US 20080058823 A1
An expandable device is introduced into a cancellous bone volume of a vertebral body through a percutaneous access path. The expandable device carries a therapeutic substance. The expandable device is expanded while disposed within the cancellous bone volume to incorporate the therapeutic substance in the cancellous bone volume.
1. A method comprising:
selecting a vertebral body for treatment, the vertebral body having a cortical wall enclosing a cancellous bone volume,
providing a therapeutic substance,
providing an expandable device including an expanded configuration and an unexpanded configuration,
placing the therapeutic substance on the expandable device,
introducing the expandable device into the vertebral body through a percutaneous access path while in the unexpanded condition,
expanding the expandable device while disposed within the cancellous bone volume from the unexpanded configuration toward the expanded configuration to incorporate the therapeutic substance in the cancellous bone volume.
2. A method according to
wherein expansion of the expandable device creates a cavity in the cancellous bone volume.
3. A method according to
further including placing a volume of filling material within the cavity.
4. A method according to
wherein the filling material hardens within the vertebral body.
5. A method according to
wherein the filling material comprises bone cement.
6. A method according to
further including controlling the expansion so that the expandable device expands more in an inferior-to-superior direction than in a lateral direction.
7. A method according to
wherein expansion is controlled by restraining expansion of the expandable device in the lateral direction.
8. A method according to
wherein expansion is restrained by providing restraints external to the expandable device.
9. A method according to
wherein expansion is restrained by providing restraints internal to the expandable device.
10. A method according to
wherein expansion is restrained by providing a wall on the expandable device that varies in wall thickness.
11. A method according to
wherein the expansion is capable of moving fractured cortical bone toward a desired anatomic position.
12. A method according to
wherein the expandable device expands by inflation.
13. A method according to
wherein the expandable device comprises a balloon.
14. A method according to
further including removing the expandable device from the vertebral body.
15. A method according to
wherein the therapeutic substance comprises an antibiotic, or a bone growth factor, or an osteoporosis drug.
16. A system comprising
a therapeutic substance, and
an expandable device including an expanded configuration and an unexpanded configuration, the expandable device carrying the therapeutic substance, the expandable device being sized and configured for introduction into a vertebral body through a percutaneous access path while in the unexpanded condition, the vertebral body having a cortical wall enclosing a cancellous bone volume, the expandable device also being sized and configured for expansion while disposed within the cancellous bone volume from the unexpanded configuration toward the expanded configuration to incorporate the therapeutic substance in the cancellous bone volume.
17. A system according to
wherein expansion of the expandable device creates a cavity in the cancellous bone volume.
18. A system according to
further including a filling material and a tool for placing a volume of the filling material within the cavity.
19. A system according to
wherein the filling material hardens within the vertebral body.
20. A system according to
wherein the filling material comprises bone cement.
21. A system according to
wherein the expandable device is sized and configured, during expansion, to move fractured cortical bone toward a desired anatomic position.
22. A system according to
wherein the expandable device expands by inflation.
23. A system according to
wherein the expandable device comprises a balloon.
24. A system according to
wherein the therapeutic substance comprises an antibiotic, or a bone growth factor, or an osteoporosis drug.
This application is a divisional of co-pending U.S. patent application Ser. No. 11/528,163, filed 27 Sep. 2006, and entitled “Systems and Methods for Removing Tissue from a Cancellous Bone Volume,” which is a divisional of U.S. patent application Ser. No. 10/958,600, filed 5 Oct. 2004, and entitled “Systems and Methods for Treating Fractured or Diseased Bone Using Expandable Bodies,” which is a divisional of U.S. patent application Ser. No. 09/754,451, filed 4 Jan. 2001 (now U.S. Pat. No. 6,899,719), which is a continuation of U.S. patent application Ser. No. 08/871,114, filed 9 Jun. 1997 (now U.S. Pat. No. 6,248,110), which is a continuation-in-part of U.S. patent application Ser. No. 08/659,678, filed Jun. 5, 1996 (now U.S. Pat. No. 5,827,289), which is a continuation-in-part of U.S. patent application Ser. No. 08/485,394, filed Jun. 7, 1995 (now abandoned), which is a continuation-in-part of U.S. patent application Ser. No. 08/188,224, filed Jan. 26, 1994 (now abandoned), each of which is incorporated herein by reference.
The invention relates to the treatment of bone conditions in humans and other animals.
When cancellous bone becomes diseased, for example, because of osteoporosis, avascular necrosis, or cancer, the surrounding cortical bone becomes more prone to compression fracture or collapse. This is because the cancellous bone no longer provides interior support for the surrounding cortical bone.
There are 2 million fractures each year in the United States, of which about 1.3 million are caused by osteoporosis alone. There are also other bone disease involving infected bone, poorly healing bone, or bone fractured by severe trauma. These conditions, if not successfully treated, can result in deformities, chronic complications, and an overall adverse impact upon the quality of life.
