VERTEBRAL INTERBODY SPACER
An interbody spacer includes an elongated body with a maximum width between opposite side walls and a maximum height between upper and lower bearing surfaces. The interbody spacer also includes a leading end nose connecting the side walls to facilitate insertion of the interbody spacer into a disc space between vertebrae in an insertion orientation, from which the interbody device is then rotated to position the upper and lower bearing surfaces in contact with the endplates of the adjacent vertebrae. The leading end nose forms a blunt convex nose between the upper and lower bearing surfaces to maximize the bearing surface area available to contact the adjacent endplates.
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The present invention relates generally to treatment of the spinal column, and more particularly relates to a vertebral interbody spacer for placement between adjacent vertebral bodies of a spine to create and maintain a desired orientation and spacing between the adjacent vertebral bodies.
It is known that if an intervertebral disc is damaged, it can be removed and the resulting space between the two adjacent vertebrae may be filled with a bone growth inducing substance to promote a boney fusion across the disc space. Fixation devices external to the disc space have been utilized to maintain the position of the adjacent vertebrae while the intervening material fuses with adjacent bone to form a boney bridge. As an alternative or in conjunction with fixation devices, load bearing spacers, such as artificial devices or bone grafts, may be placed in the empty disc space. These spacers transmit the loading from one adjacent vertebra to the other adjacent vertebra during the healing process. Further, when an intervertebral disc is damaged there is often a loss of height of the disc and a loss of the normal angle (lordosis) between the vertebra on each side of the disc. Spacers may also be used to restore the height and angle (lordosis) of a damaged intervertebral disc. Such spacers may be provided in a variety of forms.
A need exists for improvements to interbody spacers and the present invention is directed to such need.
SUMMARYThe present invention provides an improved interbody spacer adapted for spacing two adjacent vertebral bodies. The invention provides mechanisms to achieve the desired goals of distracting the intervertebral space and, when desired, of increasing the lordosis angle between the adjacent vertebral bodies. The initial increase in height is obtained by insertion of the spacer body into the disc space in one orientation whereby distraction is obtained by means of a small radius bullet shaped nose. Further increase in height and increase in lordosis is obtained by rotation of the spacer body about its longitudinal axis by, for example, a quarter turn.
Various aspects are summarized below, but it should be understood that embodiments are contemplated that incorporate any one or combination of these features, omit one or more of the following features, or include other features not specifically discussed. The interbody spacer includes an elongated body extending on a center longitudinal axis with opposite upper and lower bearing surfaces and opposite side walls that are convexly rounded along the longitudinal axis. As used herein, side walls convexly rounded along the longitudinal axis means that the side walls are curved outwardly from the longitudinal axis from a leading end portion to a trailing end of the spacer when the spacer is viewed from a direction looking orthogonally toward either its upper or lower bearing surface. The side walls diverge from the trailing end toward the leading end portion so that that spacer provides a maximum width at a location that is offset from a mid-length plane of the spacer in a direction toward the leading portion. The side walls converge from this maximum width location to the leading end portion of the spacer where the side walls define a bullet-shaped tip when viewed in a direction looking orthogonally toward one of the upper and lower bearing surfaces. The bullet-shaped tip connecting the side walls facilitates insertion of the spacer between and distraction of adjacent vertebrae when the spacer is oriented in an insertion orientation in which the side walls are positioned to face the endplates of the vertebrae. When viewed from a direction looking on the longitudinal axis of the interbody spacer toward either the leading end portion or the trailing end of the spacer, the side walls are linear from the upper bearing surface to the lower bearing surface. The leading end portion forms a blunt, convexly rounded nose extending between the upper and lower bearing surfaces that is substantially larger than the bullet-shaped tip in the transverse direction so that the length of the upper and lower bearing surfaces along the longitudinal axis available to contact the endplates is maximized. In one embodiment the complex rounded nose in the transverse direction includes a complex curve with at least two different radii from the nose to the adjacent side wall. This complex curve allows the leading end of the spacer body to have a small radius that transitions to a larger radius before intersecting the upper and lower bearing surfaces. The smaller radius curvature enhances the ability of the leading edge to distract the narrowed disc space on initial insertion while the larger radius maintains the point of intersection with the upper and lower surface at a position such that sufficient surface area of the upper and lower bearing surfaces is maintained. The upper and lower bearing surfaces define a height of the spacer and are convexly rounded along the longitudinal axis from the leading end portion to the trailing end of the spacer. The upper and lower bearing surfaces define a maximum height at a second location that is offset from the mid-length plane of the spacer toward the leading end portion of the spacer. The side walls also each define an elongated slot extending from the trailing end toward the leading end portion. The slots diverge from one another in a direction toward the leading end portion and are configured to receive an inserter instrument therein. The trailing end includes a receptacle between the slots to receive the inserter instrument. The interbody spacer also includes a central cavity that extends through the upper and lower bearing surfaces. The slots each include at least one hole that opens into the cavity. The upper and lower bearing surfaces also include elongated projections that extend between the side walls orthogonally to the longitudinal axis of the spacer.
