Abstract:
Implant delivery systems for delivering sheet-like implants include a delivery shaft, an implant expander, a sheath, and a sheet-like implant. In some embodiments, the delivery shaft has a proximal end and a distal end. The implant expander is mounted to the distal end of the delivery shaft. The implant expander includes a central portion and a plurality of leg portions radiating from the central portion. The implant expander is evertable between an unstressed configuration in which a distal surface of the implant expander defines a concave surface, and a first compact configuration in which the distal surface of the implant expander defines a convex surface. The implant expander has a first lateral extent when the implant expander is free to assume the unstressed configuration. The sheath defines a lumen having a lumen diameter. At least a portion of the delivery shaft is slidably disposed in the lumen. The lumen diameter is smaller than the first lateral extent of the implant expander so that the sheath holds the implant expander in the first compact configuration when slidably disposed therein. The sheet-like implant overlays at least a portion of the distal surface of the implant expander with portions of the sheet-like implant extending between the leg portions of the implant expander and the sheath. Methods of treating a rotator cuff of a shoulder are also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/184,198 filed on Jun. 4, 2009 and U.S. Provisional Patent Application No. 61/313,116 filed on Mar. 11, 2010, the disclosures of each incorporated herein by reference. 
       INCORPORATION BY REFERENCE 
       [0002]    The present application is related to U.S. patent application Ser. No. ______, (Attorney Docket No. 10322-705.200), entitled Methods and Apparatus for Fixing Sheet-like Materials to a Target Tissue, filed on Jun. 4, 2010; U.S. patent application Ser. No. ______, (Attorney Docket No. 10322-705.201), entitled Methods and Apparatus for Delivering Staples to a Target Tissue, filed on Jun. 4, 2010; and, U.S. patent application Ser. No. ______, (Attorney Docket No. 10322-705.203), entitled Methods and Apparatus Having a Bowstring-like Staple Delivery to a Target Tissue, filed on Jun. 4, 2010, the disclosures of each incorporated herein by reference. 
         [0003]    All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0004]    The present invention relates generally to orthopedic medicine and surgery. More particularly, the present invention relates to methods and apparatus for delivery and fixation of medical devices, such as for treating articulating joints. 
       BACKGROUND OF THE INVENTION 
       [0005]    The glenohumeral joint of the shoulder is found where the head of the humerus mates with a shallow depression in the scapula. This shallow depression is known as the glenoid fossa. Six muscles extend between the humerus and scapula and actuate the glenohumeral joint. These six muscles include the deltoid, the teres major, and the four rotator cuff muscles. As disclosed by Ball et al. in U.S. Patent Publication No. U.S. 2008/0188936 A1 and as illustrated in  FIG. 1  the rotator cuff muscles are a complex of four muscles. These four muscles are the supraspinatus, the infraspinatus, the subscapularis, and the teres minor. The centering and stabilizing roles played by the rotator cuff muscles are critical to the proper function of the shoulder. The rotator cuff muscles provide a wide variety of moments to rotate the humerus and to oppose unwanted components of the deltoid and pectoralis muscle forces. 
         [0006]    The four muscles of the rotator cuff arise from the scapula  12 . The distal tendons of the rotator cuff muscles splay out and interdigitate to form a common continuous insertion on the humerus  14 . The subscapularis  16  arises from the anterior aspect of the scapula  12  and attaches over much of the lesser tuberosity of the humerous. The supraspinatus muscle  18  arises from the supraspinatus fossa of the posterior scapula, passes beneath the acromion and the acromioclavicular joint, and attaches to the superior aspect of the greater tuberosity  11 . The infraspinatus muscle  13  arises from the infraspinous fossa of the posterior scapula and attaches to the posterolateral aspect of the greater tuberosity  11 . The teres minor  15  arises from the lower lateral aspect of the scapula  12  and attaches to the lower aspect of the greater tuberosity  11 . 
         [0007]    The mechanics of the rotator cuff muscles  10  are complex. The rotator cuff muscles  10  rotate the humerus  14  with respect to the scapula  12 , compress the humeral head  17  into the glenoid fossa providing a critical stabilizing mechanism to the shoulder (known as concavity compression), and provide muscular balance. The supraspinatus and infraspinatus provide 45 percent of abduction and 90 percent of external rotation strength. The supraspinatus and deltoid muscles are equally responsible for producing torque about the shoulder joint in the functional planes of motion. 
         [0008]    The rotator cuff muscles  10  are critical elements of this shoulder muscle balance equation. The human shoulder has no fixed axis. In a specified position, activation of a muscle creates a unique set of rotational moments. For example, the anterior deltoid can exert moments in forward elevation, internal rotation, and cross-body movement. If forward elevation is to occur without rotation, the cross-body and internal rotation moments of this muscle must be neutralized by other muscles, such as the posterior deltoid and infraspinatus. The timing and magnitude of these balancing muscle effects must be precisely coordinated to avoid unwanted directions of humeral motion. Thus the simplified view of muscles as isolated motors, or as members of force couples must give way to an understanding that all shoulder muscles function together in a precisely coordinated way—opposing muscles canceling out undesired elements leaving only the net torque necessary to produce the desired action. Injury to any of these soft tissues can greatly inhibit ranges and types of motion of the arm. 
