Abstract:
A system for assessing an intervertebral disc space comprises an elongated catheter with proximal and distal ends and an expandable body attached to the distal end of the elongated catheter. The expandable body includes proximal and distal end portions. The system further comprises a securing mechanism encircling at least one of the proximal or distal end portions of the expandable body to tighten the expandable body against the elongated catheter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 12/841,924, filed on Jul. 22, 2010, which is incorporated herein by reference herein, in its entirety. 
    
    
     BACKGROUND 
     Degenerated disc disease refers to a syndrome in which a compromised disc causes low back pain. Disc degeneration may result in disc herniation in which the central portion of the intervertebral disc, known as the nucleus pulposus, may protrude through an opening in the surrounding fibrous ring, known as the annulus fibrous. A herniated lumbar disc can push on spinal nerves causing severe, shooting, leg pain, numbness, and/or weakness. Discectomy is a surgical procedure in which the nucleus pulposus of a herniated intervertebral disc is resected or removed to relieve pressure on the spinal cord and radiating nerves. Improved tools are needed to allow physicians to evaluate the extent of discectomy that has been performed and to assess the intradiscal space for further procedures such as fusion or arthroplasty. 
     SUMMARY 
     In one embodiment of the present disclosure, a system for assessing an intervertebral disc space comprises an elongated catheter with proximal and distal ends and an expandable body attached to the distal end of the elongated catheter. The expandable body includes proximal and distal end portions. The system further comprises a securing mechanism encircling at least one of the proximal or distal end portions of the expandable body to tighten the expandable body against the elongated catheter. 
     In another embodiment of the present disclosure, a method for assessing an intervertebral disc space comprises selecting an assessment instrument including an elongated catheter with proximal and distal ends and an expandable body attached to the distal end of the elongated catheter. The expandable body includes proximal and distal end portions. The securing mechanism encircles at least one of the proximal or distal end portions of the expandable body to tighten the expandable body against the elongated catheter. The method further includes inserting the expandable body into the intervertebral disc space and expanding the expandable body within the intervertebral disc space. 
     In another embodiment of the present disclosure, a system for assessing an intervertebral disc space comprises an elongated catheter with proximal and distal sections and an expandable tube with proximal and distal ends. The distal end is attached to the distal section of the elongated catheter and the proximal end is attached to the elongated catheter between the proximal and distal sections. The system further includes a securing mechanism encircling at least one of the proximal or distal ends of the expandable tube and overlapping the at least one proximal or distal end and the elongated catheter to tighten the expandable body against the elongated catheter. 
     Further aspects, forms, embodiments, objects, features, benefits, and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a medical device for intervertebral disc assessment according to one embodiment of this disclosure. 
         FIG. 2  illustrates a side view of a portion of the medical device of  FIG. 1  in an unexpanded configuration. 
         FIG. 3  illustrates a side view of a portion of the medical device of  FIG. 1  in an expanded configuration. 
         FIG. 4  illustrates a side view of a portion of a medical device according to an alternative embodiment of this disclosure. 
         FIG. 5  describes a surgical method according to one embodiment of this disclosure. 
         FIG. 6  illustrates deployment of a medical device according to an embodiment of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates generally to the field of intervertebral disc treatment, and more particularly to systems and methods for evaluating an intervertebral disc space in conjunction with a discectomy procedure. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to embodiments or examples illustrated in the drawings, and specific language will be used to describe these examples. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alteration and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the disclosure relates. 
     Referring first to  FIG. 1 , a medical device for intervertebral disc assessment and treatment is indicated generally by the numeral  10 . The device  10  includes a catheter  12  having a proximal end  14  and a distal end  16 . An interior lumen (not shown) extends through the catheter between the ends  14 ,  16 . An expandable body  18  is attached near the distal end  16  of the catheter  12 . An inner catheter section  20  of catheter  12  is located between the proximal end  14  and the distal end  16  and extends through the expandable body  18 . One or more openings  21  extend through a side wall of inner catheter section  20  and are in communication with the interior lumen of catheter  12 . As shown more clearly in  FIGS. 2 and 3 , the expandable body  18  comprises an expandable tube  30  which extends around the inner catheter section  20 . The expandable body  18  is secured to the catheter  12  using securing members  22 . 
