Intervertebral spacer and insertion tool providing multiple angles of insertion
An intervertebral spacer includes a trailing end having a surface shaped to engage a complementary surface of an insertion tool and also includes an opening configured to receive an extending portion from the tool. While the extending portion is disposed within the spacer's trailing end, the tool may be positioned at one of a plurality of different, selectable positions relative to the spacer where the mutual engaging surfaces may secure the tool and the spacer.
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The present invention relates, in general, to artificial prosthetics and, more particularly, to intervertebral spacers.
BACKGROUNDA normal human spine is segmented with seven cervical, twelve thoracic and five lumbar segments. The lumbar portion of the spine resides on the sacrum, which is attached to the pelvis. The pelvis is supported by the hips and leg bones. The bony vertebral bodies of the spine are separated by intervertebral discs, which reside sandwiched between the vertebral bodies and operate as joints allowing known degrees of flexion, extension, lateral bending and axial rotation.
The intervertebral disc primarily serves as a mechanical cushion between adjacent vertebral bodies, and permits controlled motions within vertebral segments of the axial skeleton. The disc is a multi-element system, having three basic components: the nucleus pulposus (“nucleus”), the anulus fibrosus (“anulus”) and two vertebral end plates. The end plates are made of thin cartilage overlying a thin layer of hard, cortical bone that attaches to the spongy, richly vascular, cancellous bone of the vertebral body. The plates thereby operate to attach adjacent vertebrae to the disc. In other words, a transitional zone is created by the end plates between the malleable disc and the bony vertebrae.
The anulus of the disc forms the disc perimeter, and is a tough, outer fibrous ring that binds adjacent vertebrae together. The fiber layers of the anulus include fifteen to twenty overlapping plies, which are inserted into the superior and inferior vertebral bodies at roughly a 40 degree angle in both directions. This causes bi-directional torsional resistance, as about half of the angulated fibers will tighten when the vertebrae rotate in either direction.
It is common practice to remove a spinal disc in cases of spinal disc deterioration, disease or spinal injury. The discs sometimes become diseased or damaged such that the intervertebral separation is reduced. Such events cause the height of the disc nucleus to decrease, which in turn causes the anulus to buckle in areas where the laminated plies are loosely bonded. As the overlapping laminated plies of the anulus begin to buckle and separate, either circumferential or radial anular tears may occur. Such disruption to the natural intervertebral separation produces pain, which can be alleviated by removal of the disc and maintenance of the natural separation distance. In cases of chronic back pain resulting from a degenerated or herniated disc, removal of the disc becomes medically necessary.
In some cases, the damaged disc may be replaced with a disc prosthesis intended to duplicate the function of the natural spinal disc. In other cases it is desired to fuse the adjacent vertebrae together after removal of the disc, sometimes referred to as “intervertebral fusion” or “interbody fusion.”
In cases of intervertebral fusion, it is known to position a spacer centrally within the space where the spinal disc once resided, or to position multiple spacers within that space. Such practices are characterized by certain disadvantages including a disruption in the natural curvature of the spine. For example, the vertebrae in the lower “lumbar” region of the spine reside in an arch referred to in the medical field as having a sagittal alignment. The sagittal alignment is compromised when adjacent vertebral bodies that were once angled toward each other on their posterior side become fused in a different, less angled orientation relative to one another.
While the occurrence of successful spinal surgeries of any of the variety mentioned above has greatly improved in recent years, there continue to be challenges and room for improvement in the area of intervertebral spacers and prosthetics. In particular, a patient's precise anatomy is often not known prior to surgery although general predictions will be available. Additionally, while surgery is a well-planned process, not all conditions can be known beforehand and some variations will likely not be ideal. Accordingly, during surgery a surgeon will likely need to make decisions that balance speed, safety, and efficacy. One such decision can relate to the approach angle at which the spacer is inserted into the patient's body. This angle can vary either anteriorally or posteriorally from a lateral approach depending on the surgical conditions encountered. A spacer that is adaptable to the wide vagaries of surgical conditions that might be encountered will provide many benefits to patients and surgeons. Presently, many intervertebral spacers require an insertion tool that fixedly threads into the spacer's body thereby limiting the alignment between the tool and the spacer to a single position. Thus, there remains a need for intervertebral spacers that offer the surgeon more ease-of-use and flexibility than the spacers that are currently available.