U.S. Pat. Nos. 4,969,888 and 5,108,404 disclose apparatus and methods for the fixation of fractures or other conditions of human and other animal bone systems, both osteoporotic and non-osteoporotic. The apparatus and methods employ an expandable body to compress cancellous bone and provide an interior cavity. The cavity receives a filling material, which hardens and provides renewed interior structural support for cortical bone.
The better and more efficacious treatment of bone disease that these Patents promise can be more fully realized with improved systems and methods for making and deploying expandable bodies in bone.
The invention provides improved systems and methods for treating bone, including vertebral bodies, as well as in other bone types, using one or more expandable bodies.
According to one aspect of the invention, an expandable device is introduced into a cancellous bone volume of a vertebral body through a percutaneous access path. The expandable device carries a therapeutic substance. The expandable device is expanded while disposed within the cancellous bone volume to incorporate the therapeutic substance in the cancellous bone volume.
Features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended Claims.
The invention may be embodied in several forms without departing from its spirit or essential characteristics. The scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning and range of equivalency of the claims are therefore intended to be embraced by the claims.
This Specification describes new systems and methods to treat bones using expandable bodies. The use of expandable bodies to treat bones is disclosed in U.S. Pat. Nos. 4,969,888 and 5,108,404, which are incorporated herein by reference. Improvements in this regard are disclosed in U.S. patent application Ser. No. 08/188,224, filed Jan. 26, 1994; U.S. patent application Ser. No. 08/485,394, filed Jun. 7, 1995; and U.S. patent application Ser. No. 08/659,678, filed Jun. 5, 1996, which are each incorporated herein by reference.
The new systems and methods will be first described with regard to the treatment of vertebra. It should be appreciated, however, the systems and methods so described are not limited in their application to vertebrae. As will be described in greater detail later, the systems and methods are applicable to the treatment of diverse bone types.
I. Treatment of Vertebral Bodies
When viewed from the side, as
As FIGS. 1 to 3 show, each vertebra 12 includes a vertebral body 26, which extends on the anterior (i.e., front or chest) side of the vertebra 12. As FIGS. 1 to 3 show, the vertebral body 26 is in the shape of an oval disk. As
An opening, called the vertebral foramen 36, is located on the posterior (i.e., back) side of each vertebra 12. The spinal ganglion 39 pass through the foramen 36. The spinal cord 38 passes through the spinal canal 37.
The vertebral arch 40 surrounds the spinal canal 37. The pedicle 42′ of the vertebral arch 40 adjoins the vertebral body 26. The spinous process 44 extends from the posterior of the vertebral arch 40, as do the left and right transverse processes 46.
A. Deployment of an Expandable Body
The tool 48 includes a catheter tube 50 having a proximal and a distal end, respectively 52 and 54. The distal end 54 carries an expandable body 56.
The body 56 includes an exterior wall 58, which, in
The insertion of the body 56 into the interior volume 30 of a targeted vertebral body 26 can be accomplished in various ways.
In the described procedure, a patient lies on an operating table, while the physician introduces a conventional spinal needle assembly 60 into soft tissue in the patient's back. The patient can lie facedown on the table, or on either side, or at an oblique angle, depending upon the physician's preference. Indeed, the procedure can be performed through an open anterior procedure or an endoscopic anterior procedure, in which case the tool 48 may be introduced from the anterior aspect of the vertebral body.
The spinal needle assembly 60 comprises a stylet 62 slidable housed within a stylus 64. The assembly 60 typically has, for example, about an 18 gauge diameter. Other gauge diameters can and will be used to accommodate appropriate guide pins, as will be described in greater detail later.
Under radiologic, CT, or MRI monitoring, the physician advances the assembly 60 through soft tissue (designated S in
The physician directs the spinal needle assembly 60 to penetrate the cancellous bone 32 of the targeted vertebra 12. Preferably the depth of penetration is about 60% to 95% of the vertebral body 26.
After positioning the spinal needle assembly 60 in cancellous bone 32, the physician holds the stylus 64 and withdraws the stylet 62 (see
The materials for the catheter tube 50 are selected to facilitate advancement of the body 56 into cancellous bone through the guide sheath 72. The catheter tube 50 can be constructed, for example, using standard flexible, medical grade plastic materials, like vinyl, nylon, polyethylenes, ionomer, polyurethane, and polyethylene tetraphthalate (PET). The catheter tube 50 can also include more rigid materials to impart greater stiffness and thereby aid in its manipulation. More rigid materials that can be used for this purpose include Kevlar™ material, PEBAX™ material, stainless steel, nickel-titanium alloys (Nitinol™ material), and other metal alloys.
Once the protective sheath 73 is withdrawn, the wall 58 of the body 56 is capable of assuming an expanded geometry within the interior volume 30 (generally shown in
The lumen 80 conveys the fluid 82 into the body 56 under pressure. As a result, the wall 58 expands, as
Expansion of the wall 58 enlarges the body 56 and compacts cancellous bone 32 within the interior volume 30. As
The compaction of cancellous bone 32 forms a cavity 84 in the interior volume 30 of the vertebral body 26. The compaction of cancellous bone also exerts interior force upon cortical bone, making it possible to elevate or push broken and compressed bone back to or near its original prefracture position. Using a single transpedicular access (as
The body 56 is preferably left inflated for an appropriate waiting period, for example, three to five minutes, to allow coagulation inside the vertebral body 26. After the appropriate waiting period, the physician collapses the body 56 and removes it through the outer guide sheath 72 (see
A suction-irrigation tool (not shown) can be introduced through the outer guide sheath 72, to further flush and clear debris from the formed cavity 84 after removal of the body 56.
