Abstract:
A method for stabilizing fractured bone structure having a fractured height includes expanding the bone structure to a restored height greater than the fractured height by transitioning an expandable member inserted into the bone structure from a contracted state to an expanded state. A curable material is delivered into a cavity formed in the bone structure and allowed to harden while the expandable member maintains the bone structure at the restored height. The expandable member is then removed from the bone structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/615,573, filed Nov. 10, 2009, and entitled “Systems and Methods for Vertebral or Other Bone Structure Height Restoration and Stabilization”; and the entire teachings of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to systems and methods for stabilizing bone structures. More particularly, it relates to systems and methods for stabilizing, and restoring the height of, a bone structure, such as a vertebral body. 
     Surgical intervention of damaged or compromised bone sites has proven highly beneficial for patients, for example patients with back pain associated with vertebral damage. 
     Bones of the human skeletal system include mineralized tissue that can be generally categorized into two morphological groups: “cortical” bone and “cancellous” bone. Outer walls of all bones are composed of cortical bone, which is a dense, compact bone structure characterized by a microscopic porosity. Cancellous or “trabecular” bone forms the interior structure of bones. Cancellous bone is composed of a lattice of interconnected slender rods and plates known by the term “trabeculae”. 
     During certain bone-related procedures, cancellous bone is supplemented by an injection of a palliative (or curative) material employed to stabilize the trabeculae. For example, superior and inferior vertebrae in the spine can be beneficially stabilized by the injection of an appropriate, curable material (e.g., PMMA or other bone cement or bone curable material). In other procedures, percutaneous injection of stabilization material into vertebral compression fractures, by, for example, transpedicular or parapedicular approaches, has proven beneficial in relieving pain and stabilizing damaged bone sites. Such techniques are commonly referred to as vertebroplasty. 
     A conventional vertebroplasty technique for delivering the bone stabilizing material entails placing a cannula with an internal stylet into the targeted delivery site. The cannula and stylet are used in conjunction to pierce the cutaneous layers of a patient above the hard tissue to be supplemented, then to penetrate the hard cortical bone of the vertebra, and finally to traverse into the softer, cancellous bone underlying the cortical bone. Once positioned in the cancellous bone, the stylet is removed, leaving the cannula in the appropriate position for delivery of curable material that in turn reinforces and solidifies the target site. 
     In some instances, an effectiveness of the procedure can be enhanced by forming a cavity or void within the cancellous bone, and then depositing the curable material in the cavity. For example, a balloon or other expandable device can be initially deployed and then expanded. This action, in turn, compresses cancellous bone to form a cavity, and may also cause a “height” of the bone to increase. As a point of reference, vertebroplasty is a common treatment for a fractured vertebral body, and the height of a fractured vertebral body is oftentimes significantly less than a native or natural height. It has been postulated that the height of a fractured vertebral body can be restored or elevated to a near-normal state when subjected to internal expansion via a balloon or other expandable member. The mechanics of height restoration in conjunction with vertebroplasty stabilization is currently unclear at best. For example, conventional techniques employ a bipedicular approach in which two balloons are inserted into the vertebral body and inflated, resulting in an increase in height (and the cavity or cavities described above). The sequence of subsequent deflation and delivery of curable material is not well documented. 
     In light of the above, there exists a need in the medical device field for improved systems and methods for restoring the height of, and stabilizing, a fractured vertebral body or other bone structure. 
