Apparatuses and methods for removing solid tissue from beneath a tissue surface are described. The methods rely on positioning an energy conductive element at a target site beneath the tissue surface and energizing the element so that it can vaporize tissue. The element is then moved in a pattern which provides the desired tissue removal geometry, such as spherical, ovoid, or cylindrical. Usually, the shaft is moved, typically rotated or reciprocated, and the energy conductive element is moved relative to the shaft, typically by pivoting a rigid element or bowing a flexible element.

1. Field of the Invention
The present invention relates generally to medical devices, kits, and methods. More particularly, the present invention relates to apparatuses and methods for removing tissue from tissue regions beneath a tissue surface.
The removal of diseased and other tissues is the basis for many surgical procedures and is accomplished in many different ways. Most commonly, the target tissue is excised using a cutting blade, such as a scalpel, in open surgical procedures. Typically, the cutting blade is advanced into a tissue through an exposed tissue surface, and the target tissue is simply cut out and removed. While very effective for tissue removal at or near an exposed tissue surface, this approach is less effective for tissue removal from sites spaced below the closest exposed tissue surface.
For removal of target tissue below a tissue surface, a surgeon can simply cut down to the level of the target tissue and cut out and remove the tissue at that level. The need to cut down through xe2x80x9cnon-targetxe2x80x9d tissue is, however, disadvantageous in several respects. First, surgically cutting through the overlying healthy tissue can create a much bigger incision than is necessary for simply removing the target tissue. Moreover, the need to penetrate through relatively thick layers of overlying tissue can complicate identification of the target region, often requiring that larger volumes of tissue be removed to assure to complete removal. Additionally, the ability to cut down into internal organs during minimally invasive endoscopic procedures is significantly more limited than in open surgical procedures.
Surgical instruments for removing tissue beneath a tissue surface have been developed. For example, instruments employing specialized cutting blades for chopping or xe2x80x9cmorcellatingxe2x80x9d tissue into small pieces and aspirating the resulting debris have been developed. While such instruments are at least theoretically capable of being manipulated to remove a defined volume of tissue beneath a tissue surface, their performance suffers in various ways. Most importantly, tissue morcellation can result in significant bleeding which is difficult to staunch. Thus, these techniques would not be useful in highly vascularized tissues, such as many muscle and organ tissues. Even when combined with electrosurgical coagulation, such tissue morcellation devices are probably not useful for the removal of large tissue volumes beneath a tissue surface where bleeding control is problematic.
For all of these reasons, it would be desirable to provide improved apparatuses and methods for tissue removal beneath tissue surfaces. In particular, the devices and methods should be suitable for use in minimally invasive procedures, such as procedures where the devices are introduced through a port and viewed under endoscopic viewing. The methods and devices should further allow access to a target tissue region with minimum disruption and damage to the overlying xe2x80x9cnon-targetxe2x80x9d tissue. Additionally, it would be desirable to provide tissue removal regions with a simplified approach for removing the debris resulting from the tissue removal. It would be particularly desirable to provide such tissue removal methods and devices which result in minimum or easily controlled bleeding at the tissue removal site. Such methods and apparatuses should still further provide for removal of controlled volumes, even relatively large volumes of at least 0.5 cm3, preferably at least 50 cm3, and still more preferably at least 500 cm3, or more. The methods and apparatuses should also be useful on a wide variety of tissue types and for a wide variety of specific procedures. At least some of these objectives will be met by the invention described hereinafter.
2. Description of the Background Art
A loop electrode for radiofrequency electrosurgical excision of a tissue volume in solid tissue is described in Lorentzen et al. (1996) Min. Invas. Ther. and Allied Tecnol. 5:511-516.
Three-dimensional electrode arrays for deployment in solid tissue followed by the application of radiofrequency energy to necrose tissue volumes are described in U.S. Pat. Nos. 5,827,276; 5,735,847; and 5,728,143.
Atherectomy catheters having radially expansible blade structures intended for rotational stenotic excision in blood vessels are described in U.S. Pat. Nos. 5,556,408; 5,554,163; 5,527,326; 5,318,576; 5,100,423; and 5,030,201. In particular, U.S. Pat. No. 5,554,163, describes a catheter having a flexible xe2x80x9ccuttingxe2x80x9d element that may be radially deployed from the catheter body. U.S. Pat. No. 5,100,423, describes a cutting structure comprising a plurality of helically-shaped cutting wires that can be connected to an electrosurgical power supply to effect cutting of obstructing matter in a blood vessel. The following patents describe other electrosurgical instruments: U.S. Pat. Nos. 2,022,065; 4,660,571; 5,217,458; 5,578,007; 5,702,390; 5,715,817; 5,730,704; 5,738,683; and 5,782,828.