The injector gun 94 can comprise a cement gun made, for example, by Stryker Corporation (Kalamazoo, Mich.). This particular injector gun 94 has a manually operated injection grip 98 with a mechanical advantage of about 9 to 1. Other injection guns may be used, having more or less mechanical advantage. Non-manually operated injection guns can also be used.
The injector tip 90 can be, for example, about 4.9 mm in diameter, to accommodate the flow a relatively viscous material 96 into the cavity 84.
The physician can also check, using, for example, x-ray, for leakage of the material through cortical bone 28. Systems and methods for impeding or preventing such leakage will be described in greater detail later.
The physician flows material 96 into the cavity 84, until the material 96 reaches the distal end 74 of the outer guide sheath 72 (as
Upon removing the injector tube 92 from the outer guide sheath 72, the physician may, if necessary, tamp residual filling material 96 from the distal end 74 of the outer guide sheath 72 into the cavity 84. If fluoroscopic examination reveals void regions in the cavity 84, the physician may again insert the injector tube 92 to add more filling material 96 into the cavity 84.
As filling of the cavity 84 progresses, preferably under fluoroscopic monitoring, the physician progressively retracts the injector tip 90 from the anterior region of the cavity 84, toward the outer guide sheath 72, allowing the material 96 to progressively enter and fill the cavity 84 with the collapse of the body 56.
The outer lumen 660 communicates, via proximal tubing 668, with a source 82 of pressurized liquid. The outer lumen 660 also communicates with ports 670 formed on the distal catheter tube end 656 underlying the expandable body 662. Operation of the source 82 serves to inject pressurized liquid into the body 662 to expand it, in the manner previously described.
As earlier described, the collapsing body 662 serves to compact and spread the filling material 96 more uniformly within the cavity 84. Under fluoroscopic monitoring, the physician progressively retracts the distal end 656 of the tool 650 from the anterior region of the cavity 84 toward the outer guide sheath 72, allowing the material 96 to enter and fill the cavity 84.
Upon filling the cavity 84 with the material 96, the physician removes the outer guide sheath 72, as
In time, the filling material 96 sets to a hardened condition within the cavity 84 (see
The above described procedure, carried out in a minimally invasive manner, can also be carried out using an open surgical procedure. Using open surgery, the physician can approach the bone to be treated as if the procedure is percutaneous, except that there is no skin and other tissues between the surgeon and the bone being treated. This keeps the cortical bone as intact as possible, and can provide more freedom in accessing the interior volume 30 of the vertebral body.
B. Material Selection for the Expandable Body
The material of the body wall 58 can be selected according to the therapeutic objectives surrounding its use. For example, materials including vinyl, nylon, polyethylenes, ionomer, polyurethane, and polyethylene tetraphthalate (PET) can be used. The thickness of the body wall 58 is typically in the range of 2/1000ths to 25/1000ths of an inch, or other thicknesses that can withstand pressures of up to, for example, 250-500 psi.
If desired, the material for the wall 58 can be selected to exhibit generally elastic properties, like latex. Alternatively, the material can be selected to exhibit less elastic properties, like silicone. Using expandable bodies 56′ with generally elastic or generally semi-elastic properties, the physician monitors expansion to assure that over-expansion and wall failure do not occur. Furthermore, expandable bodies 56 with generally elastic or generally semi-elastic properties will require some form of external or internal restraints to assure proper deployment in bone.
For example, expandable bodies 56 with generally elastic properties will exhibit the tendency to backflow or creep into the outer guide sheath 72 during their expansion. It is therefore necessary to internally or externally restrain a body 56 that is subject to creeping, to keep it confined within the interior bone region. In
The physician advances the o-ring 100 along the catheter tube 50 inside the guide sheath 72 using a generally stiff stylet 102 attached to the o-ring 100. The physician locates the o-ring 100 at or near the distal end 54 of the catheter tube 50 prior to conveying the liquid 82 to expand the body 56. The o-ring 100 is held in place by the generally stiff stylet 102, which provides a counter force to prevent backward movement of the o-ring 100 in the guide sheath 72 as the body 56 expands. The o-ring 100 thereby keeps all or a substantial portion of the generally elastic body 26 confined inside the interior volume 30. The body 56 thereby serves to compact as much of the cancellous bone 32 as possible.