     SUMMARY 
     Some aspects in accordance with principles of the present disclosure relate to a method for stabilizing a fractured bone structure of a patient. The fractured bone structure has a fractured height. The method includes expanding the bone structure to a restored height that is greater than the fractured height by expanding at least a first expandable member from a contracted state to an expanded state. While the expandable member maintains the bone structure at the restored height, a curable material is delivered into a cavity formed in the bone structure. The delivered material is allowed to harden while the expandable member continues to maintain the bone structure at the restored height. The expandable member is then removed from the bone structure. In some embodiments, a second cavity is defined in the bone structure by the removed expandable member, and the curable material is then delivered into the second cavity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a curable material delivery and height restoration system in accordance with principles of the present disclosure; 
         FIGS. 2A and 2B  illustrate initial use of the system of  FIG. 1  in performing a height restoration and curable material delivery procedure relative to a vertebra, with the vertebra being shown from a superior perspective; 
         FIG. 2C  is a lateral view of the vertebral body of  FIGS. 2A and 2B ; and 
         FIGS. 3A-6  illustrate the system of  FIG. 1  in further performing the height restoration and curable material delivery procedures of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One embodiment of a curable material delivery and height restoration system  10  in accordance with principles of the present disclosure is shown in  FIG. 1 . The system  10  includes a first delivery assembly  12   a , a second delivery assembly  12   b , and at least one source of curable material  16 . The delivery assemblies  12   a ,  12   b  can be substantially identical, and each includes a cannula device  18   a ,  18   b  and a cavity-forming device  20   a ,  20   b . Details on the various components are provided below. In general terms, however, the cannula devices  18   a ,  18   b  each include a cannula  22   a ,  22   b  for insertion into a bone site of interest in a patient. In the embodiment depicted in  FIG. 1 , the bone site of interest is a vertebra  30 . Once the cannulas  22   a ,  22   b  are desirably located relative to the vertebra  30 , a portion of each of the cavity-forming devices  20   a ,  20   b  are delivered to the vertebra  30  via the corresponding cannula  22   a ,  22   b , and operated to form cavities. The second cavity-forming device  20   b  (alternatively the first cavity-forming device  20   a ) is removed, and the source of curable material  16  connected to the second cannula  22   b . In this regard, an optional delivery tube  14  can be employed, extending from the source  16  and through the second cannula  22   b . Regardless, the curable material source  16  is then operated to deliver curable material to the cavity via the second cannula  22   b  and/or the delivery tube  14 . Subsequently, the first cavity-forming device  20   a  is removed and the curable material source  16  is connected to the first cannula  22   a  (for example, via the optional delivery tube  14 ). The curable material source  16  is operated to deliver curable material into the corresponding cavity. With this approach, the systems and methods of the present disclosure can consistently restore a height of the vertebra (or other bone site)  30  to a normal or near-normal state, and the delivered curable material provides desired stabilization. 
     The system  10  can be used for a number of different procedures including, for example, vertebroplasty and other bone augmentation procedures in which curable material is delivered to a site within bone, as well as possibly to remove or aspirate material from a site within bone. The system  10  is highly useful for delivering a curable material in the form of a bone curable material. The phrase “curable material” within the context of the substance that can be delivered by the system  10  of the present disclosure described herein is intended to refer to materials (e.g., composites, polymers, and the like) that have a fluid or flowable state or phase and a hardened, solid or cured state or phase. Curable materials include, but are not limited to, injectable bone cements (such as polymethylmethacrylate (PMMA) bone curable material), which have a flowable state wherein they can be delivered (e.g., injected) by a cannula to a site and subsequently cure into hardened, cured material. Other materials such as calcium phosphates, bone in-growth materials, antibiotics, proteins, etc., can be used in place of, or to augment, bone cement (but do not affect an overriding characteristic of the resultant formulation having a flowable state and a hardened, solid, or cured state). This would allow the body to reabsorb the curable material and/or improve the clinical outcome based on the type of filler implant material. While  FIG. 1  illustrates a single source of curable material  16 , in other embodiments, two (or more) sources can be provided. The sources can contain identical curable material compositions; alternatively, the compositions can differ (e.g., a first source can contain bone cement, while a second source contains a mixture of bone cement and bone in-growth material). 
     As mentioned above, the cannula devices  18   a ,  18   b  can be substantially identical, and each includes the cannula  22   a ,  22   b . The cannula  22   a ,  22   b  is provided to be positioned in (or immediately proximate) the target or injection site for delivery of the corresponding cavity-forming device  20   a ,  20   b , as well as curable material. The cannula  22   a ,  22   b  is preferably made of a surgical grade of stainless steel, but may be made of known equivalent material(s) that are both biocompatible and substantially non-compliant at the expected operating pressures. The cannulas  22   a ,  22   b  each define a proximal region  40   a ,  40   b , a distal end  42   a ,  42   b , and a lumen  44   a ,  44   b  (referenced generally), respectively, to allow various equipment such as the cavity-forming device  20   a ,  20   b , the optional delivery tube  14 , one or more stylets (not shown), etc., to pass therethrough. 