The present invention provides improved methods, devices, and kits for removing tissue from internal target sites disposed beneath a tissue surface. The present invention can provide a number of advantages when compared to prior tissue removal techniques, including minimizing disruption of the tissue overlying the target site, i.e., between the tissue surface and an outer periphery of the target volume which is to be removed. In the preferred examples described below, access through the overlying tissue can be achieved with a single percutaneous or transcutaneous tissue tract sufficient to accommodate a single shaft of the apparatus. In addition to minimizing disruption of overlying tissue, the present invention can significantly reduce bleeding at the target site after tissue removal. In particular, by employing electrocautery as part of the tissue excision process, bleeding of the surrounding tissues can be substantially staunched. Other advantages provided by the present invention include the ability to remove relatively large tissue volumes, typically, at least 0.5 cm3, often at least 50 cm3, and sometimes as large as 500 cm3, or larger. While the present invention is particularly suited for removing large volumes. The tissue removal can be effected in many tissue types, including those specifically set forth below, and tissue debris remaining after removal can be transported from the site, typically through the single access tract described above, usually by aspirating vapors and cellular debris which are produced as the tissue excision and vaporization stages occur. In addition or as an alternative to vapor aspiration, the tissue void which is being created may optionally be flushed with a suitable liquid or gas, preferably an electrically non-conductive liquid, such as sorbitol. Further optionally, the flushing medium may carry medications or other biologically active substances, such as antibiotics, pain killers, hemostatic agents, and the like. Such flushing may occur concurrently with the cutting, during brief periods when cutting is ceased, and/or after all cutting has been completed.
The present invention is suitable for removing defined volumes of tissue from a variety of different tissue types, including breast tissue, liver tissue, kidney tissue, prostate tissue, lung, uterine, and the like. Thus, the tissue surface may be on the patient""s skin, e.g., in the case of breast tissue removal, or the tissue surface may be located subcutaneously, e.g., in the case of internal body organs. In the former case, access to the target site may be achieved transcutaneously or subcutaneously, where the removal device penetrates directly through the skin. In the latter case, a secondary procedure is needed to access the tissue surface of the internal body organ. The secondary procedure may be an open surgical procedure where the overlying skin and body structures are surgically opened. Alternatively, the secondary procedure may itself be minimally invasive where small incisions or ports are used to introduce the devices of the present invention together with any necessary or useful auxiliary devices for performing the tissue removal. Typically, such minimally invasive surgeries will be performed under endoscopic visualization where the treating physician views the procedure on a video screen. As a still further alternative, access to internal body organs may be achieved intraluminally, preferably endoscopically. Typically, such intraluminal, endoscopic access will be obtained through body lumens having natural orifices, such as the esophagus, colon, uterus, fallopian tubes, sinuses, uterus, ureter, and urethra. Such access will typically be achieved using a flexible catheter which can provide a platform for advancing the energy conductive elements, as described in more detail below.
The depth of the target site will depend on the nature of the tissue and the nature of the disease or other condition being treated. Typically, the closest periphery of the target site will be located between the adjacent or available tissue surface by distance in the range from 0.5 cm to 15 cm, usually from 5 cm to 7 cm. The volume of tissue to be removed will typically be in the range from 0.5 cm3 to 500 cm3, typically being from 5 cm3 to 300 cm3. As described in more detail below, the geometry or shape of the removal volume, i.e., the void left in tissue following tissue removal, will generally be spherical, ovoid, cylindrical, or other shape characterized by at least one axis of symmetry. The axis of symmetry will usually arise because of the manner in which the tissue removal devices are used, as described in more detail below.
In a first aspect, methods according to the present invention comprise positioning an energy conductive element at a target site in tissue beneath a tissue surface. The energy conductive element is energized and moved through successive tissue layers, where the element is energized with sufficient energy to vaporize tissue in said successive layers. Such sequential removal of successive layers of tissues will produce a desired removal volume, typically having the geometries and sizes set forth above.
In a second aspect, methods according to the present invention comprise providing an instrument having a shaft and a repositionable energy conductive element on the shaft. The element is advanced through the tissue surface to a target site in solid tissue, where the element is in a low profile configuration (e.g., radially collapsed into the shaft) and the proximal end of the shaft remains outside of the solid tissue to permit manipulation. The shaft is moved relative to the tissue surface and the element repositioned relative to the shaft while the element is being energized with sufficient energy to remove tissue. The combined movements of the shaft and the element relative to the shaft cause the element to pass through successive tissue layers at or near the target site and to vaporize said layers to produce the desired removal volume.
