BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 depicts adjacent vertebrae of the lumber region of a human spinal column.
FIG. 2 depicts a more detailed view of a portion of a human spinal column including the vertebrae of FIG. 1.
FIG. 3 depicts the spinal column portion of FIG. 2 after implantation and filling of one example of an interspinous spacer in accordance with an aspect of the present invention.
FIG. 4 is a partial cut-away view of one example of an unfilled surgical spacer with the container outside the structure, in accordance with an aspect of the present invention.
FIG. 5 depicts an example of a surgical spacer with integrated container and structure, in accordance with an aspect of the present invention.
FIG. 6 is a cross-sectional view of one example of a surgical spacer with external container, in accordance with an aspect of the present invention.
FIG. 7 depicts one example of the construction of a fabric jacket for use with one example of a surgical spacer, in accordance with an aspect of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
A surgical spacer of the present invention can be formed in situ during a procedure. The spacer includes two basic aspects: a flexible container, and a structure for at least part of the container. The flexible container can be filled or injected though an optional conduit after placement. Further, the structure may be folded in some aspects. Together with an unfilled container, in some aspects, the spacer can create a smaller footprint during implantation, which is less invasive, requires less tissue disruption for creating access for implantation, and allows the spacer to conform to the patient's anatomy. Once filled, the structure provides support and containment for the container, reducing the chances of complications like bulging of the container.
FIG. 1 depicts adjacent vertebrae 100, 102 of the lumbar region of a human spinal column. As known in the art, each vertebrae comprises a vertebral body (e.g., vertebral body 104), a superior articular process (e.g., superior articular process 106), a transverse process (e.g., transverse process 108), an inferior articular process (e.g., inferior articular process 110), and a spinous process (e.g., spinous process 112). In addition, between vertebral bodies 104 and 114 is a space 116 normally occupied by an intervertebral disc (see FIG. 2), and between spinous processes 112 and 118 is a space 120 normally occupied by an interspinous ligament (see FIG. 2).
FIG. 2 depicts the vertebrae of FIG. 1 within an area 200 of the lumbar region of a human spine. As shown in FIG. 2, spinous processes 112 and 118 are touching and pinching interspinous ligament 202, calling for spacing of the spinous processes.
FIG. 3 depicts spinous processes 112 and 118 after spacing with an interspinous spacer 300 in accordance with one aspect of the present invention. As shown in FIG. 3, interspinous ligament 202 has been removed in a conventional manner prior to insertion of spacer 300. Although shown in its filled state, in this example, spacer 300 is implanted in its unexpanded state, as described more fully below. The spacer is filled with a material described below through a conduit 302 after implantation. For example, the material may be injected into the spacer through the conduit (e.g., a one-way valve). Prior to implantation and filling, measurement of the space between the interspinous processes and determination of the spacer size and desired amount of filling can be performed. Conventional methods can be used, such as, for example, the use of templates, trials, distractors, scissor-jacks or balloon sizers.
FIG. 4 depicts a partially cut-away view of one example of a spacer 400, in accordance with one aspect of the present invention. As shown in FIG. 4, the spacer comprises an unfilled container 402 inside a structure 404. Preferably, the container is in an evacuated state during implantation and prior to being filled. Where a valve (e.g., a one-way valve) is coupled to the container, the container is preferably evacuated prior to or during the process of coupling the valve thereto. In the present example, the structure is outside the container. However, as will be described in more detail below, the container can be outside the structure, or the container and structure can be integrated. In addition, although the structure is shown to be roughly H-shaped to fit between adjacent spinous processes, the structure can have any shape necessary for the particular surgical application. For example, the structure could instead have a roughly cylindrical shape to replace an intervertebral disc. As another example, the structure could be spherically or elliptically shaped to replace part of the intervertebral disc, for example, the nucleus pulpous, leaving the rest of the disc intact. Further, although the structure is shown enveloping the container, the structure could be for only a portion of the container, depending on the particular application. For example, it may be desired to prevent bulging of the container only in a particular area. Coupled to the container is an optional conduit 406 for accepting a material that is compressible during end use. The structure provides support for and containment of the container when filled.
The container is flexible and substantially impermeable to the material it will be filled with. However, depending on the application, the container may be permeable to other materials, for example, it may be air and/or water permeable. In the present example, the container takes the form of a bag or balloon, but can take other forms, so long as flexible and substantially impermeable to the material it will be filled with. Thus, the container must be substantially impermeable to the filling material, for example, in a liquid state during filling and prior to curing. Examples of container materials include silicone, rubber, polyurethane, polyethylene terephthalate (PET), polyolefin, polycarbonate urethane, and silicone copolymers.
