Abstract:
A suturing instrument for placing mattress stitches in soft tissue, such as a rotator cuff, includes an elongate shaft with both a stationary jaw and a movable jaw disposed at the distal end thereof. The shaft is coupled to a handle grip at the proximal end, which is configured to manipulate the jaws into open and closed positions. The jaws are configured to allow for a traumatic grasping of soft tissues. The stationary jaw may include a molded tip that holds and positions opposite ends of a single strand of suture material. The serrated upper jaw is configured to grasp and immobilize the tissue to be sutured. Hooked needles are movably positioned to pierce the grasped and immobilized tissues, and to engage and retrieve the opposite ends of the single strand of suture material. The handle is released to open the moveable jaw, whereupon the instrument may be withdrawn, trailing the suture, and leaving a mattress stitch in the grasped tissue.

Description:
This application is a continuation under 35 U.S.C. 120 of U.S. patent application Ser. No. 10/308,732, filed on Dec. 3, 2002, now U.S. Pat. No. 6,770,084, which claims the benefit under 35 U.S.C. 119(e) of Provisional U.S. Application Ser. No. 60/391,676, entitled  Suture Capture Device , and filed on Jun. 26, 2002, wherein both of these applications are expressly incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method and apparatus for placing sutures in soft tissue, and more particularly to methods and devices for arthroscopic repair of a tom rotator cuff. 
     Suturing of body tissues is a time consuming aspect of most surgical procedures. Many surgical procedures are currently being performed where it is necessary to make a large opening to expose the area of, for instance, the human body that requires surgical repair. There are instruments that are becoming increasingly available that allow the viewing of certain areas of the body through a small puncture wound without exposing the entire body cavity. These viewing instruments, called “endoscopes”, can be used in conjunction with specialized surgical instrumentation to detect, diagnose, and repair areas of the body that were previously only able to be repaired using traditional “open” surgery. In the past, there have been many attempts to simplify the task of driving a needle carrying suture through body tissues to approximate, ligate and fixate them. Many prior disclosures, such as described in U.S. Pat. No. 919,138 to Drake et al, employ a hollow needle driven through the tissue with the suture material passing through the hollow center lumen. The needle is withdrawn, leaving the suture material in place, and the suture is tied, completing the approximation. A limitation of these types of devices is that they are particularly adapted for use in open surgical procedures where there is ample room for the surgeon to manipulate the instrument. 
     Others have attempted to devise suturing instruments that resemble traditional forceps, such as U.S. Pat. No. 3,946,740 to Bassett. These devices pinch tissue between opposing jaws and pass a needle from one jaw through the tissue to the other jaw. Graspers then pull the needle and suture material through the tissue. A limitation of these designs is that they also are adapted primarily for open surgery, in that they require exposure of the tissues to be sutured in order that the tissue may be grasped or pinched between the jaws of the instrument. This is a severe limitation in the case of endoscopic surgery. 
     The term “endosurgery” means “endoscopic surgery”, or surgery performed using an endoscope. In conjunction with a video monitor, the endoscope permits the surgeon to remotely visualize the operative site. Operations using an endoscope are significantly less invasive when compared to traditional open surgery. Patients usually return home the next day, or in some cases, the same day of the endosurgical procedure. This is in contrast to standard open surgical procedures where a large incision divides the muscle layers and allows the surgeon to directly visualize the operative site. Patients may stay in the hospital for 5 to 6 days or longer following open surgery. In addition, after endosurgical procedures, patients return to work within a few days versus the traditional 3 to 4 weeks recuperative period at home following open surgery. 
     Access to the operative site using endosurgical or minimally invasive techniques is accomplished by inserting small tubes, known as trocars, into a body cavity. These trocars have a diameter of, for example, between 3 mm and 30 mm and a length of about 150 mm (6 inches). There have been attempts to devise instruments and methods for suturing within a body cavity through these trocar tubes. 
     Such an instrument is disclosed by U.S. Pat. No. 4,621,640 to Mulhollan et al. Mulhollan et al. describe an instrument that may be used to hold and drive a needle, but make no provision for retrieval of the needle from the body cavity, nor the completion of the suture by tying. The instrument disclosed by Mulhollan et al. is limited, in that the arc through which the needle must be driven is perpendicular to the axis of the device. 
