WO2005079684A1

WO2005079684A1 - Methods and devices for treating bone fractures and disease

Info

Publication number: WO2005079684A1
Application number: PCT/US2005/003954
Authority: WO
Inventors: Robert M. Scribner
Original assignee: Crosstrees Medical Inc.
Priority date: 2004-02-14
Filing date: 2005-02-09
Publication date: 2005-09-01

Abstract

The present invention relates to devices and methods for treating bones and associated soft-tissue support structures suffering from fractures and/or diseases. More specifically, the present invention relates to devices and methods for repairing, reinforcing and/or treating the human spine and associated support structures using various devices, including minimally-invasive distraction, cavity-forming and disk removal/repair/replacement devices.

Description

METHODS AND DEVICES FOR TREATING BONE FRACTURES AND DISEASE

Cross-Reference to Related Application This application claims the benefit of pending United States provisional patent application number 60/544,797 filed February 14, 2004. Field of the Invention The present invention relates to devices and methods for treating bones and associated soft-tissue support structures suffering from fractures and/or diseases. More specifically, the present invention relates to devices and methods for repairing, reinforcing and/or treating the human spine and associated support structures using various devices, including minimally- invasive distraction, cavity- forming and disk removal/repair/replacement devices.

Background of the Invention The healthy human spine is an intricate framework of bones and connective tissues which desirably supports the upper body and withstands the various physiological loads experienced by an individual during his or her normal daily activities. However, unusually high loading of the spine (such as trauma, repetitive heavy physical labor or the effects of sports or other intense physical activities), or loading of a weakened spine (where disease, neglect or medical treatment has reduced the strength of the bones and/or connective tissues to below the level necessary to withstand normal physiological loads - including osteoporosis, bone cancer, arthritis, various treatments causing elevated steroid levels, as well as the excessive use of alcohol and/or tobacco), can cause significant damage to the spinal anatomy. Such spinal damage can have extremely disastrous consequences, including death, paralysis, permanent disability, disfigurement and/or intense pain. While current treatment regimens for damaged and/or weakened spinal bones and cushioning/connective tissues are improving, spinal surgery is still a very invasive procedure and causes significant trauma to the patient. According to generally accepted surgical practice, it is typically necessary to cut or otherwise distract (and generally further damage) the connective structures covering the spine itself in order to access the bones and supporting soft-tissue structures of the human spine. These connective structures, which are critical for proper spinal stability, cannot be immediately repaired once the surgery is completed, but rather often take months or even years (if ever) to heal. In fact, it is often the case that the surgical procedure itself will cause more harm and/or pain to the patient than the injury itself, which is why many patients prefer to live with existing spinal pain and injuries rather than go through the rigors and subsequent rehabilitation of a surgical procedure. Moreover, even where surgery is attempted and is successful, the patient will often suffer ill effects from the invasive surgical procedure for weeks or months, and may not regain their full strength for years, if ever. Two surgical techniques have been recently developed in an attempt to treat fractured spinal bones in a minimally-invasive procedure. One of these techniques, vertebroplasty, involves the injection of a flowable reinforcing material, usually polymethylmethacrylate (PMMA - commonly known as bone cement), through an 11 -gage spinal needle into an injured vertebral body. Shortly after cement injection, the liquid filling material polymerizes and increases in hardness, desirably supporting the vertebral body internally, alleviating pain and preventing further collapse of the injected vertebral body. In a modification of the vertebroplasty procedure, the posture of the patient is preferentially aligned by the use of external cushions or bolsters applied to pelvis and shoulder regions of the supine patient. This anatomic position attempts to decrease the compression of the injured vertebral body prior to the vertebroplasty procedure. Another technique for treating vertebral fractures, kyphoplasty, is a more recently developed modification to the vertebroplasty technique. In a kyphoplasty procedure (also known as balloon-assisted vertebroplasty), an expandable device is inserted inside the damaged vertebral body, and is then expanded within the bone. Desirably, this procedure creates a void within the bone that can be filled with bone cement or other load bearing material, rendering the fractured bone load-bearing. In effect, the procedure creates an internal "cast," protecting the bone from further fracture and/or collapse. A further technique for treating vertebral fractures is a more recently developed modification to the kyphoplasty technique. In the further modified procedure a curette is inserted to the balloon formed cavity. The curette is applied to the cancellous bone at the margins of the cavity to further fracture the cancellous bone. This fracture of cancellous bone allows further volume expansion of the balloon, or directional control of the placement of added balloon volume in the direction of the fracture formed by the curette.

Desirably, this procedure creates a greater void within the bone that can be filled with bone cement or other load bearing material, rendering the fractured bone load-bearing. The curette fracture desirably allows greater restoration of normal vertebral anatomy. While vertebroplasty and kyphoplasty have both been shown to reduce some pain associated with vertebral compression fractures, both of these procedures have proven inadequate to reliably and repeatedly restore vertebral body anatomy or treat the vast majority of spinal fractures, especially high velocity spinal fractures. Moreover, these treatments cannot be used to treat injuries to connective tissues such as the intervertebral disks.

Summary of the Invention The present invention overcomes many of the problems and disadvantages associated with current medical procedures for repairing, reinforcing and/or treating a weakened, diseased and/or fractured spinal column. In one general embodiment of the present invention, the invention includes the recognition of the need for minimally-invasive devices and methods which facilitate the safe and effective physical distraction of injured spinal segments during surgical treatment. In various preferred embodiments, the present invention may be used in concert with various minimally invasive surgical procedures, including both vertebroplasty and kyphoplasty, as well as with various joint repair/replacement techniques and devices (including those appropriate for use with intervertebral discs and/or facet joints) or more open surgical tools and techniques. In one general embodiment, the present invention comprises surgical methods and tools for the (1) reduction of the compressive loading on a fractured vertebral body, (2) distraction of the end plates of vertebral bodies (adjacent to or distant from the fractured vertebral body) - thereby increasing the distance between those distracted endplates, (3) restoration of the height of the fractured vertebral body by inflatable bone tamp reduction, curette elevation, or manual distraction using existing techniques, (4) restoration of the mechanical integrity of the fractured vertebral body by placement of a structural material capable of withstanding compressive loading (either immediately or due to natural healing over time) in the spine, and (5) removal of all surgical instruments, including the distraction devices. Desirably, this procedure will be accomplished through small surgical incisions. More desirably, this procedure will be accomplished using minimally-invasive (non- open) techniques. Most desirably, this procedure will be accomplished percutaneously with minimal damage to the patient, thereby permitting the patient to return to a normal level of activity within one or two days after surgery, and potentially even ambulate immediately after the surgical procedure. hi another general embodiment of the present invention, the invention comprises surgical methods and tools for the (1) reduction of the compressive loading on an injured intervertebral disk of the spine, (2) distraction of the end plates of the adjacent vertebral bodies (to the damaged disk) - thereby increasing the distance between those distracted bodies and relieving compressive loading of the disk, as well as potentially creating a cavity within the disk space, (3) removal, repair and/or replacement of the injured disk through less-invasive means, including Intradiscal Electrothermal

