DEVICES AND METHODS FOR THE PREPARATION OF INTERVERTEBRAL DISCS

Abstract

A power tool for removing an intervertebral disc and preparing vertebral endplates is described. The power tool may include a cutting element, and the height of the cutting element may be adjustable. The cutting element may be a braided cable and may include one or more beads to enhance the effectiveness of the cable. The cutting element may have a minimum height requirement, which may not be satisfied in patients with a collapsed disc due to degenerative disc disorder. For these patients, also described are bone tamps for increasing the intervertebral distance and providing access to tissues distal to the tamp. One type of bone tamp features an inflatable balloon with an inner lumen. Another type of bone tamp includes an expanding distal end and an inner cannula. Also described is a manual expander scraper tool that is compatible with both types of bone tamp.

Claims

1. A device for removing an intervertebral disc comprising: an outer tube having a distal end and a proximal end; an inner tube disposed within the outer tube; an expandable bone tamper attached to the distal end of the outer tube and configured to expand radially relative to a longitudinal axis of the outer tube to increase an intervertebral distance; and a cutter coupled to the inner tube and adapted to be disposed distally of the distal end of the expandable bone tamper to cut into an intervertebral disc.

2. The device of claim 1, wherein: the expandable bone tamper includes an upper longitudinal member and a lower longitudinal member facing the upper longitudinal member; and a distal end of the longitudinal members move away from each other while a proximal end of the longitudinal members remain stationary.

3. The device of claim 2, further comprising an intermediate tube disposed between the outer tube and the inner tube, wherein: the upper and lower longitudinal members are spaced from each other through an axial cut; and an inner diameter of the upper and lower longitudinal members in an unexpanded state is narrower than an outer diameter of the intermediate tube such that the upper and lower longitudinal members expand radially when the intermediate tube is advanced distally into the expandable bone tamper.

4. The device of claim 3, wherein the intermediate tube is configured to be advanced into the distal end by a threaded interface between the intermediate tube and the outer tube.

5. The device of claim 3, wherein the intermediate tube is configured to be advance distally by an auger-like mechanism.

6. The device of claim 3, wherein the inner cannula is configured to be advance into the distal end by a lever.

7. The system of claim 3, wherein the proximal end of the expandable bone tamper includes a plurality of circumferential cuts.

8. The device of claim 1, wherein the expandable bone tamper includes an inflatable balloon.

9. The device of claim 1, wherein: the expandable bone tamper includes an inflatable balloon having a collapsed state and an expanded state; the outer tube is in fluid communication with the balloon.

10. The device of claim 9, further comprising an inflation port in fluid communication with the outer tube, the inflation port configured to transport a fluid to and from the balloon to transition the balloon between the collapsed state and the expanded state.

11. A device for removing an intervertebral disc comprising: an outer tube having a distal end and a proximal end; an inner tube disposed within the outer tube; an expandable bone tamper attached to the distal end of the outer tube and configured to expand radially relative to a longitudinal axis of the outer tube to increase an intervertebral distance; a laterally adjustable cutter coupled to the inner tube and adapted to be disposed distally of the distal end of the expandable bone tamper to cut into an intervertebral disc; and an auger disposed proximally of the cutter for removing cut material.

12. The device of claim 11, wherein the laterally adjustable cutter includes a laterally adjustable U-shaped cutting element, wherein a lateral height of the U-shaped cutting element is adapted to be adjusted by longitudinally moving one end of the U-shaped cutting element relative to the other end.

13. The device of claim 11, wherein: the expandable bone tamper includes an upper longitudinal member and a lower longitudinal member facing the upper longitudinal member; and a distal end of the longitudinal members move away from each other while a proximal end of the longitudinal members remain stationary.

14. The device of claim 13, further comprising an intermediate tube disposed between the outer tube and the inner tube, wherein: the upper and lower longitudinal members are spaced from each other through an axial cut; and an inner diameter of the upper and lower longitudinal members in an unexpanded state is narrower than an outer diameter of the intermediate tube such that the upper and lower longitudinal members expand radially when the intermediate tube is advanced distally into the expandable bone tamper.

15. The device of claim 14, wherein the intermediate tube is configured to be advanced into the distal end by a threaded interface between the intermediate tube and the outer tube.