     Another such instrument, intended for endoscopic use, is described in U.S. Pat. No. 4,935,027 to Yoon. This instrument uses oppositional hollow needles or tracks pushed through the tissue and adapted to create a tract through which the suture material is pushed. It is not clear how these curved tracks would be adapted to both be able to pierce the tissue planes illustrated, parallel to the tips of the tracks, and be curved toward each other to form the hollow tract. 
     Yet another instrument and method is shown by Caspari in U.S. Pat. No. 4,923,461 issued May 8, 1990 and U.S. Pat. No. 4,957,498 issued Sep. 18, 1990. The Caspari patents disclose an endoscopic instrument suitable for use through a trocar that resembles the Yoon approach, but with a single hollow needle on one of a set of oppositional jaws. The jaws simultaneously close, grasping the tissue. The jaw opposite the hollow needle has a window through which the hollow needle passes as the jaws close, freeing the lumen of the hollow needle from the tissue. Much like Yoon, a suture or suture snare is pushed down through the lumen and retrieved from the suture site, the jaws released, and the suture pulled back out through the trocar. This device may be used to place simple stitches in tissues that have been mobilized and have an edge accessible to the jaws. A limitation of the device is the manipulation that must be done with the snare if a suture other than a monofilament is used. 
     Another instrument specifically adapted for the orthopedic surgeon for the repair of a torn anterior cruciate ligament or for meniscal repair is disclosed in U.S. Pat. No. 4,836,205 to Barrett. Barrett combines in a single instrument the functions of grasping the tissue to be sutured and the passing of the needles through that tissue. It is to be understood that this instrument is designed for use specifically under endoscopic view, and through trocars as previously described. A fairly generic endoscopic grasper is disclosed that has been adapted to allow for a hollow lumen from the handle of the grasper down to the distal tip of the grasper jaws. An elongate needle of 8 to 10 inches in length may be passed through this hollow lumen. The needle, being significantly longer than the grasper, is introduced through the handle of the grasper, and may be driven through the tissue being held in the grasping jaws of the device. The needle is then retrieved from the tissue via a trocar port placed substantially opposite the port through which the grasper is introduced. If a mattress stitch is desired, two needles attached to opposite ends of a suture are both passed through the tissue and retrieved. A limitation of this device is that there must be both visual and physical access to both sides of the tissue flap to be sutured. This requires trocars to be placed opposite each other and roughly on a line intercepting the tissue. This is a severe limitation in the instance of shoulder repair, and specifically in repair of the rotator cuff. 
     Yet another instrument adapted for use in endoscopic procedures is described by Garman et al in U.S. Pat. No. 5,499,991. This instrument has an elongated housing provided with a needle tip and a lateral opening near the sharpened needle tip. A suture engaging hook, typically formed from wire, is extendable through the lateral opening and away from the axis of the elongated housing by virtue of being predisposed to bend away from the axis in order to snare the suture. The hook is situated at the distal end of an elongated flexible support which is pre-formed in order to enable the hook to be laterally displaced from the axis of the needle tip when the support is moved distally relative to the lateral opening. When a suture is engaged by the hook, the hook is retracted proximally in order to place and hold the suture adjacent the lateral opening. The instrument is somewhat limited in the case of rotator cuff repair in that an additional instrument would need to be introduced into the joint to immobilize the tissues sufficiently to allow the needle tip to penetrate the tissues to be sutured. Also, no provision is made for capturing the two ends of a suture to place a mattress stitch, save repeating the prior steps. 
