Abstract:
A positioning and installation tool for a fixation implant is inserted through a single, simple drill hole and positioned in place. The device controls the degree to which the implant is deployed and prevents accidental disengagement of the device from the implant before deployment has completed. The device also guides the components of the implant involved in active tendon compression at the aperture of the bone tunnel. The implant is deployed simply by rotating a knob, thereby creating an anchor point of high stiffness and fixation strength. When deployment has completed, the inserter is disengaged from the affixed implant by simply pulling a release mechanism.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. 119(e) of the filing date of Provisional U.S. Application Ser. No. 61/051,671, entitled Inserter for Soft Tissue or Bone-to-Bone Fixation Device, filed on May 8, 2009, which application is expressly incorporated herein by reference, in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to devices, systems and methods for material fixation, and, more particularly, to insertion devices for fixation implants utilized to attach soft tissue to bone, for the purpose of the repair of many soft tissue injuries, such as in the reconstruction of the Anterior Cruciate Ligament (ACL). 
     SUMMARY OF THE INVENTION 
     The disclosed invention is an inserter, intended to be used in conjunction with a soft tissue or bone-to-bone fixation device that will allow a surgeon to repair many soft tissue injuries, such as an Anterior Cruciate Ligament (ACL) injury. The bone-to-bone fixation device, once loaded with a soft tissue graft, is deployed into a prepared bone tunnel using the invention described herein. The fixation implant is packaged sterile and preloaded onto the inserter. In a preferred embodiment, the disclosed inserter device may be utilized with a fixation implant of the type disclosed in commonly assigned U.S. patent application Ser. No. 11/923,526 (the &#39;526 application), entitled Methods and Systems for Material Fixation, filed on Oct. 24, 2007, and herein expressly incorporated by reference in its entirety. 
     Current ACL repairs may be difficult to perform, require more steps, additional procedure time, extra drilling, external jigs or fixtures or multiple assistants. The device is an easy to use positioning and installation tool for a femoral implant of the type disclosed in the &#39;526 application. The device is inserted through a single, simple drill hole and positioned into place. The device controls the degree to which the implant is deployed and prevents accidental disengagement from the implant before deployment has completed. The device also guides the components of the implant involved in active tendon compression at the aperture of the femoral tunnel. The implant is deployed simply by rotating a knob, thereby creating a femoral anchor point of high stiffness and fixation strength. When deployment has completed, the inserter is disengaged from the affixed implant by simply pulling a release mechanism. 
     The use of the device is straightforward, eliminating potential for confusion that may arise when using other femoral fixation technologies. No additional accessories or steps are required. The only required step in preparation for fixation is to locate and drill a single tunnel within the femur. The device is designed to be used by a single operator to minimize the time and cost required to perform the procedure. 
     More particularly, there is provided a device for positioning and deploying a fixation implant, which comprises a handle, an insertion shaft extending distally from the handle, an implant retention mechanism disposed on a distal end of the insertion shaft, an implant deployment control disposed on the handle, and an implant release control disposed on the handle. A suture cleat is also preferably disposed on the handle, on which suture may be wrapped. A safety mechanism is disposed on the device for preventing unintentional actuation of the deployment control. Preferably, the deployment control comprises a rotatable knob and the safety mechanism comprises a safety pin which is removable to permit rotation of the rotatable deployment knob. 
     The inventive insertion device further comprises a mechanism for limiting rotation of the deployment knob to only one direction, wherein because the deployment knob may only be rotated in one direction, the deployment knob may be advanced distally, but not retracted proximally. The implant retention mechanism comprises a ball detent mechanism. The ball detent mechanism comprises a detent ball, a detent ball retainer, and a ball detent rod. An insertion shaft spring is disposed on the ball detent rod. 
     The fixation implant comprises an implant screw for deploying the fixation implant. The implant screw comprises a head having a hole for engaging the detent ball. The implant release control comprises a knob which is movable proximally to disengage the implant retention mechanism from a fixation implant engaged therewith. A hex tube is disposed at the distal end of the insertion shaft. The implant retention mechanism is disposed on the hex tube and the hex tube has a recess for receiving a portion of the fixation implant. 
     The implant screw further comprises internal left-hand threads disposed on an interior surface in the head, defining the hole, so that the implant screw may be disengaged from the fixation implant. A shaft having external threads extends distally from the implant screw head. 