SUMMARYOne aspect of the present invention relates to an intervertebral spacer that includes a leading end and a trailing end. The trailing end is configured to accept therein an extending portion of an insertion tool, wherein the trailing end includes an external surface configured to securely engage a complementary surface of the insertion tool at a plurality of different angles.
Another aspect of the present invention relates to an intervertebral spacer that includes a trailing end configured to engage an insertion tool at an angle. Within this aspect, the trailing end includes a first portion configured to securely receive an extending portion of the insertion tool, and a second portion having a surface shaped to engage a complementary-shaped surface of the insertion tool at a plurality of different positions such that the angle differs for each of the different positions.
Yet a further aspect of the present invention relates to a method for using an intervertebral spacer. In accordance with this method, an extending portion of an insertion tool is received within the intervertebral spacer; and a first surface of the intervertebral spacer is securely engaged with a second surface of the insertion tool in one of a plurality of different positions, while the extending portion is disposed within the intervertebral spacer.
It is understood that other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described only various embodiments of the invention by way of illustration. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGSVarious aspects of an intervertebral spacer and insertion tool are illustrated by way of example, and not by way of limitation, in the accompanying drawings, wherein:
The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the invention.
The spacer 102 of
The spacer 102 may be used in a variety of configurations; however, the configuration of
Because the spacer 102 is designed for insertion in a patient's body, its material is selected to withstand such an environment without deteriorating or harming the patient. Exemplary materials useful in these types of circumstances include, but are not limited to, polyether ether ketone, titanium, artificial bone material, and natural bone tissue. Other similar material may be used without departing from the scope of the present invention.
These teeth 212, 214 are exemplary in nature and can vary in numerous ways, or even be absent, without departing from the scope of the present invention. For example, the teeth 212, 214 may be pointed at their peaks and have rounded, pointed, or squared valleys between adjacent peaks. The slope of the sides of the teeth 212, 214 may vary as well as the spacing between the teeth 212, 214. Similarly, the height of the teeth 212, 214 may vary as well. Because the posterior side 202 and anterior side 204 may be arcuate shaped, the teeth may be spaced variably such that they are closer at their posterior side end that at their anterior side end.
An exemplary embodiment contemplated within the scope of the present invention includes teeth 214 on the posterior side that are spaced about every 10 degrees and have a height of approximately 0.030 inches. In particular, the sides of adjacent teeth 214 adjoin one another at the bottom and form a 90 degree angle with one another. Similarly shaped teeth 212 may be located on the anterior side 204 but spaced at approximately every 5 degrees.
The trailing end 208 includes an exterior surface 210 that has a shape and other features that will be described in more detail later. In general, though, the surface 210 includes engaging surfaces shaped to actively engage a complementary-shaped engaging surface of an insertion tool.
The relative size of the spacer or height H, can vary according to its intended use. For example, the spacing between vertebrae may vary based on patient size and may also vary based on which region of the spine is being accessed. Thus, the nominal height, H, of the spacer may vary so as to provide a surgeon with a variety of different sized spacers. Exemplary spacer sizes that will accommodate most adult human situations include the following sizes. However, other sizes may be considered without departing from the scope of the present invention.
An insertion tool for using with the spacer 102 is described later in more detail. However,
According to the sized spacers already discussed, the following dimensions provide channels that are appropriate for these spacers. However, these examples of channel sizes are merely exemplary in nature and other sized channels may be provided without departing from the scope of the present invention.
In
Conceptually, the handle 404 operates to move the surface 410 towards or away from the extending portion 408. In operation, this may be accomplished by moving either the extending portion 408 or the surface 410; in either case the same relative motion is accomplished. One exemplary technique is for the extending portion 408 to be attached to a shaft that is located within the shaft 406. Twisting the handle 404 in one direction causes the outside shaft 406 to move relative to the inner shaft (not shown). This movement causes the surface 410 to move towards the extending portion 408. Rotation of the handle 404 in the opposite direction causes opposite movement of the outside shaft 406 resulting in motion of the surface 410 away from the extending portion 408. In an exemplary embodiment, the inner shaft includes a stop 409 that extends through an opening 407 so as to align the shafts and restrict the extent of movement of the outside shaft 406 in either direction of travel.