     A similar instrument is disclosed in U.S. Pat. Nos. 5,312,422 and 5,474,565 issued to Trott. These patents also describe a needle structure adapted for penetration of soft tissues and suture retrieval. A substantially flat suturing needle with a hook feature is illustrated which can engage a suture to an outer housing, thereby presenting a relatively smooth surface at the distal end of the needle to minimize tissue trauma. The limitations mentioned above are evident here as well. The requirement for additional instrumentation to immobilize the tissues, and the lack of provision for a mattress stitch are paramount. There have been other attempts to improve the methods of tissue repair. These include the development of staplers and anchoring devices. In response to some of the aforementioned problems in placing sutures in tissues endoscopically, manufacturers have developed tissue staplers. These devices utilize stainless steel or titanium staples that are constructed much like the staples used to hold papers together. The major disadvantage of these kinds of staplers is that they leave metal in the body. For some tissues this is not a problem, however in some procedures, metal staples left within the tissues can be a major hindrance to the healing process. 
     Orthopedic surgeons have begun to explore alternatives to the traditional open approach for the many indications requiring reconstruction of some aspect of the shoulder. As they did in adopting minimally invasive approaches to knee repair and reconstruction, the use of either an endoscope or a “mini-open” approach is gaining in popularity with surgeons, patients and third party payers. It is an increasingly common problem for tendons and other soft, connective tissues to tear or to detach from associated bone. One such type of tear or detachment is a “rotator cuff” tear, causing pain and loss of ability to elevate and externally rotate the arm. Complete separation can occur if the shoulder is subjected to gross trauma, but typically, the tear begins as a small lesion, especially in older patients. 
     Less invasive arthroscopic techniques are beginning to be developed in an effort to address the shortcomings of open surgical repair. Working through small trocar portals that minimize disruption of the deltoid muscle, a few surgeons have been able to reattach the rotator cuff using various bone anchor and suture configurations. The rotator cuff is sutured intracorporeally using instruments and techniques such as the Caspari punch previously described. This creates a simple stitch instead of the more desirable mattress or Mason-Allen stitch. Rather than thread the suture through trans-osseous tunnels which are difficult or impossible to create arthroscopically using current techniques, an anchor is driven into bone at a location appropriate for repair. The repair is completed by tying the cuff down against bone using the anchor and suture. 
     Early results of less invasive techniques are encouraging, with a substantial reduction in both patient recovery time and discomfort. However, as mentioned, this approach places only one loop of suture in the cuff for each anchor, reducing the fundamnental strength of the repair. The knots in the tendon can be bulky and create a painful impingement of the tendon on the bone. This is because the knots end up on top of the cuff, in the sub-acromial space, and have the opportunity to rub on the acromion as the arm is raised. Because non-absorbable suture materials are used for these types of repairs, the suture and associated knots are not absorbed into the body, and hence provide a constant, painful reminder of their presence. None of the prior art devices are adaptable to effect the placement of a mattress stitch in grasped tissues, nor are they adaptable to place sutures precisely and controllably while making provision for needle retrieval when using endoscopic techniques. None of the prior art devices make it possible to place a mattress stitch into, for example, the supraspinatus tendon utilizing an endoscopic approach. 
     What is needed, therefore, is a family of novel suturing devices that overcome the above described disadvantages of prior known devices in a simple and economical manner. The devices should be capable of arthroscopically creating a mattress stitch in a tendon to increase the soft tissue pullout strength of the repaired tendon. 
     SUMMARY OF THE INVENTION 
     Accordingly, the inventors have developed a new and novel approach to securing a mattress stitch in a tissue flap. An instrument that combines the function of both grasping the tissue and passing sutures through the tissue to form a mattress stitch is herein described. The instrument includes a pair of grasping jaws that oppose each other along a line substantially perpendicular to the long axis of the instrument. The distal end of the instrument incorporates the fixed jaw, and proximal to that jaw is a moveable jaw that is controlled by the user via a lever on the handgrip. 
     In a preferred method of the present invention the instrument is inserted through a portal known as a trocar cannula. The portal is created by first making an incision in the skin, and then inserting a cannula through the incision to the repair site. The distal end of the instrument is inserted through the cannula under direct visualization from a second trocar cannula that has been previously inserted. The visualization is accomplished via an endoscope, of a type well known in the art. The instrument is inserted until the jaws reach, for example, tom rotator cuff tissue. In operation, the distal end of the grasper aspect of the instrument is positioned at the repair site underneath the tissue to be grasped. The moveable jaw pivots toward the stationary jaw by squeezing the handle lever. The handle lever moves inward by pivoting about a pivot pin. Once the appropriate section of tissue is isolated and grasped by the jaws, the lever may be locked in its closed position using a latch mechanism. 