     Surrounding the proximal region  40   a ,  40   b  of the cannula  22   a ,  22   b  is an optional handle  46   a ,  46   b  for manipulating the cannula  22   a ,  22   b  and connecting the cannula  22   a ,  22   b  with one or more of the cavity-forming device  20   a ,  20   b  and/or the optional delivery tube  14 . In some constructions, the cannula device  18   a ,  18   b  can further include a handle connector  48   a ,  48   b  serving as a proximal end of the corresponding cannula  22   a ,  22   b . The handle connector  48   a ,  48   b  can simply be an extension of the cannula  22   a ,  22   b . Alternatively, the handle connector  48   a ,  48   b  can incorporate features forming part of a locking mechanism component of the system  10 . For example, the handle connector  48   a ,  48   b  can optionally include a luer-lock type of connector, but other known connecting mechanism may be successfully interchanged (e.g., a conventional threaded hole, a threaded locking nut arrangement, etc.). Features of the optional locking mechanism are described in U.S. Publication No. 2007/0198024, the entire teachings of which are incorporated herein by reference. 
     The cavity-forming devices  20   a ,  20   b  are substantially identical and can assume various forms appropriate for forming a void or cavity within bone. In this regard, each of the cavity-forming devices  20   a ,  20   b  includes an elongated body  60   a ,  60   b  distally connected to or forming a working end  62   a ,  62   b . The elongated body  60   a ,  60   b  is sized to be slidably inserted within the lumen  44   a ,  44   b  of the corresponding cannula  22   a ,  22   b , and can include one or more tubes, shafts, etc., necessary for operation of the corresponding working end  62   a ,  62   b . Regardless, a proximal region  64   a ,  64   b  of the elongated body  60   a ,  60   b  is optionally connected to or forms a cannula connector  66   a ,  66   b . The cannula connector  66   a ,  66   b  can assume various forms conducive for selective, rigid attachment to the corresponding handle connector  48   a ,  48   b  as described above (e.g., the cannula connector  66   a ,  66   b  and the corresponding handle connector  48   a ,  48   b  collectively form a locking mechanism), and thus can include or contain a luer-lock threaded fitting. Alternatively, the cannula connector  66   a ,  66   b  can be omitted, and depth markings (not shown) included along an exterior of the proximal region  64   a ,  64   b  that facilitate desired locating of the working end  62   a ,  62   b  relative to the corresponding cannula  22   a ,  22   b  as described below. 
     The working end  62   a ,  62   b  can include one or more components appropriate for forming a cavity or void within bone. For example, in some constructions, the working end  62   a ,  62   b  includes one or more expandable or inflatable members (e.g., a single balloon, multiple balloons, a single balloon with two or more discernable inflation zones, etc.) constructed to transition between a contracted (e.g., deflated) state in which the working end/balloon  62   a ,  62   b  can be passed through the corresponding lumen  44   a ,  44   b , and an expanded (e.g., inflated) state in which the working end/balloon  62   a ,  62   b  expands and compacts contacted cancellous bone. In this regard, a size and shape of the working end/balloon  62   a ,  62   b  can be predetermined and/or restrained with one or more additional components (not shown), such as internal and/or external restraints. Regardless, the working end/balloon  62   a ,  62   b  is structurally robust, able to withstand (e.g., not burst) at expected inflation pressures and when in contact with bone. Further, the first working end  62   a  and the second working end  62   b  can be identical or different. 
