Background

This invention relates generally to the treatment of spinal conditions, and more particularly, to the treatment of spinal stenosis using devices for implantation between adjacent spinous processes.

The clinical syndrome of neurogenic intermittent claudication due to lumbar spinal stenosis is a frequent source of pain in the lower back and extremities, leading to impaired walking, and causing other forms of disability in the elderly. Although the incidence and prevalence of symptomatic lumbar spinal stenosis have not been established, this condition is the most frequent indication of spinal surgery in patients older than 65 years of age.

Lumbar spinal stenosis is a condition of the spine characterized by a narrowing of the lumbar spinal canal. With spinal stenosis, the spinal canal narrows and pinches the spinal cord and nerves, causing pain in the back and legs. It is estimated that approximately 5 in 10,000 people develop lumbar spinal stenosis each year. For patients who seek the aid of a physician for back pain, approximately 12% - 15% are diagnosed as having lumbar spinal stenosis.

Common treatments for lumbar spinal stenosis include physical therapy (including changes in posture), medication, and occasionally surgery. Changes in posture and physical therapy may be effective in flexing the spine to decompress and enlarge the space available to the spinal cord and nerves - thus relieving pressure on pinched nerves.

Medications such as NSAIDS and other anti-inflammatory medications are often used to alleviate pain, although they are not typically effective at addressing spinal compression, which is the cause of the pain.

Surgical treatments are more aggressive than medication or physical therapy, and in appropriate cases surgery may be the best way to achieve lessening of the symptoms of lumbar spinal stenosis. The principal goal of surgery is to decompress the central spinal canal and the neural foramina, creating more space and eliminating pressure on the spinal nerve roots. The most common surgery for treatment of lumbar spinal stenosis is direct decompression via a laminectomy and partial facetectomy. In this procedure, the patient is given a general anesthesia as an incision is made in the patient to access the spine. The lamina of one or more vertebrae is removed to create more space for the nerves. The intervertebral disc may also be removed, and the adjacent vertebrae may be fused to strengthen the unstable segments. The success rate of decompressive laminectomy has been reported to be in excess of 65%. A significant reduction of the symptoms of lumbar spinal stenosis is also achieved in many of these cases.

More recently, a different surgical technique has been developed in which the vertebrae are distracted and an interspinous process spacer is implanted between adjacent spinous processes to maintain the desired separation between the segments. Currently, patient selection is based on history, physical examination, and imaging. These diagnostic modalities might be sensitive and specific to lumbar spinal stenosis, but they are limited in their ability to identify the proper interspinous process spacer candidate. Properly selecting the patients to receive an interspinous process spacer is important in assuring positive outcomes following implantation of the spacer.

It would thus be advantageous for a diagnostic device and procedure to be used to determine (i) whether an interspinous process spacer would provide relief for the patient, and (ii) the size of such a spacer that would be necessary to provide such relief. Such a diagnostic procedure could be performed in a doctor's office or other outpatient setting in addition to a standard hospital setting.

Summary

The interspinous process spacer diagnostic balloon catheter (the "balloon catheter") described herein may be disposable. It may be inserted percutaneously into the interspinous space to temporarily decompress the identified spinal motion segment and allow a physician to determine whether the patient is an appropriate candidate for implantation of an interspinous process spacer. A method of diagnosing patients to determine if they are appropriate candidates for implantation of an interspinous process spacer is also disclosed herein. The interspinous process spacer diagnostic balloon catheter has a main expandable member having a first collapsed configuration that allows percutaneous delivery of the distal portion of the balloon catheter to the appropriate site in the patient. The main expandable member can be expanded to different diameters, which is controlled by the physician, to provide the physician with control over the amount of decompression or distraction provided to the particular patient being diagnosed. In addition, two additional expandable members are located adjacent to the main expandable member, with one of the additional expandable members located on the proximal side of the main expandable member and the second additional expandable member located on the distal side of the main expandable member. The two additional expandable members, when expanded, hold the main expandable member in the proper location between adjacent spinous processes. The main expandable member may be formed from a relatively non-compliant material while the additional expandable members may be formed from a relatively compliant material.