Usually, the methods for removing tissue as described above will further comprise imaging the solid tissue and positioning the energy conductive element based on the image. The imaging may be any type of conventional, two-dimensional or three-dimensional medical imaging, including fluoroscopic imaging, ultrasonic imaging, magnetic resonance imaging, computer-assisted tomographic imaging, optical imaging, and the like. Positioning of the energy conductive device may be entirely manual, where the user may view the image of the target site either in real time, as a pre-operative image only, or a combination of real time and pre-operative images. Alternatively, the energy conductive device may be automatically positioned based directly or indirectly on the image using robotic or other automatic positioning equipment. Optionally, such automatic positioning equipment can be programmed based on a pre-operative or real time image of the target region.
The methods of the present invention will preferably further comprise collecting vapors and cellular debris produced by the tissue vaporization and removing those vapors through the overlying tissue and the tissue surface. Usually, vapor removal will comprise aspirating the vapors from the site or volume of tissue removal as the vapors are being produced. Usually, the vapors will be aspirated through a tissue tract between the tissue surface and the target site, more typically being through a lumen in the shaft of the device used for removing the tissue.
The energy conductive element is moved through a pattern of successive tissue layers which, in the aggregate, will form the desired tissue removal volume. The energy conductive element may be moved in any manner, typically being moved by manipulation of the shaft upon which it is mounted. For example, the energy conductive element may be moved relative to the shaft while the shaft itself is moved so that the combined motions of the element and the shaft define the desired removal geometry. Alternatively, the energy conductive element could be moved on the shaft while the shaft remains stationary. In the latter case, a servo or other drive mechanism could be provided within the shaft to move the energy conductive element through its desired pattern.
The shaft will usually be rotated and/or axially reciprocated in order move the energy conductive element through tissue along or about one axis. In turn, the energy conductive element may be pivoted, bowed, or otherwise moved or deflected relative to the shaft to provide further axes or dimensions of the removal volume. In a first exemplary removal method, a shaft having a rigid energy conductive member is introduced to an internal tissue target site with the element lying coaxial to the shaft. The shaft is then rotated and the element pivoted to provide a spherical or partial spherical tissue removal geometry. In a second exemplary embodiment, the energy conductive element comprises one or more flexible elements which may be bowed to form a series of arcuate tissue removal paths as the shaft is rotated. Other approaches include disposing a lateral energy conductive element beneath tissue and simultaneously rotating and reciprocating the support shaft so that a cylindrical removal volume is formed, with the length of the cylinder determined by the length of reciprocation. Other combinations of motion between the shaft and energy conductive element may also be utilized.
The type of energy transmitted or provided through the energy conductive element will preferably provide for heating of the tissue. For example, high frequency energy, such as radiofrequency or microwave energy, may be delivered in a monopolar or bipolar manner to vaporize the tissue. Typically, the radiofrequency energy will be applied with a cutting waveform at a frequency in the range from 100 kHz to 2 MHz, and a current in the range from 1 mA to 50 A, 0.5 mA to 10 A, depending on surface contact area and tissue type. Alternatively, energizing can comprise directly heating the element, typically to a temperature in the range from 100xc2x0 C. to 300xc2x0 C., usually 600xc2x0 C. to 2000xc2x0 C. Heating is preferably achieved using optical energy, e.g., laser energy, delivered through a fiberoptic element within the energy conductive element. Alternatively, heating can be achieved using an electrical resistance heater which comprises or is disposed within the energy conductive element.
The present invention further provides apparatus for removing tissue. In a first instance, a tissue ablation device comprises a shaft having a proximal end, a distal end, and a lumen therethrough. At least one flexible energy conductive element is disposed near the distal end of the shaft, and a means for bowing the element between a substantially linear profile (where the element lies directly over the shaft) and a series of arcuate profiles spaced progressively further from the shaft is provided. The bowing means will typically include a mechanism for axially advancing a proximal end of the flexible energy conductive element. By preventing or limiting axial movement of a distal end of the flexible energy conductive element, the element will be caused to bow radially outwardly in the desired arcuate configuration. Alternatively, a proximal end of the flexible energy conductive element may be fixed or limited relative to the shaft and a rod or other device for proximally retracting a distal end of the energy conductive element provided. It would further be possible to simultaneously draw both ends of the element together. Other mechanisms, such as expandable cages, parallel linkages, shape heat memory drivers, or the like, may also be provided for bowing the element radially outwardly. The tissue ablation device will further comprise an aspiration connector coupled to the lumen for aspirating vapors produced at the distal end. A power supply connector is further provided to permit electrical coupling of the energy conductive element to a desired power supply.