In operation, the portion 422 of the extending portion 408 is inserted into and fits within the channel 227 of the spacer 102. The other portion 420 is inserted within the other channel 228. In this way, the extending portion 408 securely engages the spacer 102 because the portion 420 is too large to pass through the channel 227. From this position, the surface 410 may be moved so as to be positioned closer to the extending portion 408. More particularly, the surface 410 is moved in this direction so that the engaging features 412 engage complementary-shaped features 210 on the spacer's trailing end 208.
When the engaging features 412 and 210 are engaged to one another, then the insertion tool 400 and the spacer 102 are securely, but releasably, fastened to one another such that relative motion between the two is prevented. When the engaging features are not actively engaged, the tool 400 and the spacer 102 are still securely engaged (through operation of the extending portion 408); however, relative motion is permitted because the spacer 102 can rotate around the portion 420 of the extending portion 408.
This rotation allows the spacer 102 and the tool to be repositioned so that the engaging features 412 of the tool 400 can be aligned to engage different complementary-shaped features 210 of the spacer. As a result, an angle between the major axis 405 of the tool 400 and the spacer's 250 can be changed even while the extending portion 408 is disposed within the spacer 102.
In
In
Because of the arrangement of the teeth 210, 412 and the extending portion 408, the tool 400 may be moved between the different positions of
As a result, a surgeon may alter the insertion angle of the spacer 102 during surgery in numerous and various ways to account for possible variations and conditions that might arise during surgery. Even though such flexibility is provided, the tool 400 and the spacer 102 remain fastened together so that re-securing the two relative to one another, after an adjustment, may be easily accomplished without difficulty or fear of unwanted separation.
These specific dimensions are approximate in nature and may vary significantly without departing from the spirit and scope of the present invention.
The insertion tool 950 of
The semicircular portion 962 terminates at two ends that are separated by a distance 969. In the particular example provided above, with the particular radii 967, 968, the distance 969 may be, for example, approximately 0.1850 inches. This distance depends on the arcuate circumference of the semicircular portion 962 which may vary anywhere from 180 to about 250 degrees.
As mentioned earlier, the opposing arms 1102, 1104 are resiliently arranged so that they separate from one another when extender from the tool 950 and squeeze towards one another when retracted into the tool 950. The arms 1102, 1104 are shaped and sized to securely fit within the channel 901 of the spacer 902. Thus, for example, given the dimension described with relation to
The dimensions are exemplary in nature and are provided merely as a specific example of one embodiment of the variety of different spacers and insertion tools contemplated within the scope of the present invention.
The portion 1202 of the tool 950 is the external part of the end of the tool through which the opposing arms 1102, 1104 extend. Typically, there is a first portion 1202 that engages the trailing end 908 of the spacer 902 that eventually merges into a shaft portion 1204 of the insertion tool. The first portion 1202 may, for example, have a length of approximately 0.30 inches although this length may, of course, be larger or smaller as well. The first portion 1202 is shaped to fit around the trailing end 908 of the spacer 902 and, therefore, is curved in nature to match the curvature of the spacer 902. For example, the first portion 1202 can converge outwardly at a rate 1206 of 11 degrees from a centerline such that the curvature of the first portion 1202 can accommodate the spacer 902. Of particular importance are the engaging features 1210 that are configured to engage complimentary features 910 on the upper edge 907 and lower edge 905 of the spacer 902. Depending on which complementary features 910 are engaged, the angle of engagement between the tool and the spacer can vary. In this way, the tool and the spacer may securely engage one another at one of many different, selectable engagement angles. The height of the engaging surfaces 1210 may, for example, be approximately 0.023 inches.