The present invention also provides an inserter instrument for use in combination with an interbody spacer. According to one aspect, the inserter has a gripping end with fingers that are wedged into diverging slots formed along opposite side walls of the interbody spacer when a holding member of the inserter is engaged to a trailing end of the interbody spacer.
The present invention also provides a method for inserting an improved interbody spacer. In one aspect of the method and the spacer, the inserter is oriented so that the spacer is positioned with its side walls facing respective ones of the adjacent endplates the vertebrae, and then the spacer is inserted into the disc space so that its bullet-shaped nose leads its entry into the disc space and the longitudinal convexly rounded side walls separate the adjacent vertebrae. The spacer is then rotated in situ to further distract the vertebrae as its upper and lower bearing surfaces are positioned in contact with the endplates of the adjacent vertebrae. In one aspect, the spacer includes transverse projections extending across the upper and lower bearing surfaces. In a direction between the side walls, the ends of the transverse projections lie on an arc defined by a first radius that is substantially smaller than a second arc defined by a second radius on which the upper and lower bearing surfaces lie. The increased curvature of the ridges facilitates in situ rotation of the spacer about its longitudinal axis and the smaller curvature of the upper and lower bearing surfaces provides increases stability for the spacer in its implanted orientation than would be provided if the curvature of the bearing surfaces between the side walls was the same as or greater than the curvature of the projections. In addition, the curvature of the bearing surfaces between the sidewalls reduces point loading of the interbody spacer at the edges where the upper and lower bearing surfaces join with the respective adjacent side walls, this reducing subsidence. The ends of the projections can be chamfered where they connect to the side walls to further facilitate rotation of the spacer in situ.
These and other aspects and advantages of the present invention will become apparent to those skilled in the art from the description of the illustrated embodiments set forth below.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications in the illustrated devices, and such further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
Referring now to
In one embodiment, the body of spacer 20 is formed of a radiolucent material and includes a series of radiopaque markers embedded therein to accommodate visualization of spacer 20 during and after insertion into an intervertebral disc space when the implant is formed of substantially radiolucent material. Radiopaque markers 40 are positioned at the leading end 26 of spacer 20 at the transition point between leading end portion 26 and upper bearing surface 22 and lower bearing surface 24, respectively. Radiopaque markers 52 are positioned in opposite corners of trailing end 28, respectively, adjacent respective ones of upper and lower bearing surfaces 22, 24. In one specific embodiment, radiopaque markers 40 and 52 are pins inserted into the spacer material prior to formation of its exterior geometry. Each of the radiopaque markers 40, 52 has an exterior surface substantially identical to and co-terminus with the geometry of the adjacent exterior surface of spacer 20. Thus, upon implantation, a surgeon may be able to correctly visualize through x-ray imaging or other techniques the exact relationship between the surfaces of spacer 20 and the surrounding bone structures. Various spacer materials are contemplated that may include PEEK, other polymers including resorbable polymers, ceramics, composites, bone or bone substitute materials, and biocompatible metals such as stainless steel, titanium, or tantalum. Materials are listed by way of example, and any suitable biocompatible may form the spacer body described herein. Furthermore, spacer 20 is illustrated as a body with an internal cavity 25 and of substantially uniform material. It will be appreciated that teachings of the present invention may be applied to interbody spacers having solid bodies or pores for receiving bone growth promoting material. Still further, the body of the spacer may be formed with layers of uniform or non-uniform materials, such as bone and other composite materials, to form a spacer body as described herein.
