AU2014227442B2 - A pedicle screw, joint implant system and method of surgical use - Google Patents

Abstract

A pedicle screw including: an engagement member; and a tulip, the tulip including a first portion interconnected to a second portion by an intermediate portion, the tulip being adapted to releasably receive the engagement member, wherein at least one recess extends lengthwise along the outer face of the first portion. 2060657v1 120 121 120 2060657v1 Figure 1

Description

A PEDICLE SCREW, JOINT IMPLANT SYSTEM AND METHOD OF SURGICAL

USE

FIELD OF THE INVENTION

[0001] The invention relates to a pedicle screw, joint implant system and method of surgical use. In particular, the invention relates, but is not limited, to vertebrae fusion, and therefore, will be described in this context.

BACKGROUND TO THE INVENTION

[0002] Reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge in Australia or elsewhere.

[0003] Spinal fusion is a very common procedure performed via posterior surgical approaches for degenerative and deformity spinal pathologies. Spinal fusion limits motion between adjacent vertebrae to help eliminate pain arising from vertebrae applying pressure to a nerve root or neural element.

[0004] Typically posterior spinal fusion is achieved by inter-transverse process spinal fusion. This surgical technique often involves the placement of pedicle screws within vertebral bone and then attaching associated rods to associated pedicle screws. The pedicle screws in combination with the rods provide stability to the vertebrae so that bone graft can be placed between adjacent transverse processes and bone growth can occur to create permanent fusion of the spine.

[0005] In inter-transverse spinal fusion, the accuracy with which pedicle screws are inserted has a direct effect on the surgical outcome. Of major concern is that improperly placed screws may place neural and vascular structures at risk. Moreover, misplaced screws can also lead to early structural failure of the vertebrae before fusion. In particular, wear of the facet joint may occur if the facet joint comes into contact with the pedicle screws.

[0006] Accordingly, the close proximity of many vital structures in the spine including neural and vascular, along with the facet joints, contribute to the difficulties in accurately placing the screws. To this end, reducing the size of the pedicle screws alleviates these problems to an extent. However, as screw size is reduced, the screws become more susceptible to failure. For example, pedicle screws typically include a threaded tulip that receive and hold in place a rod via a threaded cap. As the size of this threaded head is reduced, the threaded cap becomes more susceptible to loosening or ‘creeping’ due to the increased stress being carried by the cap and/or threaded tulip. This increased stress may also lead to the structural failure of the threaded tulip. Moreover, reducing the size of the pedicle screw may entail reducing the shank and threaded portion of the pedicle screw, making the screw more susceptible to structural failure.

[0007] Inter-transverse spinal fusion also suffers from other shortfalls, despite the difficulties in accurately locating pedicle screws. These are further described in applications claiming priority from Australian provisional application 2012902895.

[0008] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

OBJECT OF THE INVENTION

[0009] It is an aim of this invention to provide a pedicle screw, joint implant system and method of medical use which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative.

[0010] Other preferred objects of the present invention will become apparent from the following description.

SUMMARY OF INVENTION

[0011] In one form, although not necessarily the only or broadest form, the invention resides in a pedicle screw including: an engagement member; and a tulip having a main longitudinal axis, the tulip including a first portion interconnected to a second portion by an intermediate portion, the second portion having an outer face and the tulip being adapted to releasably receive the engagement member; wherein at least one recess extends lengthwise along an outer face of the first portion and the outer face of the first portion includes a reinforcing rib adjacent to said at least one recess, and wherein the reinforcing rib extends further from the main longitudinal axis compared to the outer face of the second portion.

[0012] Preferably, the reinforcing rib extends lengthwise along the first portion.

[0013] Normally, an outer face of the second portion is substantially radial. Alternatively, or additionally, the outer face of the second portion also includes at least one recess extending lengthwise along the outer face of the second portion. In this form, the outer face of the second portion may also include a reinforcing rib.