16. The device of claim 14, wherein the inner cannula is configured to be advance into the distal end by a lever.

17. The system of claim 14, wherein the proximal end of the expandable bone tamper includes a plurality of circumferential cuts.

18. The device of claim 11, wherein the expandable bone tamper includes an inflatable balloon.

19. The device of claim 11, wherein: the expandable bone tamper includes an inflatable balloon having a collapsed state and an expanded state; the outer tube is in fluid communication with the balloon.

20. The device of claim 19, further comprising an inflation port in fluid communication with the outer tube, the inflation port configured to transport a fluid to and from the balloon to transition the balloon between the collapsed state and the expanded state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are included to provide a further understanding of the disclosure, are incorporated in and constitute a part of this specification, illustrate aspects of the disclosure and together with the detailed description serve to explain the principles of the disclosure. No attempt is made to show structural details of the disclosure in more detail than may be necessary for a fundamental understanding of the disclosure and the various ways in which it may be practiced. In the drawings:

[0017] FIG. 1 shows a power tool for use in discectomies, according to an aspect of the disclosure;

[0018] FIG. 2 shows the interior components of the power tool of FIG. 1;

[0019] FIG. 3 shows the distal end of the shaft of the power tool of FIG. 1;

[0020] FIGS. 4A, 4B, and 4C show alternate constructions that may be used to form the cutting element of the power tool of FIG. 1;

[0021] FIG. 5 illustrates a power tool in use on a vertebra and an intervertebral disc;

[0022] FIG. 6 shows the first stage of using an inflatable bone tamp with through lumen in a discectomy;

[0023] FIG. 7 shows the bone tamp of FIG. 6 in an inflated configuration;

[0024] FIG. 8 shows the inflated bone tamp of FIG. 6 holding vertebrae apart while a power tool is used to remove an intervertebral disc;

[0025] FIG. 9 shows a detail view of the distal end of the bone tamp of FIG. 6 and the shaft of the power tool;

[0026] FIG. 10 shows the distal end of an expanding bone tamp, according to an aspect of the disclosure;

[0027] FIG. 11A shows a cross section of the distal end of an expanding bone tamp of FIG. 10 in the collapsed configuration;

[0028] FIG. 11B shows a cross section of the distal end of an expanding bone tamp of FIG. 10 in the expanded configuration;

[0029] FIG. 12A shows the expanding bone tamp of FIG. 10 after it has been inserted between two vertebrae surrounding a collapsed disc;

[0030] FIG. 12B shows a detail cross section view of the bone tamp 400 from FIG. 11A;

[0031] FIG. 13A shows the bone tamp of FIG. 10 in an expanded configuration;

[0032] FIG. 13B shows a detail cross section view of the expanded bone tamp of FIG. 12A;

[0033] FIG. 14A shows the bone tamp of FIG. 10 used in conjunction with a power tool;

[0034] FIG. 14B shows a detail partial cross section view of the bone tamp and power tool of FIG. 13A;

[0035] FIG. 15A shows an expanding scraper that may pass through the lumen of a bone tamp, according to an aspect of the disclosure;

[0036] FIG. 15B shows the expanding scraper of FIG. 14A with the tip extended;

[0037] FIG. 16 shows a cutaway view of the expanding scraper of FIG. 14A with the tip in a partially retracted position; and

[0038] FIG. 17 shows a cutaway view of the expanding scraper of FIG. 14A with the tip in an extended position.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0039] The aspects of the disclosure and the various features and advantageous details thereof are explained more fully with reference to the non-limiting aspects and examples that are described and/or illustrated in the accompanying drawings and detailed in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale, and features of one embodiment may be employed with other aspects as the skilled artisan would recognize, even if not explicitly stated herein. Descriptions of well-known components and processing techniques may be omitted so as to not unnecessarily obscure the aspects of the disclosure. The examples used herein are intended merely to facilitate an understanding of ways in which the disclosure may be practiced and to further enable those of skill in the art to practice the aspects of the disclosure. Accordingly, the examples and aspects herein should not be construed as limiting the scope of the disclosure, which is defined solely by the appended claims and applicable law. Moreover, it is noted that like reference numerals represent similar parts throughout the several views of the drawings.

[0040] An intervertebral disc is located between each pair of vertebrae in the spine, except between the first and second cervical vertebrae. The discs act as joints, allowing some degree of rotation between adjacent vertebrae. The discs also function as shock absorbers, cushioning the spine against jostling and impacts.