     For reasons made clear below, at least one, and in some embodiments both, of the working ends/balloons  62   a ,  62   b  are optionally exteriorly coated with a material adapted or tailored to resist bonding with the curable material being delivered to the vertebra  30 . The anti-sticking coating can assume various forms as a function of the selected curable material, and in some embodiments is a silicone coating. Other materials exhibiting adversion to bonding with bone cement are also envisioned, for example, polypropylene. In related embodiments, a thin-walled expandable sleeve constructed of the selected anti-sticking material (e.g., a polypropylene sleeve) can be disposed over the working end/balloon  62   a ,  62   b . Though not shown, one or both of the cavity-forming devices  20   a ,  20   b  can include a valve or similar component that operates to selectively seal the working end/balloon  62   a ,  62   b.    
     The cavity-forming devices  20   a ,  20   b  each further include one or more additional components connected or operable through the proximal region  64   a ,  64   b  for actuating the corresponding working end  62   a ,  62   b . By way of one non-limiting example, then, each of the cavity-forming devices  20   a ,  20   b  can include a source  68   a ,  68   b  of pressurized fluid (e.g., contrast medium) for inflating the balloon(s) carried or formed by the corresponding working end  62   a ,  62   b . A hand-held, syringe-type pump can be used as the pressurized source. In other embodiments, a single one of the sources of pressurized fluid  68   a  or  68   b  can be provided and employed to inflate both of the working ends/balloons  62   a ,  62   b  individually. 
     Where provided, the optional delivery tube  14  is sized for insertion within the lumens  44   a ,  44   b , and defines a distal tip  80  and a proximal section  82 . As described below, the delivery tube  14  can be employed to deliver curable material to the target site. Thus, the delivery tube  14  has an outer diameter that is smaller than a diameter of the lumens  44   a ,  44   b ; however, the outer diameter of the delivery tube  14  should not be so small as to allow curable material to readily travel around the outside of the delivery tube  14  and back into the corresponding cannula  22   a ,  22   b.    
     A cannula connector  84  is optionally coupled to, or formed by, the proximal section  82  of the delivery tube  14 . The cannula connector  84  is akin to the optional cannula connector  66   a ,  66   b  described above (e.g., combines with the selected handle connector  48   a ,  48   b  to form a locking mechanism), and thus can assume any of the forms previously described. Alternatively, the delivery tube  14 , where provided, can form depth markings (not shown) along the proximal section  82  that facilitates desired locating of the distal tip  80  relative to the cannula  22   a ,  22   b  during use. 
     The delivery tube  14  is configured for fluid coupling to the curable material source  16 . In some embodiments, a portion of the delivery tube  14  projects proximally beyond the optional cannula connector  84 , and is fluidly coupled to the curable material source  16 , for example via an injection connector  86 . Alternatively, auxiliary tubing  88  can be provided with the curable material source  16 , and fluidly connected to the delivery tube  14  via the optional cannula connector  84 . In yet other embodiments, the delivery tube  14  is omitted, and the curable material source  16  connected directly to the handle connector/proximal end  48   a ,  48   b  (e.g., the auxiliary tube  88  is connected to the connector  48   a ,  48   b ; or the tubing  88  eliminated and the curable material source  16  (e.g., a syringe) directly coupled to the connector  48   a ,  48   b ). 
     The curable material source  16  can assume various forms appropriate for delivering the desired curable material, and may typically comprise a chamber filled with a volume of curable material and employing any suitable injection system or pumping mechanism to transmit curable material out of the chamber and through the delivery tube  14 . Typically, a hand injection system is used where a user applies force by hand to an injector. The force is then translated into pressure on the curable material to flow out of the chamber. A motorized system may also be used to apply force. 
     While the system  10  has been described as including the single source of curable material  16 , in other constructions, a separate source of curable material  16  can be provided for each of the delivery assemblies  12   a ,  12   b . Similarly, two (or more) of the optional delivery tubes  14  can be included. Along these same lines, the system  10  can alternatively be configured such that the curable material source  16  is directly connected to one or both of the cavity-forming devices  20   a ,  20   b  (e.g., the elongated body  60   a  of the first cavity-forming device  20   a  can form or terminate at a nozzle proximate (e.g., distal) the working end  62   a  and through which the curable material can be directly dispensed). 