The shaft of such devices may be substantially rigid, typically having a diameter in the range from 0.5 mm to 20 mm, typically 2 mm to 7 mm, and a length in the range from 2 cm to 50 cm, usually 5 cm to 25 cm. The devices will also typically have a handle secured at or near the proximal end of the shaft, and at least one of the aspiration and power supply connectors will usually be disposed on the handle. Optionally, a motor may be provided in the handle or separate from the handle to help drive the device. For example, the motor could be connected to rotate and/or reciprocate the shaft relative to the handle in order to drive the device in a desired manner. Alternatively or additionally, the motor could be connected to bow the flexible energy conductive element in a controlled manner. In the exemplary embodiments, however, all motions of both the shaft and the energy conductive element will be manual.
The shaft of such devices may also be flexible, typically in the form of a catheter having a diameter in the range from 0.5 mm to 10 mm, and a length in the range from 25 cm to 250 cm. Usually, when used for access to natural body lumens, such as the colon, uterus, esophagus, fallopian tubes, sinuses, uterus, ureter, and the urethra, the shafts will be introduced through or as part of an endoscope. The cutting elements for performing the tissue removal will then be deployed from or near the distal end of the catheter. Typically, the cutting elements will be deployed laterally from the catheter and a stylet or other introducer will be utilized to permit subcutaneous introduction as required by the present invention. In other cases, the devices may be introduced intravascularly, typically through the femoral or other veins, to target organs, such as liver, kidney, prostate, lung, and uterus. The cutting elements can then be deployed from the catheters through the blood vessel wall into the target organ.
The energy conductive elements may be configured to provide for any of the energy delivery modes set forth above. In particular, energy conductive elements may comprise electrodes suitable for the delivery of high frequency electrical energy, typically radiofrequency energy having the particular frequencies and other characteristics set forth above. Alternatively, the energy conductive elements may be configured to provide for direct heating of the elements themselves, usually comprising either an optical fiber for delivering light energy or comprising an electrical resistance heater together with the necessary wiring to connect the resistance heater to a suitable power source.
The flexible energy conductive elements may take a wide variety of forms. A first exemplary form will be a simple elastic or super elastic metal wire, typically having a diameter in the range from 0.1 mm to 5 mm, preferably from 0.5 mm to 2 mm. The wire may be formed from any suitable material, including stainless steel, nickel titanium alloy, tungsten, or the like. The wire may be composed of single material or may be a composite material, e.g., where a portion of the wire is selected for high electrical conductivity while another portion of the wire selected for elastic or other properties. The electrically conductive elements may also be in the form of ribbons, i.e., having a width substantially greater than its thickness. Such ribbon structures will have greater mechanical rigidity when they are radially expanded through their narrow dimension. Often times, different types of energy conductive elements may be combined in a single device. In an exemplary device, a pair of wire elements are disposed on opposite sides of the shaft with a pair of ribbon elements offset by 90xc2x0. Each of the four elements is coupled to the other so that they open and close (be xe2x80x9cbowedxe2x80x9d and relaxed) synchronously. Usually, such structures will be formed for bipolar operation, where the ribbon elements will have a much greater surface area than the wire elements so that the ribbons connect as a dispersible electrode, i.e., an electrode where minimum cutting takes place. In such cases, the ribbon electrode can also serve to act as a surface coagulation electrode to help control bleeding. In some instances, it will be desired that the wire cutting electrodes be advanced slightly radially ahead of the ribbon electrodes. Such a design allows the ribbons to open under a spring force to xe2x80x9cautomaticallyxe2x80x9d expand as the wire electrodes remove successive layers of tissue.
A second exemplary tissue ablation device comprises a shaft having a proximal end, a distal end, and lumen therethrough. A substantially rigid energy conductive element is pivotally attached to the shaft near its distal end. The device further includes a means for causing the element to pivot, such as a push wire, pull wire, rack and pinion driver, gear driver, or the like. The device will further include aspiration and power supply connectors, both as generally described above.
The nature of the shaft and the types of energy conductive elements which may be deployed are all similar to corresponding aspects of the first embodiment of the tissue ablation device described above. The nature of the pivotally connected energy conductive element will, however, differ. The pivotally attached energy conductive element will usually be straight, typically being in the form of a cylindrical pin having a length in the range from 1 mm to 75 mm, and a width or diameter in the range from 0.5 mm to 5 mm. A preferred geometry includes a circular or flat cross-section. The rigid element may be pivotally attached near its middle, near one end thereof, or anywhere else along its length. In an illustration example, the element is pivotally attached near its middle in order to effect a spherical tissue removal volume as the device is rotated and the pin pivoted through 90xc2x0 or more, as described in detail below.