         [0009]    With its complexity, range of motion and extensive use, a fairly common soft tissue injury is damage to the rotator cuff or rotator cuff tendons. Damage to the rotator cuff is a potentially serious medical condition that may occur during hyperextension, from an acute traumatic tear or from overuse of the joint. With its critical role in abduction, rotational strength and torque production, the most common injury associated with the rotator cuff region is a strain or tear involving the supraspinatus tendon. A tear in the supraspinitus tendon  19  is schematically depicted in  FIG. 2 . A tear at the insertion site of the tendon with the humerus, may result in the detachment of the tendon from the bone. This detachment may be partial or full, depending upon the severity of the injury. Additionally, the strain or tear can occur within the tendon itself. Injuries to the supraspinatus tendon  19  and recognized modalities for treatment are defined by the type and degree of tear. The first type of tear is a full thickness tear as also depicted in  FIG. 2 , which as the term indicates is a tear that extends through the thickness of the supraspinatus tendon regardless of whether it is completely torn laterally. The second type of tear is a partial thickness tear which is further classified based on how much of the thickness is torn, whether it is greater or less than 50% of the thickness. 
         [0010]    The accepted treatment for a full thickness tear or a partial thickness tear greater than 50% includes reconnecting the torn tendon via sutures. For the partial thickness tears greater than 50%, the tear is completed to a full thickness tear by cutting the tendon prior to reconnection. In contrast to the treatment of a full thickness tear or a partial thickness tear of greater than 50%, the treatment for a partial thickness tear less than 50% usually involves physical cessation from use of the tendon, i.e., rest. Specific exercises can also be prescribed to strengthen and loosen the shoulder area. In many instances, the shoulder does not heal and the partial thickness tear can be the source of chronic pain and stiffness. Further, the pain and stiffness may cause restricted use of the limb which tends to result in further degeneration or atrophy in the shoulder. Surgical intervention may be required for a partial thickness tear of less than 50%, however, current treatment interventions do not include repair of the tendon, rather the surgical procedure is directed to arthroscopic removal of bone to relieve points of impingement or create a larger tunnel between the tendon and bone that is believed to be causing tendon damage. As part of the treatment, degenerated tendon may also be removed using a debridement procedure in which tendon material is ablated. Again, the tendon partial tear is not repaired. Several authors have reported satisfactory early post operative results from these procedures, but over time recurrent symptoms have been noted. In the event of recurrent symptoms, many times a patient will “live with the pain”. This may result in less use of the arm and shoulder which further causes degeneration of the tendon and may lead to more extensive damage. A tendon repair would then need to be done in a later procedure if the prescribed treatment for partial tear was unsuccessful in relieving pain and stiffness or over time the tear propagated through injury or degeneration to a full thickness tear or a partial thickness tear greater than 50% with attendant pain and debilitation. A subsequent later procedure would include the more drastic procedure of completing the tear to full thickness and suturing the ends of the tendon back together. This procedure requires extensive rehabilitation, has relatively high failure rates and subjects the patient who first presented and was treated with a partial thickness tear less than 50% to a second surgical procedure. 
         [0011]    As described above, adequate treatments do not currently exist for repairing a partial thickness tear of less than 50% in the supraspinatus tendon. Current procedures attempt to alleviate impingement or make room for movement of the tendon to prevent further damage and relieve discomfort but do not repair or strengthen the tendon. Use of the still damaged tendon can lead to further damage or injury. Prior damage may result in degeneration that requires a second more drastic procedure to repair the tendon. Further, if the prior procedure was only partially successful in relieving pain and discomfort, a response may be to use the shoulder less which leads to degeneration and increased likelihood of further injury along with the need for more drastic surgery. There is a large need for surgical techniques and systems to treat partial thickness tears of less than 50% and prevent future tendon damage by strengthening or repairing the native tendon having the partial thickness tear. 
       SUMMARY OF THE INVENTION 
       [0012]    According to aspects of the invention, implant delivery systems for delivering sheet-like implants are disclosed. In some embodiments, the implant delivery system includes a delivery shaft, an implant expander, a sheath, and a sheet-like implant. In these embodiments, the delivery shaft has a proximal end and a distal end. The implant expander is mounted to the distal end of the delivery shaft. The implant expander includes a central portion and a plurality of leg portions radiating from the central portion. The implant expander is evertable between an unstressed configuration in which a distal surface of the implant expander defines a concave surface, and a first compact configuration in which the distal surface of the implant expander defines a convex surface. The implant expander has a first lateral extent when the implant expander is free to assume the unstressed configuration. The sheath defines a lumen having a lumen diameter. At least a portion of the delivery shaft is slidably disposed in the lumen. The lumen diameter is smaller than the first lateral extent of the implant expander so that the sheath holds the implant expander in the first compact configuration when slidably disposed therein. The sheet-like implant overlays at least a portion of the distal surface of the implant expander with portions of the sheet-like implant extending between the leg portions of the implant expander and the sheath. 
         [0013]    In some embodiments, a free end of each leg portion of the implant expander is disposed distally of the central portion when the implant expander is assuming the unstressed configuration. The free end of each leg portion is disposed proximally of the central portion when the implant expander is assuming the first compact configuration. The delivery shaft distal end may be fixed to the central portion of the implant expander to urge relative movement between the implant expander and the sheath such that the implant expander and the sheet-like implant can be advanced through a distal opening defined by the sheath so the implant expander is free to assume a deployed configuration. 