The tool 950 may be positioned such that the opposing arms 1102, 1104 are located within the channel 966 around the semicircular portion 962. As the first portion is extended (relative to the opposing arms) towards the spacer 902, the opposing arms are forced together so that they grip the exterior surface of the semicircular portion 962. Even though the tool 950 and spacer 902 are somewhat securely engaged at this point, the tool 950 can still be twisted relative to the spacer 902 because the mechanical force applied to the tool 950 by a doctor can overcome the frictional engagement between the opposing arms 1102, 1104 and the channel 966. Thus, the angle between the tool 950 and the spacer 902 can be adjusted even though the tool 950 and spacer 902 are connected in a manner in which they will not inadvertently separate. Eventually, the engaging surfaces 1210 will engage complementary surfaces 910 on the spacer 902. At this point, the angle between the tool 950 and the spacer 902 will be fixed in one of the many different selectable angles that are possible. To reposition the tool 950 at a different angle, the first portion 1202 is retracted from the spacer so that the engaging surfaces of the tool and spacer disengage. The tool 950 can once again be twisted relative to the spacer 902 so that when they are reengaged they are at a different angle relative to one another.
In particular, the external portion 1202 includes wings, or arms, 1220, 1222 that are shaped so that they contact the opposing arms 1102, 1104 and squeeze these arms 1102, 1104 together. Thus, when the opposing arms 1102, 1104 are withdrawn back towards the external portion 1202, the outside surfaces of the arms 1102, 1104 come in contact with a respective wing 1220, 1222 which forces the opposing arms 1102, 1104 in a direction towards one another. When the opposing arms 1102, 1104 are extended outwardly from the external portion 1202, they are free to expand once they clear the wings 1220, 1222. As the opposing arms 1102, 1104 transition form the “open” to the “closed” position, the grip on the spacer becomes tighter and more secure. Between the two positions of “open” and “closed” there is a range of intermediate positions where the insertion tool securely grips the spacer but still permits rotation of the tool relative to the spacer.
The previous description is provided to enable any person skilled in the art to practice the various embodiments described herein. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments. Thus, the claims are not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” All structural and functional equivalents to the elements of the various embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”
Claims
1. An intervertebral spacer comprising:
- a leading end; and
- a trailing end, configured to accept therein an extending portion of an insertion tool, the trailing end comprising an external surface configured to securely engage a complementary surface of the insertion tool at a plurality of different angles.
2. The intervertebral spacer of claim 1, further comprising:
- an anterior side connecting the leading end and the trailing end; and
- a posterior side opposite the anterior side and connecting the leading end and the trailing end.
3. The intervertebral spacer of claim 2, wherein the anterior side and the posterior side are arcuate.
4. The intervertebral spacer of claim 3, wherein the anterior side and the posterior side have different respective radii of curvature.
5. The intervertebral spacer of claim 2, wherein the anterior side, the posterior side, the leading end, and the trailing end are arranged to form a cage having a cavity.
6. The intervertebral spacer of claim 2, further comprising:
- a generally planar superior side, generally perpendicular to the posterior and anterior sides and extending substantially from the leading end to the trailing end; and
- a generally planar inferior side, opposite the superior side, and generally perpendicular to the posterior and anterior sides and extending substantially from the leading end to the trailing end.
7. The intervertebral spacer of claim 6, wherein a first height of the anterior side is greater than a second height of the posterior side such that the superior side slopes downwardly from the anterior side to the posterior side.
8. The intervertebral spacer of claim 6, wherein a first height of the anterior side is greater than a second height of the posterior side such that the inferior side slopes upwardly from the anterior side to the posterior side.
9. The intervertebral spacer of claim 2, wherein the leading end comprises:
- a first, generally actuate, portion; and
- a second, substantially straight, portion adjoining the first portion.
10. The intervertebral spacer of claim 2, wherein the trailing end comprises:
- a first, generally actuate, portion; and
- a second, substantially straight, portion adjoining the first portion.
11. The intervertebral spacer of claim 9, wherein the second portion adjoins the posterior side and the first portion adjoins the anterior side.
12. The intervertebral spacer of claim 1, wherein the trailing end further comprises:
- a first channel configured to receive the extending portion; and
- a second channel substantially collinear with the first channel, and extending from the exterior surface to the first channel.