Annuloplasty (IDET), insertion of a polymer, hydrogel, or other artificial disc nucleus, insertion of an artificial disc, injection of protein polymer for disc reconstruction, inflatable bone tamp reduction, curette elevation, or manual distraction using existing techniques, (4) restoration of the integrity of the spinal column tlirough disk fusion, disk implants (flexible or inflexible) or disk replacement devices mimicking the spinal motion segment, and (5) removal of all surgical instruments. Desirably, this procedure will be accomplished tlirough small surgical incisions. More desirably, this procedure will be accomplished using minimally-invasive (non-open) techniques. Most desirably, this procedure will be accomplished percutaneously with minimal damage to the patient, thereby permitting the patient to return to a normal level of activity within one or two days after surgery, and potentially even ambulate immediately after the surgical procedure. In another general embodiment of the present invention, the invention comprises surgical methods and tools for the (1) reduction of the compressive loading on an injured segment of the spine (the injured segment including a damaged vertebral body and damaged superior and inferior intervertebral disks adjacent the damaged body), (2) distraction of the vertebral bodies superior and inferior to the damaged segment - thereby increasing the distance between those distracted bodies and relieving compressive loading of the injured spinal segment, (3) removal, repair/reconstruction and/or replacement of the injured vertebral body, (4) removal, repair/reconstruction and/or replacement of injured intervertebral disks, (5) restoration of the integrity of the injured spinal segment using various devices and techniques previously disclosed, and (6) removal of all surgical instruments. Desirably, this procedure will be accomplished through small surgical incisions. More desirably, this procedure will be accomplished using minimally-invasive (non- open) techniques. Most desirably, this procedure will be accomplished percutaneously with minimal damage to the patient, thereby permitting the patient to return to a normal level of activity within one or two days after surgery, and potentially even ambulate immediately after the surgical procedure. In another general embodiment of the method and devices of the present invention, a mechanical distraction device is attached to two vertebral bones in a patient's spine, these bones being located above and below an injured region of the spine. The attachment devices can comprise pedicle anchoring devices, and are inserted via trans-pedicular accesses into the targeted vertebral bones. The proximal ends of these devices are then connected to a distraction element, which distracts the vertebral bones apart from the area of trauma, desirably reducing, eliminating and/or reversing compressive loading of the spine in the injured area. The injured area of the spinal column is then treated using one or more treatment approaches or techniques, including minimally-invasive distraction and/or bone repair techniques (such as kyphoplasty and vertebroplasty), open surgical techniques (such as vertebral body repair using curettes as well as bone replacement and implants), and vertebral disk/facet joint repair and replacement. The distraction and subsequent repair of the injured level(s) will significantly restore the spinal column's ability to withstand compressive and torsional loading, through a minimally-invasive surgical procedure. The distraction element and anchoring devices can then be removed after surgery (if spinal stability is restored), or can remain in position in the patient to facilitate natural healing of the injured level(s), or to allow for bone filling materials to develop suitable mechamcal strength by means of time dependent chemical or healing processes. In a similar manner, other general embodiments of the method and devices can be utilized to treat an injured disk of the spine. In one such embodiment, the attachment devices are attached to vertebral bones locate above and below the injured disk segment. The attachment devices are inserted by trans-pedicular accesses into the targeted vertebral bones. The proximal ends of the devices are then connected to a distraction element, which distracts the vertebral bones apart from the area of trauma, thereby reducing and/or eliminating compressive loading on the injured area. The damaged disk material can then be removed and/or repaired through conventional techniques, and a disk replacement introduced, or disc repair material applied if necessary. Once the damaged disk is capable of handling compressive loading (such as where the disk replacement can bear compressive loads or natural healing has taken place, or chemical processes for disc repair materials have completed), the distraction element and the attachment devices can be removed. In another general embodiment of the disclosed method and devices, simultaneous or sequential treatment of injured bone(s) and disk(s) can be accomplished utilizing the teachings of the present invention. One embodiment of a distraction element constructed in accordance with the teachings of the present invention will be substantially located outside of the patient's body, with only a portion of each of the anchoring devices secured to the targeted bones through the skin and soft tissues. Distraction of the anchoring devices (due to manipulation of the distraction element) will distend soft tissues while distracting the vertebral levels apart, thereby accomplishing the distraction goal of the present invention without requiring removal/disruption of overlying skin or soft tissues. Once the surgical technique is completed, and the distraction element is no longer required or desired, the distraction force can be released and the anchoring devices removed from the patient, h this manner, the present invention obviates the need for a large incision and significant damage and disruption to the connective tissues of the spinal column. The use of radio graphic imaging to precisely determine vertebral body position and alignment, in combination with further distraction or adjustment of the alignment, allows more precise anatomic reconstruction than conventional open surgical technique which is limited to direct visualization of the posterior vertebral body elements. Further embodiments of the present invention facilitate distraction of the upper and lower levels in a deliberate and controlled manner. Depending upon the type of injury and the desired treatment goals, differing amounts and types of distraction may be desired. For example, it may be desirous to distract the anterior regions of the spinal column to a differing degree than the posterior regions for a given surgical technique, such as the treatment of compression fractures or degenerative disc disease, hi another embodiment, it may be desirous to provide anterior distraction - to remove compressive loads on the anterior spinal column (allowing repair of anterior spinal elements such as the fractured vertebral body) - followed by longitudinal translation - to distract the posterior longitudinal ligament (allowing repair of spinal disc elements). Other treatment regimens, such as the treatment of trauma, might necessitate different distraction techniques, hi certain instances, a physician may wish to completely immobilize the injured sections of the spinal column during distraction, especially where the posterior wall of the vertebral bone is compromised, nerve integrity is in danger, or the intervertebral facet joints have been injured or compromised. Moreover, depending upon the stage of the surgical procedure, differing amounts and types of distraction may be required to accomplish the specific goals of specific portions of the surgical procedure, hi addition, alteration of the amount or type of distraction during the surgical procedure may simplify, accelerate and/or improve the surgery and its eventual outcome. Various embodiments of the present invention allow for such alteration of the distraction in a controlled and deliberate manner. A further embodiment of the present invention may be used to facilitate computer controlled and/or guided surgical procedures. Because the devices of the present invention are secured to the bones of the spinal column, they are well suited to be used as reference points and/or assistive devices for various computer controlled and/or assisted surgical system and tools, including computer aided guidance and mapping equipment such as the systems commercially available from manufacturers such as BrainLab Corporation, General Electric Corporation, or other manufacturers of image guidance systems using X-ray, computed tomography, magnetic resonance imaging, or other medical imaging technologies. Further embodiments of the present invention comprise the use of bone filling materials which are capable of withstanding compressive loading once introduced into the spinal column,, fiowable materials which set to a hardened condition, fiowable materials which cure to higher durometer properties, bone fillers that increase in strength due to natural healing, bone fillers which are osteoconductive or osteoinductive, autograft or allograft bone, as well as bone fillers which increase in volume (expanding or foaming agents) upon introduction into the cancellous bone of the vertebral body or surgically created bone cavity. Other objects, advantages, and embodiments of the invention are set forth in the description which follows, will be obvious from this description, or may be learned from the practice of the invention.