     The proximal end  14  of the catheter  12  carries a connection assembly  24  interconnecting the catheter with a material delivery instrument  26 . A suitable material delivery instrument may be, for example, a syringe for containing an inflation medium to be delivered to the expandable body  18 . The connection assembly  24  includes a two-way stopcock  25  and one or more luer lock connectors  27 , and is configured to control the flow of the inflation medium between the material delivery instrument  26  and the catheter  12 . 
     Suitable materials may be selected for the fabrication of the components of the disc assessment device  10 . The catheter may have a shaft that is flexible and resistant to kink formation. The materials for the catheter may also be selected to facilitate advancement of the expandable body. The catheter can be constructed, for example, using standard flexible, medical grade plastic materials, like vinyl, nylon, polyethylenes, ionomer, polyurethane, and polyethylene tetraphthalate (PET). An elastomeric material, polyether block amide, which is offered by Arkema of Puteaux, France under the tradename Pebax may be suitable for some embodiments. The catheter can also be fabricated from more rigid materials to impart greater stiffness and thereby aid in its manipulation. More rigid materials that can be used for this purpose include stainless steel, nickel-titanium alloys, and other metal alloys. 
     The expandable tube may be formed of a highly compliant, elastomeric material capable of generally conforming to surrounding tissue when the expandable body  18  is inflated. Suitable materials may include silicone, latex, or neoprene. In some embodiments, a thermoplastic rubber elastomer offered by AdvanSource Biomaterial Corporation of Wilmington, Mass. under the tradename ChronoPrene may be particularly suitable. Alternatively, the expandable tube may be formed of a material, such as vinyl, nylon, or PET, having relatively inelastic properties. 
     To permit radiographic positioning of the expandable body  18 , radiopaque markers  32  may be applied to the expandable body or the catheters. The markers  32  may be bands secured to the catheter  12  by crimping, swaging, or other techniques known in the art. A platinum-iridium alloy may be a suitable material for fabricating radiopaque markers. To aid in the positioning of the expandable body  18  without fluoroscopic guidance, distance markers  33  may be printed or otherwise formed on the catheter  12  to permit visual monitoring of the catheter insertion depth. 
     As shown in greater detail at  FIGS. 2 and 3 , securing members  22  attach the expandable tube  30  to the catheter  12 . The securing members  22  may be, for example, sections of heat shrinkable tubing which encircle and contact both the expandable tube  30  and the catheter  12 . When heat is applied, to the heat shrinkable tubing, the tubing shrinks to tighten the expandable tube  30  against the catheter  12 . The applied tubing maintains flexibility which allows it to elongate or otherwise deform when the expandable body is expanded, all the while maintaining a grip on the expandable tube and the catheter. Suitable heat shrinkable tubing may be medical-grade heat-shrinkable polyolefin tubing which includes an inner layer of adhesive. The heat-shrinkable tubing may include a modified polyolefin which has been cross linked by irradiation. Such tubing may be offered by Tyco Electronics Corporation of Berwyn, Pa. under the tradename Altera MT5000. In alternative embodiments, other forms of heat shrinkable material, including tape may be suitable. Applying the heat shrinkable tubing so that it overlaps both the expandable tube and the catheter may help prevent the expandable tube from slipping relative to the catheter, but in alternative embodiments, the heat shrinkable tubing may contact just the expandable tube. The use of heat shrinkable material may be particularly useful when used with expandable tubes or catheters formed of materials that are resistant to conventional forms of attachment such as laser bonding, thermal bonding, adhesives, or coextrusion. Alternatively, the heat shrinkable material may be used to supplement these or other forms of attachment. 
     Although the securing members  22  may be used alone to secure the catheter  12  to the expandable tube  30 , additional bonding material may provide greater adherence. The use of a medical grade adhesive  34  may be used to further promote adherence of the expandable tube  30  to the catheters. A ring of adhesive  34  applied at the opposite ends of the tube  30  at the base of the securing mechanisms  22  may prevent slipping of the shrink tubing along the catheters  12 ,  20 . Suitable medical grade adhesive may include biocompatible products that cure in the presence of ultraviolet light. 