The use of an external sealing element 100 to restrain the expandable body 56 may not be necessary when relatively inelastic materials are selected for the body 56. For example, the material for the body wall 58 can be selected to exhibit more inelastic properties, to limit expansion of the wall 58 prior to wall failure. The body wall 58 can also include one or more restraining materials, particularly when the body wall 58 is itself made from more elastic materials. The restraints, made from flexible, inelastic high tensile strength materials, limit expansion of the body wall 58 prior to wall failure. Representative examples of generally inelastic wall structures will be described in greater detail later.
C. Selection of Shape and Size for the Expandable Body
As will also be demonstrated later, when relatively inelastic materials are used for the body wall 58, or when the body wall 58 is otherwise externally restrained to limit its expansion prior to failure, a predetermined shape and size can be imparted to the body 56, when it is substantially expanded. The shape and size can be predetermined according to the shape and size of the surrounding cortical bone 28 and adjacent internal structures, or by the size and shape of the cavity 84 desired to be formed in the cancellous bone 32.
In one embodiment, which is generally applicable for treating bones experiencing or prone to fracture, the shape and size of the body 56, when substantially expanded, can be designed to occupy at least about 30% of the volume of cancellous bone 32 in the interior volume 30. A body 56 having a substantially expanded size and shape in the range of about 40% to about 99% of the cancellous bone volume is preferred.
In another embodiment, which is applicable for treating bones having more localized regions of fracture or collapse caused, for example, by avascular necrosis, the shape and size of the body 56 can be designed to occupy as little as about 10% of the cancellous bone volume. In this embodiment, the drilled passage 78 extends directly to the localized site of injury, to enable targeted introduction of the body 26.
The shape of the cancellous bone 32 to be compressed, and the presence of surrounding local anatomic structures that could be harmed if cortical bone were moved inappropriately, are generally understood by medical professionals using textbooks of human skeletal anatomy, along with their knowledge of the site and its disease or injury. The physician is also able to select the materials and geometry desired for the body 56 based upon prior analysis of the morphology of the targeted bone using, for example, plain films, spinous process percussion, or MRI or, CRT scanning. The materials and geometry of the body 56 are selected to create a cavity 84 of desired size and shape in cancellous bone 32 without applying harmful pressure to the outer cortical bone 28 or surrounding anatomic structures.
In some instances, it is desirable, when creating the cavity 84, to move or displace the cortical bone 28 to achieve the desired therapeutic result. Such movement is not per se harmful, as that term is used in this Specification, because it is indicated to achieve the desired therapeutic result. By definition, harm results when expansion of the body 56 results in a worsening of the overall condition of the bone and surrounding anatomic structures, for example, by injury to surrounding tissue or causing a permanent adverse change in bone biomechanics.
D. Deployment of Multiple Expandable Bodies
Formation of a desired cavity geometry in cancellous bone 32 using an expandable body 56 can be accomplished in diverse ways to achieve the desired therapeutic effect. The foregoing disclosure envisions the deployment of a single expandable body 56 to compact cancellous bone 32 and, by itself, form a cavity 84 having a desired shape and size to receive a filling material 96.
Alternatively, a cavity 84 having a desired shape and size in cancellous bone 32 can be formed by the deployment of more than one expandable body 56 in a targeted region of cancellous bone 32, either sequentially or simultaneously.
In the alternative embodiment shown in
For the sake of illustration,
Alternatively, as shown in
The selection of size and shape of the array 108, whether symmetric or asymmetric, depends upon the size and shape of the targeted cortical bone 28 and adjacent internal structures, or by the size and shape of the cavity 84 desired to be formed in the cancellous bone 32. The deployment of multiple expandable bodies 56 makes it possible to form cavities 84 having diverse and complex geometries within bones of all types. Multiple expandable bodies having generally the same geometry can be deployed in different ways to create cavities of different geometries.
It should be appreciated that the various styles of multiple expandable bodies 56 shown in FIGS. 9 to 11 are deployed in a distally straightened condition (as
Access for expandable bodies 56 can be achieved through multiple access sites and in many different ways. For example, multiple expandable bodies can access the vertebral body from different regions of a targeted vertebra.
Deployed from dual access sites as shown in
As another example, multiple expandable bodies 56A and 56B can access the vertebral body 26 from the same general region of the vertebra.
Deployed from these access sites (see
By way of another example,
Systems for treating bone using multiple expandable bodies can include directions 79 (see
In any of the above-described examples, each guide sheath 72A or 72B can itself accommodate a single expandable body or multiple expandable bodies. The size and shape of the bodies may be the same, or they may vary, according to the desired objectives of the physician for the targeted vertebral body.
E. Representative Embodiments of Expandable Bodies to Treat Vertebrae
i. Constrained Donut-Shaped Geometries
The parts 212 and 214 are connected together by an adhesive which can be of any suitable type. Parts 212 and 214 are doughnut-shaped, as shown in
A tubes 315 direct liquid under pressure into the body units 310, 312 and 314 to expand the units and cause compaction of cancellous bone. The restraints 317 limit expansion of the body units prior to failure, keeping the opposed sides 377 and 379 substantially flat and parallel with each other.
ii. Constrained Kidney-Shaped Geometries
The details of these and other expandable bodies usable to treat vertebral bodies are described in U.S. patent application Ser. No. 08/188,224, filed Jan. 26, 1994, which is incorporated herein by reference.