     In another aspect of the invention, there is provided a fixation implant for securing soft tissue to bone or bone to bone, wherein the fixation implant comprises an implant screw for deploying the fixation implant. The implant screw comprises a head having a hole for engaging a detent ball forming part of an implant retention mechanism on an insertion tool. The implant screw further comprises internal left-hand threads disposed on an interior surface in the head, defining said hole, so that the implant screw may be disengaged from the fixation implant, and a shaft having external threads, extending distally from the head. 
     In still another aspect of the invention, there is disclosed a method for inserting a deployable fixation implant into an opening in bone. This method comprises steps of retaining the fixation implant on a distal end of an insertion tool, positioning the insertion tool in a desired bone opening, disengaging a safety mechanism so that a deployment control on the insertion tool may be actuated to deploy the fixation implant, and actuating the deployment control to advance of component of the fixation implant distally, so that portions of the fixation implant are expanded radially to engage adjacent bone. The disengaging step comprises removing a safety pin from the insertion tool to thereby permit rotation of the deployment control, and the actuation step comprises rotating a knob of the deployment control. The inventive method further comprises a step of releasing the fixation implant from the insertion tool. 
     The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying illustrative drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of an insertion device constructed in accordance with the principles of the present invention; 
         FIG. 2  is an exploded view of the insertion device illustrated in  FIG. 1 ; 
         FIG. 3  is a plan view of the insertion device of  FIGS. 1 and 2  as it is being utilized for deploying an implant into a bone tunnel; 
         FIG. 4A  is a plan view of an implant screw which forms a part of the implant being deployed, utilized on conjunction with the insertion device of  FIGS. 1-3  for deploying an implant; 
         FIG. 4B  is a perspective view of the implant screw shown in  FIG. 4A ; and 
         FIG. 4C  is a cross-sectional view of the implant screw of  FIG. 4B , taken along line  4 C- 4 C. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The device  10  of the present invention is an inserter, used for positioning and deployment of a fixation implant like that described in the &#39;526 application. The user interface features of the inserter  10 , depicted in  FIG. 1 , are a handle  12 , a safety pin  14 , an insertion shaft  16 , a deployment knob  18 , a release knob  20 , and suture cleats  22 . 
     At the end of the insertion device  10 , a sutured soft tissue graft (not shown) is loaded onto the implant (not shown), and the free suture strands (not shown) are secured to the suture cleats  22  to allow for suture management and easy insertion of the graft complex. The suture cleats  22  are designed to be easily and quickly wrapped with suture. After the suture has been attached to the cleats, the inserter is placed inside a femoral tunnel  24  in the femur  26  of a patient ( FIG. 3 ). When it has reached the desired deployment location, the inserter and implant are deployed. Deployment is performed by removing the safety pin  14  and rotating the deployment knob  18  in a clockwise fashion until the deployment knob  18  comes into contact with the inserter handle  12 , or until it can no longer be turned. An implant (not shown) is attached to the tip of the insertion shaft  16  by means of a ball detent mechanism ( FIG. 2 ), comprising a detent ball  28 , a detent ball retainer  30 , and a ball detent rod  32 , on which is disposed an insertion shaft spring  34 . The ball detent mechanism engages with a hole  36  ( FIG. 4A ,  4 B,  4 C) in an implant screw  38 . Deployment motion of the inserter  10  is ratcheted and is limited to the clockwise direction to prevent accidental undeployment. By rotating the deployment knob  18 , the diamond wedge of the implant expands the implant arms outward, which provide fixation by engaging against the wall of the femoral tunnel  24 . To disengage the implant from the inserter  10 , the implant release knob  20  is pulled, releasing the detent mechanism. The insertion device can then be removed from the soft tissue graft implant site after any suture has been detached from the suture cleats  22 . 
     The device may come preloaded with the fixation implant attached to the inserter tip  40  ( FIG. 3 ).  FIGS. 4A-4C  show the implant screw  38 , held to a hex tube  42  of the inserter  10  by means of the aforementioned ball detent mechanism and hole  36  in the implant screw. The head  44  of the implant screw  38  has internal left hand threads  46  ( FIG. 4C ) in order to remove the screw if a revision of the implant should be necessary. To remove the screw, a left-hand threaded removal tool is screwed into the hex head  44  of the screw, securing the screw to the removal tool. The tool is then rotated in a counterclockwise direction to unscrew and disengage the screw from the implant. 