[0014] The recess is suitably adapted to avoid interacting with adjacent structures. For example, the recess is adapted to avoid engaging with a facet joint in a spine when the engagement member engages a pedicle portion in the spine. The reinforcing rib is adapted to increase the stiffness of the first and/or second portion. For example, the reinforcing rib is further from a main longitudinal axis of the tulip compared to the recess of the first portion and/or the radial face of the second portion.

[0015] Normally, the first and second portions extend substantially parallel to the main longitudinal axis of the tulip. Preferably, the reinforcing rib and the recess also extend substantially parallel to the main longitudinal axis of the tulip. Alternatively, or additionally, the reinforcing rib and the recess are angled to the main longitudinal axis.

[0016] Preferably, the reinforcing rib and the recess extend substantially along the first and/or second portion. Alternatively, the reinforcing rib and the recess may extend partly along the first and/or second portion.

[0017] Typically, the outer face of the first and/or second portion includes two recesses. Preferably, the reinforcing rib is located between the two recesses.

[0018] Preferably, the intermediate portion includes an aperture that releasably receives the engagement member. Normally, the engagement member extends from a lower opening in the aperture of the intermediate portion. Preferably, the engagement member includes a threaded portion.

[0019] Preferably, the pedicle screw further includes a saddle adapted to partially close an upper portion of the aperture in the intermediate portion to releasably retain the engagement member.

[0020] Preferably, the engagement member pivots in a ball-and-socket type motion relative to the tulip or vice versa. Normally, the aperture in the intermediate portion is substantially spherical in shape and is adapted to engage with a spherical shaped head portion of the engagement member allowing for the ball-and-socket type motion.

[0021] Preferably, the engagement member includes a drive portion. Preferably, the drive portion is in the form of a torx drive.

[0022] Preferably, an inner surface of the first and second portions includes a threaded portion.

[0023] In another form the invention resides in a tulip having a main longitudinal axis, the tulip including: a first portion; and a second portion having an outer face and interconnected to the first portion by an intermediate portion; wherein at least one recess extends lengthwise along an outer face of the first portion and the outer face of the first portion includes a reinforcing rib adjacent to said at least one recess, and wherein the reinforcing rib extends further from the main longitudinal axis than the outer face of the second portion.

[0024] Preferably, the reinforcing rib extends lengthwise along the first portion.

[0025] Normally, an outer face of the second portion is substantially radial. Alternatively, or additionally, the outer face of the second portion also includes at least one recess extending lengthwise along the outer face of the second portion. In this form, the outer face of the second portion may also include a reinforcing rib.

[0026] The recess is suitably adapted to avoid interacting with adjacent structures. For example, the recess is adapted to avoid engaging with a facet joint in a spine when the engagement member engages a pedicle portion in the spine. The reinforcing rib is adapted to increase the stiffness of the first and/or second portion. For example, the reinforcing rib is further from a main longitudinal axis of the tulip compared to the recess and/or the radial face of the second portion.

[0027] Normally, the first and second portions extend substantially parallel to the main longitudinal axis of the tulip. Preferably, the reinforcing rib and the recess also extend substantially parallel to the main longitudinal axis of the tulip. Alternatively, or in addition, the reinforcing rib and the recess are angled to the main longitudinal axis.

[0028] Preferably, the reinforcing rib and the recess extend substantially along the first portion and/or second portion. Alternatively, the reinforcing rib and the recess may extend partly along the first portion and/or second portion.

[0029] Typically, the outer face of the first portion and/or second portion includes two recesses. Preferably, the reinforcing rib is located between the two recesses.

[0030] Preferably, the intermediate portion includes an aperture that releasably receives an engagement member. Preferably, the tulip further includes a saddle adapted to partially close an upper portion of the aperture in the intermediate portion to releasably retain the engagement member.

[0031] Preferably, an inner surface of the first and second portions includes a threaded portion.