     In alternative embodiments, adhesive, including ultraviolet adhesive, may be used without a securing member  22  to adhere the expandable tube to the catheters. In still another alternative, the securing member may be formed of a radiopaque material, including a radiopaque shrink tubing, to supplement or eliminate the need for the radiopaque markers. 
     As shown in  FIG. 4 , an alternative medical device  10   a  may be substantially similar to medical device  10  described above, but may include the differences to be described. The device  10   a  may include a catheter  12   a  which carries an expandable body  18   a . An expandable tube  30   a  is attached to catheter  12   a  by securing members  36  which may be a wire band. The band may be crimped, swaged, or otherwise tightened to secure the expandable tube to the catheters. In alternative embodiments, other types of external gripping devices including rings, wires, ties, and clamps may be used to apply an external gripping force to hold the expandable tube to the catheters. In further alternative embodiments, the catheter may include a feature such as a protruding ridge or a recessed channel which may engage the securing member to promote adherence between the catheter and the expandable tube and to limit the expandable tube from slipping relative to the catheter. 
     As described in  FIG. 5 , the device  10  may be used by a practitioner to assess space within an intervertebral disc according to the method  50 . At step  52 , a conventional discectomy procedure may be performed to remove all or a portion of a nucleus pulposus from an intervertebral disc space D located between vertebral bodies V 1  and V 2  ( FIG. 6 ). To determine if further discectomy is needed and to determine the location for any additional discectomy, the disc assessment device  10  may be used. 
     At step  54 , the material delivery instrument  26  may be prepared. For example, the material delivery instrument may be an empty 20 cc locking syringe with a non-rotating male luer lock. This may be attached to the connection assembly  24  which in this embodiment includes a two-way stopcock and a luer connection. Optionally, the expandable body  18  and catheter  12  may be vacuumed prior to use to eliminate or minimize air bubbles when inflation medium is later added. The stopcock may be used to retain the vacuum in the expandable body and catheter while the syringe is detached and filled with an inflation medium such as radiopaque contrast media. The syringe is then reattached to the stopcock. 
     At step  56 , the expandable body  18  and catheter  12  may be introduced into a cannula  70  which provides access to the intervertebral disc space D located between vertebral bodies V 1  and V 2 . In this embodiment, a percutaneous and unilateral access technique is used, but in alternative embodiments an open procedure or multilateral approach may be used. The placement of the expandable body  18  and the catheter  12  may be guided by fluoroscopy. 
     At step  58 , the expandable body  18  is gradually inflated under fluoroscopy using radiopaque contrast media. The practitioner may detect increasing resistance to inflation as the expandable body  18  expands and may stop further inflation when the expandable body  18  contacts the tissue remaining in the disc space D after the discectomy. 
     As shown in  FIG. 3 , the securing members  22  may securely hold the expandable body  18  on the catheters  12 ,  20  when the expandable body is inflated. When formed from resilient material, as shown in  FIG. 3 , the securing members  22  may permit limited stretching, folding, deformation, or other reconfiguration that permit the securing member to adapt to the changing shape of the expandable body. 
     At step  60 , the practitioner may assess whether further discectomy is necessary. Under fluoroscopy, the practitioner may determine whether the sufficient discectomy has been performed by determining whether the expandable body  18 , in the inflated condition, contacts the endplates of the superior and inferior vertebral bodies and whether the expandable body has inflated past the midline of the contralateral portion of the disc. The discectomy and assessment procedures may be repeated until the practitioner is satisfied with the extent of discectomy. 
     At step  62 , after final assessment is performed, the practitioner may compare the initial volume of the inflation media in the material delivery instrument  26  prior to expansion with the final volume of the inflation media in the material delivery instrument after expansion. The difference in volumes can be used to provide a volumetric estimate of the extent of the discectomy procedure which can be used to determine the amount of bone graft or other filling material to be implanted for fusion. 
     It is understood that the device  10  is not limited to use within an intervertebral disc space, but could be used to create, treat, or assess cavities in other regions of a body including regions within vasculature, organs, other soft tissue, or bone, including a vertebral body. 
     While the present invention has been illustrated by the above description of embodiments, and while the embodiments have been described in some detail, it is not the intention of the applicant to restrict or in any way limit the scope of the invention to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant&#39;s general or inventive concept. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.