         [0014]    In some embodiments, a projection extends distally from the distal surface of the central portion of the implant expander to hold the position of delivery system when the projection is held against a target tissue. The implant expander may generally conform to the surface of a target tissue when the implant expander assumes the deployed configuration. In some embodiments, the distal surface of the implant expander defines a concave surface when the implant expander is assuming the deployed configuration and the target tissue has a generally convex shape. A free end of each leg portion may be disposed distally of the central portion when the implant expander is assuming the deployed configuration and the target tissue has a generally convex shape. In some embodiments, the implant expander causes the sheet-like implant to conform to the surface of a target tissue when the implant expander assumes the deployed configuration. 
         [0015]    In some embodiments, the implant expander assumes a second compact configuration when the implant expander is retracted proximally into the lumen of the sheath after having assumed the deployed configuration. The distal surface of the implant expander may define a concave surface when the implant expander is assuming the second compact configuration. In some embodiments, the free end of each leg portion is disposed distally of the central portion when the implant expander is assuming the second compact configuration. 
         [0016]    In some embodiments, the implant expander is integrally formed of a single material. The sheet-like implant may define a plurality of pockets. Each pocket may be dimensioned to receive a distal portion of a leg portion of the implant expander. In some of these embodiments, the sheet-like implant can be selectively separated from the implant expander by withdrawing the distal portions of the legs from the pockets. In some embodiments, the implant expander further includes a plurality of retainers to engage the sheet-like implant such that the sheet-like implant moves when the implant expander is moved. In some of these embodiments, the sheet-like implant can be selectively separated from the implant expander by withdrawing the retainers from the sheet-like implant. 
         [0017]    According to aspects of the present invention, methods of treating a rotator cuff of a shoulder are disclosed. In some embodiments, the method includes the steps of providing an implant delivery system, inflating the shoulder to create a cavity therein, placing the sheet-like implant and the implant expander inside the cavity, allowing the implant expander to assume a deployed configuration, attaching the sheet-like implant to the tendon, urging the implant expander to assume a second compact configuration, and removing the implant expander from the cavity. In these embodiments, the implant delivery system that is provided includes an implant expander. The implant expander has a central portion and a plurality of leg portions radiating from the central portion. The implant expander is evertable between an unstressed configuration in which a distal surface of the implant expander defines a concave surface, and a first compact configuration in which the distal surface of the implant expander defines a convex surface. A sheet-like implant overlays at least a portion of the distal surface of the implant expander. A sheath is disposed about the sheet-like implant and the implant expander. The sheath holds the implant expander in the first compact configuration. When the sheet-like implant and the implant expander are placed inside the cavity, a tendon is contacted with at least a portion of the implant while the implant expander is assuming the first compact configuration. When allowing the implant expander to assume a deployed configuration, the implant expander urges the sheet-like implant against a surface of the tendon. When urging the implant expander to assume a second compact configuration, the distal surface of the implant expander defines a concave surface. 
         [0018]    In some embodiments, the implant expander includes a projection extending distally from its central portion. The projection holds the position of the delivery system relative to the tendon when the sheet-like implant and implant expander are placed in the cavity against the tendon. 
         [0019]    In some embodiments, the step of allowing the implant expander to assume the deployed configuration includes urging relative movement between the implant expander and the sheath such that the implant expander and the sheet-like implant are advanced through a distal opening defined by the sheath. With this arrangement, the implant expander is free to assume the deployed configuration. In some embodiments, urging relative movement between the implant expander and the sheath includes withdrawing the sheath in a proximal direction relative to the implant expander. In some embodiments, urging relative movement between the implant expander and the sheath includes advancing the implant expander in a distal direction along the lumen of the sheath. In some embodiments, urging the implant expander to assume the second compact configuration includes advancing the sheath over the implant expander so that the implant expander is disposed inside the lumen defined by the sheath. In some embodiments, urging the implant expander to assume the second compact configuration includes drawing the implant expander proximally into the lumen defined by the sheath. In some embodiments, urging the implant expander to assume the second compact configuration includes drawing the implant expander and the projection that extends distally from the central portion of the implant expander proximally into the lumen defined by the sheath. 
         [0020]    According to aspects of the invention, methods of preparing a delivery system are disclosed. In some embodiments, these methods include the steps of providing a delivery sheath and an implant expander, covering at least a portion of the distal surface with a sheet-like implant, and deflecting the implant expander. The sheath defines a lumen having a lumen diameter. The implant expander includes a central portion and a plurality of leg portions radiating from the central portion. The implant expander is evertable between an unstressed configuration in which a distal surface of the implant expander defines a concave surface, and a first compact configuration in which the distal surface of the implant expander defines a convex surface. The implant expander has a first lateral extent when the implant expander is free to assume the unstressed configuration. The first lateral extent is greater than the lumen diameter of the sheath. When the implant expander is deflected, the implant expander assumes the first compact configuration and the implant expander and the sheet-like implant are placed in the lumen defined by the sheath. The sheath holds the implant expander in the first compact configuration with portions of the sheet-like implant being interposed between the leg portions of the implant expander and an inner surface of the sheath. 
         [0021]    Further aspects of the present invention will become apparent upon review of the Detailed Description with reference to the following drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a simplified perspective view of the human rotator cuff and associated anatomical structure. 