[0032] In another form, the invention resides in a method of implanting a joint implant system, the method including the steps of: securing an engagement member of a first pedicle screw to an upper vertebra; securing an engagement member of a second pedicle screw to a lower vertebra; releasably engaging a rod between the first and second pedicle screws; and orientating the first and/or second pedicle screws such that a recess of the first and/or second screws do not engage with adjacent structures, wherein the first pedicle screw and/or the second pedicle screw are as set out above.

[0033] Preferably, the adjacent structures include a facet joint in a spine and/or other neural and vascular structures adjacent the spine.

[0034] Preferably, the method further includes inserting a facet joint implant into the facet joint between the upper and lower vertebrae.

[0035] Further features and advantages of the present invention will become apparent from the following detailed description of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] By way of example only, preferred embodiments of the invention will be described more fully hereinafter with reference to the accompanying figures, wherein:

Figure 1 illustrates a perspective view of a pedicle screw according to an embodiment of the invention;

Figure 2 illustrates a section view of the pedicle screw illustrated in Figure 1;

Figure 3 illustrates a top view of the pedicle screw illustrated in Figure 1; and

Figure 4 illustrates a perspective view of a joint implant system in use according to an embodiment of the invention;

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Figures 1 to 3 illustrates a pedicle screw 100 according to an embodiment of the invention. Pedicle screw 100 includes a tulip 120 and an engagement member 160.

[0038] The tulip 120 includes a first portion 122, a second portion 124 and an intermediate portion 126. The lower ends of the first and second portions 122, 124 are connected together by the intermediate portion 126. A main longitudinal axis 121 extends through the tulip 120. A channel 128 extends through the tulip 120 separating the first portion 122 from the second portion 124. Inner faces of the first and second portions 122, 124 include a threaded portion.

[0039] An outer face of the first portion 122 includes two recesses 132 and a reinforcement rib 134. An outer face of the second portion 124 is substantially radial in shape. In comparison to the outer radial shape of the second portion 124, the outer face of the reinforcement rib 134 extends further from the main longitudinal axis 121. The faces of the recesses 132 are closer to the main longitudinal axis 121 than the outer face of the second portion 124. As further discussed below, it will be appreciated that one recess may be implemented instead of two recesses 132 on the outer face of the first portion 122. Furthermore, the outer face of the second portion 124 may alternatively include one or two recesses 132 and a reinforcement rib 134.

[0040] The reinforcement rib 134 and recesses 132 extend lengthwise along the first portion 122. That is, the reinforcement rib 134 and recesses 132 extend substantially from the top of the tulip 120 to the bottom of the tulip 120. The reinforcement rib 134 and recesses 132 also extend substantially parallel to the main longitudinal axis 121. Flowever, it will be appreciated by a person skilled in the art that the reinforcement rib 134 and recesses 132 may be angled to the main longitudinal axis 121 (i.e. tapered towards the main longitudinal axis 121). Moreover, the reinforcement rib 134 and recesses 132 may alternatively extend partly along the first portion 122. If the reinforcement rib 134 extends partly along the first portion 122, it will typically extend from the bottom portion of the first portion 122 and/or the tulip 120.

[0041] The intermediate portion 126 includes a retaining portion 140 adapted to receive the engagement member 160. As best seen in figure 2, the retaining portion 140 includes an aperture 142 and a saddle 146. Aperture 142 includes a socket portion 143 and a lower opening 144. The saddle 146 is adapted to partially close the upper portion of the aperture 142.

[0042] The engagement member 160 includes a threaded portion 162 and a head portion 164. The threads of the threaded portion 162 are self tapping. The engagement member 160 is retained in the retaining portion 140 of the tulip 120 via the saddle 146. The outer surface of the head portion 164 of the engagement member 160 includes a substantially spherical portion 166 that is adapted to be received into socket portion 143. This allows the engagement member 160 to move in a ball-and-socket type motion relative to the socket portion 143 or vice versa. The threaded portion 162 of the engagement member 160 extends through the lower opening 144 of the aperture 142.