A method of using the balloon catheter described herein is also provided. Once the main expandable member is properly located within the patient, the additional expandable members are expanded first to lock the main expandable member in place between adjacent spinous processes. Thereafter, the main expandable member is expanded to an initial size. At that point, the balloon catheter can be manipulated to allow the patient to become ambulatory to determine if the symptoms of lumbar spinal stenosis have been alleviated. If not, the main expandable member can be expanded to a second size, the device manipulated, and the patient becomes ambulatory to determine the effect of the device on the patient. This process would continue until the symptoms have been allieviated or until the main expandable member reaches some upper limit on its size. Thereafter, all of the expandable members can be deflated to their initial collapsed configuration and the balloon catheter removed from the patient. If the patient realizes relief from the symptoms of lumbar spinal stenosis during the diagnostic procedure, the physician can schedule a follow up surgical procedure to implant an appropriately sized interspinous process spacer as determined during the diagnostic procedure. If the patient does not obtain relief, the physician may determine that the patient may not be a candidate for implantation of an interspinous process spacer and evaluate other options for the patient.

Brief Description of the Drawings

FIG. 1 is a perspective view of an interspinous process spacer diagnostic balloon catheter in the fully expanded configuration;

FIG. 2 A is a cross-sectional view taken along line 2 - 2 of the interspinous process spacer diagnostic balloon catheter shown in FIG. 1 illustrating one configuration for the catheter lumens;

FIG. 2B is a cross-sectional view taken along line 2 - 2 of the interspinous process spacer diagnostic balloon catheter shown in FIG. 1 illustrating a second configuration for the catheter lumens;

FIG. 2C is a cross-sectional view taken along line 2 - 2 of the interspinous process spacer diagnostic balloon catheter shown in FIG. 1 illustrating a third configuration for the catheter lumens;

FIG. 2D is a cross-sectional view taken along line 2 - 2 of the interspinous process spacer diagnostic balloon catheter shown in FIG. 1 illustrating a fourth configuration for the catheter lumens;

FIG. 3 is a cross-sectional view taken along line 3 - 3 of the interspinous process spacer diagnostic balloon catheter shown in FIG. 1 with the expandable members in the collapsed configuration and providing a schematic view of a portion of a spine where the interspinous process spacer diagnostic balloon catheter would be placed;

FIG. 4 is an enlarged cross-sectional view of the distal portion of the interspinous process spacer diagnostic balloon catheter shown in FIG. 3;

FIG. 5 is a cross-sectional view similar to FIG. 3 but with the proximal and distal expandable members in an expanded configuration;

FIG. 6 is an enlarged cross-sectional view of the distal portion of the interspinous process spacer diagnostic balloon catheter shown in FIG. 5;

FIG. 7 is a cross-sectional view similar to FIG. 5 but with the main, central expandable member in the expanded configuration as well; FIG. 8 is a cross-sectional view of the distal portion of the interspinous process spacer diagnostic balloon catheter shown in FIG. 7; and

FIG. 9 is a flowchart describing a diagnostic method using an interspinous process spacer diagnostic balloon catheter.

Detailed Description

As used in this specification and the appended claims, 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, and "a material" is intended to mean one or more materials, or a combination thereof. Furthermore, the words "proximal" and "distal" refer to directions closer to and away from, respectively, an operator (e.g., surgeon, physician, nurse, technician, etc.) who would insert the medical device into the patient, with the tip-end (i.e., distal end) of the device inserted inside a patient's body first. Thus, for example, the device end first inserted inside the patient's body would be the distal end of the device, while the device end last to enter the patient's body would be the proximal end of the device.

As used in this specification and the appended claims, the term "body" when used in connection with the location where the device is to be placed to treat lumbar spinal stenosis, or to teach or practice implantation methods for the device, means a mammalian body. For example, a body can be a patient's body, or a cadaver, or a portion of a patient's body or a portion of a cadaver.

As used in this specification and the appended claims, the term "parallel" describes a relationship, given normal manufacturing or measurement or similar tolerances, between two geometric constructions (e.g., two lines, two planes, a line and a plane, two curved surfaces, a line and a curved surface or the like) in which the two geometric constructions are substantially non-intersecting as they extend substantially to infinity. For example, as used herein, a line is said to be parallel to a curved surface when the line and the curved surface do not intersect as they extend to infinity. Similarly, when a planar surface (i.e., a two-dimensional surface) is said to be parallel to a line, every point along the line is spaced apart from the nearest portion of the surface by a substantially equal distance. Two geometric constructions are described herein as being "parallel" or "substantially parallel" to each other when they are nominally parallel to each other, such as for example, when they are parallel to each other within a tolerance. Such tolerances can include, for example, manufacturing tolerances, measurement tolerances or the like.

