Patent Document

CROSS REFERENCE TO RELATED CO-PENDING APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 61/728,479 filed on Nov. 20, 2012 and entitled SYSTEM AND METHOD FOR FORMING A CURVED TUNNEL IN BONE, which is commonly assigned and the contents of which are expressly incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system and a method for forming a curved tunnel in a bone and in particular to device that uses a tube with a slotted front end to form a U-shaped tunnel in the bone. 
     BACKGROUND OF THE INVENTION 
     In several surgical procedures opening of curved tunnels in bone is needed. Examples of these type of surgical procedures include rotator cuff repair and Achilles tendon repair where re-attaching of muscle and ligaments to bone is performed. 
     Prior art technologies for performing these type of surgical procedures involve drilling two separate openings that have intersecting screw paths in order to form the attachment point. These prior art procedures are invasive because they require drilling two separate intersecting openings from two different directions. There is also the possibility that the two drilled openings do not intersect, due to miscalculations of the drill path or inaccuracy in the drilling process. This may result in drilling additional openings in the bone, which increases the level of complexity of the procedure, increases the operation time and also increases the bleeding risk of the patient. 
     Accordingly, systems and methods that simplify the above mentioned surgical procedures are desirable. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system and a method for forming a curved tunnel in a bone by using a drill bit guidance device. The drill bit guidance device includes a tube with a slotted front end, whereby the slots collapse and cause the tube to curve at a predetermined radius as the drill bit moves forward. 
     The present invention also provides a system and a method for attaching a ligament to a bone by forming a curved tunnel in a bone. The method includes first providing a drill and a drill bit guidance device that guides the drill bit to form a U-shaped curved tunnel. Next, drilling a U-shaped tunnel into a bone by entering into a first bone location with the guided drill bit and exiting from a second bone location. Next, threading a suture through the opened U-shaped tunnel and through the ligament that needs to be attached to the bone, and then attaching the ligament to the bone with the threaded suture. 
     In general, in one aspect, the invention features drill system for forming a curved tunnel in a bone including a drill bit guidance device. The drill bit guidance device includes an elongated stationary outer tube extending along a first axis and an elongated inner tube. The elongated inner tube is configured to slidably move within the elongated stationary outer tube along the first axis and to exit from a distal end of the elongated outer tube. The elongated inner tube has a partially slotted distal end portion including a plurality of semi-cross-sectional slots extending perpendicular to the first axis. Each slot is configured to collapse inward in the slot direction when exiting the distal end of the elongated outer tube, thereby curving the distal end portion of the elongated inner tube. 
     Implementations of this aspect of the invention may include one or more of the following features. The drill bit guidance device further includes a drive shaft, a flexible shaft, a drill bit and a flexible actuator rod. The elongated inner tube surrounds the drive shaft, the flexible shaft, and the flexible actuator rod. The drill bit is attached to a distal end of the flexible shaft and a distal end of the drive shaft is attached to a proximal end of the flexible shaft. The flexible actuator rod is arranged parallel to the drive shaft and a distal end of the flexible actuator is attached to the distal end of the elongated inner tube. The curving of the distal end of the elongated inner tube is configured to curve the flexible shaft and to guide the attached drill bit along a curved path. The radius of the curved path is configured to remain constant by maintaining constant the ratio of the length of the drive shaft to the length of the collapsed slotted distal end portion of the elongated inner tube. The drill bit guidance device further includes a universal grip, a handle block, a thrust assembly, and a linkage assembly. The universal grip is attached to the handle block and the handle block has a first through-opening dimensioned to receive the elongated outer tube. The thrust assembly is pivotally linked to the handle block via the linkage assembly and includes a shank chuck, a tube bushing, a thrust end cap, first and second thrust bushings and an actuator slide. The actuator slide has a first through-opening dimensioned to receive the elongated inner tube and the proximal end of the drive shaft is connected to the shank chuck. The proximal ends of the elongated inner tube, the drive shaft and the flexible actuator rod are linked together via the linkage assembly, and the linkage assembly is configured to maintain constant the ratio of the length of the drive shaft to the length of the collapsed slotted distal end portion of the elongated inner tube. The linkage assembly includes first and second vertical links configured to pivotally link the handle block to the elongated inner tube. The linkage assembly further includes first and second horizontal links configured to pivotally link the actuator slide to first and second vertical links, respectively. The linkage assembly further includes third and fourth horizontal links configured to pivotally link the actuator slide to the thrust end cap. The flexible shaft comprises Nitinol wire or stainless steel wire. Each of said slots is wider at the bottom than at the top. The drill system further includes a drill driver having a front opening configured to receive removable attachments, and the drill bit guidance device is configured to be removably attached to the front opening of the drill driver. The thrust assembly is linked to the handle block via a gear mechanism or a cam mechanism. 