F. Selection of Desired Geometry
The eventual selection of the size and shape of a particular expandable body or bodies to treat a targeted vertebral body 26 is based upon several factors. When multiple expandable bodies are used, the total combined dimensions of all expandable bodies deployed, when substantially expanded, should be taken into account.
The anterior-posterior (A-P) dimension (see
The appropriate side to side dimension L (see
The lumbar vertebral body tends to be much wider in side to side dimension L then in A-P dimension. In thoracic vertebral bodies, the side to side dimension and the A-P dimensions are almost equal.
The height dimensions H of the expandable body or bodies (see
The dimensions of expandable body or bodies for use in vertebrae are patient specific and will vary across a broad range, as summarized in the following table:
A preferred expandable body 56 for use in a vertebral body is stacked with two or more expandable members of unequal height (see
II. Treatment of Long Bones
Like vertebrae, the interior regions of long bones substantially occupied by cancellous bone can be treated with the use of one or more expandable bodies.
As for vertebral bodies, expandable bodies possess the important attribute of being able, in the course of forming cavities by compressing cancellous bone, to also elevate or push broken or compressed cortical bone back to or near its normal anatomic position. This is a particularly important attribute for the successful treatment of compression fractures or cancellous bone fractures in the appendicular skeleton, such as the distal radius, the proximal humerus, the tibial plateau, the femoral head, hip, and calcaneus.
Representative examples of expandable bodies for the treatment of cancellous bone regions of long bones will be next described.
A. Expandable Body for the Distal Radius
The selection of an appropriate expandable to treat a fracture of the distal radius (Region 602 in
The body 260 has a lower, conical portion 259 which extends downwardly into the hollow space of the distal radius 252. This conical portion 259 increases in cross section as a central distal portion 261 is approached. The cross section of the body 260 is shown at a central location (
The shape of the body 260 is determined and restrained by tufts formed by string restraints 265. These restraints are optional and provide additional strength to the body 260, but are not required to achieve the desired configuration.
The body 260 is placed into and taken out of the distal radius in the same manner as that described above with respect to the vertebral bone.
Typical dimensions of the distal radius body vary as follows:
The proximal end of the body 260 (i.e. the part nearest the elbow) is cylindrical in shape and will vary from 0.4×0.4 cm to 1.8×1.8 cm.
The length of the distal radius body will vary from 1.0 cm to 12.0 cm.
The widest medial to lateral dimension of the distal radius body, which occurs at or near the distal radio-ulnar joint, will measure from 0.5 cm to 2.5 cm.
The distal anterior-posterior dimension of the distal radius body will vary from 0.4 to 3.0 cm.
B. Expandable Body for Proximal Humerus Fracture
The selection of an appropriate expandable body 266 to treat a given proximal humeral fracture (Region 606 in
A mesh 270, embedded or laminated and/or winding, may be used to form a neck 272 on the body 266. A second mesh 270 a may be used to conform the bottom of the base 272 a to the shape of the inner cortical wall at the start of the shaft. These mesh restraints provide additional strength to the body 266, but the configuration can be achieved through molding of the body.
The body 266 has a catheter tube 277 into which liquid under pressure is forced into the body to expand it to compact the cancellous bone in the proximal humerus. The body 266 is inserted into and taken out of the proximal humerus in the same manner as that described above with respect to the vertebral bone.
Typical dimensions of the expandable body 266 shown in
The spherical end of the body will vary from 0.6×0.6 cm to 3.0×3.0 cm.
The neck of the proximal humeral fracture body will vary from 0.5×0.5 cm to 3.0×3.0 cm.
The width of the base portion or distal portion of the proximal numeral fracture body will vary from 0.5×0.5 cm to 2.5×2.5 cm.
The length of the body will vary from 3.0 cm to 14.0 cm.
C. Expandable Body for Proximal Tibial Plateau Fracture
The selection of an expandable body to treat a given tibial plateau fracture (Region 604 in
The body 280, when substantially inflated (as
The restraints 288 can be in the form of strings or flexible members of any suitable construction. The restraints 288 limit expansion of the body 280 prior to failure. The restraints 288 make the sides 285 and 287, when the body 280 is substantially expanded, substantially parallel with each other and, thereby, non-spherical.
A tube 290 is coupled to the body 280 to direct liquid into and out of the body to expand it. The body is inserted into and taken out of the tibia in the same manner as that described above with respect to the vertebral bone.
Other geometries and configurations can also be used. For example, as
As another example, as
The thickness or height of the body will vary from 0.3 cm to 5.0 cm.
The anterior-posterior (front to back) dimension will vary from 1.0 cm to 6.0 cm.
The medial to lateral (side-to-side) dimension will vary from 1.0 cm to 6.0 cm.