           [0023]      FIG. 2  is a schematic depiction of a full thickness tear in the supraspinatus tendon of the rotator cuff of  FIG. 1 . 
           [0024]      FIG. 3  is a stylized anterior view of a patient with a shoulder being shown in cross-section for purposes of illustration. 
           [0025]      FIG. 4  is a stylized anterior view of a shoulder including a humerus and a scapula. The head of the humerus is shown mating with the glenoid fossa of the scapula at a glenohumeral joint. 
           [0026]      FIG. 5  is a stylized perspective view illustrating an exemplary procedure for treating a shoulder of a patient. 
           [0027]      FIG. 6  is an enlarged perspective view further illustrating the procedure shown in the previous Figure. 
           [0028]      FIG. 7  is an enlarged perspective view showing the delivery system shown in the previous Figure. 
           [0029]      FIG. 8  is a stylized perspective view of a shoulder including a supraspinatus muscle having a distal tendon. 
           [0030]      FIG. 9  is an additional perspective view further illustrating a delivery system in accordance with this disclosure. 
           [0031]      FIG. 10A  through  FIG. 10E  are a series of stylized plan views illustrating an exemplary method in accordance with the present detailed description. 
           [0032]      FIG. 11  is a stylized diagram illustrating four configurations of an exemplary implant expander. 
           [0033]      FIG. 12  is a perspective view illustrating an exemplary delivery system in accordance with this disclosure. 
           [0034]      FIG. 13  is a plan view illustrating an exemplary assembly in accordance with the present detailed description. 
           [0035]      FIG. 14  is a plan view illustrating an exemplary assembly in accordance with the present detailed description. 
           [0036]      FIG. 15A  through  FIG. 15F  are a series of stylized plan views illustrating exemplary methods and apparatus in accordance with the present detailed description. 
           [0037]      FIG. 16  is a stylized depiction of a kit that may be used, for example, for delivering a sheet-like implant to a target location within the body of a patient. 
           [0038]      FIG. 17A  is an enlarged plan view illustrating a delivery aid included in the kit of  FIG. 16 .  FIG. 17B  is a partial cross-sectional perspective view further illustrating the delivery aid shown in  FIG. 17A . 
           [0039]      FIG. 18A  through  FIG. 18I  are a series of stylized plan views illustrating exemplary methods and apparatus in accordance with the present detailed description. 
           [0040]      FIG. 19  is a plan view showing a locating guide included in the kit of  FIG. 16 . 
           [0041]      FIG. 20  is a plan view showing a locating guide removal tool included in the kit of  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]    The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. 
         [0043]      FIG. 3  is a stylized anterior view of a patient  20 . For purposes of illustration, a shoulder  22  of patient  20  is shown in cross-section in  FIG. 3 . Shoulder  22  includes a humerus  14  and a scapula  12 . In  FIG. 3 , a head  24  of humerus  14  can be seen mating with a glenoid fossa of scapula  12  at a glenohumeral joint. With reference to  FIG. 3 , it will be appreciated that the glenoid fossa comprises a shallow depression in scapula  12 . The movement of humerus  14  relative to scapula  12  is controlled by a number of muscles including: the deltoid, the supraspinatus, the infraspinatus, the subscapularis, and the teres minor. For purposes of illustration, only the supraspinatus  26  is shown in  FIG. 3 . 
         [0044]    With reference to  FIG. 3 , it will be appreciated that a distal tendon  28  of the supraspinatus  26  meets humerus  14  at an insertion point. Scapula  12  of shoulder  22  includes an acromium  32 . In  FIG. 3 , a subacromial bursa  34  is shown extending between acromium  32  of scapula  12  and head  24  of humerus  14 . In  FIG. 3 , subacromial bursa  34  is shown overlaying supraspinatus  26 . Subacromial bursa  34  is one of the hundreds of bursae found the human body. Each bursa comprises a fluid filled sac. The presence of these bursae in the body reduces friction between bodily tissues. Injury and/or infection of the bursa can cause it to become inflamed. This condition is sometimes referred to as bursitis. 
         [0045]    The exemplary methods and apparatus described herein may be used to fix tendon repair implants to various target tissues. For example, a tendon repair implant may be fixed to one or more tendons associated with an articulating joint, such as the glenohumeral joint. The tendons to be treated may be torn, partially torn, have internal micro-tears, be untorn, and/or be thinned due to age, injury or overuse. Applicants believe that the methods and apparatus of the present application and related devices may provide very beneficial therapeutic effect on a patient experiencing joint pain believed to be caused by partial thickness tears and/or internal microtears. By applying a tendon repair implant early before a full tear or other injury develops, the implant may cause the tendon to thicken and/or at least partially repair itself, thereby avoiding more extensive joint damage, pain, and the need for more extensive joint repair surgery. 
         [0046]      FIG. 4  is a stylized anterior view of a shoulder  22  including a humerus  14  and a scapula  12 . In  FIG. 4 , a head  24  of humerus  14  is shown mating with a glenoid fossa of scapula  12  at a glenohumeral joint. A supraspinatus  26  is also shown in  FIG. 4 . This muscle, along with others, control the movement of humerus  14  relative to scapula  12 . A distal tendon  28  of supraspinatus  26  meets humerus  14  at an insertion point  30 . 