As used in this specification and the appended claims, the terms "normal",

perpendicular" and "orthogonal" describe a relationship between two geometric constructions (e.g., two lines, two planes, a line and a plane, two curved surfaces, a line and a curved surface or the like) in which the two geometric constructions intersect at an angle of approximately 90 degrees within at least one plane. For example, as used herein, a line is said to be normal, perpendicular or orthoganal to a curved surface when the line and the curved surface intersect at an angle of approximately 90 degrees within a plane. Two geometric constructions are described herein as being "normal", "perpendicular", "orthogonal" or "substantially normal", "substantially perpendicular", "substantially orthogonal" to each other when they are nominally 90 degrees to each other, such as for example, when they are 90 degrees to each other within a tolerance. Such tolerances can include, for example, manufacturing tolerances, measurement tolerances or the like.

One embodiment of the interspinous process spacer diagnostic balloon catheter 100 is shown in the figures. Balloon catheter 100 is configured for unilateral insertion into the patient without requiring distraction of tissue on the contralateral side.

Balloon catheter 100 includes a main expandable member ("main balloon") 20, a distal expandable member ("distal balloon") 25a, and a proximal expandable member

("proximal balloon") 25b. All of these expandable members may be balloons formed from a relatively low compliant plastic such as nylon, polyethylene (PE) or polyethylene terephthalate (PET). Compliance is quantified based on the amount of change from the initially formed dimensions. Lower compliant materials are capable of stretching between about 5% to about 50% before failure, while a more compliant material such as polyurethane is capable of a change of about 300%. Generally, the lower the compliance of the balloon the higher its pressure capacity. Nylon and PET balloons are capable of withstanding a maximum pressure of about 300 psi. In contrast, a more compliant polyurethane balloon is capable of withstanding a maximum pressure of only about 125 psi. Main balloon 20 may be formed from a lower compliant material so that its inflation pattern is well controlled and understood. The inflation pattern, e.g. balloon diameter at specific volumes, will be used to determine the height of the interspinous space and thus the size of any permanent interspinous process spacer that is to be implanted into the patient to treat the condition. Also, the higher pressure capability of the lower compliant material may be instrumental in separating the spinous processes and maintaining the interspinous space. In contrast, distal balloon 25a and proximal balloon 25b may be formed from a more compliant material such as polyurethane, silicone or a thermoplastic rubber elastomer sold under the ChronoPrene™ trademark. Distal balloon 25a and proximal balloon 25b should be capable of expanding to a significantly larger diameter as compared to main balloon 20. A compliant material helps to minimize the profile of the distal portion of balloon catheter 100 and reduce the size of the incision necessary to access the particular location in the patient's anatomy. However, it is also within the scope of this invention to form distal balloon 25 a and proximal balloon 25b from a less compliant material similar to the material used to form main balloon 20. This would facilitate catheter assembly, but the resulting device would require a larger access channel. Main balloon 20, distal balloon 25a and proximal balloon 25b are configured so they can move from a collapsed or closed configuration as illustrated in FIG. 3 to an expanded or deployed configuration as illustrated in FIGS. 1 and 8.

Main balloon 20, distal balloon 25a and proximal balloon 25b are affixed to a catheter 30 in a standard manner. For example, adhesives, thermal bonding, laser bonding or adhesive-lined heat shrinking may be used. In order to facilitate bonding of main balloon 20 to catheter tube 30, main balloon 20 may be formed from a three layer balloon tube where the middle layer is a less compliant material and the top and bottom layers are a more compliant material similar to the material used to form distal balloon 25 a and proximal balloon 25b.

Distal balloon 25 a and proximal balloon 25b may be inflated independently of main balloon 20. This would allow distal balloon 25 a and proximal balloon 25b to be inflated first to lock balloon catheter 100 in place with main balloon 20 located between the desired adjacent spinous processes. Main balloon 20 could then be inflated separately and independently. Independent control of main balloon 20 may be necessary to correctly size the interspinous space. Alternatively, distal balloon 25a, main balloon 20 and proximal balloon 25b may be combined as a single balloon. Such a unitary configuration would mean that the single balloon would have a dumbbell shape with larger diameter distal and proximal portions and a smaller diameter central portion that all would be inflated simultaneously.

