Abstract:
A system and method for attaching soft tissue to bone. The invention comprises the provision and use of a novel two-part anchor for attaching soft tissue and the like to bone. In one form of the invention, the two-part anchor generally comprises a stake and a cap. The stake is adapted to be positioned in bone and form a stake for impalement by a piece of soft tissue. The cap is adapted to cap soft tissue which has been impaled on the stake and thereby bind the soft tissue to the stake and, hence, to the bone in which the stake is set.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
   This patent application claims the benefit of pending prior U.S. Provisional Patent Application Ser. No. 60/301,596, filed Jun. 28, 2001 by Mary Sinnot et al. for SYSTEM AND METHOD FOR ATTACHING SOFT TISSUE TO BONE), which patent application is hereby incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates to medical devices and procedures in general, and more particularly to systems and methods for attaching soft tissue to bone. 
   BACKGROUND OF THE INVENTION 
   The complete or partial detachment of ligaments, tendons and/or other soft tissues from their associated bones within the body are relatively commonplace injuries, particularly among athletes. Such injuries are generally the result of excessive stresses being placed on these tissues. By way of example, tissue detachment may occur as the result of an accident such as a fall, over-exertion during a work-related activity, during the course of an athletic event, or in any one of many other situations and/or activities. 
   In the case of a partial detachment, the injury will frequently heal itself, if given sufficient time and if care is taken not to expose the injury to further undue stress. In the case of complete detachment, however, surgery may be needed to re-attach the soft tissue to its associated bone or bones. 
   Numerous devices are currently available to re-attach soft tissue to bone. Examples of such currently-available devices include screws, staples, suture anchors and tacks. 
   In soft tissue re-attachment procedures utilizing screws, the detached soft tissue is typically moved back into its original position over the bone. Then the screw is screwed through the soft tissue and into the bone, with the shank and head of the screw holding the soft tissue to the bone. 
   Similarly, in soft tissue re-attachment procedures utilizing staples, the detached soft tissue is typically moved back into its original position over the bone. Then the staple is driven through the soft tissue and into the bone, with the legs and bridge of the staple holding the soft tissue to the bone. 
   In soft tissue re-attachment procedures utilizing suture anchors, an anchor-receiving hole is generally first drilled in the bone at the desired point of tissue re-attachment. Then a suture anchor is deployed in the hole using an appropriate installation tool. This effectively locks the suture to the bone, with the free end(s) of the suture extending out of the bone. Next, the soft tissue is moved into position over the hole containing the deployed suture anchor. As this is done, the free end(s) of the suture is (are) passed through or around the soft tissue, so that the free end(s) of the suture reside(s) on the far (i.e., non-bone) side of the soft tissue. Finally, the suture is used to tie the soft tissue securely to the bone. 
   Alternatively, in some soft tissue re-attachment procedures utilizing suture anchors of the type described above, the soft tissue may first be moved into position over the bone. Then, while the soft tissue lies in position against the bone, a single hole may be drilled through the soft tissue and into the bone. Next, a suture anchor is passed through the soft tissue and deployed in the bone using an appropriate installation tool. This results in the suture anchor being locked to the bone, with the free end(s) of the suture extending out of the bone and through the soft tissue. Finally, the suture is used to tie the soft tissue securely to the bone. 
   In some cases, the suture anchor may include drill means at its distal end, whereby the suture anchor can be drilled into the bone, or drilled through the soft tissue and into the bone, whereby the aforementioned drilling and anchor-deployment steps are effectively combined. 
   Similarly, in soft tissue re-attachment procedures utilizing tacks, the detached soft tissue is typically moved back into its original position over the bone, and then a tack-receiving hole is generally drilled through the soft tissue and into the bone. Then the tack is driven through the soft tissue and into the bone, so that the shaft and head of the tack will hold the soft tissue to the bone. 
   While systems and methods based on the aforementioned screws, staples, suture anchors and tacks are generally effective, they also all suffer from one or more disadvantages. 
   SUMMARY OF THE INVENTION 
   Accordingly, one object of the present invention is to provide a novel system and method for re-attaching soft tissue to bone which improves upon the prior art devices and techniques discussed above. 
   Another object of the present invention is to provide a novel system and method for re-attaching soft tissue to bone which is easy to use and simple to perform. 
   And another object of the present invention is to provide a novel system and method for re-attaching soft tissue to bone which expedites and facilitates the reattachment procedure. 
   Still another object of the present invention is to provide a novel system and method for re-attaching soft tissue to bone which minimizes trauma to the patient during the re-attachment procedure. 
   Yet another object of the present invention is to provide a novel system and method for re-attaching soft tissue to bone which can be used in both open surgical procedures and in closed surgical procedures (e.g., arthroscopic or endoscopic surgical procedures) where access to the surgical site is provided by one or more cannulas. 