Brief Description of the Drawings FIG. 1 is a cross-sectional side view of a spinal segment showing an injured vertebral body and associated injured intervertebral disks; FIG. 2 is a top plan view of the vertebral body of FIG. 1; FIG. 3 is a cross-sectional side view of the spinal segment of FIG. 1, showing an insertion device utilized in one embodiment of the present invention; FIG. 4 is a cross-sectional side view of the spinal segment of FIG. 3; depicting a further step of one embodiment of the present invention; FIG. 5 is a cross-sectional side view of the spinal segment of FIG. 4; with percutaneous guidewires placed in accordance with the teachings of the present invention; FIG. 6 is a cross-sectional side view of the spinal segment of FIG. 5; showing advancement of anchoring devices in accordance with one embodiment of the present invention; FIG. 7 is a cross-sectional side view of the spinal segment of FIG. 6; with anchoring devices implanted in accordance with one embodiment of the present invention; FIG. 8 is a top plan view of one embodiment of a distraction element constructed in accordance with the teachings of the present invention; FIG. 9 is a cross-sectional side view of the spinal segment of FIG. 7, showing attachment of the embodiment of the distraction element of FIG. 8 to the anchoring devices; FIG. 10 is a cross-sectional side view of the spinal segment of FIG. 9, with the distraction element in one desired position prior to distraction; FIG. 11 is a cross-sectional side view of the spinal segment of FIG. 10, with the embodiment of the distraction element manipulated in a desired manner to distract the injured portion(s) of the bone and disk(s); FIG. 12 is a cross-sectional side view of the distracted spinal segment of FIG. 11, with an access cannula leading through skin and soft tissue into a cavity created within the injured bone; FIG. 13 is a cross-sectional side view of the spinal segment of FIG. 12, with the access cannula removed and the cavity filled with a suitable bone filling material; FIG. 14 is a cross-sectional side view of the spinal segment of FIG. 13, with the embodiment of the distraction element and anchoring devices removed and all bone cavities filled with suitable bone filling materials; FIG. 15 is a cross-sectional side view of a spinal segment showing an alternate embodiment of a distraction element constructed in accordance with the teachings of the present invention; and FIG. 16 is a top plan view of an alternate embodiment of a distraction element constructed in accordance with the teachings of the present invention.

Description of the Invention As embodied and broadly described herein, the present invention is directed to surgical methods and associated tools for repairing, reinforcing and/or treating weakened, diseased and/or fractured spinal columns. In accordance with the teachings of the present invention, the primary goal of vertebral body and/or disk replacement or repair is the restoration of the spine's ability to withstand normal physiological loading. Another objective is to accomplish such restoration through minimally-invasive procedures, desirably minimizing the amount of pain and suffering the patient will experience during the surgery and subsequent rehabilitation process. A third objective is to restore the normal anatomical features of the spine, including the normal anatomical size and shape of the vertebral bodies as well as the articulating motion of the injured spinal segment. The present invention is also directed to various devices for facilitating such surgical methods. It should be understood, however, that the various disclosed embodiments could be used in association with the treatment of various other bones and joints within the human body, with varying results, including (but not limited to) the knee, wrist, hip, shoulder and/or ankle joints. FIG. 1 depicts a segment of a typical human spine 1, in which injuries to a vertebral bone 10 and associated vertebral disks 15 and 20 have occurred.