         [0047]    In the embodiment of  FIG. 4 , distal tendon  28  includes a first damaged portion  36 . A number of loose tendon fibers  40  in first damaged portion  36  are visible in  FIG. 4 . First damaged portion  36  includes a first tear  42  extending partially through distal tendon  28 . First tear  42  may therefore be referred to as a partial thickness tear. With reference to  FIG. 4 , it will be appreciated that first tear  42  begins on the side of distal tendon  28  facing the subacromial bursa (shown in the previous Figure) and ends midway through distal tendon  28 . Accordingly, first tear  42  may be referred to as a bursal side tear. 
         [0048]    With reference to  FIG. 4 , it will be appreciated that distal tendon  28  includes a second damaged portion  38  located near insertion point  30 . In the embodiment of  FIG. 4 , second damaged portion  38  of distal tendon  28  has become frayed and a number of loose tendon fibers  40  are visible in  FIG. 4 . Second damaged portion  38  of distal tendon  28  includes second tear  44 . With reference to  FIG. 4 , it will be appreciated that second tear  44  begins on the side of distal tendon  28  facing the humerus  14 . Accordingly, second damaged portion  38  may be referred to as an articular side tear. 
         [0049]    In the embodiment of  FIG. 4 , a sheet-like implant  50  has been placed over the bursal side of distal tendon  28 . With reference to  FIG. 4 , it will be appreciated that sheet-like implant  50  extends over insertion point  30 , first tear  42  and second tear  44 . Some useful methods in accordance with this detailed description may include placing a tendon repair implant on the bursal side of a tendon regardless of whether the tears being treated are on the bursal side, articular side or within the tendon. In some cases the exact location and nature of the tears being treated may be unknown. A tendon repair implant may be applied to the bursal side of a tendon to treat shoulder pain that is most likely caused by one or more partial thickness tears in the tendon. In the embodiment of  FIG. 4 , sheet-like implant  50  is fixed to distal tendon  28  by a plurality of staples. 
         [0050]      FIG. 5  is a stylized perspective view illustrating an exemplary procedure for treating a shoulder  22  of a patient  20 . The procedure illustrated in  FIG. 5  may include, for example, fixing tendon repair implants to one or more tendons of shoulder  22 . The tendons treated may be torn, partially torn, have internal micro-tears, be untorn, and/or be thinned due to age, injury or overuse. 
         [0051]    Shoulder  22  of  FIG. 5  has been inflated to create a cavity therein. In the exemplary embodiment of  FIG. 5 , a fluid supply  52  is pumping a continuous flow of saline into the cavity. This flow of saline exits the cavity via a fluid drain  54 . A camera  56  provides images from inside the cavity. The images provided by camera  56  may be viewed on a display  58 . 
         [0052]    Camera  56  may be used to visually inspect the tendons of shoulder  22  for damage. A tendon repair implant in accordance with this disclosure may be fixed to a bursal surface of the tendon regardless of whether there are visible signs of tendon damage. Applicants believe that the methods and apparatus of the present application and related devices may provide very beneficial therapeutic effect on a patient experiencing joint pain believed to be caused by internal microtears, but having no clear signs of tendon tears. By applying a tendon repair implant early before a full tear or other injury develops, the implant may cause the tendon to thicken and/or at least partially repair itself, thereby avoiding more extensive joint damage, pain, and the need for more extensive joint repair surgery. 
         [0053]    A delivery system  60  can be seen extending from shoulder  22  in  FIG. 5 . Delivery system  60  comprises a sheath that is fixed to a handle. The sheath defines a lumen and a distal opening fluidly communicating with the lumen. In the embodiment of  FIG. 5 , the distal opening of the sheath has been placed in fluid communication with the cavity created in shoulder  22 . 
         [0054]    A tendon repair implant is at least partially disposed in the lumen defined by the sheath of delivery system  60 . Delivery system  60  can be used to place the tendon repair implant inside shoulder  22 . Delivery system  60  can also be used to hold the tendon repair implant against the tendon. In some embodiments, the tendon repair implant is folded into a compact configuration when inside the lumen of the sheath. When this is the case, delivery system  60  may be used to unfold the tendon repair implant into an expanded shape. 
         [0055]    The tendon repair implant may be fixed to the tendon while it is held against the tendon by delivery system  60 . Various attachment elements may be used to fix the tendon repair implant to the tendon. Examples of attachment elements that may be suitable in some applications include sutures, tissue anchors, bone anchors, and staples. In the exemplary embodiment of  FIG. 5 , the shaft of a fixation tool  70  is shown extending into shoulder  22 . In one exemplary embodiment, fixation tool  70  is capable of fixing the tendon repair implant to the tendon with one or more staples while the tendon repair implant is held against the tendon by delivery system  60 . 
         [0056]      FIG. 6  is an enlarged perspective view further illustrating the procedure shown in the previous Figure.  FIG. 6  also illustrates the interior structure of shoulder  22  shown in the previous Figure. With reference to  FIG. 6 , it will be appreciated that shoulder  22  includes a humerus  14  and a scapula  12 . In  FIG. 6 , a head  24  of humerus  14  is shown mating with a glenoid fossa of scapula  12  at a glenohumeral joint. A supraspinatus  26  is also shown in  FIG. 6 . A distal tendon  28  of supraspinatus  26  can be seen meeting a tuberosity of humerus  14  in  FIG. 6 . 