In the embodiment shown in
In the illustrated embodiment (as
The expanded first body 614 creates a barrier 630 within the interior region 628. Due to the less expanded top-to-bottom geometry of the first body 614, a substantially uncompacted region 632 of cancellous bone is left above the body 614, which extends from the formed barrier 630 upward to the fracture 622. In a representative deployment, the uncompacted region 632 extends about 2 cm below the tibial plateau fracture 622.
It should be appreciated that one or more expandable bodies can be used as platforms or barriers to direct the expansion of one or more other expandable bodies in other localized interior bone regions. The barrier makes possible localized cavity formation in interior bone regions. Use of the barrier preserves healthy regions of cancellous bone, while directing the main compacting body toward localized fractures or localized regions of diseased cancellous bone.
D. Expandable Body for Femoral Head
The size of an expandable body for use in the femoral head (Region 608 in
The femoral head is generally spherical in configuration, and the body 300 can have either a hemispherical (see
The body 300 is inserted into and taken out of the femoral head in the same manner as that described with respect to the vertebral bone.
Typical dimensions of an expandable body for use in treating the femoral head vary as follows:
The diameter of the expandable body will vary from 0.5 cm to up to 4.5 cm. The dimensions of the hemispherical body (
E. Expandable Body for Prevention of Hip Fracture
Patients with bone density in the hip (Region 612 in
Expansion of the body 410 is limited to achieve the described geometry by rings 430 of inelastic material. The rings 430 are held in a spaced apart relationship along one side of the body 410 by attachment to an inelastic band 416, which runs the length of that side of body 410. The rings 430 are held in a farther spaced apart relationship along the opposite side of the body 410 by attachment to another, longer inelastic band 417, which runs the length of the opposite side of the body 410. A tube 419 conveys liquid to inflate the body 410.
Prior to deployment within the body, the body 410 is collapsed and rolled up and held against the inflation tube 419 using, for example, with frangible connectors that will break as the body is subject to expansion. To deploy the body 410 into the hip, the surgeon uses a power drill under radiographic guidance to create a cavity 420, which is, for example, about 4 to 6 mm wide starting at the lateral femoral cortex 421 and proceeding into the femoral head 411. The body 410 is deployed through a guide sheath 423, following the cavity 420. The body 410 is deployed, prior to expansion, facing the lesser trochanter 414, so that expansion occurs toward the femoral diaphysis 413, and not toward the greater trochanteric region 422.
The expansion of the body 410 is guided by the rings 430 and bands 416 and 417, which cause bending of the body 410 downward into the lesser trochanter 414. Optionally, a second cavity can be drilled down into the diaphysis 413, starting from the same entry point or from the other side.
The body length is chosen by the physician to extend about 0.5 cm from the end of the femoral head, through the femoral neck and into the proximal femoral diaphysis, usually about 4 to 8 cm below the lesser trochanter. The body diameter is chosen by measuring the inner cortical diameter of the femoral neck (the most narrow area) and subtracting 0.5 cm. The preferred dimensions of the body 410 are a total length of 10-20 cm and a diameter of about 1.0-2.5 cm.
Patients having the lowest bone densities in the femoral head may require greater compacting in the femoral head, which may, for example, be provided by using two bodies, one after the other: the bent body 410 followed by the femoral head body (inserted at the same point and expanded prior to inserting any supporting material). Alternatively, the bent body 410 may be adapted to have a distal portion that approximates the shape of the femoral head body.
The geometry of the single, restrained body 410 can be approximated by multiple expandable bodies deployed separately, or coupled together, or stacked together.
A second expandable body 410(2) is introduced through a second outer guide sheath 423(2) in the greater trochanter 422 of the femur. The first body 419(1) is deployed in the direction of the femoral diaphysis 413.
Other approaches can be used. For example, one body can be introduced through the femoral neck 480, and the other body can be introduced along the shaft of the femur.
One or both of the bodies 410(1) and 410(2) can include external restraints to limit expansion, in the manner described with regard to the body 410. Expansion of the bodies 410(1) and 410(2) compacts cancellous bone to form a cavity having a geometry approximating that formed by the single body 410.
F. Expandable Body for Calcaneus Fracture
The size of an expandable body for use in treating fracture of the calcaneus (heel bone) (Region 610 in
Expansion of the body 450 is limited within the confines of the calcaneus by inelastic peripheral bands 454 (see
The pear-shaped geometry has a smaller, minor dimension occupying the region of the anterior facet 458 of the calcaneus, near the calcaneal-cuboid joint 460, between the calcaneus and cuboid bone 462.
Expansion of the body 410 compacts cancellous bone 470 within the calcaneus 452. The expansion also lifts a depression fracture of the posterior facet 454 back to or near its original anatomic elevation adjacent the talus 456. When collapsed and removed, the body 410 leaves a cavity in cancellous bone into which filling material can be introduced in the manner previously described.
III. Selection of Other Expandable Bodies (Further Overview)
Different sizes and/or shapes of expandable bodies may be used at sites not specified above, such as the jaw bones, the midshaft of the arm and leg bones, the cervical vertebral bodies, the foot and ankle bones, the pelvis, the ribs, and the like.