   And another object of the present invention is to provide a novel system and method for re-attaching soft tissue to bone which is also usable in the attachment of prosthetic devices, and/or grafts of natural and/or synthetic material, to bone or bone-like structures. 
   These and other objects of the present invention are achieved by the provision and use of a novel two-part anchor for attaching soft tissue and the like to bone. In one form of the invention, the two-part anchor generally comprises a stake and a cap. The stake is adapted to be positioned in bone and form a stake for impalement by a piece of soft tissue. The cap is adapted to cap soft tissue which has been impaled on the stake and thereby bind the soft tissue to the stake and, hence, to the bone in which the stake is set. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
       FIG. 1  is a perspective view of a novel two-part anchor formed in accordance with the present invention; 
       FIG. 2  is a perspective view of the stake used in the two-part anchor shown in  FIG. 1 ; 
       FIG. 3  is a side view of the stake used in the two-part anchor shown in  FIG. 1 ; 
       FIG. 4  is a perspective view of the cap used in the two-part anchor shown in  FIG. 1 ; 
       FIG. 5  is a perspective view of an alternative form of cap; 
       FIG. 6  is a perspective view showing the cap of  FIG. 5  mounted on the stake shown in  FIG. 2 ; 
       FIG. 7  is a stake inserter formed in accordance with the present invention; 
       FIGS. 8-21  are a series of views showing a cap inserter adapted for use with the cap shown in  FIG. 5 ; and 
       FIGS. 22-31  are a series of views showing the two-part anchor of  FIG. 6  securing soft tissue to bone. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Looking first at  FIGS. 1-4 , there is shown a two-part anchor  5  which generally comprises a stake  100  and a cap  200 . 
   Stake  100  is adapted to be positioned in bone and form a stake for impalement by a piece of soft tissue. To this end, stake  100  generally comprises an elongated body  103  having a distal end  105  and a proximal end  110 . Stake  100  has a first exterior thread  115  formed on the distal end thereof. Thread  115  preferably begins at the stake&#39;s distal end  105  and extends for approximately half of the total length of the stake. Thread  115  is preferably a buttress thread to initially facilitate turning stake  100  into bone and to thereafter resist a pulling withdrawal of stake  100  from bone. The proximal end  110  of stake  100  terminates in a sharp point  117 . Intermediate first exterior thread  115  and sharp point  117  is a second exterior thread  118 . Second exterior thread  118  is also a buttress thread, but oriented with a reverse orientation from that of the aforementioned first exterior thread  115 , such that thread  118  will initially facilitate the pushing insertion of cap  200  thereover and to thereafter resist a pulling withdrawal of cap  200  from stake  100 . Stake  100  also comprises a passageway  120 . Passageway  120  opens on the proximal end  110  of stake  100  and preferably extends for substantially the entire length of stake  100 . Passageway  120  has a non-circular cross-section, such that the passageway may receive a driving tool therein and stake  100  may thereafter be turned by the driving tool so as to set stake  100  into bone. By way of example but not limitation, passageway  120  may comprise a hexagonal cross-section, such that stake  100  may be turned by a hexagonal driver of the sort generally known in the orthopedic arts. 
   Cap  200  is adapted to cap soft tissue which has been impaled on stake  100  and thereby bind the soft tissue to the stake  100  and, hence, to the bone in which stake  100  is set. To this end, cap  200  generally comprises a flat body  205  having a distal end  210  and a proximal end  215 . A passageway  220  opens on the proximal end  215  of cap  200  and extends completely through cap  200 , whereby cap  200  can be pushed over the proximal end  110  of stake  100  once tissue has been impaled on the stake, with the distal end  210  of cap  200  engaging the top surface of the tissue impaled on stake  100 . If necessary, cap  200  can be removed from stake  100  by unscrewing the cap from the stake. 
   In  FIG. 4 , cap  200  is shown as having a substantially round profile when viewed in end view. However, if desired, cap  200  may have a substantially elliptical profile such as is shown in  FIGS. 5 and 6 , and may have two or more distally projecting feet  225  formed thereon for engaging tissue captured distal to the cap. 
   Looking next at  FIG. 7 , there is shown a stake inserter  300  which is adapted to set stake  100  into bone. Stake inserter  300  generally comprises a shaft  305  having a distal end  310  and a proximal end  315 . A tip  320  extends distally from the shaft&#39;s distal end  310 . Tip  320  has as non-circular cross-sectional configuration corresponding to the non-circular cross-sectional configuration of the passageway  120  of stake  100 , whereby tip  320  can be inserted into passageway  120  and transfer rotary motion of stake inserter  300  to stake  100 . The tip  320  of stake inserter  300  is preferably long enough to drive stake  100  over the entire length of stake  100 , whereby to spread torsional loads over the entire stake  100 . If desired, tip  320  may be formed long enough to extend out of the end of stake  100 , and may be formed with a share distal tip; in this event, it may be possible to set stake  100  in some types of bone without pre-drilling the bone. Stake inserter  300  also comprises a handle  325  which is secured to the proximal end  315  of shaft  305 , whereby stake inserter  300  may be turned by a surgeon. 