Conduit 406 accepts the material being used to fill the container. Preferably, the conduit comprises a one-way valve, however, a two-way valve is also contemplated, as another example. Also preferably, the conduit is constructed to be used with a delivery system for filling the container, such as, for example, a pressurized syringe-type delivery system. However, the delivery system itself forms no part of the present invention. As noted above, the conduit is optional. Other examples of how to fill the container comprise the use of a self-sealing material for the container, or leaving an opening in the container that is closed (e.g., sewn shut) intraoperatively after filling. Using a curable material to fill the container may also serve to self-seal the container.
In use, the container is filled with a material that is compressible during end use. The compressibility characteristic ensures that the material exhibits viscoelastic behavior and that, along with the structure, the spacer can accept compressive loads. Of course, the degree of compressibility will depend on the particular application for the surgical spacer. For example, if a spacer according to the present invention is used between adjacent spinous processes, the spacer would need to accept compressive loads typically experienced in the posterior region of the spine, for example, up to about 80 shore A. In other words, the spacer is preferably capable of resisting compressive motion (or loads) with a stiffness of about 40 to about 240 N/mm (newtons per millimeter). The material is preferably injectable, and may be compressible immediately or after a time, for example, after curing. For purposes of the invention, the compressibility characteristic is necessary during end use, i.e., after implantation. Materials that could be used include, for example, a plurality of beads (e.g., polymer beads) that in the aggregate are compressible, or materials that change state from exhibiting fluid properties to exhibiting properties of a solid or semi-solid. Examples of such state-changing materials include two-part curing polymers and adhesive, for example, platinum-catalyzed silicone, epoxy, polyurethane, etc.
As noted above, the structure provides support for and containment of the container when filled. The structure comprises, for example, a structural mesh comprising a plurality of fibers 408. For example, the structure can take the form of a fabric jacket, as shown in FIG. 4. The structure, a fabric jacket in this example, also contains and helps protect the container from bulging and damage from forces external to the container. The fibers comprise, for example, PET fabric, polypropylene fabric, polyethylene fabric, and/or steel, titanium or other metal wire. Depending on the application, the structure may be permeable in some respect. For example, if bone or tissue growth is desired to attach to the structure, permeability to the tissue or bone of interest would be appropriate. As another example, permeability of the structure may be desired to allow the material used to fill the container to evacuate air or water, for example, from the container, in order to prevent bubbles from forming inside. Where a mesh is used, for example, the degree of permeability desired can be achieved by loosening or tightening the weave.
Although the structure is shown in its final, roughly H-shape in the example of FIG. 4, it will be understood that in practice, the structure can be made to be folded (e.g., a fabric mesh) and/or unexpanded. Further, the structure can have a shape other than that shown. A folded or unexpanded state facilitates implantation, allowing for a smaller surgical opening, and unfolding or expansion in situ upon filling of the container.
One example of the construction of a fabric jacket 700 for use as one example of a structure of the present invention will now be described with reference to FIG. 7. Two roughly cylindrical fabric members 702 and 704 are sewn together around a periphery 706 of an opening along a side (not shown) in each. An opening 708 is created in one of the members for accepting the container, for example, by laser cut. In one example, a conduit described above would poke through opening 708. The ends of the cylindrical members (e.g., end 710) are then trimmed and sewn shut, as shown in broken lines (e.g., lines 712) in FIG. 7.
FIG. 5 depicts an outer view of another example of a surgical spacer 500 in accordance with the present invention. A container conduit 501 is shown pointing outward from an opening 503. As shown, the structure 502 limits the expansion of the spacer and may create a rough final shape, in this example, a rough H-shape. The structure comprises a fabric jacket 504, similar to that described above with respect to FIG. 4, that is soaked through with a dispersion polymer 506 (e.g., silicone). The dispersion polymer (after curing) acts as the container and is shown filled in FIG. 5. This is one example of the container and the structure being integral.
FIG. 6 is a cross-sectional view of another example of a surgical spacer 600 in accordance with the present invention. Surgical spacer 600 is similar to the spacer of FIG. 5, except that instead of being soaked in a dispersion polymer, a fabric jacket 602 is coated with a dispersion polymer (e.g., silicone) 604 or other curable liquid appropriate for the container material, creating an outer container. The coating can be done in a conventional manner, for example, by dip molding on the outside of the fabric jacket.
Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.
Patent Application
20070276497