The choice of the shape and size of a expandable body takes into account the morphology and geometry of the site to be treated. As before stated, the shape of the cancellous bone to be compressed, and the local structures that could be harmed if bone were moved inappropriately, are generally understood by medical professionals using textbooks of human skeletal anatomy along with their knowledge of the site and its disease or injury. Precise dimensions for a given patient can be further determined by X-ray of the site to be treated.
As one general guideline, the selection of the geometry of the expandable body should take into account that at least 40% of the cancellous bone volume needs to be compacted in cases where the bone disease causing fracture (or the risk of fracture) is the loss of cancellous bone mass (as in osteoporosis). The preferred range is about 30% to 90% of the cancellous bone volume. Compacting less of the cancellous bone volume can leave too much of the diseased cancellous bone at the treated site. The diseased cancellous bone remains weak and can later collapse, causing fracture, despite treatment.
Another general guideline for the selection of the geometry of the expandable body is the amount that the targeted fractured bone region has been displaced or depressed. The expansion of the body within the cancellous bone region inside a bone can elevate or push the fractured cortical wall back to or near its anatomic position occupied before fracture occurred.
However, there are times when a lesser amount of cancellous bone compaction is indicated. For example, when the bone disease being treated is localized, such as in avascular necrosis, or where local loss of blood supply is killing bone in a limited area, the expandable body can compact a smaller volume. This is because the diseased area requiring treatment is smaller.
Another exception lies in the use of an expandable body to improve insertion of solid materials in defined shapes, like hydroxyapatite and components in total joint replacement. In these cases, the body shape and size is defined by the shape and size of the material being inserted.
Yet another exception is the delivery of therapeutic substances, which will be described in greater detail later. In this case, the cancellous bone may or may not be diseased or adversely affected. Healthy cancellous bone can be sacrificed by significant compaction to improve the delivery of a drug or growth factor which has an important therapeutic purpose. In this application, the size of the expandable body is chosen by the desired amount of therapeutic substance sought to be delivered. In this case, the bone with the drug inside is supported while the drug works, and the bone heals through exterior casting or current interior or exterior fixation devices.
Generally speaking, providing relatively inelastic properties for the expandable body, while not always required, is nevertheless preferred when maintaining a desired shape and size within the bone is important, for example, in bone graft placement or in a vertebral body, where the spinal cord is nearby. Using relatively inelastic bodies, the shape and size can be better predefined, taking into account the normal dimensions of the outside edge of the cancellous bone. Use of relatively inelastic materials also more readily permits the application of pressures equally in all directions to compress cancellous bone. Still, substantially equivalent results can usually be achieved by the use of multiple expandable bodies having highly elastic properties, if expansion is controlled by either internal or external restraints, as previously disclosed.
IV. Confinement of Filling Material
A. Dual Stage Filling
Use of the multi-stage process is indicated when pre-examination of the targeted bone reveals that a portion of the cortical wall 28 has fractured or failed (as
The process begins at the point where the outer guide sheath 72 has been positioned and the guide pin removed in the manner previously described. The physician introduces a first expandable body 502 into the cancellous bone 32 near the failed cortical bone region, as
The physician expands the first expandable body 502, compacting a relatively small region of cancellous bone. Upon collapse and removal of the first body 502, a small cavity 504, caused by the compaction, remains (as
The physician introduces the injector tip 90 and injects an aliquot of filling material 96(1) (for example, about 1 cc to about 9 cc) into the formed small cavity 504 (as
In a short time interval (before the filling material 96(1) is allowed to substantially set and harden), the physician withdraws the injector tip 90 and introduces a second expandable body 506 into the cancellous bone 32 (see
B. Interior Mesh
Use of the mesh 510 is indicated when pre-examination of the targeted bone reveals a failed cortical bone region (as
The mesh 510 comprises a woven structure made from biocompatible material like Goretex™ material, Nitinol™ material, or Dacron™ material. The mesh presents a surface area, which is about ⅓rd to ½ of the interior area of the main therapeutic cavity 84 formed by the selected expandable body.
Before deploying the injector tip 90 into the formed cavity 84 (which is deployed in
V. Delivery of Therapeutic Materials
A cavity created in cancellous bone by any of the expandable bodies described above can be filled with a medically-appropriate formulation of a drug or a growth factor.
An expandable body can compact infected cancellous bone to create a space which can be filled with the antibiotic gel in an open or minimally invasive procedure. The cavity places and holds the required amount of drug right at the site needing treatment, and protects the drug from being washed away by blood or other fluids.
Not only can the dose be optimized, but additional doses can be applied at later times without open surgery, enhancing the therapeutic outcome. If the required cavity for the optimal drug dose weakens the bone, the bone can be protected from future fracture with a cast or with current internal or external metal or plastic fixation devices.
The therapeutic substance put into bone may act outside the bone as well. A formulation containing chemotherapeutic agent could be used to treat local solid tumors, localized multiple myeloma or even a nearby osteosarcoma or other tumor near that bone.