     Once the surgeon is satisfied with the placement of the grasper on the grasped tissue, the surgeon can then deploy the suture needles to create a mattress stitch in the tissues, for example, the above-mentioned torn rotator cuff. In operation, the suture needles may be advanced through the grasped tissues by pulling on a second lever. The lever is directly connected to the needles via a connecting rod, and the lever is pulled against the force of a return spring. In turn, the connecting rod pushes a needle carriage, with suture needles held in the carriage. The needle carriage resides behind the proximal moveable jaw of the instrument, and, at the urging of the lever via the connecting rod, is able to move distally with the needles passing around the moveable jaw. As the carriage moves distally, the tips of the suture needles begin to clear the distal edge of apertures created in a more proximal portion of the stationary jaw, and begin to penetrate through the top of the grasped tissue and advance distally towards the more distal portion of the stationary jaw. 
     The stationary distal jaw incorporates two apertures that are adapted to receive the ends of the suture. Secondary open channels perpendicular to the suture apertures are configured with a specific geometry designed to direct the suture needles across the apertures containing the ends of the sutures. As the suture needles approach the end of their stroke, the distal ends of the needles have passed completely through the grasped tissues and begin to enter the secondary open channels in the stationary distal jaw. 
     At this point, any pull force being applied by the grasper on the grasped tissues is relaxed. Once the tissue is in a relaxed state, the jaws of the grasper are then opened. The handle lever is unlocked from the locking mechanism and returns to an open position due to the pull force exerted on it by means of a return spring. As the return spring pulls on the lever, it pivots about a pin. 
     To complete the pull out of the suture needles, it is necessary to pull on the grasper, and to remove it from the repair site. The instrument can be retracted back through the portal via the trocar cannula. As the instrument is removed from the suture site, the free ends of the suture are retrieved as well. This causes the suture to pass through the tissues at the puncture sites. As the suture is pulled through, the loop end of the suture is pulled snug against the underside of the tissues to form what is referred to as a mattress stitch. This process may be repeated as necessary, depending on the number sutures required for the particular procedure being undertaken. 
     Now it may be seen by those skilled in the art, that the combination of grasping tissues to be sutured and precisely placing a mattress stitch in the grasped tissues, while working through a trocar port, effects a significant advance in the art. Advantages of the present invention thus include providing an endoscopic instrument adapted for the grasping of tissues and creating a mattress stitch within those tissues, as well as the provision of a suturing instrument that allows for the reloading of additional sutures for placement of subsequent stitches. Additionally, the inventive system is advantageous in that it provides for direct capture of the suture material. 
     More particularly, there is provided in one preferred embodiment of the present invention a suturing device, comprising a distal portion which is engaged with a length of suture, as well as a needle which is axially movable distally and proximally. A soft tissue receiving portion, preferably comprising a clamp having first and second jaws, wherein one of the first and second jaws is movable relative to the other to grasp soft tissue therein, is disposed proximally of the distal portion. A ramp portion for moving the needle radially inwardly and outwardly as the needle moves axially over the ramp portion is also provided. 
     In a preferred embodiment, the distal portion for retaining the suture comprises a suture cartridge with a molded tip, having grooves for accommodating the suture. The ramp portion comprises a radially outwardly sloping entrance ramp for moving the needle radially outwardly as the needle moves axially in a distal direction, as well as a radially inwardly sloping retraction ramp for moving the needle radially inwardly as the needle moves axially in a proximal direction. The needle comprises a distal point, a proximal shaft, and a hook defining a suture holding area. 
     The hook portion of the needle is uniquely designed to provide a positive tactile indication as to when the suture has been capture within the suture holding area. This design includes a terminus of the hook, which is cantilevered proximally from a distal end of the needle. A bump on the needle in a location opposed to the hook terminus is provided, so that the hook terminus and the bump together provide a tactile sensation to a user when suture passes thereover into the suture holding area. 