The injury has caused the top and bottom plates 25 and 30 of the bone 10 to depress generally towards the center of the vertebra and away from a pre- fracture, normally parallel orientation, decreasing the anterior vertebral height, hi a similar manner, the upper and lower intervertebral disks 15 and 20 have been damaged to some extent, with the anterior walls of these disks bulging in the anterior direction, with disruption of the annulus and nucleus pulposus. Disruption of the disc may occur in a lateral or posterior direction depending upon the cause of injury and anatomy of the individual. FIG. 2 depicts a coronal (top) view of the damaged vertebra of FIG. 1. Vertebra 10 includes a vertebral body 50, which extends on the anterior (i.e. front or chest) side of the vertebra 10. Vertebral body 50 is approximately the shape ofan oval disk, with an anterior wall 60 and a posterior wall 65. The geometry of the vertebral body 50 is generally symmetric. Vertebral body 50 includes an exterior formed from compact cortical bone 70. The cortical bone 70 encloses an interior volume of reticulated cancellous, or spongy, bone 75 (also called medullar bone or trabecular bone). The spinal canal 80 is located on the posterior (i.e. back) side of each vertebra 10. The spinal cord 85 passes through the spinal canal 80. A vertebral arch 90 surrounds the spinal canal 80. Left and right pedicles 95 of the vertebral arch 90 adjoin the vertebral body 50. The spinous process 100 extends from the posterior of the vertebral arch 90, as do the left and right transverse processes 105 and the mamillary processes 110. Current medical practice for repairing a spinal bone injury caused by trauma, especially one involving significant damage to the anterior or lateral walls of the vertebral body, a posterior fracture threatening the spinal cord, or damage to the facet joints 115, would be for the physician to create a large incision midline on the patient's back. This incision would extend from one or two vertebral levels above the damaged vertebral body and disks to one or two levels below the injured body and disks. The physician would then cut and/or distract the muscles and connective tissues as well as any other soft tissues exposed by the incision, eventually exposing the injured area of the spinal column as well as the adjacent upper and lower vertebral level(s) (this technique is generally referred to as an "open" surgical procedure). The physician would then perform desired surgical procedures (to remove and/or repair the damage region(s) through the opened incision), and then typically install hardware (generally consisting of rods, screws and possibly plates) designed to stabilize the injured area, maintain the position of the adjacent levels relative to the injured level, and/or promote fusion of the damaged level of the spine to the next adjacent upper and lower levels (or potentially fuse even more levels). The soft tissues would then be set back into place, the incision closed, and the surgery would be completed. Due to the invasive nature of this surgical procedure, as well as the effects of the original injury itself, the patient would then typically be bed-ridden for an extended period of time. In contrast, the spinal repair procedure of the present invention can be performed on an outpatient or inpatient basis by a medical professional properly trained and qualified to perform the disclosed procedures. Desirably, the patient will be placed under either general or local anesthetic for the duration of the surgical procedures and the procedure will be accomplished in a minimally invasive manner. Upon completion of the surgical procedure, the stability of the spinal column will desirably be restored, and the patient will undergo a very limited healing process or be able to ambulate virtually immediately.

PLACING THE DISTRACTION ANCHORS Referring back to FIG. 1, the injured section of the spinal column, containing the damaged vertebral body and disks, is flanked by an immediately adjacent upper vertebral bone 100 (hereinafter referred to as the "upper level") and the immediately adjacent lower vertebral bone 110 (hereinafter referred to as the "lower level"). Desirably, both the upper and lower levels 100 and 110 are fully intact, with the damaged level(s) located between. The damaged level may be injured as a result of trauma or degenerative diseases including osteoporosis or malignant neoplasms. As best seen in FIG. 3, a pedicle of the upper level 100 is desirably located by the physician and a spinal needle 130 is inserted through the skin 120 and soft tissues to the pedicle of the upper level 100 in a known manner. The needle 130 is preferably comprised of a strong, non-reactive, and medical grade material such as surgical steel (for example, an eleven gauge biopsy needle commercially available from Becton Dickinson & Co of Franklin Lakes, NJ). If desired, the needle is attached to a manipulating assembly (not shown) which can be comprised of a non-reactive and medical grade material including, but not limited to, thermoelastic or thermoset plastics or surgical steel. While the disclosed spinal needle is an 11 gage surgical needle, it should be understood that various size needle assemblies, including needles of six to 14 gage, could be used with the devices and methods of the present invention, with varying results. The initial approach to the vertebral body may also be performed using a rigid metal tool of small diameter such as a guide wire or K-wire. During insertion, the location of the needle is desirably monitored using various visualization equipment such as real-time X-Ray, CT scanning equipment, MRI, or any other monitoring equipment commonly used by those of skill in the art, including computer aided guidance and mapping equipment such as the systems commercially available from BrainLab Corporation or General Electric Corporation. The needle 130 is inserted tlirough the skin 120 and soft tissues of the back and into the targeted vertebral body via a transpedicular approach (through the pedicle). While various other approaches could be used, including lateral, extrapedicular and/or anterior approaches, depending upon the level treated and/or intervening anatomical features well known to those of ordinary skill in the art, the transpedicular access is most desired in the present embodiment as the pedicle can easily be visualized using a fluoroscope or real-time CT scan, the trans-pedicular access is relatively easy to accomplish for a trained physician, and the pedicle and vertebral body desirably provide a very secure anchoring location for the anchoring devices. Desirably, the trabecular and cancellous bone of the pedicle, as well as the trabecular and cancellous bone of the vertebral body, will provide the most secure anchorage to permit significant distraction forces to be transmitted to the spinal segment. The spinal needle 130 is advanced tlirough the pedicle into the targeted vertebral body. A guide- wire or K-wire 180 may then be then introduced into the vertebral body through a lumen (not shown) in the needle 170, and the spinal needle 130 removed in a known manner. This procedure may be repeated for each pedicle of the upper and lower levels 100 and 110, as desired. See FIGs. 4 and 5. As best shown in FIGs. 6 and 7, an anchoring device 205, such as a cannulated threaded screw can then be advanced over the K-wire 180, and the distal, threaded tip 206 of each screw is advanced through the target pedicles and secured into the vertebral bones of the upper level 100, with the proximal end 207 of the screw extending through the soft tissues overlying the spine and out through the patient's skin 120. Desirably, the anchoring device will have a cross-section which is small enough to limit soft-tissue damage and allow safe transit through the pedicle, but large enough to transmit significant forces without screw fracture or significant deformation, thereby allowing distraction of the upper level 100 in accordance with the teachings of the present invention. Desirably, the anchoring device will have a diameter of 5.0 mm to 9.0 mm, with a length of 100 mm to 300 mm. More desirably, the anchoring device can comprise a body having a diameter of approximately 6.5 mm and a length of approximately 200 mm. Various embodiments of the anchor device may include a center lumen for insertion over a K-wire, or a threaded distal section for secure attachment to the bone. In a similar manner, an anchoring device is similarly secured into and tlirough one or more of the pedicles of the lower level 110. THE DISTRACTION ELEMENT In accordance with the teachings of the present invention, a distraction element 300 (see FIGs. 8 and 9), comprising a suitable compression distraction mechanism, is then positioned over or around the proximal ends 207 of the anchoring devices 205. As best shown in FIG. 8, the distraction element comprises a central adjustable link 305 having an internally-threaded bore 307. The device further includes an upper arm 310 and a lower arm 315, each arm having a corresponding proximal eye 320, a body 322 and a threaded distal shank 325. The threaded shanks 325 are threaded into the bore 307, creating an adjustable length device with an eye 320 at either end of the element 300. A handle 309, located on the exterior surface of the link 305, facilitates rotation of the link 305 in a clockwise or counter-clockwise direction and can be textured to be manipulated by the physician's hand, or a surgical wrench or the like. Each eye 320 is desirably sized to accommodate the distal ends 207 of each anchoring device 205, and desirably the element 300 can be slid over the ends 207 of the devices 205 and positioned flush to the patient's skin 120. If the element requires adjustment to its length H during such installation, the central link 305 may be rotated to alter the distance between the eyes 320. If desired, each eye 320 may incorporate a locking mechanism or set screw (not shown) to secure the eye to the device 205 and prevent further lateral motion. If desired, each eye 320 may include an opening (not shown) to allow placement of the element to the anchoring device laterally, not requiring placement over the proximal end of the anchoring device. The orientation of the eye 320 to the upper arm 310 and a lower arm 315 maybe variable to accommodate various angles of entry of the anchoring device to the pedicles, and varying relative position and angles of the anchoring devices placed to the upper level and lower level. Each upper arm 310 and lower arm 315 may include an angle relative to central link 305 (not shown). The angle in the upper arm 310 and lower arm