[0041] Each disc is made of two main components. An outer layer of fibrocartilage, called the annulus fibrosus, that surrounds the inner matrix, the nucleus pulposus. The fibers of the annulus fibrosus contain the nucleus pulposus and distribute pressure across the disc. The nucleus pulposus has a jelly-like consistency and acts as the main shock absorber in the disc.

[0042] As people age, the nucleus pulposus gradually dehydrates, degrading its ability to absorb shock and stresses to the spine. These stresses are instead transferred to the annulus fibrosus, which can cause structural degradation. Dehydration of the nucleus pulposus and damage to the annulus fibrosus can cause pain, which can be severe and debilitating in some patients. This condition is known as degenerative disc disorder (DDD).

[0043] The annulus fibrosus can be torn due to injury or trauma, and it is more likely to be torn as a result of changes due to the natural aging process. When the annulus is torn, the nucleus pulposus may extrude through the tear. This condition is commonly referred to as a herniated disc, although it may also be known as a prolapsed disc, ruptured disc, or slipped disc. The herniated disc can press against nerves, causing severe pain, numbness, tingling, and decreased strength or range of motion. A herniated disc can also cause pain when the nucleus pulposus, which contains inflammatory chemicals, directly contacts nerves.

[0044] Both degenerative disc disease and herniated discs may be treated with a discectomy, the removal of the affected disc. A discectomy may be performed either as a stand-alone procedure or in conjunction with a spinal fusion. Discectomies and spinal fusions may also be used to treat other conditions, including back pain, spinal tumors, and vertebral fractures.

[0045] Traditionally, discectomies are performed as open surgical procedures. Muscles and ligaments surrounding the spine are carefully cut and peeled away until the surgeon can access the vertebrae directly. The damaged or diseased disc is removed with specialized hand tools. This procedure is lengthy, and the damage to the surrounding tissues is magnified by the time spent on the operating table.

[0046] More recently, minimally invasive surgery (MIS) techniques have been developed to permit surgery without as much disruption to the surrounding and supporting tissues. However, these procedures are still typically performed with hand tools. The injury to the patient could be further reduced by performing the procedure more quickly. Power tools have been developed to quickly remove the disc material. However, existing power tools suffer from one or more defects or shortcomings, including an insufficient cutting height, insufficient removal of disc material, and clogging.

[0047] According to one aspect of the disclosure, a rotary power tool 100 may incorporate a variable height cutting element 111. The power tool 100 may be capable of rapidly removing disc material, especially the nucleus pulposus, and preparing vertebral endplates for a spinal fusion procedure. The variable height of the cutting element 111 can accommodate varying geometries and distances between vertebrae, which may result in cleaner and more thorough removal and preparation. In addition, the variable height cutting element 111 may pass through the inner lumen of an inflatable bone tamp, such as the one described below.

[0048] FIG. 1 shows a power tool 100 for use in discectomies, according to an aspect of the disclosure. The power tool 100 may include a shaft 110, a handle 120, and a body 130. A cutting element 111 may be located at the distal end of the shaft 110.

[0049] FIG. 2 shows the interior components of the power tool 100. One or more batteries 121 may be located in the power tool, for example handle 120. The batteries may be of any type and/or number sufficient to provide required power to the components of the power tool 100, as will be understood by one having ordinary skill in the art. A switch 122 may be located in the handle and may control operation of the power tool 100.

[0050] The body 130 may include a control for controlling the height of cutting element 111. As shown in FIG. 2, the control may be a trigger-type apparatus 133, although the control may be implemented with different configurations without departing from the spirit and scope of the disclosure and/or claims, as will be understood by one having ordinary skill in the art. During operation, a user of the power tool 100 may squeeze the trigger 133, causing it to rotate about pivot 136. The rotation of the trigger 133 may push plunger 134 in the direction of the shaft 110. Plunger 134 may be connected to one or more components of the shaft, including the inner core 115 (see FIG. 3). As plunger 134 moves with respect to shaft 110, it may lengthen the inner core 115 in comparison to the overall length of the shaft 110. This relative increase in length may in turn increase the height of the cutting element 111, as described in detail below with respect to FIG. 3. In certain aspects of the disclosure, the cutting element 111 may be adjustable in height between 0 mm and 20 mm. In further aspects of the disclosure, the cutting element 111 may be adjustable in height between 4 mm and 16 mm.