Referring now to
Spacer 20 has a length L1 from leading end portion 26 to trailing end 28. Length L1 is sized to extend substantially across a vertebral endplate of the vertebrae to be supported. For example, length L1 can vary from 18 millimeters to 32 millimeters, although other lengths are not precluded. The convexly curved upper and lower bearing surfaces 22, 24 fit with the concavity of the vertebral endplates to provide an intimate fit therewith. Each of the upper bearing surface 22 and the lower bearing surface 24 include a series of projections 32 and 34, respectively. Each projection includes a truncated crest defined by a curved surface that is connected with the respective bearing surface 22, 24 with concavely rounded transitions that blend into the respective portion of the bearing surface 22, 24 extending between adjacent projections. As shown in
Each of the corners or edges of spacer body 20 that connect the adjacent side wall 30, 36 with the adjacent upper or lower bearing surface 22, 24 are defined by an arcuate surface, such as arcuate surface S1 in
In
The bullet-shape profile of leading end portion 26 in the direction between side walls 30, 36 facilitates insertion of spacer 20 into a collapsed disc space with spacer 20 oriented so that side walls 30, 36 face respective ones of the vertebral endplates. Furthermore, the transition of the aggressively rounded leading end portion 26 to the more subtly rounded side wall portions defined by radius R5 allows spacer 20 to initially distract and maintain this initial distraction with a sufficient length of weight bearing surface along side walls 30, 36 without cutting into the vertebral endplates. In addition, the length of upper and lower bearings surfaces 22, 24 can be maximized and extended to a location that is only slightly offset from the leading most end nose portion 26, as shown in
Referring now to
Referring now to
The above described spacer includes a variety of improved features. While all of these features have been disclosed with reference to the described embodiment, it will be appreciated that one or any combination of features may be utilized with an improved interbody spacer. Further, while specific dimensions were disclosed suitable for spinal anatomy in the lumbar spine of some patients, a spacer may be configured with other dimensions suitable for interbody spacers at various levels, lumbar, thoracic, and cervical, of the spine for a variety of patient populations. For example, in an average patient population the anterior height of the device may range from 4 millimeters to 18 millimeters. Similarly, the posterior height of the device may range from 2 millimeters to 16 millimeters. Within this range, the longitudinal offset of the center point defining the arc of the upper and lower bearing surfaces may be adjusted to create lordotic angulations ranging from 0 to 30 degrees.
As shown in
Although various embodiments have been described as having particular features and/or combinations of components, other embodiments are possible having a combination of any features and/or components from any of embodiments as discussed above. As used in this specification, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, the term “a member” is intended to mean a single member or a combination of members, “a material” is intended to mean one or more materials, or a combination thereof. Furthermore, the terms “proximal” and “distal” refer to the direction closer to and away from, respectively, an operator (e.g., surgeon, physician, nurse, technician, etc.) who would insert the medical implant and/or instruments into the patient. For example, the portion of a medical instrument first inserted inside the patient's body would be the distal portion, while the opposite portion of the medical device (e.g., the portion of the medical device closest to the operator) would be the proximal portion.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that all changes and modifications that come within the spirit of the invention are desired to be protected.