315 moves the central link further lateral from the midline of the spine. This lateral position places the central link and distraction assembly lateral to the injured vertebra when viewed in an anterior to posterior imaging projection, allowing improved imaging views and surgical access to the injured vertebra. DISTRACTION Once the element has been properly positioned (See FIG. 10), the element may be manipulated to safely and effectively distract the injured area. In one embodiment, shown in FIG. 11, rotation of the central adjustable link 305 shortens the length of the element 300 to the length H, which in this example is approximately equal in length to the normal anatomical distance "A" between the facet joints of the upper and lower level 100 and 110. Where the facet joints 115 are intact, and are capable of withstanding the resulting compressive loading induced by the element 300 and anchors 205, the injured vertebral body 10 and vertebral disks 15 and 20 may be distracted and separated in a controlled and desired manner. Desirably, the soft tissues and skin 120 through which the screws 205 extend will permit such distraction to occur by compression and/or stretching (distending), allowing the spinal column in the injured area to be distracted to varying degrees without requiring the removal and/or significant disruption to these tissues overlying such injured areas. Such distraction can reduce, eliminate or reverse localized compressive loading experienced by the injured level during the remainder of the surgical procedure, and may similarly be used to realign the injured level(s) in a desired fashion. Desirably, such distraction will be monitored using fluoroscopy or other non-invasive monitoring methods, to ensure that desired anatomic position and alignment of the vertebra is achieved.

TREATMENT OF THE INJURED TISSUES In accordance with the teachings of the present invention, once the surgical site has been prepared by distracting the upper and lower levels in the previously-described manner, the damaged vertebral body and/or disk is then easily repaired and/or replaced using minimally invasive techniques including but not limited to bone repair using bone cement or calcium phosphate or calcium sulfate, disc nucleus replacement, disc arthroplasty, or protein polymer injection to the damaged disc. At the conclusion of the surgical procedure, when the stability and load-bearing capability of the patient's spine has been restored, the distraction hardware is removed, and the patient is able to ambulate very quickly with little or no discomfort from the surgery itself. By minimizing the amount of soft tissue damage required to access the damaged areas, and allowing for repair of the spinal column in a minimally- invasive manner, the present invention eliminates the need for extended bed rest and long recovery times for the patient. Desirably, the distraction device will be capable of generating a distraction force in excess of one pound of force. The distraction device will be capable of generating a distraction force suitable to the body mass of the injured patient, including a range of up to 80% of body weight, which can correspond to normal load bearing in the anterior spinal column. The range of distraction force may vary from one to 300 pounds of distraction force (and may be significantly in excess of the patient's body weight if so desired). If desired, the element 300 can incorporate force measurement devices, such as stress/strain gages and/or load cells (not shown), which allow the physician to determine the exact amount of force used to distract the targeted tissues.

