Patent Application
20070060939
The invention relates generally to devices and methods for performing minimally invasive, percutaneous surgeries. More particularly, the invention is an expandable and retractable cannula.
Traditional surgical procedures often require a long incision, extensive muscle stripping, and prolonged retraction of tissues to access the desired surgical site as well as denervation and devascularization of surrounding tissue. This is particularly the case with spinal applications because of the need for access to locations deep within the body. Such surgical procedures can cause significant trauma to intervening tissues and potential damage to good tissue due to the amount and duration of tissue retraction, resulting in increased recovery time, permanent scarring, and pain that can be more severe than the pain that prompted the original surgical procedure. This is further exacerbated by the need to make a large incision so that the surgeon can properly view the areas inside the body that require attention.
Endoscopic, or minimally invasive, surgical techniques allow a surgical procedure to be performed on a patient's body through a smaller incision in the body and with less body tissue disruption. Endoscopic surgery typically utilizes a tubular structure known as a cannula (or portal) that is inserted into an incision in the body. A typical cannula is a fixed diameter tube, which a surgeon uses to hold the incision open and which serves as a conduit extending between the exterior of the body and the local area inside the body where the surgery is to be performed. Thus, cannulae can be used for visualization, instrument passage, and the like.
The typical cannula, however, presents at least two disadvantages. First, insertion of the cannula typically requires an incision the full depth and diameter of the cannula. Although this incision is often relatively smaller than incisions made for surgical procedures performed without a cannula, there is still trauma to healthy tissue. Additionally, endoscopic surgical techniques may be limited by the size of the cannula because some surgical instruments, such as steerable surgical instruments used in posterior discectomies, are sometimes larger than the size of the opening defined by the cannula. Therefore, there is a need for a cannula that can be inserted with minimal incision of tissue yet still provide an entrance opening and conduit sized for sufficient instrument passage and operation.
The invention is generally directed to a device and method for performing minimally invasive, percutaneous surgeries to access the spine or other bone structures, organs, or locations of the body. In one embodiment, the invention is an expandable cannula having a tubular body that may be moved between a first, or expanded, size state and a second, or relatively reduced, size state. An actuating mechanism on the tubular body can be actuated to move the tubular body between the first and second size states. In one embodiment, the actuating mechanism is actuated to move the tubular body between the first and second size states, thereby increasing the size at a distal end of the tubular body. In an alternative embodiment, the size at the distal end of the tubular body is decreased by actuating the actuating mechanism to move the tubular body between the first and second size states.
Another embodiment of the invention is a method for using the expandable and retractable cannula to access an internal body part.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:
While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described herein. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
An expandable cannula 10 in accordance with one embodiment of the invention is shown in
The illustrated embodiment of the tubular body 3 is connected at a proximal end to the actuating mechanism 5 and includes a frame 21 formed by ribs 23 and a skirt 25 supported by the ribs 23. Together with the frame 21 and the skirt 25, the tubular body 3 defines a conduit 31 as shown in
The illustrated embodiment of the actuating mechanism 5 includes a rotating member 7 having a textured or roughened perimeter surface 9 to better grip the rotating member 7. The illustrated embodiment of the actuating mechanism 5 also includes a stationary member 29 connected to the rotating member 7.
As shown in
The ribs 23 of the frame 21 are elongated curvilinear members positioned about a circumference of the tubular body 3 in the embodiment shown in
The quantity of ribs 23 used to form the frame 21 can be varied to best suit the intended application of the expandable cannula 10. For example, in the illustrated embodiment, the frame 21 is formed by four ribs 23 (the fourth rib 23 is hidden by the skirt 25). In other embodiments (not shown), the frame 21 is formed by three ribs 23, 5 ribs 23 or a greater number of ribs 23 as desired.
The shape of the ribs 23 used to form the frame 21 can also be varied to best suit the intended application of the expandable cannula 10. For instance,
The ribs 23 are generally bowed as shown in
The overall length of the ribs 23 can be set to suit the particular application and the anatomy of the surgical site. Accordingly, various lengths are contemplated by the invention. In one embodiment, the overall length of the ribs 23 is about 5 inches. In another embodiment, the overall length of the ribs 23 is about 7 inches. In yet another embodiment, the overall length of the ribs 23 is about 9 inches.