[0051] A motor 131 may be located in the body 130 just above the handle 120, and the motor may function to rotate one or more components of the shaft 110, as described in detail below with respect to FIG. 3. A spring 135 may press plunger 134 thereby acting to decrease the height of cutting element 111 in the absence of pressure on the trigger 133. Connector 132 may connect plunger 134 to the motor 131. In addition, connector 132 may allow the distance between the plunger 134 and the motor 131 to vary, such as when the trigger is squeezed, without disengaging plunger 134 from motor 131.

[0052] FIG. 3 shows the distal end of shaft 110. The shaft 110 may include an outer sheath 112. The outer sheath 112 may be connected to body 130 and may not rotate. In contrast, inner core 115 may be connected to plunger 134 and may be rotated by motor 131. Inner core 115 may include a cutting element 111. When the trigger is squeezed and the inner core 115 increases in length relative to shaft 110, the extra length is taken up by the cutting element 111, which increases in height. As shown in FIG. 3, the cutting element may be a braided cable, and the braided cable may be fitted with one or more beads 118 to enhance the effectiveness of the cutting element 111.

[0053] Shaft 110 may also include an outer core 113. The outer core 113 may provide an auger 115 to aid in the removal of tissue and bone material that has been cut by the cutting element 111. Outer core 113 may rotate by a mechanical linkage to the inner core 115 or other arrangement as will be understood by one having ordinary skill in the art. Cutting element 111 may be attached to a ring 116, which may provide some stability to the cutting element. Shaft 110 may also have a smooth, rounded distal end 117.

[0054] FIGS. 4A, 4B, and 4C show alternate materials and constructions that may be used to form the cutting element 111 in place of the braided cable discussed above. FIG. 4A shows a linked chain 160 that may be arranged in a manner similar to cutting element 111. The linked chain 160 may be arranged in outer core 113. FIG. 4B shows a dual blade having blades 142, 144 that are held by a cap 148 and ring 146, movement of the ring 146 relative to the cap 148 extends blades 142, 148, movement may be caused by a connection of the cap 148/ring 146 to the push plunger 134 to move each relative to one another. FIG. 4C shows a flexible member 152 that moves out of a window 154 through actuation of push plunger 134 to change the relative position of the flexible member 152 to outer core 163. Additional implementations of the cutting element 111 are contemplated and are within the spirit and scope of the disclosure and claims. The cutting element, in any implementation or embodiment, may be made from any appropriate material, including, e.g., metal, superelastic metal, and polymer.

[0055] FIG. 5 illustrates the power tool 100 in use on a vertebra 200 and an intervertebral disc 201. The disc 201 is divided into two zones: zone 201b may be reachable with the shaft 110 in a straight configuration. Zone 201a may be unreachable with a straight tool. In some aspects of the disclosure, the inner core and outer core may be made of flexible materials to permit axial articulation, as well as axial rotation. This type of articulating instrument may be able to remove material from zone 201a.

[0056] Performing a discectomy is difficult when a disc has collapsed or compressed due to degenerative disc disease. Collapsed discs present an additional obstacle for power tools, such as power tool 100, because the tool may require a minimum height for its cutting element to operate properly. Traditionally, collapsed discs can be ameliorated somewhat during surgery by the use of inflatable or expanding bone tamps, which are inserted between the vertebrae and then push them apart. These bone tamps, however, may block a power tool from reaching much of the disc, thus negating the advantages of power tools.

[0057] One solution is to use a bone tamp that provides a passage for the power tool through the tamp's expansion apparatus. An example of such a tamp may be seen in FIGS. 6-9, which illustrate an exemplary inflatable bone tamp with a through lumen, according to aspects of the disclosure.

[0058] FIG. 6 shows the first stage of using an inflatable bone tamp with through lumen in a discectomy. The bone tamp 300 may be inserted between two vertebrae 200 where the intervertebral disc 201 has collapsed. While the bone tamp 300 is shown inserted between the vertebral bodies, the tamp 300 may also or alternatively be inserted between the processes, pedicles, or laminae of the vertebrae. The tamp 300 may include a balloon 304, which is deflated at this stage, and a lumen 303 that passes through the balloon 304. The lumen 303 may be straight and connected to a lumen port 301 at the proximal end of the bone tamp 300 and to a distal port 305 at the distal end of the tamp 300. The bone tamp 300 may also include an inflation port 302 for providing a gas or liquid under pressure to the balloon 304.