Similarly, the element can incorporate indexing marks to inform the physician of the exact length of the components and distance of distraction without requiring an additional external measuring device. Once the injured area has been distracted and positioned for surgery, the physician has various options for treating the injured areas. The physician may perform a percutaneous access and repair procedure on the injured bone and/or disk (possibly an injection of stabilizing bone repair material - through a vertebroplasty, kyphoplasty, or other procedure - or a minimally invasive repair of the damaged disk nucleus). VERTEBRAL BODY REPAIR If the injury to the bone is more extensive, or the bone has been significantly compressed, the physician may choose to perform a kyphoplasty or kyphoplasty-like procedure to repair the fractured bone, hi one embodiment of the present invention, the surgical method could comprise inserting one or more inflatable devices percutaneously into the injured vertebral bone(s), through a targeted area of the back, h addition, various other instruments, such as those described in U.S. Patent Nos. 4,969,888, 5,108,404, 5,827,289, 5,972,015, 6,048,346 and 6,066,154, the disclosures of which are all incorporated herein by reference, could be used in accordance with the teachings of the present invention, with varying results. A cavity- forming device, which is comprised of a biologically compatible and medically acceptable material, can be a small mechanical tamp, reamer, hole punch, balloon catheter or any appropriate device which is capable of displacing cancellous bone. Once the cavity-forming device is positioned within the vertebral body, it is used to displace cancellous bone, thereby creating a cavity. Once in a desired position within the injured vertebral body, the balloon catheter may be filled with a pressurized filling medium appropriate for use in medical applications including, but not limited to, air, nitrogen, saline or water. In a preferred embodiment, the filling medium is a radiopaque fluid (such as Conray® fluid available commercially from Mallinkrodt, Inc., of St. Louis, MO), which allows the physician to visualize the catheter during inflation. If desired, alternate ways of creating a cavity within the vertebral body, including mechamcal expanders, jacks, expanding springs and/or expanding agents, could be used. Desirably, the removal of the compressive loading on the injured bone (by virtue of the distraction element and anchor devices) will further facilitate movement of cortical bone in response to expansion of the catheter (or other expanding structure). Unlike presently-performed vertebroplasty and kyphoplasty procedures, the present invention permits reduction or elimination of the compressive loading on some or all of the injured bone(s), and increased volume of the compressed disc or vertebral body, thereby greatly improving the opportunity to move surrounding cortical bone and restoring some or all of the original vertebral body height. Accordingly, the disclosed cavity forming device(s) may further be used to displace cortical bone, if necessary. Once a cavity has been created and the cavity-forming device is removed (see FIG. 12), bone filler can be introduced into the vertebral body using any type of plunger, extruder and/or feed line assembly compatible with the surgical procedure. See, for example, U.S. Patent No. 6,641,587, the disclosure of which is incorporated herein by reference. If desired, a portion of the balloon catheter could be temporarily or permanently left within the injured vertebral body. For example, after cavity formation and removal of the inflation medium, a balloon catheter used to create the cavity could be refilled with bone filler and left within the vertebral body as a permanent or semi-permanent implant. Alternatively, the inflation medium itself could comprise bone filler. After the balloon catheter is filled with such an inflation medium, at least a portion of the catheter could be left permanently within the cavity. In an alternate embodiment, the catheter which is intended to remain with the cavity could comprise a bio-absorbable material and/or fabric/mesh material as the expandable structure. In one embodiment of the present invention, after cavity formation, the cavity-forming device can be removed from the injured vertebral body and an amount of a material, such as a bone filler, is introduced into the cavity within the injured vertebral body under low pressure. Desirably, introduction of the bone filler will continue until the cavity is completely filled and/or the physician determines that sufficient bone filler has been injected into the bone. If desired, the physician can utilize the cavity-forming device to create additional cavities for bone filler, or complete the procedure by removal of the distraction instruments. The bone filler could be any appropriate filling material used in orthopedic surgery, including, but not limited to, allograft or autograft tissue, hydroxyapatite, epoxy, PMMA bone cement, or synthetic bone substitutes