The ribs 23 can generally be constructed of biocompatible materials that are sufficiently strong and resilient to withstand pressure exerted by the surrounding tissue and body parts. Examples of suitable materials include metals, such as a surgical stainless steel, and shape memory alloys, such as nitinol, as well as plastics, such as polycarbonate and Delrin®, or other sufficiently strong polymers. In some applications, the ribs 23 are constructed of reusable, durable, sterilizable materials. Alternatively, the ribs 23 are constructed of disposable materials or more lightweight materials.
In one embodiment, the ribs 23 are detachable from the actuating mechanism 5. Thus, the ribs 23 may be more easily sanitized for later use or replaced with new ribs 23 so that the expandable cannula 10 can be used with a subsequent patient or repaired in the event damage occurs to one of the ribs 23.
In the illustrated embodiment, the skirt 25 is supported by the frame 21 such that actuation of the actuating mechanism 5 causes the skirt 25 to move with the frame 21 between the first and second size states. The skirt 25 is generally wrapped around the perimeter of the frame 21 formed by the ribs 23. In the illustrated embodiment, the skirt 25 has compartments 27, or pockets, for engaging the ribs 23 as shown in
The skirt 25 can be secured to the frame 21 at the proximal end of the frame 21 to prevent the skirt 25 from sliding off of the frame 21 during insertion and removal of the expandable cannula 10. For example, the proximal end of the skirt 25 may be adhesively secured to the proximal end of the frame 21. In one embodiment (not shown), the pockets 27 are closed and/or reinforced at a distal end so that the skirt 25 resists being pushed along the ribs 23 toward the proximal end of the frame 21 during insertion of the expandable cannula 10, which would expose portions of the ribs 23 and potentially compromise the conduit 31. Although it is intended that the skirt 25 remain in place during insertion and removal of the expandable cannula 10, the skirt 25 should also be detachable such the skirt 25 is disposable. Alternately, the skirt 25 may be formed of a material that allows it to be sterilized for later, repeated use.
The skirt 25 is preferably constructed of a biocompatible, elastic material that retains a substantially smooth surface when the skirt 25 moves with the frame 21 between the first and second size states. In one embodiment, the skirt 25 is constructed of a material that returns to its original, unstretched form in the absence of mechanical force without wrinkling. In another embodiment, the skirt 25 is provided with pre-stressed or fold lines, for example, pleats, along which the skirt 25 tends to bend when moving between size states. The skirt 25 preferably also resists stretching against forces typically exerted by retracted tissues, body parts, and bodily fluids yet stretches enough against the mechanical force of the frame 21 as it moves between the first and second size states. The skirt 25 can also be constructed of a material that has minimal tendency to grip the surrounding tissue or body parts, which may cause damage to the tissue or body parts. Suitable materials of construction for the skirt 25 include materials such as silicone, latex or of C-Flex®, a general purpose, thermoplastic elastomer sold by Linvatec Corporation, Clearwater, Fla. Other suitable materials include shape memory materials or nitinol. The skirt 25 can also be constructed of an elastic, biodegradable material that may be left in the body to be reabsorbed by the body without damaging tissues in the body. In one embodiment, the biodegradable skirt 25 can further include a coating that has therapeutic benefits, promotes tissue growth, prevents infection, etc. It is also contemplated that the skirt 25 can be constructed of a transparent material for increased visibility.
The actuating mechanism 5 can be actuated by rotating the rotating member 7 in either a clockwise or counterclockwise direction, resulting in movement of the tubular body 3 between the first and second size states. In one embodiment, the rotating member 7 is operated manually but it is also contemplated that other tools and methods can be employed to rotate the rotating member, such as in situations where access to the rotating member is limited or additional leverage is required. The stationary member 29 can also be used for leverage or as a counter force when rotating the rotating member 7 so that actuation of the actuating mechanism 5 does not simply cause the expandable cannula 10 to be shifted from its position within the body. In one embodiment as illustrated by
In the illustrated embodiment, the mechanical linkage 11 is a gear system having a plurality of gears 15, each mounted to one of the ribs 23, and a gear ring 13 on the rotating member 7.