     Regardless of an exact configuration, the system  10  in accordance with principles of the present disclosure is highly useful in performing a wide variety of height restoration and bone stabilization procedures as part of an overall curable material delivery procedure. To this end,  FIG. 2A  illustrates initial use of the system  10  in restoring the height of, and delivering curable material into, a target site of a vertebra  100 . In general terms, the vertebra  100  includes pedicles  102   a ,  102   b  and a vertebral body  104  defining a vertebral wall  106  surrounding bodily material  108  (e.g., cancellous bone, blood, marrow, and soft tissue). The pedicles  102   a ,  102   b  extend from the vertebral body  104  and surround a vertebral foramen  110 . As a point of reference, systems of the present disclosure are suitable for accessing a variety of bone sites. Thus, while the vertebra  100  target site is illustrated, it is to be understood that other bone sites can be accessed and treated by the system  10  (e.g., femur, long bones, ribs, sacrum, etc.). 
     The first and second cannulas  22   a ,  22   b  are initially employed to form first and second access paths to first and second target site locations  120   a ,  120   b . For example, the cannulas  22   a ,  22   b  are inserted in a bipedicular fashion through respective ones of the pedicles  102   a ,  102   b  and into the bodily material  108 . The cannulas  22   a ,  22   b  provide access to the corresponding target site  120   a ,  120   b  at the open distal ends  42   a ,  42   b  thereof. One or more stylets (not shown) can be employed to assist in forming/accessing the target sites  120   a ,  120   b . For example, a series of differently-sized or configured (e.g., sharpened and blunt) stylets can be successively delivered through the respective cannula  22   a ,  22   b  to form a channel to the target site  120   a ,  120   b . Alternatively, or in addition, an outer guide cannula (not shown) can initially be deployed to form an access path for subsequent insertion of the cannulas  22   a ,  22   b.    
     Once the cannulas  22   a ,  22   b  are positioned within the bodily material  108  at the desired target sites  120   a ,  120   b , the cavity-forming devices  20   a ,  20   b  are assembled to the corresponding cannula  22   a ,  22   b . For example, and as shown in greater detail in  FIG. 2B , the elongated body  60   a ,  60   b  is slidably inserted within the corresponding cannula  22   a ,  22   b , with the respective working end  62   a ,  62   b  being distally advanced therethrough. More particularly, with configurations in which the working end  62   a ,  62   b  is a balloon or other expandable member format, the working end/balloon  62   a ,  62   b  is transitioned to a contracted state (e.g., deflated) so as to be slidably received through the lumen  44   a ,  44   b . The elongated body  60   a ,  60   b  is positioned relative to the corresponding cannula  22   a ,  22   b  such that the respective working end/balloon  62   a ,  62   b  extends distal the corresponding cannula distal end  42   a ,  42   b . For example, where the elongated body  60   a ,  60   b  includes depth markings as described above, the appropriate depth marking is aligned with the corresponding handle connector  48   a ,  48   b  ( FIG. 1 ), thereby ensuring that the working end/balloon  62   a ,  62   b  is fully deployed or extended beyond the corresponding cannula distal end  42   a ,  42   b . In other constructions, upon connection of the optional cannula connector  66   a ,  66   b  and the corresponding handle connector  48   a ,  48   b , the working end/balloon  62   a ,  62   b  is distal the corresponding distal end  42   a ,  42   b  and is positioned at the corresponding target site  120   a ,  120   b . Regardless, placement of the cavity-forming devices  20   a ,  20   b  can be performed simultaneously or consecutively. 
     As a point of reference,  FIG. 2C  provides a lateral view of the vertebral body  104  in which the first working end/balloon  62   a  has been deployed (and in the contracted state). As shown, the vertebral body  104  is fractured (referenced generally at  122 ) and thus exhibits a fractured height H F  that is less than a natural or native height H N  (designated generally). 