The cavity formed by an expandable body can be filled with an appropriate supporting material, like acrylic bone cement or biocompatible bone substitute, which carries a therapeutic substance. Alternatively, the therapeutic substance can be separately delivered before injection of the filling material. Thus, using an expandable body, the physician is able to treat a fracture while also delivering a desired therapeutic substance (like an antibiotic, bone growth facer or osteoporosis drug) to the site.
As an alternative, to deliver therapeutic substances, bodies can be dipped in a medical formulation (often a dry powder, liquid or gel) containing a medically-effective amount of any desired antibiotic, bone growth factor or other therapeutic agent to coat the body with the above-mentioned substance before it is inserted into a bone being treated. Optionally, the body can be wholly or partially expanded before the coating is performed. Optionally, the coated body can be dried with air or by other means when the applied formulation is wet, such as a liquid or a gel. The body is refolded as required and either used immediately or stored, if appropriate and desired. Coated on the body, therapeutic substances can be delivered while cancellous bone is being compressed, or with an additional body once the cavity is made.
The methods described above can also be used to coat Gelfoam or other agents onto the body before use. Inflating the Gelfoam-coated body inside bone will further fill any cracks in fractured bone not already filled by the compressed cancellous bone.
As shown in
Delivering a therapeutic substance on the outside of expandable body used to compact the bone, or with an expandable body introduced after the bone is compacted, is qualitatively different than putting formulated drug into the cavity. When delivered while the bone is compressed, the therapeutic substance becomes incorporated into the compacted bone. This can serve as a way to instantly formulate a slow release version of the substance. The cavity formed by the expandable body can be filled with an appropriate supporting material, like acrylic bone cement or biocompatible bone substitute, as before described.
Medically-effective amounts of therapeutic substances are defined by their manufacturers or sponsors are generally in the range of 10 nanograms to 50 milligrams per site, although more or less may be required in a specific case.
For example, the cavity can accommodate a typical dose of the antibiotic, gentamicin, to treat a local osteomyelitis (bone infection). A typical dose is about 1 gram, although the therapeutic range for gentamicin is far greater, from 1 nanogram to 100 grams, depending on the condition being treated and the size of the area to be covered. A medically-suitable gel formulated with appropriate gel materials, such as Polyethylene glycol, can contain 1 gram of gentamicin in a set volume of gel, such as 10 cc.
Other antibiotics that can be used to treat bone infection include, for example, ancef, nafcillin, erythromycin, tobramycin, and gentamicin. Typical bone growth factors are members of the Bone Morphogenetic Factor, Osteogenic Protein, Fibroblast Growth Factor, Insulin-Like Growth Factor and Transforming Growth Factor alpha and beta families. Chemotherapeutic and related agents include compounds such as cisolatin, doxcrubicin, daunorubicin, methotrexate, taxol and tamoxifen. Osteoporosis drugs include estrogen, calcitonin, diphosphonates, and parathyroid hormone antagonists.
VI. Delivery of Biomaterials
A cavity created in cancellous bone by any of the expandable bodies described above can also be filled with biomaterials.
Biomaterials which do not flow into the formed cavity, like hydroxyapatite granules or bone mineral matrix, can be pushed down a tube with a long pin whose diameter is slightly more narrow than the inner-diameter of the outer guide sheath, using the minimally-invasive procedure. During open surgery, the physician can approach the bone in the same way.
If the biomaterial to be inserted does not flow and should not be pushed into the cavity through the guide sheath (as in the case of the hydroxyapatite block, because that can cause damage), the physician can form the cavity using a minimally invasive approach, then punch a hole using standard tools (such as a punch, gouge or rasp) into one side of the cortical bone to allow insertion of the block.
VII. Bone Marrow Harvesting
Any of the expandable bodies described above can also be used in the harvesting of bone marrow for diagnostic or therapeutic purposes, for example, in the diagnosis of multiple myeloma or in the treatment of advanced cancers with bone marrow transplants.
The system 700 employs a bone marrow harvesting tool 704. The tool 704 includes a catheter tube 706, which carries an expandable body 708 at its distal end. The tool 704 can be deployed into the bone 702 using a minimally invasive approach, as previously described.
The catheter tube 706 has three concentric and independent lumens 710, 712, and 714 (see
The body 708 is deployed in a substantially collapsed condition, as already described. Inflation liquid, which is preferably radiopaque, is convey from the source 718 into the body 708 to expand it. As
The body 708 is collapsed, and suction is applied through the lumen 714. The suction draws the component-rich suspension 732 from the area 726 into the collection container 722.
The above sequence of expansion, rinsing, collapse, and aspiration can be repeated to collect additional component-rich suspension 732 in the container 722. The position of the expandable body 708 in the bone 702 can be changed, if desired, to maintain a component-rich suspension 732 for harvesting.
Use of the expandable body 708 to form the long but shallow compaction area 726 permits the harvest of a significant concentration of therapeutic biological components with less damage to bone that conventional harvesting methods if desired, standard casts or other fixation devices can be applied to the bone 702 after bone marrow harvesting until the bone 702 heals.
The features of the invention are set forth in the following claims.