     In general, in another aspect, the invention features a method for forming a curved tunnel in a bone including providing a drill and a drill bit guidance device comprising an elongated stationary outer tube extending along a first axis and an elongated inner tube. The elongated inner tube is configured to slidably move within the elongated stationary outer tube along the first axis and to exit from a distal end of the elongated outer tube. The elongated inner tube comprises a partially slotted distal end portion comprising a plurality of semi-cross-sectional slots extending perpendicular to the first axis. Each slot is configured to collapse inward in the slot direction when exiting the distal end of the elongated outer tube, thereby curving the distal end portion of the elongated inner tube. 
     In general, in another aspect, the invention features a method for a method for attaching a ligament to a bone including the following steps. First, providing a drill comprising a drill bit guidance device. The drill bit guidance device guides a drill bit to drill and form a U-shaped tunnel in the bone. Next, drilling a U-shaped tunnel into the bone by entering into a first bone location and exiting through a second bone location. Next, threading a suture through the U-shaped tunnel and through a ligament, and then attaching the ligament to the bone by tying the suture. 
     Among the advantages of this invention may be one or more of the following. The invention provides a method for attaching a ligament to a bone without the use of screws. This eliminates the need for introducing screws or other foreign objects in the bone, which in turn reduces the risks of infection and rejection of the foreign object. The method opens a single curved path, rather than opening at least two separate paths from two different directions and then trying to orient them so that they intersect each other. This reduces the complexity of the surgical procedure, reduces the operation time and reduces the risk of prolonged bleeding. Furthermore, there no need for a separate device for pulling a suture through the intersecting straight paths. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and description bellow. Other features, objects and advantages of the invention will be apparent from the following description of the preferred embodiments, the drawings and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the figures, wherein like numerals represent like parts throughout the several views: 
         FIG. 1A - FIG. 1E  depict schematic views of the steps for performing a ligament re-attachment procedure according to this invention; 
         FIG. 1F  is a process diagram of a ligament re-attachment procedure according to this invention; 
         FIG. 2A  is a perspective view of a drill bit guidance device according to this invention; 
         FIG. 2B  is a perspective view of the drill bit guidance device of  FIG. 2A  with the slotted tube in the “straight” position; 
         FIG. 2C  is a perspective view of the drill bit guidance device of  FIG. 2A  with the slotted tube in the “curved” position; 
         FIG. 3  is a partially exploded view of the drill bit guidance device of  FIG. 2A ; 
         FIG. 4  is an exploded view of the distal end of the drill bit guidance device of  FIG. 2A ; 
         FIG. 5A  is a transparent view of the distal end of the drill bit guidance device of  FIG. 2A ; 
         FIG. 5B  depicts the distal end of the drill bit guidance device of  FIG. 2A  with the slotted tube in the “straight” position; 
         FIG. 5C  depicts the distal end of the drill bit guidance device of  FIG. 2A  with the slotted tube in the “straight” position; 
         FIG. 5D  depicts the distal end of the drill bit guidance device of  FIG. 2A  with the slotted tube in the “curved” position; 
         FIG. 6A  depicts a side view of another embodiment of the drill bit guidance device with the slotted tube in the “straight” position; 
         FIG. 6B  depicts a side view of the embodiment of  FIG. 6A  of the drill bit guidance device with the slotted tube in the “curved” position; 
         FIG. 7A  depicts an enlarged right side view of the thrust assembly of the drill bit guidance device of  FIG. 2A ; 
         FIG. 7B  depicts an enlarged left side view of the thrust assembly of the drill bit guidance device of  FIG. 2A ; 
         FIG. 8A  depicts components of the proximal end of the drill bit guidance device of  FIG. 2A ; and 