     In preferred embodiments, a second needle, as well as a second ramp portion, is provided, so that a mattress stitch may be created. A sheath, which is slidable relative to the needle, is provided for selectively covering each needle, particularly when the needle is being retracted proximally through the soft tissue, to prevent unnecessary damage thereto. 
     In another aspect of the invention, there is provided a needle for a suturing device, which comprises a distal point, a proximal shaft, and a hook defining a suture holding area. As noted above, the needle preferably further comprises a terminus of the hook, which is cantilevered proximally from a distal end of the needle, as well as a bump on the needle in a location opposed to the hook terminus. 
     In still another aspect of the invention, there is described a method of suturing soft tissue using a suturing device, which comprises steps of retaining a portion of soft tissue to be sutured, and moving a needle having a hook which defines a suture holding area distally, so that the hook is disposed in a location past the portion of soft tissue and past a length of suture which is retained on a distal portion of the suturing device. Then, the needle is moved proximally in order to capture the suture so that it is retained in the suture holding area. Once the suture is captured, the needle is moved a further distance proximally, so that the needle draws the suture through the portion of soft tissue, thereby suturing the soft tissue. Preferably, when the needle is moved distally, it is also moved radially outwardly in order to avoid contacting, and possibly damaging, the length of suture. Additionally, when the needle is moved proximally, it is also moved radially inwardly in order to ensure proper capture of the suture. In preferred methods, it is further desirable to cover the needle with a sheath prior to retracting the needle proximally through the soft tissue. 
     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 
         FIGS. 1A through 1E  are detail plan views of the distal end of an instrument constructed in accordance with the principles of the present invention, illustrating the general structure and operation of the instrument; 
         FIGS. 2A through 2E  are detail side views of the distal end of the instrument of  FIGS. 1A through 1E , which again illustrate the general structure and operation of the present invention; 
         FIGS. 3A through 3E  are cross sectional plan views of the distal end of the instrument of  FIGS. 1A through 1E , showing the relationship between the body structure and the needle geometry; 
         FIG. 4  is a detailed view of a needle of the present invention; 
         FIG. 5  is a detailed view of the needle of  FIG. 4  with an associated sleeve; 
         FIG. 6  is a detailed view of an alternative embodiment of a needle of the present invention; 
         FIG. 7  is a detailed view of another alternative embodiment of a needle of the present invention; 
         FIG. 8  is a detailed view of still another alternative embodiment of a needle of the present invention; and 
         FIG. 9  is a perspective view of the needle of  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention relates to a method and apparatus for the arthroscopic repair of tom tissue and bone at a surgical repair site using an inventive device which is a combination tissue grasper and suture placement device. Although the present invention is described primarily in conjunction with the repair of a tom rotator cuff, the apparatus and method could also be used in arthroscopic repair at other sites, such as the knee, elbow, hip surgery, and for other surgical techniques for securing suture in the soft tissues of the body. 
     A description of the basic functional elements of suture capture and retrieval, in accordance with the principles of the invention, follows. 
     Referring to  FIGS. 1A through 1E , there may be seen a plan view of the distal end of a suturing device  10  that includes a pair of needles  12   a  and  12   b , a lower jaw  14 , and a suture cartridge  16 . The needles  12   a ,  12   b  further include sliding tubes or sheaths  18   a  and  18   b , needle shafts  20   a  and  20   b , needle points  22   a  and  22   b , and hooks  24   a  and  24   b . The suture cartridge  16  comprises a molded tip  26  with grooves  28   a  and  28   b , into which the two ends  30   a  and  30   b  of a length of suture are threaded. 
     Referring to  FIG. 1B , the needles  12   a ,  12   b  are advanced distally toward the suture cartridge  16  in preparation for capture and retrieval of the two ends  30   a ,  30   b  of the length of suture. It is to be understood that the entire length of the suture which includes the two ends  30   a ,  30   b  is not seen in this illustration. The loop of suture between the two ends  30   a ,  30   b  trails beneath the distal end of the suturing device  10  and is thus not visible. It will be described more fully later how the capture of the two ends of a suture can be used to create what is known in the art as a mattress stitch. 