         [0057]    Delivery system  60  is also shown in  FIG. 6 . In the embodiment of  FIG. 6 , a distal end of delivery system  60  has been positioned near distal tendon  28  of supraspinatus  26 . Delivery system  60  comprises a sheath  102  that is fixed to a handle  104 . Sheath  102  defines a lumen  108  and a distal opening fluidly communicating with the lumen. In the embodiment of  FIG. 6 , a central portion of a sheet-like implant  50  can be seen extending through the distal opening defined by sheath  102 . In the embodiment of  FIG. 6 , sheet-like implant  50  is overlaying an implant expander. The implant expander and sheet-like implant  50  are both assuming a compact configuration. The majority of sheet-like implant  50  is disposed inside sheath  102 . A central portion of sheet-like implant  50  is extending out of sheath  102 . This central portion of sheet-like implant  50  is contacting an outer surface of distal tendon  28  in the embodiment of  FIG. 6 . 
         [0058]      FIG. 7  is an enlarged perspective view showing delivery system  60  shown in the previous Figure. In the embodiment of  FIG. 7 , sheath  102  of delivery system  60  has been moved in a proximal direction P relative to handle  104 . By comparing  FIG. 7  to the previous Figure, it will be appreciated that sheet-like implant  50  and implant expander  120  are now disposed outside of lumen  108  defined by sheath  102 . Implant expander  120  comprises a central portion  122  and a plurality of leg portions  124  radiating from central portion  122 . In  FIG. 7 , leg portions  124  of implant expander  120  are shown overlaying sheet-like implant  50 . Hub  126  is shown overlaying central portion  122  of implant expander  120  in  FIG. 7 . Implant expander  120  can be used to expand sheet-like implant  50  and hold sheet-like implant  50  against the surface of a target tissue. Sheet-like implant  50  may be fixed to the target tissue while the implant is held against the target tissue by implant expander  120 . 
         [0059]      FIG. 8  is a stylized perspective view of a shoulder  22  including a supraspinatus  26  having a distal tendon  28 . With reference to  FIG. 8 , it will be appreciated that a tendon repair implant  50  has been fixed to a surface of distal tendon  28 . Tendon repair implant  50  may comprise, for example, various sheet-like structures without deviating from the spirit and scope of the present detailed description. In some useful embodiments, the sheet-like structure may comprise a plurality of fibers. The fibers may be interlinked with one another. When this is the case, the sheet-like structure may comprise a plurality of apertures comprising the interstitial spaces between fibers. Various processes may be used to interlink the fibers with one another. Examples of processes that may be suitable in some applications including weaving, knitting, and braiding. In some embodiment, the sheet-like structure may comprise a laminate including multiple layers of film with each layer of film defining a plurality of micro-machined or formed holes. The sheet-like structure of the tendon repair implant may also comprise a plurality of electro-spun nanofiber filaments forming a composite sheet. Additionally, the sheet-like structure may comprise a synthetic sponge material that defines a plurality of pores. The sheet-like structure may also comprise a reticulated foam material. Reticulated foam materials that may be suitable in some applications are available from Biomerix Corporation of Fremont, Calif. which identifies these materials using the trademark BIOMATERIAL™. The sheet-like structure may be circular, oval, oblong, square, rectangular, or other shape configured to suit the target anatomy. 
         [0060]    Various attachment elements may be used to fix tendon repair implant  50  to distal tendon  28  without deviating from the spirit and scope of this detailed description. Examples of attachment elements that may be suitable in some applications include sutures, tissue anchors, bone anchors, and staples. In the exemplary embodiment of  FIG. 8 , a plurality of staples are fixing tendon repair implant  50  to distal tendon  28 . In some exemplary methods, a plurality of staples may be applied using a fixation tool. The fixation tool may then be withdrawn from the body of the patient. Distal tendon  28  meets humerus  14  at an insertion point  30 . With reference to  FIG. 8 , it will be appreciated that sheet-like implant  50  extends over insertion point  30 . Tendon repair implant may be applied to distal tendon  28 , for example, using the procedure illustrated in the previous Figure. In various embodiments, staples may straddle the perimeter edge of the sheet-like implant (as shown in  FIG. 8 ), may be applied adjacent to the perimeter, and/or be applied to a central region of the implant. In some embodiments, the staples may be used to attach the implant to soft tissue and/or to bone. 
         [0061]      FIG. 9  is an additional perspective view further illustrating delivery system  60 . Delivery system  60  comprises a sheath  102  that is fixed to a handle  104 . Sheath  102  defines a lumen  108  and a distal opening  128  fluidly communicating with lumen  108 . In the embodiment of  FIG. 9 , a delivery aid  130  can be seen extending through distal opening  128  defined by sheath  102 . 
         [0062]    In the embodiment of  FIG. 9 , delivery aid  130  comprises a hub  126  that is disposed at the distal end of a control rod  132 . An implant expander  120  is attached to hub  126 . Implant expander  120  comprises a central portion  122  and a plurality of leg portions  124  radiating from central portion  122 . In  FIG. 9 , a sheet-like implant  50  is shown overlaying a distal surface of implant expander  120 . In the exemplary embodiment of  FIG. 9 , implant expander  120  is urging sheet-like implant  50  against a generally spherical surface (not shown in  FIG. 9 ). 