         FIG. 8B  depicts exploded components of the proximal end of the drill bit guidance device of  FIG. 2A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1A - FIG. 1E , a ligament re-attachment surgical procedure in the rotator cuff area  80  includes the following. First, a drill  90  and a drill bit guidance device  100  are provided. Drill bit guidance device  100  is placed in front of drill  90  and includes a mechanism that guides the drill bit to drill a U-shaped curved tunnel. Next, the surgeon creates access to the bone area  82 , and holds the distal end  101  of device  100  firmly against the bone  82  with one hand, while the other hand holds the power drill  90  that is attached to the proximal end  102  of the device  100 . Next, the surgeon operates the drill  90  so that it rotates and he pushes the drill forward in the direction indicated by arrow  103  toward the distal end  101  of device  100 , as shown in  FIG. 1A . During this process, a drill bit or burr feeds through the distal end  101  of device  100  and enters a first bone location  83   a . As the drill bit feeds out, it is guided by a tube  110  that causes the drill bit to move through a curved path, as shown in  FIG. 1C . The curved path has a predetermined radius and forms a U-shaped tunnel  83 . The drilling process continues until the drill bit exits the bone from a second bone location  83   b . Next, while still holding the device  100  in place, the surgeon retracts the power drill  90  leaving behind an open U-shaped curved tunnel  83 . The process is repeated again and a second U-shaped tunnel  84  is opened. Next, sutures  85   a ,  85   c  are threaded through the opened U-shaped tunnels  83 ,  84 , respectively, and through the ligament  81  that needs to be attached to the bone  82 , as shown in  FIG. 1D . Finally, the sutures  85   a ,  85   b  are tied and ligament  81  is attached to the bone  82 , as shown in  FIG. 1E . 
     Referring to  FIG. 1F , the process diagram  200 , for attaching a ligament to a bone includes the following. First, providing a drill and a drill bit guidance device that guides the drill bit to form a U-shaped tunnel ( 201 ). Next, drilling a U-shaped tunnel into a bone by entering into a first bone location with the guided drill bit and exiting from a second bone location ( 202 ). Next, threading a suture through the opened U-shaped tunnel and through the ligament that needs to be attached to the bone, and then attaching the ligament to the bone with the threaded suture ( 206 ). 
     Referring to  FIG. 2A , a drill bit guidance device  100  includes a handle  106 , a universal grip  104 , an outer stationary tube  108 , an inner tube assembly  112  and a thrust assembly  140 . Thrust assembly  140  transfers the power drill drive motion to a drive shaft  114  that is housed within the inner tube assembly  112 , as shown in  FIG. 4 . The universal grip  104  is attached to handle  106  and is used to hold the device with one hand while holding the power drill  90  with the other hand. Inner rod assembly  112  is housed within the outer stationary tube  108 . Handle  106  has a first through opening dimensioned to receive and hold the outer stationary tube  108 . Handle  106  also has a second through opening dimensioned to receive and hold a guide rod  148 , shown in  FIG. 3 . Thrust assembly  140  is pivotally linked to handle  106  with link assembly  146 . 
     Referring to  FIG. 3  and  FIG. 4 , inner tube assembly  112  includes a tube  110  with a slotted front portion (“slotted tube”), drive shaft  114 , flexible shaft  116 , flexible actuator rod  118  and drill bit  120 . Drive shaft  114  has a distal end attached to the flexible shaft  116  and flexible shaft  116  is attached to the drill bit  120  with a front end bushing  161 . Flexible shaft  116  allows the drill bit  120  to curve and follow the curving of the slotted tube  110 , as will be described below. In one example, flexible shaft  116  is made of Nitinol wire, stainless steel wire or cable. Flexible actuator rod  118  is arranged parallel to the drive shaft  114  and has a distal end that is connected to the distal end of the slotted tube  110 . The assembled drive shaft  114 , flexible shaft  116 , drill bit  120 , and actuator rod  118  are dimensioned to be housed and move within the slotted tube  110  and slotted tube  110  is dimensioned to be housed and move within the stationary outer tube  108 . A front end tube bushing  109   a  supports the distal end of the drive shaft assembly within the front end of the outer tube  108 . Similarly, a back end tube bushing  109   b  supports the proximal end of the drive shaft assembly within the back end of the outer tube  108   b , as shown in  FIG. 8A . The slotted front portion of slotted tube  110  includes slots  122  that are slightly wider at the bottom of each slot  124  than at the top of the slot, as shown in  FIG. 5C . 