   Looking next at  FIGS. 8-21 , there is shown a cap inserter  400  which is adapted to set cap  200  onto the sharpened proximal end of the stake after tissue has been impaled on the stake. Cap inserter  400  generally comprises a shaft  405  having a distal end  410  and a proximal end  415 . A first recess  420  is formed in distal end  410  and is sized and shaped to receive cap  200  therein. By way of example, cap inserter  400  shown in  FIGS. 8-21  has a substantially elliptically-shaped recess  420  formed therein, wherein the cap inserter may receive the elliptical cap of  FIGS. 5 and 6  therein. Cap inserter  400  also comprises a second recess  425  formed in its distal end  410 . Second recess  425  is sized and shaped to receive the proximal end of a stake  100  when cap inserter  100  is deploying a cap  200  on a stake  100  and trimming off the proximal end of the stake, as will hereinafter be described. 
   Cap inserter  400  also comprises a guillotine cutter assembly  430  which is adapted to trim off the sharp proximal end of stake  100  after cap  200  has been installed thereon. Guillotine cutter  430  comprises an arm  435  which is pivotally attached to shaft  405 , and a blade  440  which is connected to arm  435  and adapted to move radially inwardly as arm  435  is forced parallel to the longitudinal axis of shaft  405 . An outer tube  445  is placed concentrically around shaft  405 ; forcing outer tube  445  distally forces blade  440  radially inwardly, so as to cut off the sharp proximal end of a stake extending into the inserter&#39;s second recess  425 .  FIGS. 8-21  illustrate the structure and operation of the cutter assembly  430 . In  FIGS. 14 ,  15 ,  17 ,  18 ,  20  and  21 , the distal extent of the stake threads  118  is shortened for clearer illustration of the cap inserter tool second recess. 
   Two-part anchor  5  may be used as follows. 
   First, as shown in  FIG. 22 , a hole  500  is formed in a bone  505 . Next, stake  100  is loaded onto the distal end of stake inserter  300  ( FIG. 23 ) and then screwed down into the hole  500  formed in bone  505 . Then stake inserter  300  is withdrawn, leaving stake  100  set in bone  505  with its sharp proximal end protruding. This process is repeated as many times as desired, until one or more stakes  100  are left protruding from bone  505  (FIG.  24 ). Next, a piece of soft tissue  600  is pulled over the sharp protruding proximal ends of stakes  100  and impaled on the stakes (FIG.  25 ). Then a cap  200  is loaded onto cap inserter  400  (FIG.  26 ), aligned with one of the deployed stakes  100 , and then set down over the protruding sharp proximal end of the stake. As this occurs, cap  200  is forced over the proximal end of the stake, so that the cap engages threads  118  and locks thereon. Then outer tube  445  is moved distally, whereby to trim off the sharp proximal end of stake  100 , leaving only cap  200  standing proud over the upper surface of the soft tissue (FIG.  28 ). 
     FIGS. 29-31  illustrate an alternative form of cap  200 . Here, cap  200  is formed with a blind hole  220  extending proximally from its distal end. This blind hole  220  receives the sharp proximal end of stake  100 , whereby cap  200  can envelope and shield the sharp proximal end of stake  100  (FIG.  31 ). 
   Stake  100  and cap  200  can be formed out of a variety of suitable biocompatible materials. In one preferred embodiment of the invention, stake  100  and cap  200  are formed out of bioabsorbable materials. In this form of the invention, stave  100  and cap  200  are preferably configured so that they absorb at different rates, with cap  200  absorbing more quickly and stake  100  absorbing more slowly. Stake  100  is preferably also configured so as to be osteogenic, i.e., so as to encourage bone ingrowth and/or remodeling. By way of example but not limitation, stake  100  may be formed out of PLA, PGA, PDS, polycaprolactone, hydroxyapetite, tricalcuim phosphate, osteogenic proteins, allograft bone, synthetic bone, etc. By way of further example but not limitation, cap  200  may be formed out of PLA, PGA, PDS, polycaprolactone, etc. In this respect it should be appreciated that by forming stake  100  so that it may be driven over substantially the entire length of the stake, such that torsional loads are spread over substantially the entire length of the stake, a broader range of materials and compositions can be used for fabricating stake  100 .