         [0063]    Sheath  102  of delivery system  60  is coupled to a button  134 . It will be appreciated that various other operative mechanisms may be used in addition to button  134 . Relative motion between button  134  and handle  104  will cause similar relative motion between sheath  102  and handle  104 . In the exemplary embodiment of  FIG. 9 , sheath  102  will be moved distally (relative to handle  104 ) when button  134  is moved distally (relative to handle  104 ). Additionally, sheath  102  will be moved proximally (relative to handle  104 ) when button  134  is moved proximally (relative to handle  104 ). 
         [0064]    In  FIG. 9 , implant expander  120  is shown residing outside of lumen  108  defined by sheath  102 . In  FIG. 9 , implant expander  120  is shown assuming a deployed configuration. Implant expander  120  can be selectively urged to assume a compact configuration, for example, by placing implant expander inside lumen  108  defined by sheath  102 . Implant expander can be placed inside lumen  108 , for example, by advancing sheath  102  over implant expander  120 . 
         [0065]      FIG. 10A  through  FIG. 10E  are a series of stylized plan views illustrating an exemplary method in accordance with the present detailed description.  FIG. 10A  through  FIG. 10E  may be referred to collectively as  FIG. 10 . A proximal direction is illustrated with an arrow P in  FIG. 10 . A distal direction is illustrated with another arrow D in  FIG. 10 . The exemplary method of  FIG. 10  may be used, for example, to fix a sheet-like implant  50  to a surface  136  of a target tissue  138 . 
         [0066]      FIG. 10A  is a partial cross-sectional view illustrating a distal portion of a delivery system  60  in accordance with this detailed description. In the embodiment of  FIG. 10 , the distal portion of delivery system  60  has been positioned near a target tissue  138 . Delivery system  60  comprises a sheath  102  that is fixed to a handle. Sheath  102  defines a lumen  108  and a distal opening fluidly communicating with the lumen. In the embodiment of  FIG. 10A , a central portion of a sheet-like implant  50  can be seen extending through the distal opening defined by sheath  102 . In the embodiment of  FIG. 10 , sheet-like implant  50  is overlaying an implant expander. The implant expander and sheet-like implant  50  are both assuming a compact configuration. With reference to  FIG. 10 , it will be appreciated that the majority of sheet-like implant  50  is disposed inside sheath  102 . A central portion of a sheet-like implant  50  is extending out of sheath  102 . 
         [0067]    Implant expander  120  of  FIG. 10  comprises a central portion  122  and a plurality of leg portions  124  radiating from central portion  122 . In the embodiment of  FIG. 10A , implant expander  120  is assuming a first compact configuration. With reference to  FIG. 10A , it will be appreciated that the free end of each leg portion  124  is disposed proximally of central portion  122  when implant expander  120  is assuming the first compact configuration. With continuing reference to  FIG. 10 , it will be appreciated that a distal surface  140  of implant expander  120  defines a convex surface when implant expander  120  is assuming the first compact configuration  142 . Portions of sheet-like implant  50  can be seen extending between leg portions  124  of implant expander  120  and the wall of sheath  102 . In  FIG. 10 , a fold  146  comprising a portion of sheet-like implant  50  can also be seen extending between an adjacent pair of leg portions  124 . 
         [0068]    In the embodiment of  FIG. 10B , a central portion of sheet-like implant  50  is trapped between implant expander  120  and surface  136  of target tissue  138 . By comparing  FIG. 10A  and  FIG. 10B , it will be appreciated that sheet-like implant  50  has been advanced distally so that central portion of sheet-like implant  50  is contacting surface  136  of target tissue  138 . 
         [0069]    In the embodiment of  FIG. 10B , delivery system  60  includes a projection  148  extending distally from distal surface  140  of central portion  122  of implant expander  120 . In some applications, projection  148  may be used to temporarily hold the position of delivery system  60  while sheet-like implant  50  is held against surface  136  of target tissue  138 . In the exemplary embodiment of  FIG. 10B , projection  148  comprises a spike  150  having a generally cone-like shape. In the embodiment of  FIG. 10B , spike  150  has been advanced so that a distal portion of spike  150  has pierced target tissue  138 . Spike  150  can be seen extending through sheet-like implant  50  in  FIG. 10B . Spike  150  may be used to temporarily center implant expander  120  and sheet-like implant  50  on a target location. Once sheet-like implant  50  has been fixed to target tissue  138 , spike  150  can be withdrawn from target tissue  138  and sheet-like implant  50 . 
         [0070]    In  FIG. 10C , implant expander  120  of delivery system  60  is shown assuming a deployed configuration. By comparing  FIG. 10C  and  FIG. 10B , it will be appreciated that sheath  102  has been retracted in proximal direction P. In the embodiment of  FIG. 10C , leg portions  124  of implant expander  120  are conforming to the shape of surface  136 . In the exemplary embodiment of  FIG. 10 , surface  136  has a generally planar shape. Sheet-like implant  50  is resting between implant expander  120  and surface  136  of target tissue  138 , with sheet-like implant  50  overlaying surface  136 . With reference to  FIG. 10C , it will be appreciated that implant expander  120  is causing sheet-like implant  50  to generally conform to the shape of surface  136 . 