Although spur gears are illustrated, other gear systems such as bevel gears, gear and belt systems, and cam systems are contemplated by the invention. It is further contemplated that the gears 15 can be of varying diameters to allow for localized expansion from one side of the expandable cannula 10 and not the other, for example. Additionally, the gear ring 13 can be located around an exterior perimeter such that the gears 15 rotate around the outside of the gear ring 13 instead of the inside of the gear ring 13 as shown in
Suitable materials of construction for the actuating mechanism 5, including the rotating member 7, mechanical linkage 11, gear ring 13, and gears 15, include materials of sufficient strength to be able to withstand the pressure of the tissues being retracted by the expandable cannula 10, such as stainless steel. The actuating mechanism 5 is preferably constructed of materials that can withstand autoclave temperatures, such that they can be sterilized for subsequent use. The actuating mechanism 5 can also be constructed of biocompatible materials such as surgical stainless steel. Other suitable materials of construction can be used in this invention and one of skill in the art could readily select the appropriate materials based upon the intended application. For example, other materials can be used if the actuating mechanism 5 or other parts of the cannula 10 are integrated for single use applications.
As illustrated in
As is shown in
The invention is not limited to particular sizes for the conduit 31, or the first and second size states, because the actual dimensions of the expandable cannula 10 will depend upon the anatomy of the surgical site and the type of surgery being performed. Accordingly, various sizes are provided by the invention. In one embodiment, the size of the first and second size states can vary between about 19 mm to 25 mm. In another embodiment, the size of the first and second size states can vary between about 19 mm to 40 mm. In the illustrated embodiment, the proximal end of the expandable cannula 10 will retain a constant size. In a particular embodiment, this size is about 19 mm. In other embodiments, the proximal end of the expandable cannula 10 has varying size states. It is further contemplated that the expandable cannula 10 can be continuously adjusted to allow the surgeon to “dial in” to the appropriate first or second size state. Thus, the surgeon may incrementally increase the size or cross-sectional area at the distal end of the expandable cannula 10, permitting the surrounding body tissues to slowly stretch, adapt to the new position, and relax.
The invention has many uses in the surgical field including the spinal surgical field, specifically percutaneous surgical procedures such as laminotomies, laminectomies, foramenotomies, facetectomies, or discectomies. It is also contemplated that the invention may be used for other surgical applications, particularly where minimally invasive surgical fields and still other applications are desired.
The invention additionally provides a method of accessing an internal body part by using the expandable cannula 10 previously described. The method includes the step of forming an opening in the body, such as by an incision in the epidermis. The expandable cannula 10 is then inserted into the body through the opening in a contracted state. In some embodiments, the opening is formed through blunt dissection and the cannula 10 is guided into the opening with the surgeon's fingers. In this embodiment, the cannula 10 is its own dilator. In other embodiments, the opening is formed at more shallow angles and the cannula 10 is guided into the opening with a separate dilator, and possibly a guide wire. With the expandable cannula 10 in position, the conduit 31 forms a working channel. In some instances, it may also be desirable to hold the expandable cannula 10 in place by use of a fixation device such as a mounting bracket attached to a flexible support arm (not shown). This fixation device can be readily adjusted into a fixed position to support for the expandable cannula 10 and provide the surgeon with increased accessibility to the conduit 31. The selection of the appropriate fixation device can be readily accomplished by one of skill in the arm.
Following insertion of the contracted expandable cannula 10 into the body, the surgeon can further expose an internal body part by actuating the actuating mechanism 5 of the expandable cannula 10 to cause the tubular body 3 to move between first and second size states. The surgeon can gradually and incrementally actuate the actuating mechanism 5 until a desired size state is obtained. The surgeon can then lock the expandable cannula 10 by activating the locking device 19.
Once the desired size state has been reached, the surgeon can conduct the surgical procedure through the conduit 31 as necessary, including inserting necessary tools and instruments such as standard surgical implements and visualization scopes. Upon completion of the surgical procedure and removal of the tools and instruments, the surgeon can deactivate the locking device 19 and then gradually decrease the size or cross-sectional area at the distal end of the cannula until a desired size state is obtained by actuating the actuating mechanism 5 to cause the tubular body 3 to move between the first and second size states. If the expandable cannula 10 has been attached to a fixation device, the fixation device is removed, allowing the expandable cannula 10 to be removed from the body. The incision may then be closed using standard surgical procedures.
Following use, the expandable cannula 10 can be sanitized for future use, such as by use of an autoclave or other chemical sanitation processes. In one embodiment, the skirt 25 and/or ribs 23 are also detached from the actuating mechanism 5 and either sanitized for future use or replaced with a new skirt 25 and/or ribs 23.
The particular embodiments disclosed above are intended to be illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above can be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
