the outer receiver against the head of the bone fastener to fix the position of the bone fastener relative to the outer receiver.
4. The bone fixation system of claim 1 further including an elongate fixation rod located between the two arms of the inner receiver and in the at least one channel of the inner receiver; wherein rotation of the second locking cap downwardly onto the rod fixes the position of the rod relative to the inner receiver and further rotation of the second locking cap rotates the inner receiver relative to the outer receiver into the locked position in which the longitudinal positions of the inner receiver and rod are fixed with respect to the outer receiver.
5. The bone fixation system of claim 1 further including at least one spring located between the inner receiver and the first locking cap.
6. The bone fixation system of claim 1 wherein one or more of the cooperating interlocking surface on the inner surface of each arm of the outer receiver, the interlocking surface in the bone fastener receiving location, the interlocking outer surface of the fastener locking cap, the interlocking inner surface of each arm of the inner receiver, the interlocking outer surface of each arm of the inner receiver, and the interlocking outer surface of the second locking cap is a threaded surface.
7. The bone fixation system of claim 1 the interlocking inner surface of one arm is opposite from the interlocking inner surface of the other arm and the smooth surface of one arm is opposite from the smooth surface of the other arm;
8. A bone fixation system, comprising:
- a bone fastener including: a bone engaging portion; and a head integrally connected to the bone engaging portion;
- an outer receiver having a proximal end, a distal end and a longitudinal axis; the outer receiver including: a sidewall extending between the proximal end and the distal end and having an inner surface and an outer surface; an inner bore extending between a top opening at the proximal end and a bottom opening at the distal end; the bone fastener being connected to the outer receiver such that the bone engaging portion extends through the bottom opening; two oppositely disposed arms defined by the sidewall and at least one rod channel defined between the two arms; the at least one rod channel being interconnected with the top opening and the inner bore; the inner surface of each arm having a longitudinally extending interlocking inner surface adjacent to a longitudinally extending smooth surface; an interlocking inner surface at the distal end;
- a first locking cap located inside the inner bore of the outer receiver; the first locking cap having an interlocking outer surface configured to interlock with the interlocking inner surface at the distal end of the outer receiver;
- an inner receiver sized to fit inside the outer receiver; the inner receiver including a base and two oppositely disposed arms extending upwardly from the base; the inner receiver includes at least one channel between the arms; each arm has an interlocking inner surface; the inner receiver is located inside the inner bore of outer receiver such that the oppositely disposed arms of the inner receiver are disposed in the location of the smooth surfaces and the interlocking inner surface of each arm is flush with the adjacent interlocking surfaces of the outer receiver;
- a second locking cap located between the arms of the inner receiver and having an interlocking outer surface configured to interlock with both the interlocking inner surface of the arms of the inner receiver and the adjacent interlocking inner surface of the arms of the outer receiver;
- wherein the inner receiver includes an unlocked position in which the inner receiver is free to translate longitudinally with respect to the outer receiver and a locked position in which the inner receiver is fixed with respect to the outer receiver; and
- wherein the locked position is achieved by the interlocking outer surface of the second locking cap engaging both the interlocking inner surface of the outer receiver and the interlocking inner surface of the inner receiver.
9. The bone fixation system of claim 8 wherein the bone fastener includes an unlocked position in which the bone fastener angulates with respect to the outer receiver and a locked position in which the bone fastener is fixed with respect to the outer receiver; the locked position is achieved by rotation of the first locking cap into interlocking engagement with the interlocking inner surface at the distal end and downwardly within the bore of the outer receiver against the head of the bone fastener to fix the position of the bone fastener relative to the outer receiver.
10. The bone fixation system of claim 8 further including an elongate fixation rod located between the two arms of the inner receiver and in the at least one channel of the inner receiver; wherein rotation of the second locking cap downwardly onto the rod fixes the position of the rod relative to the inner receiver.
11. The bone fixation system of claim 8 wherein the first locking cap is accessible from the at least one rod channel for being moved relative to the outer receiver.
12. The bone fixation system of claim 8 further including at least one spring located between the first locking cap and the inner receiver.
13. The bone fixation system of claim 8 the interlocking inner surface of one arm is opposite from the interlocking inner surface of the other arm and the smooth surface of one arm is opposite from the smooth surface of the other arm;
14. A bone fixation system, comprising:
- an outer receiver including a sidewall that defines an inner bore and an open proximal end; the sidewall has an inner surface and an outer surface that defines at least one channel opening to the inner bore and the open proximal end; the outer receiver includes an interlocking outer surface formed on the outer surface;
- an inner receiver including a sidewall that defines an interior, an open proximal end, and an inner base at a distal end; the sidewall having an inner surface and an outer surface that defines at least one channel opening to the interior and the open proximal end; the inner receiver includes an interlocking inner surface formed on the inner surface; the inner receiver being located inside the outer receiver such that the at least one channel of the inner receiver is substantially aligned with the at least one channel of the outer receiver; the inner receiver being movable along a longitudinal axis relative to the outer receiver in an unlocked position; and
- a locking cap having an interlocking outwardly-facing surface and an interlocking inwardly-facing surface; the interlocking outwardly-facing surface being movable independently and relative to the interlocking inwardly-facing surface; the interlocking outwardly-facing surface being located in the inner receiver and interlocked with the interlocking inner surface of the inner receiver in a first locked position and the interlocking inwardly-facing surface being interlocked with the interlocking outer surface of the outer receiver in a second locked position; wherein the second locked position prevents the longitudinal translation of the inner receiver relative to the outer receiver.
15. The bone fixation system of claim 14 further including a rod disposed inside the at least one channel of the inner receiver; wherein the first locked position fixes the rod to the inner receiver between the base and the locking cap.
16. A bone fixation system, comprising:
- an outer receiver having an inner bore and an open proximal end;
- an inner receiver having an inner bore and an open proximal end; the inner receiver being located inside an outer receiver; the inner receiver being movable along a longitudinal axis relative to the outer receiver in an unlocked position and the inner receiver being longitudinally fixed relative to the outer receiver in a locked position;
- a set screw located inside the inner receiver and movable rotationally about and along the longitudinal axis relative to the inner receiver;
- wherein converting between the locked and unlocked positions is achieved by rotation of the inner receiver relative to the outer receiver;
- wherein the locked position is achieved by rotation of the set screw downwardly relative to the inner receiver.
17. The bone fixation system of claim 16 further including a bone engaging portion configured to anchor in bone coupled to the outer receiver.
18. The bone fixation system of claim 16 further including an elongate fixation rod located inside the inner receiver and under the set screw; the elongate fixation rod being movable longitudinally with the inner receiver.
19. The bone fixation system of claim 16 wherein in the unlocked position the bone engaging portion is movable with respect to the outer receiver and in the locked position the bone engaging portion is fixed with respect to the outer receiver.
20. The bone fixation system of claim 16 wherein the set screw engages both the inner receiver and the outer receiver directly to effect the locked position.
21. The bone fixation system of claim 16 wherein the set screw engages the inner receiver which in turn engages the outer receiver to effect the locked position.
Type: Application
Filed: Dec 14, 2020
Publication Date: Apr 1, 2021
Inventors: Muralidhara Rudhra Raju (Fountain Valley, CA), Amir Ali Akhavi (Irvine, CA)
Application Number: 17/121,635