such Osteoset® from Wright Medical Technology, medical grade plaster of

paris, Skeletal Repair System (SRS ) cement from Norian Corporation, or

Collagraft from Zimmer. As bone filler is introduced into the vertebral body, the introduction is desirably monitored by x-ray fluoroscopy, or any other appropriate monitoring device or method, to ensure that bone filler does not flow outside of the vertebral body. To facilitate visualization, the bone filler may be mixed with a fluoroscopic agent, such as radiopaque barium sulfate. In another embodiment, the bone filler could comprise a mixture of bone cement and a thixotropic material which desirably limits and/or prevents extravazation of the bone cement. By creating one or more cavities within the cancellous bone, the cavity-forming devices of the present invention desirably create preferred flowpaths for the bone filler. In addition, the cavity-forming devices can also desirably close and/or block other natural flowpaths out of the cavity, such as veins and/or cracks in the cancellous bone. Moreover, methods and devices disclosed herein can be used to manipulate bone filler already introduced into the bone. Thus, the present invention reduces opportunities for cement leakage outside of the vertebral body and/or improves the distribution of bone filler throughout significant portions of the vertebral body, hi addition, the creation of cavities and desired flowpaths described in the present invention permits the placement of biomaterial more safely, under greater control and under lower pressures. INTERVERTEBRAL DISK TREATMENT In a similar manner, the present invention facilitates the treatment of one or more damaged intervertebral disks, either alone or in concert with the damaged vertebral body. By placement of the distraction elements to the vertebral bodies, and distracting the vertebra by the methods herein described, the disc space can be enlarged, and the distance between vertebra increased. Where the disk damage is severe, and the load-bearing capacity of the spine has been significantly compromised, the physician may choose to remove some or all of the injured material and either (1) fuse the vertebral bones across the injured disk, or (2) replace some or all of the injured disc with an artificial motion segment. Where the physician desires to induce a fusion across the damaged disc, the physician may first choose to remove some or all of the injured disk tissue using minimally invasive access tools and arthroscopic cutters/rongeurs, and subsequently insert one or more fusion elements (such as a threaded fusion cage or a cortical bone dowel) into the disk space in a known manner, such as described in U.S. Patent No. 5,609,636, the disclosure of which is incorporated herein by reference. Once the fusion elements have been properly positioned, the distraction element and anchoring devices can then be removed in the previously-described manner. If the physician desires to maintain the motion segment of the affected level, an artificial disk implant may be used. For example, the physician may utilize the disk replacement system described in United States Patent No. 6,443,988, assigned to Disc Dynamics of Minnetonka, Minnesota, USA, the disclosure of which is incorporated herein by reference. Alternatively, various other artificial disk implant systems, including the ProDisc® system from Spine Solutions, the SB Charite III system from Link Spine Group, the PDN device from Raymedica Inc., the hydrogel injectable material from Replication Medical Inc., the protein polymer material from Protein Polymer Technologies Inc., or other reconstructive devices or materials known to those skilled in the art could be used in concert with the teachings of the present invention with varying results. In order to implant such devices, after distracting the disk space in accordance with the teachings of the present invention, the physician will desirably prepare the disk space using arthroscopic tools under arthroscopic visualization. Such preparations can include removal of the disk nucleus, as well as removal of some or all of the annular disk material, depending upon the treatment goals and extent of injuries to the disk tissue. Desirably, the distraction of the disk space will (1) permit removal of disk tissue, thereby creating a cavity or space appropriate for arthroscopic visualization of the disk space, (2) restore disk height prior to implantation of the disk repair or replacement, and (3) facilitate implantation of the disk repair or replacement. Once the disk repair or replacement has been implanted, the distraction element and anchoring devices can then be removed in the previously- described manner. In addition, where the disk injury has resulted in misalignment of the spinal segment, the physician may also desire to realign the spinal segment during the surgery. The distraction devices of the present invention can facilitate and simplify such realignment. For example, where the vertebral bones have slid laterally relative to each other, the distraction element (once in position) may be manipulated to distract the affected vertebral levels apart, and then further manipulated to reposition the affected vertebral bodies to a more normal anatomical positions relative to each other. The disk repair or replacement can then be implanted and the distraction element and anchoring devices removed. In such a case, the physician could further incorporate flexible posterior stabilization instrumentation to secure the affected vertebral level to adjacent vertebral levels, while still preserving the motion segment. Such flexible instrumentation could include the Dynamic Stabilization System (Dynesys™) commercially available from Zimmer Inc. ADDITIONAL USES In addition to the specific uses described above, the cavity-forming devices and methods described herein would also be well-suited for use in treating and/or reinforcing weakened, diseased and/or fractured bones and other tissues/organs in various locations throughout the body. For example, the disclosed devices and methods could be used to deliver reinforcing materials and/or medications, such as cancer drugs, replacement bone cells, collagen, bone matrix, demineralized calcium, and other materials/medications, directly to a fractured, weakened and/or diseased bone, thereby increasing the efficacy of the materials, reinforcing the weakened bone and/or speeding healing of the targeted tissues. Moreover, injection of such materials into one bone within a body could permit the medication/material to migrate and/or be transported to other bones and/or organs in the body, thereby improving the quality of bones and/or other organs not directly injected with the materials and/or medications. In the case of a very extensive injury, the physician may choose to "open" and expose the injured level, permitting direct visualization and repair of the injured tissue(s). Because the injured area has been distracted in a percutaneous manner, however, there is little need for a large incision extending up and down the spinal column. Rather, the physician can choose to expose only those specific areas requiring treatment under direct visualization, and treat the remainder of the injured tissue in a less invasive manner. Moreover, because the methods and devices of the present invention enable distraction of the injured tissue in a safe and repeatable manner, and can immobilize the injured spinal segment during the surgery, these devices may be particularly useful during surgery involving reconstruction of extensive damage to the spinal column, including the insertion of vertebral blocks and spacers. Depending upon the extent and severity of the injuries, and the potential for multiple types of a given injury to affect various location of the spinal column, the physician may perform any combination of the above, if desired. COMPLETION OF SURGERY After the surgical removal, repair and/or replacement of the injured tissue has been completed (See FIG. 13), the distraction element 300 will desirably be loosened and detached from the anchoring devices 205. After the element is removed, the anchoring devices 205 are removed from the upper and lower levels 100 and 110. If desired, a small amount of bone filling material (not shown) may be introduced into the voids left in the pedicles of the upper and lower levels 100 and 110 (left by removal of the devices 205), and the skin overlying these areas may be sutured and/or bandaged closed. See FIG. 14. Alternatively, the physician may choose to keep the element in place to facilitate healing and/or patient ambulation, or the element can be adjusted to partially load or further unload the spine, or can be completely removed if spinal stability is restored to a safe level. The element may also be readjusted to facilitate surgical treatment of other locations in the spine column. By locating the distraction element outside of the patient's body, the various embodiments of the present invention bring with them one or more attendant advantages. For example, because the skin and soft tissues overlying the surgical site are largely undisturbed during the disclosed procedures, the likelihood of post-surgical infection is greatly reduced (as opposed to a large surgical incision). Another advantage is that much of the connective tissue and supporting structure for the spine remains intact, thereby greatly improving spinal stability after surgery as well as significantly reducing recovery time and pain. Another advantage is that the use of distraction to reduce and/or reverse compressive loading on the spine greatly increases the opportunity to move cortical bone for vertebral fracture repair and/or remove/displace/repair disk material, resulting in more complete restoration of the vertebral bone and disk height. Another advantage is that the use of distraction greatly improves the ability of the physician to visualize (using laparoscopic or open visualization) the injured disk space, which can be drawn apart to further facilitate the surgical procedure. Another advantage is that the devices and methods of the present invention allow a physician to access the injured tissues much more quickly than in traditional surgeries, as well as greatly reducing wound closure time, thereby reducing overall surgical time. Another advantage is that the methods disclosed in the present invention significantly reduce the amount of blood and fluid loss during surgery, thereby making the surgery safer for the patient. Another advantage is that the devices and methods of the present invention prevent the need to remove refractors during prolonged surgical procedures, allowing improved blood flow to the retracted tissues, while adding to the amount of time the surgeon has available to complete the surgery.

ADDITONAL ALTERNATE EMBODIMENTS hi certain instances, it may not be desired or possible to allow the facet joints to withstand compressive loading during the distraction procedure. For example, where one or more of the facet joints 115 have been injured or compromised (and may even require repair/replacement themselves), or where the distraction forces required may be substantial, or where the physician desires complete immobilization and control of the spinal distraction, the physician may choose to utilize a distraction device such as the one disclosed in FIG. 15. In this embodiment, the element comprises a pair of distraction mechanisms 370 and 380 (hereinafter referred to as "inner element 370" and "outer element 380"). i the disclosed embodiment, the construction of each of these mechanisms is similar to that described in connection with element 300. After the anchoring devices 205 have been attached to the targeted spinal segment as previously described, the inner element 370 and the outer element 380 are secured to the devices 205, with the inner element 370 flush against the skin 370 and the outer element 380 proximate the end 207 of the devices 205. i order to distract the spinal segment, the physician need merely shorten the length Lo of the outer element 380 (causing the distraction distance D_D to increase), or the physician can lengthen the length Li of the inner element 370 (similarly causing the distraction distance Dp to increase), resulting in distraction of the spinal segment without significant compressive loading of the facet joints 115. By establishing length Losing inner element