[0043] As can be seen in figure 3, the head portion 164 also includes a drive portion in the form of a torx drive 168. However, it would be appreciated by a person skilled in the art that other drive portions such as a hex drive may be used. The saddle 146 includes an opening that allows a tool to be passed through the saddle 146 to drive the engagement member 160.

[0044] Figure 4 illustrates a joint implant system 10 for fusing upper and lower vertebrae 12, 12’ together according to an embodiment of the invention. The joint implant system 10 includes a plurality of pedicle screws 100, rods 180, caps 190 and facet joint implants 200. A longitudinal axis 13 extends through the upper and lower vertebrae 12, 12’. The facet joint implants 200 are described in applications claiming priority from Australian provisional application 2012902895.

[0045] Pilot holes for the pedicle screws 100 are generally prepared using a probe or drill. Pedicle screws 100 are located in each of the upper and lower vertebrae 12, 12’ either side of the longitudinal axis 13. More specially, the engagement member 160 of the pedicle screws 100 are screwed into the pilot holes located in the pedicle portions 14, 14’ of the upper and lower vertebrae 12, 12’ via the torx drive 168. This leaves the pedicles screws 100 substantially inline with each other in the longitudinal direction either side of the longitudinal axis 13. That is, the tulips 120 are located between the facet joints 16 and the transverse processes 18, 18’ of the upper and lower vertebrae 12, 12’. Moreover, the tulips 120 are able pivot in a ball-and-socket type motion relative to the engagement members 160 when they are secured in the pedicle portions 14, 14’.

[0046] Rods 180 are received into the openings 128 of the tulips 120. The rods 180 are releasably retained in the openings 128 by screwing the caps 190 along the threaded portions of the inner faces of the first and second portions 122,124. The rods 180 extend substantially in a longitudinal direction between the respective pedicle screws 100 either side of the longitudinal axis 13.

[0047] When the rods 180 are secured in the tulips 120, the pivotal movement of the tulip 120 relative to the engagement member 160 is substantially restrained. In this embodiment, before the movement of the tulips is restrained, the recessed portions 132 are located such that they substantially follow the contours of the joint facets 16 and avoid other vital structures such as neural and vascular.

[0048] The combination of the rods 180 and pedicle screws 100 are used to at least temporarily or permanently stabilise the joint facets 16. This substantially assists in fusion between the facet joint implants 200 and the facet joints 16. In particular, when the rods 180 are in place they substantially resist movement between the upper and lower vertebra 12, 12’ allowing the facet joints 16 to fuse together.

[0049] However, fusion of the facet joints 16 may be affected in a number of ways. In particular, any movement between the vertebrae (albeit minor) will likely cause the facet joints 16 to wear away if contact exists between the pedicle screws 100 and facet joints 16. To this end, the recesses 132 substantially assist in allowing the pedicle screws 100 to avoid contact with the facet joints 16. Moreover, the recesses 132 also assist in avoiding other neural and vascular structures adjacent the spine, reducing the risks to patient health. Furthermore, this also allows for preservation of the joint facet, and preparation and insertion of the facet joint implants 200 into the joint facet in a relatively easy manner.

[0050] The reinforcement rib 134 increases the strength and stiffness of the first and/or second portions 122, 124. Accordingly, the first portion 122 of the tulip 120 is substantially prevented from bending due to the loads transferred from the rods 180 as they resist movement between the upper and lower vertebra 12, 12’. Moreover, the caps 190 are prevented from loosening as such bending is substantially prevented.

[0051] In this specification, adjectives such as first and second, left and right, top and bottom, and the like may be used solely to distinguish one element or action from another element or action without necessarily requiring or implying any actual such relationship or order. Where the context permits, reference to an integer or a component or step (or the like) is not to be interpreted as being limited to only one of that integer, component, or step, but rather could be one or more of that integer, component, or step etc.