[0059] FIG. 7 shows the bone tamp 300 in an inflated configuration. As the balloon 304 is inflated, it pushes the vertebrae 200 apart, as indicated by the arrows. Any appropriate gas or liquid may be used to inflate the balloon 304, including, e.g., saline, air, and nitrogen.

[0060] FIG. 8 shows the inflated bone tamp 300 holding vertebrae 200 apart while power tool 100 is used to remove the intervertebral disc 201. The shaft 110 of power tool 100 may be inserted into the lumen port 301 of the bone tamp 300. The lumen 303 passes through the balloon 304 and connects to distal port 305. The inflated balloon 304 provides at least the minimum clearance between vertebrae 200 for power tool 100 to be used. In particular, the balloon 304 provides sufficient space between the vertebrae for cutting element 111 to rotate and remove soft tissue. The cutting element 111 may optionally include one or more beads 118 to assist in the removal of soft tissue. A surgeon or operator may monitor the removal of tissue and the overall discectomy using arthroscopic or endoscopic techniques or any other appropriate means, as will be understood by one skilled in the art of minimally invasive surgery.

[0061] FIG. 9 shows a detail view of the distal end of the bone tamp 300 and the shaft 110 of the power tool 100. Lumen 303 passes through the middle of balloon 304 without affecting the seal or integrity of the balloon. Thus, the balloon 304 will remain inflated even when an instrument is passed through the lumen, and the instrument or tool is able to access tissues and areas that are distal to the balloon 304 and bone tamp 300. The tool illustrated in FIG. 9 may be power tool 100, although many other types of tools may be passed through the lumen. Once the shaft 110 of the tool exits the distal port 305, it is able to turn or rotate freely, and cutting element 111 may begin, for example, to remove the soft tissue of the intervertebral disc. The balloon 304 may provide the minimal height for the cutting element 111 to operate. If the vertebrae 200 are further apart, the surgeon or operator may adjust the height of the cutting element 111, as described above with respect to the power tool 100.

[0062] FIG. 10 shows the distal end of an expanding bone tamp, according to an aspect of the disclosure. As an alternative to the inflatable bone tamp, a surgeon may wish to use an expanding bone tamp 400 instead. Expansion of the bone tamp 400 is made possible by the design of its distal end, an example of which is shown in FIG. 10. The distal end may include a pair of axial cuts 401 on opposite sides of the outer tube 408. The proximal end of the axial cuts may be formed into an enlarged opening 402. The distal end may also include one or more circumferential cuts 403, as well as a distal opening 404.

[0063] FIG. 11A shows the interior of the distal end of the bone tamp 400, including an inner cannula 405 and a threaded interface between the cannula 405 and the outer tube 408. The threaded interface may include female threads 410 on the interior of the outer tube 408 and male threads 409 on the exterior of the cannula 405. The threads 410 and 409 may be structured and arranged such that rotating cannula 405 relative to outer tube 408 may draw the cannula along the outer tube 408. Rotation in one direction may bring the distal port 406 of the cannula 405 closer to the distal opening 404 of the outer tube 408, while rotation in the opposite direction may increase the distance between the distal port 406 and the distal opening 404. As outer tube 408 may have a narrowed inner diameter in its distal end, bringing the distal ends of the tube 408 and the cannula 405 closer together may result in expansion of the distal end of the outer tube 408, as described below with respect to FIGS. 12A-14B.

[0064] FIG. 12A shows the expanding bone tamp 400 after it has been inserted between two vertebrae 200 surrounding a collapsed disc 201, and FIG. 12B shows a detail view of the bone tamp 400 from FIG. 12A. While the bone tamp 400 is shown inserted between the vertebral bodies, the tamp may also or alternatively be inserted between the processes, pedicles, or laminae of the vertebrae. The bone tamp 400 may include an outer tube 408 and an inner cannula 405. Internally, the distal end of the outer tube 408 may include a narrowed inner diameter 407. The inner cannula 405 may be disposed within the outer tube 408, and the width of the cannula 405 may be wider than the narrowed inner diameter 407 of the outer tube 408. The cannula 405 may include a distal port 406.