     Referring now to  FIG. 1C , it may be seen that the needles  12   a ,  12   b  are further advanced distally toward the suture cartridge  16  and past the two ends  30   a ,  30   b  of the suture, placing the hooks  24   a ,  24   b  in position past the two suture ends  30   a ,  30   b  in preparation for capture. As it may be seen in  FIG. 1D , as the needles  12   a ,  12   b  are retracted proximally, the hooks  24   a ,  24   b  engage the two suture ends  30   a ,  30   b  and capture them for retrieval. As the needles  12   a ,  12   b  are further retracted proximally as shown in  FIG. 1E , the sliding tubes  18   a ,  18   b , held stationary by frictional forces exerted by tissue (not shown), cover the hooks  24   a ,  24   b  and assist in the engagement of the two ends  30   a ,  30   b.    
     Having understood the basic structure and nature of the suture retrieval mechanism, a more complete disclosure of how this mechanism may be used to place a stitch, and more specifically, a mattress stitch, in soft tissues will now be described. Referring now to  FIGS. 2A through 2E , there may be seen detail side views of the same suturing device  10  as described in  FIGS. 1A through 1E . The inventive device  10  includes the suture ends  30   a ,  30   b  of a single strand of suture  32 , and an upper jaw  34 , which includes teeth  36 . Referring now to  FIG. 2B , soft tissue  38  is introduced into the space between the upper jaw  34  and the lower jaw  14 . By means of a mechanism not discussed or shown herein, but of a type well known to those skilled in the art, the upper jaw  34  is pivoted about an axis, causing it to clamp or grasp the soft tissue  38  and immobilize it between the teeth  36  of the upper jaw  34  and the lower jaw  14 . Referring now to  FIG. 2C , it may be seen that the needles  12  have been advanced distally through the soft tissue  38  and in engagement with the suture cartridge  16  with the needle points  22   a ,  22   b  advancing beyond the suture ends  30   a ,  30   b.    
     It is to be understood that in this view, only one needle  12   a  of the two needles  12   a    12   b  may be visualized, but that a concomitant needle  12   b  is penetrating the tissue along a substantially parallel path, as previously illustrated in  FIG. 1C . The relative position of the needles  12   a ,  12   b  in  FIGS. 1C and 2C  is substantially the same. As seen in  FIG. 2D , the needles  12   a ,  12   b  are retracted proximally, trailing the suture  32  by virtue of having captured the suture ends  30 . In this way, the suture  32  is placed through the soft tissue. Referring to  FIG. 2E , it may be seen that the upper jaw  34  has been pivoted away from the soft tissue  38 , allowing the suturing device  10  to be retracted away from the soft tissue  38 , pulling the suture  32  completely through the soft tissue  38 . The result of this action is the placement of a mattress stitch in the grasped tissues in a manner similar to that previously described. 
     As will now be shown, there are certain characteristics, geometries and interfaces between parts that combine to optimize the performance of the suture capture mechanism. Repeatable capture of the suture material, as well as minimizing damage to the suture ends are objects of the present invention. By referring to  FIGS. 3A  through  3 E, the specific methods and devices that facilitate suture capture in accordance with the principles of the invention will be described. 
       FIGS. 3A through 3E  depict cross sections taken along the lines  3 - 3  in  FIG. 2A . Referring now to  FIG. 3A , there is seen the suture device  10  which includes the needles  12   a ,  12   b , lower jaw  14 , suture cartridge  16 , and suture ends  30   a ,  30   b . The upper jaw  34  and the soft tissue  38  have not been shown in these figures for clarity. It is possible to now see entrance ramps  40   a ,  40   b  and retraction ramps  42   a ,  42   b  that are in the path of the needles  12   a ,  12   b . By referring to  FIG. 3B , it may be seen that as the needles  12   a ,  12   b  move distally in the direction of the suture cartridge  16 , the tips of the needles  12   a ,  12   b  engage the entrance ramps  40   a ,  40   b . The engagement with the entrance ramps  40   a ,  40   b  deflects the needles  12   a ,  12   b  such that the needle points  22   a ,  22   b  are directed over and away from the suture ends  30   a ,  30   b , preventing the needle points  22   a ,  22   b  from piercing or otherwise damaging the suture ends  30   a ,  30   b . Further distal movement of the needles  12   a ,  12   b , as shown in  FIG. 3C , allows the hooks  24   a ,  24   b  to be disposed distally of the suture ends  30   a ,  30   b  and in position to capture the suture upon retraction. It is to be noted that, at this juncture, the sliding tubes  18   a ,  18   b  have entered the area of the entrance ramps  40   a ,  40   b , and have begun to ride up the entrance ramps  40   a ,  40   b , thus further deflecting the needles  12   a ,  12   b.    