Claims
1-25. (canceled)
26. A method for positioning an interbody spacer between vertebrae, comprising:
- providing an interbody spacer comprising a body extending along a longitudinal axis between a leading end and an opposite trailing end, the body comprising a pair of opposite lateral side walls extending between the leading and trailing ends, the body comprising opposite upper and lower surfaces each extending between the leading and trailing ends and between the side walls, the upper and lower surfaces each including a series of spaced apart projections that extend transverse to the longitudinal axis;
- positioning the spacer between the vertebrae such that one of the side walls faces a superior vertebra and the other one of the side walls faces an adjacent inferior vertebra; and
- rotating the spacer between the vertebrae about the longitudinal axis such that the projections of one of the top and bottom surfaces engage the superior vertebra and the projections on the other of the top and bottom surfaces engages the inferior vertebra.
27. A method according to claim 26, wherein:
- the leading end defines a bullet-shaped nose; and
- positioning the spacer between the vertebrae includes inserting the spacer into a disc space between the vertebrae such that the bullet-shaped nose leads entry of the spacer into the disc space.
28. A method according to claim 26, wherein a corner connects each of the side walls to a respective one of the upper and lower surfaces and each of the corners is defined by an arcuate surface.
29. A method according to claim 28, wherein a tangent of at least one of the arcuate surfaces at an intersection of the arcuate surface with the side wall is closer to lying on the side wall than a tangent of the arcuate surface at an intersection with the respective one of the upper and lower surfaces is to lying on the respective surface.
30. A method according to claim 26, wherein:
- the body defines a mid-length plane that is orthogonal to the longitudinal axis; and
- the side walls each define a continuous convexly curved profile extending from the leading end to the trailing end, the continuous convexly curved profiles defining a maximum width of the body between the side walls at a second location that is offset from the mid-length plane toward the leading end portion.
31. A method according to claim 30, wherein the continuous convexly curved profile of each of the side walls are defined by a first arc having a first radius with the first arc extending from the trailing end to the second location, and the continuous convexly curved profile of each of the side walls is defined by a second arc having a second radius with the second arc extending from the second location to the leading end, the first radius being greater than the second radius so that the side walls converge toward the leading end.
32. A method according to claim 26, wherein:
- the projections each have a truncated crest extending between the side walls, each of the truncated crests defining a first arc having a first radius; and
- the upper and lower surfaces are each defined by a second arc having a second radius, the second radius being greater than the first radius.
33. A method according to claim 32, wherein opposite ends of each projection are rounded from an adjacent one of the side walls to the crest of the projection to facilitate rotation of the spacer about the longitudinal axis.
34. A method according to claim 32, wherein:
- the truncated crests of the projections on at least one of the upper and lower surfaces lie on a third arc having a third radius with the third arc extending from the leading end to the trailing end;
- at least one of the upper and lower surfaces lies on a fourth arc having a fourth radius with the fourth arc extending from the leading end to the trailing end; and
- the truncated crests define a maximum height of the body portion at a location that is offset toward the trailing end from a junction of the upper and lower surfaces and the leading end.
35. A method according to claim 26, wherein:
- the upper surface is continuously curved between the leading end and the trailing end; and
- the lower surface is continuously curved between the leading end and the trailing end.
36. A method according to claim 26, wherein:
- the body defines a mid-length plane that is orthogonal to the longitudinal axis; and
- the upper and lower surfaces define a maximum height between the upper and lower surfaces at a first location that is offset from the mid-length plane toward the leading end.
37. A method according to claim 36, wherein the side walls each include an elongated slot therein that extends from the trailing end to an opposite end of the slot that is located adjacent the mid-length plane.
38. A method according to claim 36, wherein the slots each include a height that increases from the trailing end toward the leading end.
39. A method according to claim 26, wherein at least one of the side walls includes projections.
40. A method according to claim 26, wherein:
- the body defines a cavity that extends between and opens at each of the upper and lower surfaces;
- the side walls each include an opening extending therethrough that is in communication with the cavity; and
- the method comprises inserting bone growth promoting material in the cavity prior to positioning the spacer between the vertebrae.