The present invention still further provides kits comprising a device having an energy conductive element which is connectable to a power supply and which provides energy sufficient to vaporize successive layers of tissue as the element is moved therethrough. The device may have any of the configurations described above. The kit will further comprise instructions for use setting forth a method as in any of the methods described above. Typically, at least the device will be present in a sterile package, and the instructions for use may printed on a portion of the package or may be on a separate instruction sheet accompanying the package. Suitable packages include pouches, trays, boxes, tubes, or the like. Suitable sterilization techniques include gamma radiation, ethylene oxide treatment, or the like.

Apparatuses and methods for interstitial tissue removal


A flexible connection unit for spinal stabilization, including: a first end portion having a first longitudinal channel and configured to be coupled to a first securing member secured to a patient's spine; a second end portion having a second longitudinal channel and configured to be coupled to a second securing member secured to the patient's spine; and a flexible wire extending through at least a portion of the first and second longitudinal channels and flexibly linking the first and second end portions.

1. Field of the Invention
The present invention relates to a method and system for fixing and stabilizing a spinal column and, more particularly, to a method and system of spinal fixation in which one or more screw type fixing members are implanted and fixed into a portion of a patient's spinal column and flexible, semi-rigid rods or plates are connected and fixed to the upper ends of the fixing members to provide dynamic stabilization of the spinal column.
2. Description of the Related Art
Degenerative spinal column diseases, such as disc degenerative diseases (DDD), spinal stenosis, spondylolisthesis, and so on, need surgical operation if they do not take a turn for the better by conservative management. Typically, spinal decompression is the first surgical procedure that is performed. The primary purpose of decompression is to reduce pressure in the spinal canal and on nerve roots located therein by removing a certain tissue of the spinal column to reduce or eliminate the pressure and pain caused by the pressure. If the tissue of the spinal column is removed the pain is reduced but the spinal column is weakened. Therefore, fusion surgery (e.g., ALIF, PLIF or posterolateral fusion) is often necessary for spinal stability following the decompression procedure. However, following the surgical procedure, fusion takes additional time to achieve maximum stability and a spinal fixation device is typically used to support the spinal column until a desired level of fusion is achieved. Depending on a patient's particular circumstances and condition, a spinal fixation surgery can sometimes be performed immediately following decompression, without performing the fusion procedure. The fixation surgery is performed in most cases because it provides immediate postoperative stability and, if fusion surgery has also been performed, it provides support of the spine until sufficient fusion and stability has been achieved.
Conventional methods of spinal fixation utilize a rigid spinal fixation device to support an injured spinal part and prevent movement of the injured part. These conventional spinal fixation devices include: fixing screws configured to be inserted into the spinal pedicle or sacral of the backbone to a predetermined depth and angle, rods or plates configured to be positioned adjacent to the injured spinal part, and coupling elements for connecting and coupling the rods or plates to the fixing screws such that the injured spinal part is supported and held in a relatively fixed position by the rods or plates.
U.S. Pat. No. 6,193,720 discloses a conventional spinal fixation device, in which connection members of a rod or plate type are mounted on the upper ends of at least one or more screws inserted into the spinal pedicle or sacral of the backbone. The connection units, such as the rods and plates, are used to stabilize the injured part of the spinal column which has been weakened by decompression. The connection units also prevent further pain and injury to the patient by substantially restraining the movement of the spinal column. However, because the connection units prevent normal movement of the spinal column, after prolonged use, the spinal fixation device can cause ill effects, such as "junctional syndrome" (transitional syndrome) or "fusion disease" resulting in further complications and abnormalities associated with the spinal column. In particular, due to the high rigidity of the rods or plates used in conventional fixation devices, the patient's fixed joints are not allowed to move after the surgical operation, and the movement of the spinal joints located above or under the operated area is increased. Consequently, such spinal fixation devices cause decreased mobility of the patient and increased stress and instability to the spinal column joints adjacent to the operated area.