13. The intervertebral spacer of claim 12, wherein a first height of the first channel is greater than a second height of the second channel.
14. The intervertebral spacer of claim 12, wherein the first channel extends from a first end at the exterior surface of the trailing end to a second end within the intervertebral spacer.
15. The intervertebral spacer of claim 14, wherein the first end is located substantially at a juncture between the anterior side and the trailing end.
16. The intervertebral spacer of claim 14, wherein the first end is located substantially at a juncture between the posterior side and the trailing end.
17. The intervertebral spacer of claim 1, further comprising:
- a first major axis and, wherein the insertion tool comprises a second major axis.
18. The intervertebral spacer of claim 17, further comprising:
- a plurality of teeth configured to engage one or more complementary teeth on the complementary surface, in a plurality of different engagement positions, wherein an angle between the first and second major axis differs at each of the different engagement positions.
19. The intervertebral spacer of claim 18, wherein the plurality of teeth are one of rounded, squared, and pointed in shape.
20. The intervertebral spacer of claim 18, wherein the trailing end is generally arcuate and the plurality of teeth are disposed radially along the exterior surface.
21. The intervertebral spacer of claim 18, wherein the trailing end further comprises:
- a first channel configured to receive the extending portion; and
- a second channel substantially collinear with the first channel, and extending from the exterior surface to the first channel.
22. The intervertebral spacer of claim 21, wherein the plurality of teeth engage the complementary teeth when the extending portion is disposed within the first channel.
23. The intervertebral spacer of claim 21, wherein the plurality of teeth are configured to be moved in and out of engaging contact with the complementary teeth while the extending portion is disposed within the first channel.
24. The intervertebral spacer of claim 21, wherein the plurality of teeth are configured to be changed from one engagement position to a second engagement position while the extending portion is disposed within the first channel.
25. The intervertebral spacer of claim 1, wherein the spacer is generally kidney-shaped.
26. The intervertebral spacer of claim 1, wherein the spacer is substantially a cage having a central cavity.
27. The intervertebral spacer of claim 1, wherein the trailing end further comprises:
- an upper edge;
- a lower edge; and
- a semicircular channel positioned between the upper edge and the lower edge.
28. An intervertebral spacer comprising:
- a trailing end configured to engage an insertion tool at an angle,
- the trailing end comprising: a first portion configured to securely receive an extending portion of the insertion tool; and a second portion having a surface shaped to engage a complementary-shaped surface of the insertion tool at a plurality of different positions such that the angle differs for each of the different positions.
29. The intervertebral spacer of claim 28, wherein the surface is configured to be moved from a first position to a second position while the extending portion is disposed within the first portion.
30. The intervertebral system of claim 28, wherein the first portion comprises a channel having an opening on an exterior of the spacer.
31. The intervertebral spacer of claim 28, wherein the second portion comprises a plurality of teeth.
32. The intervertebral spacer of claim 28, wherein the first portion includes:
- an upper edge;
- a lower edge; and
- a semicircular channel positioned between the upper edge and the lower edge.
32. A method for using an intervertebral spacer comprising the steps of:
- receiving an extending portion of an insertion tool within the intervertebral spacer; and
- securely engaging a first surface of the intervertebral spacer with a second surface of the insertion tool in one of a plurality of different adjustable positions, while the extending portion is disposed within the intervertebral spacer.
33. The method of claim 32 further comprising the step of:
- changing from the one position to a different position among the plurality of positions while the extending portion remains disposed within the intervertebral spacer.
34. The method of claim 32, wherein the first surface has a plurality of shaped protrusions and the second surface has a complementary shape configured to mate with at least one of the shaped protrusions.
35. The method of claim 32, wherein the first surface and second surface comprises respective pluralities of teeth.
Type: Application
Filed: Mar 8, 2006
Publication Date: Sep 13, 2007
Applicant:
Inventors: Colin Smith (Dana Point, CA), Leah Schermerhorn (San Diego, CA)
Application Number: 11/371,539
International Classification: A61F 2/44 (20060101);