     Now referring more particularly to  FIG. 2 , a threaded ratchet shaft  48  has a multitude of cuts running parallel to its length, designed to engage a pawl  50 , limiting its rotation to the clockwise direction. The pawl  50  is fitted over a pawl axle  52  which rests inside a mated cavity in a handle bottom  54 . As the threaded ratchet shaft  48  rotates clockwise, the pawl  50  is deflected downwards towards the handle bottom  54 . When the pawl  50  comes into contact with one of the cuts in the threaded ratchet shaft  48 , it is returned to the engaging antirotation position by a torsion spring  56 . If motion is attempted in the counterclockwise direction, the flat face of the cutout in the threaded ratchet shaft  48  engages the flat face of the pawl  50 , preventing antirotation. A leaf spring may be substituted for the pawl  50  and torsion spring  56  if it is positioned such that it engages the flat face of the threaded ratchet shaft  48 . 
     The deployment knob  18  may be attached to the threaded ratchet shaft  48  by means of an alignment pin  58 . As the deployment knob  18  rotates the threaded ratchet shaft  48  in a clockwise direction, it is translated linearly forward by a stationary translation nut  60 . The translation nut  60  is fitted inside a cavity in the handle bottom  54  and the handle top  62 . The deployment tube  64 , which engages with and turns the implant screw, is affixed to the threaded ratchet shaft  48 . The threaded ratchet shaft  48  and implant screw are threaded so that the turn to travel ratio are 1:1 between the two components. Therefore, as the threaded ratchet shaft  48  and deployment tube  64  rotate, the per-turn linear travel of the threaded ratchet shaft  48  is equal to the linear travel of the implant screw within the implant body. 
     The inserter tip  40  interfaces with the compression pads on the femoral implant to prevent implant rotation and assists in aligning and guiding the compression pads as they separate. The insertion shaft  16  is preferably a hollow cylindrical collar that is allowed to freely slide over the deployment tube  64 . An anti-rotation washer  66  has a machined groove that aligns to a longitudinal rib in the handle top  62 . The anti-rotation washer has a positive spring bias created by the insertion shaft spring  34 . The insertion shaft spring  34  is constrained by a rib within the handle top  62 . As the assembly of the inserter tip  40 , insertion shaft  16 , and anti-rotation washer  66  moves distally during the course of implant deployment, the insertion shaft spring  34  compresses, providing a reaction force that ensures the inserter tip  40  remains engaged with the implant. 
     The deployment tube  64  contains a hollow cylindrical center portion that allows the ball detent rod  32  to slide freely within. The ball detent rod  32  also fits within the detent ball retainer  30  that is fixed inside the tip of the deployment tube  64 . The purpose of the detent ball retainer  30  is to retain the detent ball  28  within the deployment tube  64  and to constrain its motion inwards and outwards from the engaging hex face of the deployment tube  64 . The inside engaging hex face of the deployment tube  64  is drilled in such a manner that the detent ball  28  is prevented from falling out of the assembly yet is still allowed to protrude enough for significant engagement with the implant screw. 
     The detent ball  28  is sandwiched above the detent ball retainer  30  and below the engaging hex face of the deployment tube  64 . As the ball detent rod  32  slides into the detent ball retainer  30 , it pushes the detent ball  28  from the engaging hex face of the deployment tube  64 . In this state, the detent ball  28  protrudes a distance out of the engaging hex face of the deployment tube  64  and is prevented from retracting back into the engaging hex face by the support of the ball detent rod  32  underneath. 
     The ball detent rod  32  is connected to a spring shaft  68  which is equipped with an engagement spring  70  that translates a positive engagement force to the ball detent rod  32 . The engagement spring  70  is confined within the deployment knob  18  and a deployment knob cover  72  which it is compressed by when the spring shaft  68  is retracted. 
     It is to be understood that the figures of the bone and anchors seen above are purely illustrative in nature, and are not intended to limit the application of the inventive embodiments to any particular physiological application or purpose. The invention is applicable to many different types of procedures involving, in particular, the attachment of connective or soft tissue to bone. All of the terms used herein are descriptive rather than limiting, and many changes, modifications, and substitutions may be made by one having ordinary skill in the art without departing from the spirit and scope of the invention, which is to be limited only in accordance with the following claims.