     Referring now to  FIG. 3D , it may be appreciated that as the needles  12   a ,  12   b  are retracted proximally, the needle hooks  24   a ,  24   b  ride down the retraction ramps  42   a ,  42   b  and under the suture ends  30   a ,  30   b , thereby capturing the suture ends  30   a ,  30   b  in the hooks  24   a,b , and allowing the suture ends  30   a ,  30   b  to be peeled away from the suture cartridge  16  and retracted proximally. It may also be appreciated that as the needle shafts  20   a ,  20   b  retract, the sliding tubes  18   a ,  18   b  remain motionless in the soft tissue (not shown), allowing the sliding tubes to cover the gap made by the hooks  24   a ,  24   b  and allowing smooth passage through the tissue. This retraction may be appreciated by comparing the position of the sliding tubes  18   a ,  18   b  relative to the hooks  24   a ,  24   b  in  FIGS. 3D and 3E . Once the sliding tubes  18   a ,  18   b  have covered the gap, they retract along with the needle shafts  20   a ,  20   b  back through the soft tissue  38 . 
     A more complete and detailed description of the construction and operation of the needles may be understood by referring to  FIGS. 4 ,  5  and  9 , where there may be seen, in isolation, a needle  112  constructed in accordance with the principles of the present invention, wherein like elements to those described in prior embodiments bear like reference numerals, preceded by the numeral 1. It is intended that the needles described in connection with these figures may be utilized in the embodiments shown in  FIGS. 1-3 . The needle  112  thus includes a needle shaft  120 , and a flattened distal portion  154 . The flattened distal portion  154  of the needle  112  includes a hook  124 , comprising a bump  158 , a hook terminus  160 , a hook entrance  162 , a suture holding area  164 , and a needle point  122 . The specific geometry of the needle  112  that is described herein is to be understood as being representative of a family of configurations that embody the design parameters that are now to be described. For instance, the needle point  122  shown herein is a beveled cutting point, but may be, for example, a conical or trocar point. Further, the position of the bump  158  may be on the opposite side of the hook entrance  162 . These, and other nuances will be discussed in more detail further below. 
     When the needle  112  has been introduced through soft tissue (not shown) and has been driven past the suture to be captured as previously illustrated in  FIGS. 1C ,  2 C, and  3 C and has begun to be retracted back through the soft tissue, the hook terminus  160  rides along one of the retraction ramps  42   a ,  42   b  and underneath one of the ends  30   a ,  30   b  of the suture, thus forcing the suture through the hook entrance  162  and past the bump  158  into the suture holding area  164 . The hook terminus  160 , being cantilevered, has some flexibility, and opens slightly as the suture passes the bump  158 , creating a subtle tactile sensation as the suture seats in the suture holding area  164 . The suture holding area  164  is sized so that its cross sectional area is slightly smaller than the cross sectional area of the suture it is designed to capture, thus creating some compression of the captured suture by virtue of the spring loading provided by the above described deformation of the hook terminus  160 . 
     It is important to understand that this particular configuration of needle  112 , and indeed all of the needles described in connection with the present invention, are configured to capture a section of suture substantially near one of the ends of the suture. As such, and because the needle is not capturing the suture near the center of the stand of suture where the drag on both legs of the suture as it is retracted through the tissue would be equalized, it is important to prevent the suture from migrating in or through the suture holding area  164 . It is also important to secure the suture in the needle while the instrument is being withdrawn, to form and complete, for example, a mattress stitch. Therefore, the combination of deformation, tactile sensation, and compression conspires to hold the suture securely. 