41. A method for positioning an interbody spacer between vertebrae, comprising:
- providing an interbody spacer comprising a body extending along a longitudinal axis between a leading end and an opposite trailing end, the leading end defining a bullet-shaped nose, the body comprising a pair of opposite side walls extending between the leading and trailing ends, the side walls each defining a continuous convexly curved profile extending from the leading end to the trailing end, wherein a corner connects each of the side walls to a respective one of the upper and lower surfaces and each of the corners is defined by an arcuate surface, the body comprising an upper surface and an opposite lower surface each extending between the leading and trailing ends and between the side walls, the upper and lower surfaces being continuously curved between the leading and trailing ends, the upper and lower surfaces each including a series of spaced apart projections that extend transverse to the longitudinal axis, the body defining a cavity that extends between and opens at each of the upper and lower surfaces, the side walls each including an opening extending therethrough that is in communication with the cavity;
- inserting bone growth promoting material in the cavity;
- inserting the spacer into a disc space between the vertebrae such that the bullet-shaped nose leads its entry into the disc space;
- positioning the spacer between the vertebrae such that one of the side walls faces a superior vertebra and the other one of the side walls faces an adjacent inferior vertebra; and
- rotating the spacer between the vertebrae about the longitudinal axis such that the projections of one of the top and bottom surfaces engage the superior vertebra and the projections on the other of the top and bottom surfaces engages the inferior vertebra.
42. A method for positioning an interbody spacer between vertebrae, comprising:
- providing an inserter comprising an outer member comprising an inner surface defining a passage and an outer surface engaging a handle, a distal end of the outer member comprising a pair of spaced apart fingers, the inserter comprising an inner member movably disposed within the passage,
- providing an interbody spacer comprising a body extending along a longitudinal axis between a leading end and an opposite trailing end including a central receptacle, the body comprising a pair of opposite lateral side walls extending between the leading and trailing ends, the side walls each including an elongated slot therein that has a concave profile and extends from the trailing end, the body comprising an upper surface and an opposite lower surface each extending between the leading and trailing ends and between the side walls, the upper and lower surfaces each including a series of spaced apart projections that extend transverse to the longitudinal axis;
- engaging the fingers with the slots to prevent rotation of the inserter relative to the spacer;
- disposing a distal end of the inner member in the receptacle;
- positioning the spacer between the vertebrae with the inserter such that one of the side walls faces a superior vertebra and the other one of the side walls faces an adjacent inferior vertebra; and
- rotating the outer member to rotate the spacer between the vertebrae about the longitudinal axis such that the projections of one of the top and bottom surfaces engage the superior vertebra and the projections on the other of the top and bottom surfaces engages the inferior vertebra.
43. A method according to claim 42, wherein the fingers include convexly curved facing surfaces that match the concave profile of the slots and diverge to provide an intimate fit therewith.
44. A method according to claim 42, wherein:
- the distal end of the outer member comprises a first flange positioned between the fingers and a second flange positioned between the fingers opposite the first flange; and
- the method further comprises engaging the first flange with one of the upper surface and the lower surface and engaging the second flange with the other one of the upper surface and the lower surface simultaneously with engaging the fingers with the slots.
45. A method according to claim 42, wherein:
- the distal end of the inner member includes a first thread form and the receptacle includes a second thread form; and
- engaging a distal end of the inner member in the receptacle engaging the first thread form with the second thread form.
Type: Application
Filed: Sep 30, 2013
Publication Date: Jan 30, 2014
Applicant: Warsaw Orthopedic, Inc. (Warsaw, IN)
Inventors: Kidong YU (Memphis, TN), Keith E. Miller (Germantown, TN), William D. Armstrong (Memphis, TN), Charles Branch (Advance, NC), Kevin T. Foley (Germantown, TN), Peter McCombe (Brisbane), Anthony J. Melkent (Memphis, TN), William R. Sears (Warrawee Sydney)
Application Number: 14/041,656
International Classification: A61F 2/44 (20060101); A61F 2/46 (20060101);