Catheter tube 30 includes various lumens extending therethrough and that are used to expand the various balloons of balloon catheter 100. For example, as shown in FIG. 2A, a first lumen 31 is in fluid communication with both distal balloon 25 a and proximal balloon 25b, while second lumen 32 is in fluid communication with main balloon 20. By having first lumen 31 in fluid communication with both distal balloon 25a and proximal balloon 25b, both balloons can be inflated simultaneously. Second lumen 32 is separate to allow main balloon 20 to be inflated separately once the physician locks the distal portion of balloon catheter 100 in place. In addition, a guide wire lumen 37 extends through catheter tube 30 to allow balloon catheter 100 to be inserted percutaneously over a guide wire. As shown in FIG. 2A, first lumen 31 extends around a portion of the axis of catheter tube 30, second lumen 32 extends around a separate portion of the axis of catheter tube 30 and guide wire lumen 37 is disposed coaxially between first lumen 31 and second lumen 32. If desired, distal balloon 25 a and proximal balloon 25b could be in fluid communication with separate lumens. This will allow greater flexibility to the physician to initially position and adjust the specific location of the distal portion of balloon catheter 100 in the patient. For example, as shown in FIG. 2D, first lumen 31 could be split into two separate lumens 31a and 31b where lumen 31a could be in fluid communication with proximal balloon 25b and lumen 31b could be in fluid communication with distal balloon 25 a or vice versa. These separate lumens would allow proximal balloon 25b to be inflated first, and deflated if necessary to reposition the distal portion of balloon catheter 100. Thereafter, distal balloon 25b could be inflated. Alternatively, distal balloon 25 a could be inflated, and deflated if necessary, before proximal balloon 25b is inflated. Alternatively, the lumens may be oriented so they are all coaxial. See FIG. 2B. In this embodiment, first lumen 31 ' could be coaxially disposed within catheter tube 30, with second lumen 32' coaxially disposed between first lumen and guidewire lumen 37. In another embodiment, see FIG. 2C, a single lumen 35 may be in fluid communication with main balloon 20, distal balloon 25 a and proximal balloon 25b. Single lumen 35 may be coaxially disposed about guidewire lumen 37. Alternatively a lumen configuration as should in FIG. 2 A could be used without the need for second lumen 32.

The proximal end of catheter tube 30 is connected to a hub 40 having at least one port therein. The number of ports used depends on the lumen configuration desired for balloon catheter 100. Where a single lumen is used to inflate all three balloons, a single port is needed, in addition to any access device desired for the guidewire, if used. If two lumens are used, two ports are used. And where three lumens are used to inflate the three balloons, three ports are used. As an illustration, where the lumen configuration of FIG. 2A is used, a first port 41, a second port 42 and a guidewire port 47 are located on hub 40. First port 41 and second port 42 may each include a luer lock on its proximal end to allow an inflation device, such as a syringe to be locked on to each port. Guidewire port 47 allows a guide wire to extend completely through catheter tube 30 to facilitate proper placement of balloon catheter 100 between adjacent spinous processes as described more fully hereinafter. First port 41 and second port 42 each include seals, not shown, that allow independent control of the relevant balloons.

In the collapsed configuration, main balloon 20, distal balloon 25a and proximal balloon 25b each has a reduced profile that facilitates insertion of the distal end of balloon catheter 100 into the patient into the targeted interspinous space. If desired, a guidewire 50, may be first inserted into the patient so that it extends between the adjacent spinous processes under investigation. Balloon catheter 100 may then be inserted into the patient over the guidewire, with the guidewire extending through guidewire lumen 37, such that distal balloon 25a extends past the adjacent spinous processes of interest and is distal of the distal lateral faces of the superior spinous process and inferior spinous process. In this position, main balloon 20 is located between the adjacent spinous processes and proximal balloon 25b is located proximal of the other lateral faces of the superior spinous process and the inferior spinous process. At this point, distal balloon 25a and proximal balloon 25b may be expanded or "inflated" by injecting biocompatible fluid, such as saline, through first lumen 31 where the lumen configuration of FIG. 2A is used. Alternatively, where distal balloon 25 a and proximal balloon 25b are to be inflated separately, such as by using the lumen configuration as shown in FIG. 2D, either distal balloon 25a or proximal balloon 25b may be inflated first to temporarily hold the distal portion of balloon catheter 100 in place while the physician confirms that the distal portion is properly located. If not, the initially inflated balloon may be deflated to allow the physician to properly relocate the distal portion of balloon catheter 100. This process may be repeated until the physician is satisfied with the placement of balloon catheter 100. Once fully inflated, distal balloon 25 a and proximal balloon 25b will have a height that is greater than the space between the adjacent spinous processes, and greater than the height of main balloon 20 when it is fully inflated. Since distal balloon 25 a and proximal balloon 25b are relatively compliant, they can conform better to the surrounding anatomy to hold balloon catheter 100 in place.

Thus, with distal balloon 25a and proximal balloon 25b fully inflated, balloon catheter 100 is held in place in the patient's anatomy such that main balloon 20 is located between the adjacent spinous processes.