It has been reported that excessive rigid spinal fixation is not helpful to the fusion process due to load shielding caused by rigid fixation. Thus, trials using load sharing semi-rigid spinal fixation devices have been performed to eliminate this problem and assist the bone fusion process. For example, U.S. Pat. No. 5,672,175, U.S. Pat. No. 5,540,688, and U.S. Pub No 2001/0037111 disclose dynamic spine stabilization devices having flexible designs that permit axial load translation (i.e., along the vertical axis of the spine) for bone fusion promotion. However, because these devices are intended for use following a bone fusion procedure, they are not well-suited for spinal fixation without fusion. Thus, in the end result, these devices do not prevent the problem of rigid fixation resulting from fusion.
To solve the above-described problems associated with rigid fixation, non-fusion technologies have been developed. The Graf band is one example of a non-fusion fixation device that is applied after decompression without bone fusion. The Graf band is composed of a polyethylene band and pedicle screws to couple the polyethylene band to the spinal vertebrae requiring stabilization. The primary purpose of the Graf band is to prevent sagittal rotation (flexion instability) of the injured spinal parts. Thus, it is effective in selected cases but is not appropriate for cases that require greater stability and fixation. See, Kanayarna et al, Journal of Neurosurgery 95(1 Suppl):5-10, 2001, Markwalder & Wenger, Acta Neurochrgica 145(3):209-14.). Another non-fusion fixation device called "Dynesys" has recently been introduced. See Stoll et al, European Spine Journal 11 Suppl 2:S170-8, 2002, Schmoelz et al, J of spinal disorder & techniques 16(4):418-23, 2003. The Dynesys device is similar to the Graf band except it uses a polycarburethane spacer between the screws to maintain the distance between the heads of two corresponding pedicle screws and, hence, adjacent vertebrae in which the screws are fixed. Early reports by the inventors of the Dynesys device indicate it has been successful in many cases. However, it has not yet been determined whether the Dynesys device can maintain long-term stability with flexibility and durability in a controlled study. Because it has polyethylene components and interfaces, there is a risk of mechanical failure. Furthermore, due to the mechanical configuration of the device, the surgical technique required to attach the device to the spinal column is complex and complicated.
U.S. Pat. Nos. 5,282,863 and 4,748,260 disclose a flexible spinal stabilization system and method using a plastic, non-metallic rod. U.S. patent publication no. 2003/0083657 discloses another example of a flexible spinal stabilization device that uses a flexible elongate member. These devices are flexible but they are not well-suited for enduring long-term axial loading and stress. Additionally, the degree of desired flexibility vs. rigidity may vary from patient to patient. The design of existing flexible fixation devices are not well suited to provide varying levels of flexibility to provide optimum results for each individual candidate. For example, U.S. Pat. No. 5,672,175 discloses a flexible spinal fixation device which utilizes a flexible rod made of metal alloy and/or a composite material. Additionally, compression or extension springs are coiled around the rod for the purpose of providing de-rotation forces on the vertebrae in a desired direction. However, this patent is primarily concerned with providing a spinal fixation device that permits "relative longitudinal translational sliding movement along [the] vertical axis" of the spine and neither teaches nor suggests any particular designs of connection units (e.g., rods or plates) that can provide various flexibility characteristics. Prior flexible rods such as that mentioned in U.S. Pat. No. 5,672,175 typically have solid construction with a relatively small diameter in order to provide a desired level of flexibility. Because they are typically very thin to provide suitable flexibility, such prior art rods are prone to mechanical failure and have been known to break after implantation in patients.
Therefore, conventional spinal fixation devices have not provided a comprehensive and balanced solution to the problems associated with curing spinal diseases. Many of the prior devices are characterized by excessive rigidity, which leads to the problems discussed above while others, though providing some flexibility, are not well-adapted to provide varying degrees of flexibility. Additionally, existing flexible fixation devices utilize non-metallic components that are not proven to provide long-term stability and durability. Therefore, there is a need for an improved dynamic spinal fixation device that provides a desired level of flexibility to the injured parts of the spinal column, while also providing long-term durability and consistent stabilization of the spinal column.
Additionally, in a conventional surgical method for fixing the spinal fixation device to the spinal column, a doctor incises the midline of the back to about 10-15 centimeters, and then, dissects and retracts it to both sides. In this way, the doctor performs muscular dissection to expose the outer part of the facet joint. Next, after the dissection, the doctor finds an entrance point to the spinal pedicle using radiographic devices (e.g., C-arm flouroscopy), and inserts securing members of the spinal fixation device (referred to as "spinal pedicle screws") into the spinal pedicle. Thereafter, the connection units (e.g., rods or plates) are attached to the upper portions of the pedicle screws in order to provide support and stability to the injured portion of the spinal column. Thus, in conventional spinal fixation procedures, the patient's back is incised about 10˜15 cm, and as a result, the back muscle, which is important for maintaining the spinal column, is incised or injured, resulting in significant post-operative pain to the patient and a slow recovery period.