370 the relative position of the facet joints 115 can remain constant during distraction of the anterior vertebral bodies by adjustment of outer element 380 and reduction of length Lo. Aside from reducing or eliminating this compressive loading of the facet joints 115 during distraction, the present embodiment also greatly enhances the physician's control of the spinal segment distraction. If the physician desires to change the orientation of the anchors relative to each other, or desires to increase distraction forces in a specific area of the spinal segment without affecting the entirety of the spinal segment, the disclosed embodiment permits the physician to manipulate the inner and outer elements 370 and 380 to accomplish such goals. For example, if the physician wishes to distract the anterior portion of the spinal segment to a greater degree, without significantly increasing the separation of the facet joints, the physician can choose to decrease the length Lo of the outer element while also decreasing (but to a lesser degree) the length Li of the inner element 370, thereby increasing the anterior distraction distance while leaving the facet joints 115 unaffected. FIG. 16 depicts another alternate embodiment of a distraction element 400 constructed in accordance with the teachings of present invention, fri this embodiment, distraction element 400 comprises an adjustable framework having four eyes 420, desirably sized to accommodate four corresponding anchoring devices (not shown), and four adjustable links 405 for adjusting the length of each individual side in a manner similar to that disclosed in connection with distraction element 300. Desirably, this element can be adjusted to accommodate anchoring devices (not shown) secured to the left and right pedicles of two vertebral bodies of a spinal segment. After being attached to a targeted spinal segment (not shown), and used in the previously described manner to distract the spinal segment, the physician will be free to access the injured vertebral tissue through the opening 450 in the middle of the distraction element 300. DISTRACTION TECHNIQUES: Depending upon the extent of injury, and the desired treatment goal, various distraction techniques and tools may be employed. To treat a relatively "simple" vertebral body fracture (such as a simple compression fracture), where the posterior vertebra including pedicle and facet joint are still intact, a single-arm distraction device (as disclosed in FIG. 8) utilizing a pair of anchoring devices (one each for the upper and lower levels) may be useful to accomplish the goal of reducing and repairing the fracture, hi the case of more complex fractures, involving fractures of the vertebral body and pedicles/facet joints, a more elaborate multi-arm distraction device may be necessary to distract and repair the involved soft and hard tissue damage. See FIGs. 15 and 16. In addition, where greater distraction forces are desired, the distraction device could anchor to three or more vertebral levels of the spinal column using multiple levels of anchoring devices. It should also be understood that other distraction devices, such as lever-operated or infiatable/defiatable distraction tools and elements, could be incorporated into the distraction device of the present invention, with varying results. Other embodiments and uses of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. All documents referenced herein are specifically and entirely incorporated by reference. The specification and examples should be considered exemplary only with the true scope and spirit of the invention indicated by the following claims. As will be easily understood by those of ordinary skill in the art, variations and modifications of each of the disclosed embodiments can be easily made within the scope of this invention as defined by the following claims.

Claims

I claim: 1. A method for treating an injured spinal segment comprising the steps of: inserting a first anchoring device into an upper vertebral body located above the injured portion of the spinal segment; inserting a second anchoring device into a lower vertebral body located below the injured portion of the spinal segment; distracting the upper vertebral body from the lower vertebral body; treating the injured portion of the spinal segment; removing the first anchoring device from the upper vertebral body; and removing the second anchoring device from the lower vertebral body.

2. The method of claim 1 wherein the inserting steps comprise percutaneously inserting the anchoring devices into the upper and lower vertebral bodies through a skin surface extending over the injured spinal segment.

3. The method of claim 1 wherein the treating step comprises surgically treating an injured vertebral body of the spinal segment.

4. The method of claim 1 wherein the treating step comprises surgically treating an injured intervertebral disk of the spinal segment.

5. The method of claim 1 further comprising a distraction device, said distraction device secured to and distracting apart the anchoring devices.

6. The method of claim 5 wherein the distraction device is positioned outside of a skin surface covering the injured spinal segment.

7. The method of claim 5, wherein the distraction device does not extend within a patient's body.

8. The method of claim 3, wherein the treating step comprises creating a cavity within an injured vertebral body of the spinal segment.

9. The method of claim 3, wherein the treating step comprises placement of a bone repair material within the injured vertebral body.

10. The method of claim 3, wherein the treating step comprises manipulation of fractured bone within the injured vertebral body.

11. The method of claim 4, wherein the treating step comprises placement of an artificial disc nucleus within the injured intervertebral disc.

12. The method of claim 4, wherein the treating step comprises disc arthroplasty within the injured intervertebral disk.

13. The method of claim 4, wherein the treating step comprises injection of a protein polymer for disc nucleus repair within the injured intervertebral disc.

14. The method of claim 8, wherein the treating step comprises creating a cavity by expanding an expandable structure within the injured vertebral body.

15. The method of claim 14, wherein the expandable structure is a balloon catheter.

16. A method for treating an injured spinal bone comprising the steps of: inserting a first anchoring device into an upper vertebral body located above the injured spinal bone; inserting a second anchoring device into a lower vertebral body located below the injured spinal bone; distracting the first anchoring device from the second anchoring device; treating the injured spinal bone; removing the first anchoring device from the upper vertebral bone; and removing the second anchoring device from the lower vertebral bone.

17. The method of claim 16, wherein the treating step comprises injecting a filler material into the injured spinal bone.

18. The method of claim 17 wherein the filler material is polymethylmethacrylate.

19. The method of claim 17 wherein the filler material comprises a material capable of withstanding compressive loading.

20. A method for treating an injured joint space comprising the steps of: inserting a first anchoring device into a first bone adjacent the joint space; inserting a second anchoring device into a second bone adjacent the joint space; distracting the first anchoring device from the second anchoring device; treating the joint space; removing the first anchoring device from the first bone; and removing the second anchoring device from the second bone.

21. The method of claim 20 wherein the joint space comprises an intervertebral disk.

22. The method of claim 20 wherein the joint space comprises an intervertebral facet joint.

23. A device for percutaneously distracting a first bone from a second bone, comprising: a first anchoring mechanism having a proximal end and a distal end, the distal end of the first mechanism being suited for anchoring into bone; a second anchoring mechanism having a proximal end and a distal end, the distal end of the second mechanism being suited for anchoring into bone; an adjustment mechanism for adjusting the displacement between the distal end of the first anchoring mechanism and the distal end of the second anchoring; a locking device for locking the adjustment mechanism in a desired position.

24. The device of claim 23, wherein the first and second anchoring mechanisms comprise pedicle screws.