[0065] FIG. 13A shows the bone tamp 400 in an expanded configuration, and FIG. 13B shows a detail view of the expanded bone tamp 400 of FIG. 13A. The outer tube 408 may be expanded by advancing the inner cannula 405 toward the distal opening 404. Since the cannula 405 is wider than the narrowed inner diameter 407 of the distal end, the advancement of the cannula 405 forces the distal end to expand along axial cuts 401. Circumferential cuts 403 and opening 402 may aid the expansion by creating a hinge-like section of the outer tube 408. In particular, cuts 403 may collapse or be compressed to accept the dimensional changes that accompany expansion of the outer tube 408, as shown in FIG. 13B. Cannula 405 may be advanced through the bone tamp 400 by means of threads, a screw-like mechanism, an auger-like mechanism, a lever, or any other appropriate means, as will be understood by one skilled in the art of medical devices.

[0066] FIG. 14A shows a bone tamp 400 used in conjunction with a power tool 100, and FIG. 14B shows a detail view of the bone tamp 400 and power tool shaft 110 of FIG. 14A. Cannula 405 provides a clear passage for a straight instrument to be inserted between the vertebrae 200 following expansion by the outer tube 408. One example of such an instrument is the shaft 110 of power tool 100. FIG. 14A shows a shaft 110 inserted through the cannula 405, exiting at the cannula's distal port 406 and operating on the intervertebral disc 201. The bone tamp 400 may provide a minimal operating height, or more, between the vertebrae 200 for the cutting element 111 to operate. If the distance is greater than the minimum needed by the cutting element, the cutting height of the cutting element 111 may be adjusted by the surgeon or user, as described above with respect to power tool 100. A surgeon or operator may monitor the removal of tissue and the overall discectomy using arthroscopic or endoscopic techniques or any other appropriate means, as will be understood by one skilled in the art of minimally invasive surgery.

[0067] While automated tools, such as the power tool 100 described above, are superior to manual tools in many situations, there are nonetheless circumstances that call for the use of manual tools. For example, a manual tool may be necessary for creating an initial cavity for a bone tamp or power tool. Many manual tools, however, do not have a shape that is compatible with either the inflatable bone tamp or expanding bone tamp described above. These tools may have shapes with protrusions or other features that would prevent the tool from passing through the inner lumen of the bone tamps. One solution to this problem is to provide an expanding manual tool that can change its shape once it passes through the lumen to the site of surgery.

[0068] FIG. 15A shows an expanding scraper 500 that may pass through the lumen of a bone tamp, according to an aspect of the disclosure. The scraper may include a T-handle 501, a rotating control knob 502, a shaft 503, and a tip 504. Twisting the knob 502 may cause extension or retraction of curved tip 504 through a threaded mechanical connection between knob 502 and shaft 503. FIG. 15B shows the expanding scraper 500 with the tip 504 extended.

[0069] FIG. 16 shows a cutaway view of the expanding scraper 500 with the tip 504 in a retracted position, and FIG. 17 shows a cutaway view of the expanding scraper with the tip 504 in an extended position. Inner core 505 may be fixed to the handle 501. Outer shaft 503 may surround the inner core 505 and may provide a window 507 for the extension of the tip 504. Twisting the control knob 502 may draw the outer shaft 503 along the inner core 505. Twisting knob 502 in one direction may cause the shaft 503 to retract and expose the tip 504, while twisting knob 502 in the opposite direction may cause shaft 503 to extend and withdraw the tip 504. The outer shaft 503 may be keyed to the handle 501 so that when the handle 501 is rotated, the shaft 503 does not rotate relative to the inner core 505. The mechanical connection between shaft 503 and knob 502 may take the form of threads or the like.

[0070] The inner core 505 may be made of a superelastic metal, such as, e.g., nitinol. The tip 504 may include a sharp point 506, as well as sharp edges, to facilitate cutting through both soft tissue, such as the intervertebral disc, and cancellous bone. The distal end of the outer shaft 503 may be a domed closure 508.

[0071] While the disclosure has been described in terms of exemplary aspects, those skilled in the art will recognize that the disclosure can be practiced with modifications in the spirit and scope of the appended claims. These examples given above are merely illustrative and are not meant to be an exhaustive list of all possible designs, aspects, applications or modifications of the disclosure.