     With reference to  FIG. 3A , the cavity-forming devices  20   a ,  20   b  are operated to cause the corresponding working ends/balloons  62   a ,  62   b  to form first and second cavities or voids  124   a ,  124   b , respectively, in the bodily material  108 . For example, the working ends/balloons  62   a ,  62   b  can be expanded (e.g., inflated) substantially simultaneously. Alternatively, with embodiments in which a single inflation source  68   a  or  68   b  ( FIG. 1 ) is provided, the first working end/balloon  62   a  is initially inflated and then sealed in the expanded or inflated state. The inflation source  68   a  or  68   b  is then fluidly connected to the second working end/balloon  62   b  and operated to cause expansion thereof. Following expansion of the working ends/balloon  62   a ,  62   b , the expanded working ends  62   a ,  62   b  are both supporting the vertebral body  108 . In this regard, and as best illustrated in  FIG. 3B , expansion of the working ends/balloons  62   a ,  62   b  not only forms the cavities  124   a ,  124   b , but also restores or enhances a height of the fractured vertebral body  104 . More particularly, a restored height H R  is established that beneficially approximates the natural height H N . The restored height H R  may be the same as, slightly less than, or slightly greater than, the natural height H N  ( FIG. 2C ); regardless, the restored height H R  is greater than the fractured height H F  ( FIG. 2C ). 
     Returning to  FIG. 3A , the second cavity-forming device  20   b  is then operated to transition the second working end/balloon  62   b  from the expanded state to the contracted state (e.g., the second balloon  62   b  is deflated). In the contracted state of the second working end/balloon  62   b , the second cavity-forming device  20   b  can be removed from the second cannula  22   b  as shown in  FIG. 4A . Subsequently, and with reference to  FIG. 4B , the optional delivery tube  14  is disposed within the second cannula  22   b , and the source of curable material  16  ( FIG. 1 ) operated to deliver curable material  130  into the second cavity  124   b . With other constructions, the delivery tube  14  is omitted and the curable material  130  is delivered to the second cavity  124   b  directly through the second cannula  22   b . Once a desired volume of the curable material  130  has been delivered to the second cavity  124   b , the delivery tube  14  (where provided) and optionally the second cannula  22   b  are removed from the patient. Throughout this portion of the procedure, the first working end/balloon  62   a  remains expanded and in place, maintaining the vertebral body  104  at the restored height H R  ( FIG. 3B ). It will be understood that it is equally acceptable to reverse the order and instead initially fill the first cavity  124   a  with the curable material  130  (i.e., the first cavity-forming device  20   a  removed from the vertebral body  104  while the second working end/balloon  62   b  remains in place during subsequent dispensement of the curable material  130  into the first cavity  124   a ). 
     Once the curable material  130  within the second cavity  124   b  has sufficiently hardened or cured, the second cannula  22   b  can be removed and the first working end/balloon  62   a  is transitioned from the expanded state to the contracted state (e.g., the first balloon  62   a  is deflated) as shown in  FIG. 5 . In this regard, the hardened, curable material  130  in the second cavity  124   b  supports and maintains the vertebral body  104  at the restored height H R  ( FIG. 3B ) while the first working end/balloon  62   a  is transitioned (e.g., deflated). Further, the optional anti-sticking coating on the first working end/balloon  62   a  resists bonding with the curable material  130  delivered to the second cavity  124   b  such that the hardened curable material  130  in the second cavity  124   b  will not prevent the first working end/balloon  62   a  from deflating should the curable material  130  come into contact with an exterior of the first working end/balloon  62   a . Regardless, in the contracted state, the first cavity-forming device  20   a  can be removed from the patient, and is optionally replaced with the delivery tube  14 . Finally, as shown in  FIG. 6 , curable material  132  is delivered into the first cavity  124   a  (either through the optional delivery tube  14  or directly through the first cannula  22   a  with embodiments in which the delivery tube  14  is omitted). 
     Systems and methods in accordance with the present disclosure provide a marked improvement over previous designs and techniques. By inflating and dispensing curable material in a step-wise fashion, the height of a fractured vertebral body (or other bone site of interest) can be restored and retained. 
     Although the present disclosure has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present disclosure.