Recently, to reduce patient trauma, a minimally invasive surgical procedure has been developed which is capable of performing spinal fixation surgery through a relatively small hole or "window" that is created in the patient's back at the location of the surgical procedure.
Through the use of an endoscope, or microscope, minimally invasive surgery allows a much smaller incision of the patient's affected area. Through this smaller incision, two or more securing members (e.g., pedicle screws) of the spinal fixation device are screwed into respective spinal pedicle areas using a navigation system. Thereafter, special tools are used to connect the stabilizing members (e.g., rods or plates) of the fixation device to the securing members. Alternatively, or additionally, the surgical procedure may include inserting a step dilator into the incision and then gradually increasing the diameter of the dilator. Thereafter, a tubular retractor is inserted into the dilated area to retract the patient's muscle and provide a visual field for surgery. After establishing this visual field, decompression and, if desired, fusion procedures may be performed, followed by a fixation procedure, which includes the steps of finding the position of the spinal pedicle, inserting pedicle screws into the spinal pedicle, using an endoscope or a microscope, and securing the stabilization members (e.g., rods or plates) to the pedicle screws in order to stabilize and support the weakened spinal column.
One of the most challenging aspects of performing the minimally invasive spinal fixation procedure is locating the entry point for the pedicle screw under endoscopic or microscopic visualization. Usually anatomical landmarks and/or radiographic devices are used to find the entry point, but clear anatomical relationships are often difficult to identify due to the confined working space. Additionally, the minimally invasive procedure requires that a significant amount of the soft tissue must be removed to reveal the anatomy of the regions for pedicle screw insertion. The removal of this soft tissue results in bleeding in the affected area, thereby adding to the difficulty of finding the correct position to insert the securing members and causing damage to the muscles and soft tissue surrounding the surgical area. Furthermore, because it is difficult to accurately locate the point of insertion for the securing members, conventional procedures are unnecessarily traumatic.
Radiography techniques have been proposed and implemented in an attempt to more accurately and quickly find the position of the spinal pedicle in which the securing members will be inserted. However, it is often difficult to obtain clear images required for finding the corresponding position of the spinal pedicle using radiography techniques due to radiographic interference caused by metallic tools and equipment used during the surgical operation. Moreover, reading and interpreting radiographic images is a complex task requiring significant training and expertise. Radiography poses a further problem in that the patient is exposed to significant amounts of radiation.
Although some guidance systems have been developed which guide the insertion of a pedicle screw to the desired entry point on the spinal pedicle, these prior systems have proven difficult to use and, furthermore, hinder the operation procedure. For example, prior guidance systems for pedicle screw insertion utilize a long wire that is inserted through a guide tube that is inserted through a patient's back muscle and tissue. The location of insertion of the guide tube is determined by radiographic means (e.g., C-arm flouroscope) and driven until a first end of the guide tube reaches the desired location on the surface of the pedicle bone. Thereafter, a first end of the guide wire, typically made of a biocompatible metal material, is inserted into the guide tube and pushed into the pedicle bone, while the opposite end of the wire remains protruding out of the patient's back. After the guide wire has been fixed into the pedicle bone, the guide tube is removed, and a hole centered around the guide wire is dilated and retracted. Finally, a pedicle screw having an axial hole or channel configured to receive the guide wire therethrough is guided by the guide wire to the desired location on the pedicle bone, where the pedicle screw is screw-driven into the pedicle.
Although the concept of the wire guidance system is a good one, in practice, the guide wire has been very difficult to use. Because it is a relatively long and thin wire, the structural integrity of the guide wire often fails during attempts to drive one end of the wire into the pedicle bone, making the process unnecessarily time-consuming and laborious. Furthermore, because the wire bends and crimps during insertion, it does not provide a smooth and secure anchor for guiding subsequent tooling and pedicle screws to the entry point on the pedicle. Furthermore, current percutaneous wire guiding systems are used in conjunction with C-arm flouroscopy (or other radiographic device) without direct visualization with the use of an endoscope or microscope. Thus, current wire guidance systems pose a potential risk of misplacement or pedicle breakage. Finally, because one end of the wire remains protruding out of the head of the pedicle screw, and the patient's back, this wire hinders freedom of motion by the surgeon in performing the various subsequent procedures involved in spinal fixation surgery. Thus, there is a need to provide an improved guidance system, adaptable for use in minimally invasive pedicle screw fixation procedures under endoscopic or microscopic visualization, which is easier to implant into the spinal pedicle and will not hinder subsequent procedures performed by the surgeon.