     Another aspect of the present invention that is to be understood is the mechanism described to effect smooth passage of the needle hook with captured suture back through the soft tissue as the needles are retracted. To that end,  FIG. 5  illustrates the needle  112  together with a sliding tube  118 , which includes an inner lumen  170 , and a lumen opening  172 . The sliding tube  118  is dimensioned so that the needle shaft  120  may slide freely through the inner lumen  170 , but does not allow sufficient clearance between the inner lumen  170  and the needle shaft  120  to permit tissue to enter the lumen opening  172 . As the needle  112  is retracted through the tissue as previously described, the sliding tube  118  remains motionless, closing the opening formed by the hook terminus  160  and the suture holding area  164 . The lumen opening  170  ultimately bottoms out against needle shoulders  174   a ,  174   b , and assists in pinching and holding any suture that may be captured in the needle hook  124 . 
     An alternative needle embodiment is illustrated in  FIG. 6 , wherein like elements to those of the embodiment of  FIGS. 4 and 5  are denoted by like reference numerals, except that they are increased by 100. In this embodiment, there may be found a needle  212  that has features similar to that of the needle  112  described above. In this embodiment, a barb  276  is included as part of the suture holding area  264 , and is configured to penetrate the suture weave and assist in immobilizing the suture. Needle shaft is denoted in  FIG. 6  by reference numeral  252   
       FIGS. 7 and 8  illustrate additional embodiments of the needle, and as above, like elements are denoted by like reference numerals, except in the case of  FIG. 7 , the labels are increased by 100 respective to  FIG. 6 , and in  FIG. 8 , increased by 200 respective to  FIG. 6 . 
     Accordingly, in  FIG. 7  there may be seen a needle  312  that includes a needle shaft  320 , and a flattened distal portion  354 . The flattened distal portion  354  of the needle  312  includes a hook  329 , comprising a bump  358 , a hook terminus  360 , a hook entrance  362 , a suture holding area  364 , and a needle point  322 . The needle  312  is illustrated along with a sliding tube  318  which includes an inner lumen  370 , and a lumen opening  372 , and lumen end  374 . It is important to note from this illustration that the sliding tube  318  may bottom out on the end of the hook  324  as opposed to covering it as previously described. Also, the bump  358  is shown here on the opposite side of the hook entrance  362 . 
     Referring now to  FIG. 8 , there may be seen a needle  412  that includes a needle shaft  420 , and a flattened distal portion  454 . The flattened distal portion  454  of the needle  412  includes a hook  429 , comprising a bump  458 , a hook terminus  460 , a hook entrance  462 , a suture holding area  464 , and a needle point  422 . This embodiment is provided to illustrate that the suture holding area  464  may take on a shape different from that previously disclosed. 
     To those skilled in the art, the use of a beveled point needle may seem to solve some of the aforementioned problems of spearing the suture by creating a needle that, by virtue of its completely beveled nature, is able to smoothly move over the suture material without snagging. However, it must be noted that a beveled needle, when forced through soft tissue, has a pronounced tendency to wander, and targeting of the needle in order to place it in an advantageous position for the retrieval of the suture material is quite challenging. In fact, this wandering tendency in the direction of the bevel is uncontrollable to the degree that repeatable suture capture is not possible. Another way of ensuring that the needle point does not spear the suture is to have the needle diameter be more than twice the suture diameter, so that the pointed face that interfaces with the suture puts the needle point above the profile of the suture diameter. This, however is a limitation, in that the hole left by the needle as it penetrates the soft tissues is considerably larger than the suture material left in its place. 
     Although an apparatus for the placement of mattress stitches has been disclosed here, instruments for other stitches, for example, a simple stitch, require only a single needle. Such instruments comprising only a single needle, or, in other instances, perhaps more than two needles, are within the scope of the present invention. 
     The apparatus and method of the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.