[0052] The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. The invention is intended to embrace all alternatives, modifications, and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.

[0053] In this specification, the terms ‘comprises’, ‘comprising’, ‘includes’, ‘including’, or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.

Claims (20)

1. The claims defining the invention are as follows:

   1. A pedicle screw including: an engagement member; and a tulip having a main longitudinal axis, the tulip including a first portion interconnected to a second portion by an intermediate portion, the second portion having an outer face and the tulip being adapted to releasably receive the engagement member, wherein at least one recess extends lengthwise along an outer face of the first portion and the outer face of the first portion includes a reinforcing rib adjacent to said at least one recess, and wherein the reinforcing rib extends further from the main longitudinal axis compared to the outer face of the second portion.
2. 2. The pedicle screw of claim 1, wherein the reinforcing rib extends lengthwise along the first portion.
3. 3. The pedicle screw according to either claim 1 or claim 2, wherein the reinforcing rib is further from the main longitudinal axis of the tulip compared to the recess.
4. 4. The pedicle screw according to any one of claims 1 to 3, wherein the reinforcing rib is further from the main longitudinal axis of the tulip compared to the second portion.
5. 5. The pedicle screw according to any one of claims 1 to 4, wherein the reinforcing rib is located between two recesses.
6. 6. The pedicle screw according to any one of the preceding claims, wherein the outer face of the second portion is substantially radial.
7. 7. The pedicle screw according to any one of the preceding claims, wherein the recess is adapted to avoid engaging with a facet joint in a spine when the engagement member engages a pedicle portion in the spine.
8. 8. The pedicle screw according to any one of the preceding claims, wherein the recess extends substantially along the first portion.
9. 9. The pedicle screw according to any one of claims 2 to 8 wherein the reinforcing rib extends partly along the first portion adjacent to the recess.
10. 10. A tulip having a main longitudinal axis, the tulip including: a first portion; and a second portion having an outer face and interconnected to the first portion by an intermediate portion, wherein at least one recess extends lengthwise along an outer face of the first portion and the outer face of the first portion includes a reinforcing rib adjacent to said at least one recess, and wherein the reinforcing rib extends further from the main longitudinal axis than the outer face of the second portion.
11. 11. The tulip of claim 10, wherein the reinforcing rib extends lengthwise along the first portion.
12. 12. The tulip according to either claim 10 or claim 11, wherein the reinforcing rib is further from the main longitudinal axis of the tulip compared to the recess.
13. 13. The tulip according to any one of claims 10 to 12, wherein the reinforcing rib is further from the main longitudinal axis of the tulip compared to the second portion.
14. 14. The tulip according to any one of claims 10 to 13, wherein the reinforcing rib is located between two recesses in the outer face of said first portion.
15. 15. The tulip according to any one of claims 10 to 14, wherein the outer face of the second portion is substantially radial.
16. 16. The tulip according to any one of claims 10 to 15, wherein the recess extends substantially along the first portion.
17. 17. The tulip according to any one of claims 11 to 16 wherein the reinforcing rib extends partly along the first portion adjacent to the recess.
18. 18. A method of implanting a joint implant system, the method including the steps of: securing an engagement member of a first pedicle screw to an upper vertebra; securing an engagement member of a second pedicle screw to a lower vertebra; releasably engaging a rod between the first and second pedicle screws; and orientating the first and/or second pedicle screws such that a recess of the first and/or second screws do not engage with adjacent structures, wherein the first pedicle screw and/or the second pedicle screw are in accordance with any one of claims 1 to 9.
19. 19. The method of claim 18 further including the step of inserting a facet joint implant into the facet joint between the upper and lower vertebrae.
20. 20. The method of either claim 18 or claim 19, wherein the adjacent structures include a facet joint in a spine and/or other neural and vascular structures adjacent the spine.