As discussed above, existing methods and devices used to cure spinal diseases are in need of much improvement. Most conventional spinal fixation devices are too rigid and inflexible. This excessive rigidity causes further abnormalities and diseases of the spine, as well as significant discomfort to the patient. Although some existing spinal fixation devices do provide some level of flexibility, these devices are not designed or manufactured so that varying levels of flexibility may be easily obtained to provide a desired level of flexibility for each particular patient. Additionally, prior art devices having flexible connection units (e.g., rods or plates) pose a greater risk of mechanical failure and do not provide long-term durability and stabilization of the spine. Furthermore, existing methods of performing the spinal fixation procedure are unnecessarily traumatic to the patient due to the difficulty in finding the precise location of the spinal pedicle or sacral of the backbone where the spinal fixation device will be secured.

Method and apparatus for flexible fixation of a spine


A new and distinct variety of peach Prunus persica, tree having the following unique combination of desirable features:

The new peach tree (Prunus persica) (hereinafter referred to as the P.F. 20-007 peach tree) was originated by Paul Friday in the experimental orchard, which is maintained for the purpose of breeding peach trees, at Paul Friday Farms Inc., located in Coloma, Mich. Coloma is located in the southwest section of Michigan.
In an ongoing mass selection breeding program, superior seedlings of unrecorded parentage are maintained as seed sources for the production of seeds which are collected and planted in mass. The seed producing parent trees are maintained solely as proprietary trees for breeding purposes and have not been released from the experimental orchard, where such trees can be evaluated for their adaptability to local and regional growing conditions. Seeds resulting from open pollination of the trees in the experimental orchard are regularly planted in mass to produce new populations of seedlings which are cultured and monitored to maturity. Trees with superior attributes are retained for further observation and testing, and contribute seeds to advancing generations of new populations of seedlings.
The tree of this application, P.F. 20-007, was a selection from one such cultivated seedling population, and was based on the numerous superior genetic attributes of this tree which are described in the botanical descriptions to follow. While not exhaustive, the botanical descriptions to follow are believed to represent a reasonably complete botanical description of the new peach tree which is sufficiently detailed to distinguish the tree from the most closely related trees within the same market class.
The new and distinct variety of peach tree was asexually propagated by budding onto xe2x80x98Baileyxe2x80x99 rootstock as performed in the experimental orchard of Paul Friday Farms Inc., located in Coloma, Mich. The so stated propagation demonstrates that such reproduction of the characteristics of the tree are consistent and are established and transmitted through succeeding propagation.
The new and distinct variety of peach tree is of moderate spreading growth. A distinct characteristic of the P.F. 20-007 peach tree is that it has large, strong right angle branching to support its heavy crops of large fruit. While fruit set is medium, this variety yields very big crops due to large fruit size, providing extraordinary yields and is a regular and productive bearer of large peaches.
The blossoms of the present peach tree bloom in mid-season and are characterized as being non-showy and do not open much past a vertical state only, opening to a diameter of about xc2xd inch diameter during full bloom with its pistil protruding beyond the plane of the opened blossom petals.
The fruit at maturity has crisp flesh of very clear yellow with red around the pit.
The skin is smooth, having little down, and is sixty to eighty percent red or more overlying medium-yellow color. At maturity, the peach is spherical, having an average diameter ranging between 2xc2xd inches to 3 inches.
The fruit has a firm flesh and may be described as resilient to the extent that the flesh is yieldable and restorable to its original state when subjected to impact forces which may cause permanent deformities in peaches of commercial varieties. The firmness of fruit facilitates handling and packaging of the peaches without damaging the same for shipment. This results in less spoilage and also increases the shelf life.
The fruit matures in the mid-part of the peach growing season in southwestern Michigan.

Peach tree named xe2x80x98P.F. 20-007xe2x80x99

Abstract: 1. The new and distinct variety of peach is of spreading growth and a regular and productive bearer of large peaches having a diameter of between 2xc2xdxe2x80x3 and 3xe2x80x3 while bearing heavy crops exceeding 600 bushels per acre in a test block in Michigan. The tree planting was based on 300 trees per acre.

Abstract: 2. Producing a very firm fruit having a resilient flesh texture.

Abstract: 3. Blossoms are non-showy when in full bloom.

Abstract: 4. A substantially spherical to oblate fruit with skin of red overlaying a medium yellow color at maturity.

Abstract: 5. Mid-season maturing fruit of good taste.

Abstract: 6. A mid-season maturing fruit of good storage and shelf life.