With main balloon 20 properly positioned, the physician can then inflate main balloon 20 by injecting a biocompatible fluid, such as saline, through second lumen 32 when the lumen configuration of FIG. 2A is used. Main balloon 20 has a predetermined geometry at fixed volumes. Thus, during inflation of main balloon 20, the physician will note the volume of fluid that is injected into main balloon 20. At a first volume corresponding to a particular diameter for main balloon 20, the physician will allow the patient to become ambulatory and seek feedback from the patient to determine if the amount of distraction represented by the first volume of fluid injected into main balloon 20 provides pain relief for the patient. If there is no pain relief, the physician can inject an additional volume of fluid into main balloon 20 representing a larger diameter for main balloon 20. The physician again allows the patient to become ambulatory and seeks feedback from the patient regarding any pain relief. This process continues until the patient experiences pain relief of the maximum rated volume of fluid has been injected into main balloon 20. If the patient experiences pain relief, the injected volume of fluid can be matched to the geometry of a permanent interspinous process spacer that would be permanently implanted in the patient. If the patient does not experience pain relief the physician may determine that the patient is not a candidate for the implantation of an interspinous process device.

The geometry of main balloon 20 includes a diameter that represents the distance between the adjacent spinous processes. The geometry also includes a width for main balloon 20 that should be approximately the width of a typical spinous process, or slightly larger. This ensures that main balloon 20 is provided with enough surface area to engage the adjacent spinous processes and also prevents force from concentrating along a smaller portion of the adjacent spinous processes. In such a situation, it is possible for

osteoporotic bone, or bone that has been weakened, such as by disease or trauma, to fracture. The performance characteristics of main balloon 20, distal balloon 25a and proximal balloon 25b should be balanced against the desire to have a small profile for balloon catheter 100 when main balloon 20, distal balloon 25a and proximal balloon 25b are folded to facilitate the insertion of balloon catheter 100 to the proper location in the patient's anatomy.

FIG. 9 is a flow chart illustrating a method of using an interspinous process spacer diagnostic balloon catheter to determine whether a particular patient is a candidate for implantation of an interspinous process spacer to alleviate the symptoms of lumbar spinal stenosis. The interspinous process space under investigation is first accessed with a guidewire or a trocar such that the distal end of the guidewire or trocar is adjacent to the desired location. Balloon catheter 100 is then inserted percutaneously over the guidewire or through the trocar to position main balloon 20 in the interspinous space. If desired, the guidewire or trocar can be removed from the patient. Distal balloon 25 a and proximal balloon 25b are ultimately expanded to hold the distal portion of balloon catheter 100 in place. Main balloon 20 is then expanded to a first expanded diameter. The patient then walks to determine if main balloon 20 has any affect on the lumbar spinal stenosis symptoms. If the pain has been alleviated, the physician notes the volume of fluid used to expand main balloon 20 and thus can determine the diameter of main balloon with that volume of fluid injected into main balloon 20. Fluid is then withdrawn from main balloon 20 so it collapses and balloon catheter 100 can then be removed from the patient. The physician uses the information from this diagnostic procedure to determine the size of an interspinous process spacer that can be used to treat the patient and schedules a follow up procedure to implant such a device. If the pain is not alleviated, the physician may expand main balloon 20 to a second expanded diameter. The patient then walks again to determine if there has been any pain relief. This process continues until the patient obtains relief or until main balloon 20 has reached its maximum rated diameter. If main balloon 20 reaches its maximum rated diameter, or if the physician so judges, the physician can conclude that the patient is not a candidate for an interspinous process spacer to treat lumbar spinal stenosis. The physician can then evaluate other treatment options for the patient.

Instead of using a single device having an expandable member that is expanded to different diameters, different devices having different sized expandable members may be inserted into the patient and then removed and replaced with a larger expandable member if the previous expandable member did not provide relief. This process is less desirable because of the additional material and process steps that need to be used and performed in order to achieve the information obtained using the method described above.

Balloon catheter 100 may be used in connection with a living patient for the treatment of various spinal disorders. Balloon catheter 100 may also be used in a non-living object, such as within a cadaver, model, and the like. The non-living object may be for one or more of testing, training, and demonstration purposes.

The elements of balloon catheter 100 may be positioned in the patient to contact various vertebral members. This contact may include direct contact with balloon catheter 100 actually touching the vertebral members, and may also include indirect contact with balloon catheter 100 actually touching the surrounding ligaments and tissue. In both instances, balloon catheter 100 includes a similar effectiveness for treating the spinal disorder for which it was implanted.

The interspinous process spacer diagnostic balloon catheter may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics described herein. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.