     Referring to  FIG. 7A ,  FIG. 7B ,  FIG. 8A  and  FIG. 8B , thrust assembly  140  includes a shank chuck  142  that connects to the drive shaft  114 , a tube bushing  144 , a thrust end cap  150 , thrust bushings  152   a ,  152   b , and actuator slide  154 . Thrust assembly  140  is pivotally connected to handle  106  and to actuator slide  154  via linkage assembly  146 . Linkage assembly  146  includes left and right vertical links  146   a ,  146   b  that link the handle  106  to the inner tube assembly  112  via a pivot connection  147 . Linkage assembly  146  also includes left and right links  156   a ,  156   b  that provide a straight link between the left and right links  146   a ,  146   b  and the actuator slide  154 . In the embodiment of  FIG. 6A  and  FIG. 6B , linkage assembly  146  also includes left and right links  158   a ,  158   b  that provide a straight link between the actuator slide  154  and the thrust end cap  150 . 
     In operation, as the drill bit  120  feeds out of the outer tube  108 , the slotted front end of tube  110  that is connected to the drill bit  120  follows. As each slot  122  of the slotted tube front exits the outer tube  108 , it collapses inward in the slot direction. This inward collapse of the slots  122  causes the length of the slotted tube  110  to become shorter than the length of the drive shaft  114  and this results in curving of the flexible shaft  116 , which in turn causes the drill bit  120  to follow a curved path as it moves forward. The ratio of the length of the drive shaft  114  to the length of the collapsed slotted tube  110  remains constant throughout the entire range of the drill bit movement causing the radius of the curved path to remain constant. Flexible actuator rod  118  is connected to the distal end of the slotted tube  110  and causes each slot  122  to collapse as it exits the outer tube  108 . In this embodiment, the actuator slide  154  and the slotted tube  110  move at different rates, thereby causing the slots  122  to collapse. Drill bit  120  and drive shaft  114  move the same amount as the slotted tube  110 . The length of the slotted tube  110  is different than the length of the flexible shaft  116  in the curved position. This results in the drill bit  120  moving away from the front end bushing  161 . Flexible actuator rod  118 , drive shaft  114  with the attached drill bit  120  and the slotted tube  110  are connected through a linkage assembly  146  at the proximal end of the device. The linkage  146  provides the proper feed ratio so that the drill bit  120  moves in a curved path with a predetermined radius.  FIG. 2A  depicts the drill bit guidance device  100  with the slotted tube in the start position.  FIG. 2B  depicts the drill bit guidance device  100  with the slotted tube in the “straight” position.  FIG. 2C  depicts the drill bit guidance device  100  with the slotted tube in the “curved” position.  FIG. 5C  depicts the distal end of the slotted tube in the “straight” position and  FIG. 5D  depicts the distal end of the slotted tube in the “curved” position. 
       FIG. 6A  and  FIG. 6B  depict side views of another embodiment of the drill bit guidance device  100  with the slotted tube in the “straight” and “curved” positions, respectively. In this embodiment, linkage assembly  146  includes left and right vertical links  146   a ,  146   b , left and right links  156   a ,  156   b  and left and right links  158   a ,  158   b . Left and right vertical links  146   a ,  146   b  link the handle  106  to the inner tube assembly  112  via a pivot connection  147 . Left and right links  156   a ,  156   b  provide a straight link between the left and right links  146   a ,  146   b  and the actuator slide  154 . Left and right links  158   a ,  158   b  provide a straight link between the actuator slide  154  and the thrust end cap  150 . In this embodiment, slotted tube  110 , actuator slide  154  and drive shaft assembly feed out at different ratios. This keeps the drill bit  120  and the front end bushing  16  at the same spacing throughout the entire range of motion. In other embodiments, a gear mechanism or a cam mechanism is used instead of the linkage assembly  146  to control the ratio of the slotted tube  110  and actuator rod  118  length to the length of the drive shaft  114 . 
     Several embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

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