         [0071]    In  FIG. 10D , implant expander  120  of delivery system  60  is shown assuming an unstressed configuration. By comparing  FIG. 10C  and  FIG. 10D , it will be appreciated that implant expander  120  has been lifted in proximal direction P. In the embodiment of  FIG. 10D , no external forces are acting on leg portions  124  and implant expander  120  is free to assume the unstressed configuration shown in  FIG. 10D . With reference to  FIG. 10D , it will be appreciated that the free end of each leg portion  124  is disposed distally of central portion  122  when implant expander  120  is assuming the unstressed configuration. With continuing reference to  FIG. 10 , it will be appreciated that the distal surface  140  of implant expander  120  defines a concave surface when implant expander  120  is assuming the unstressed configuration. 
         [0072]    In  FIG. 10E , implant expander  120  of delivery system  60  is shown assuming a second compact configuration. By comparing  FIG. 10E  and  FIG. 10D , it will be appreciated that implant expander  120  and sheath  102  have been moved relative to each other. With reference to  FIG. 10E , it will be appreciated that implant expander  120  may be urged to assume the second compact configuration moving implant expander  120  and sheath  102  relative to one another so that implant expander  120  is disposed in lumen  108  defined by sheath  102 . With reference to  FIG. 10 , it will be appreciated that the free end of each leg portion  124  is disposed distally of central portion  122  when implant expander  120  is assuming the second compact configuration  144 . With continuing reference to  FIG. 10 , it will be appreciated that the distal surface  140  of implant expander  120  defines a concave surface when implant expander  120  is assuming the second compact configuration  144 . 
         [0073]      FIG. 11  is a stylized diagram illustrating four configurations of an exemplary implant expander  120 . The step of transitioning between one configuration and another configuration is represented by three arrows in  FIG. 11 . A proximal direction is illustrated with another arrow P in  FIG. 11 . A distal direction is illustrated with an additional arrow D in  FIG. 11 . 
         [0074]    Implant expander  120  of  FIG. 11  comprises a central portion  122  and a plurality of leg portions  124  radiating from central portion  122 . A first arrow  1  represents a transition between a first compact configuration  142  and a deployed configuration  154 . With reference to  FIG. 11 , it will be appreciated that the free end of each leg portion  124  is disposed proximally of central portion  122  when implant expander  120  is assuming the first compact configuration  142 . With continuing reference to  FIG. 11 , it will be appreciated that a distal surface  140  of implant expander  120  defines a convex surface when implant expander  120  is assuming the first compact configuration  142 . In some exemplary methods, implant expander  120  is held in the first compact configuration  142  while implant expander  120  is disposed in a lumen of a sheath. In these exemplary methods, implant expander  120  may be allowed to assume deployed configuration  154  when the sheath is retracted from around implant expander  120 . Implant expander  120  may also be allowed to assume deployed configuration  154  when implant expander  120  is moved in a distal direction so that implant expander  120  exits the lumen via a distal opening of the sheath or when the sheath moves proximally to reveal the implant expander from within the distal opening of the sheath and relieve stress within leg portions  124 . 
         [0075]    In the exemplary embodiment of  FIG. 11 , leg portions  124  of implant expander  120  conform to the shape of a target tissue when implant expander  120  is in the deployed configuration. In  FIG. 11 , implant expander  120  is shown conforming to the shape of a generally planar surface (not shown in  FIG. 11 ) while implant expander is assuming the deployed configuration. A second arrow  2  represents a transition between the deployed configuration  154  and an unstressed configuration  152 . In some exemplary methods, implant expander  120  is free to assume unstressed configuration  152  when implant expander  120  is lifted off of a target surface so that no external forces are acting on leg portions  124  of implant expander  120 . With reference to  FIG. 11 , it will be appreciated that the free end of each leg portion  124  is disposed distally of central portion  122  when implant expander  120  is assuming unstressed configuration  152 . With continuing reference to  FIG. 11 , it will be appreciated that the distal surface  140  of implant expander  120  defines a concave surface when implant expander  120  is assuming the unstressed configuration  152 . 
         [0076]    A third arrow  3  represents a transition between the unstressed configuration  152  and a second compact configuration  144 . In some exemplary methods, implant expander  120  is urged to assume second compact configuration  144  by drawing implant expander  120  proximally into a lumen of a sheath. With reference to  FIG. 11 , it will be appreciated that the free end of each leg portion  124  is disposed distally of central portion  122  when implant expander  120  is assuming the second compact configuration  144 . With continuing reference to  FIG. 11 , it will be appreciated that the distal surface  140  of implant expander  120  defines a concave surface when implant expander  120  is assuming the second compact configuration  144 . 
         [0077]      FIG. 12  is a perspective view illustrating an exemplary delivery system  360 . Delivery system  360  comprises a sheath  302  that is fixed to a handle  304 . Sheath  302  defines a lumen  308  and a distal opening  328  fluidly communicating with lumen  308 . In the embodiment of  FIG. 12 , a delivery aid  330  can be seen extending through distal opening  328  defined by sheath  302 . In the embodiment of  FIG. 12 , delivery aid  330  comprises a hub  326  that is disposed at the distal end of a control rod  332 . An implant expander  320  is attached to hub  326 . Implant expander  320  comprises a central portion  322  and a plurality of leg portions  324  radiating from central portion  322 . 
         [0078]    Sheath  302  of delivery system  360  is coupled to an actuator  356 . Relative motion between actuator  356  and handle  304  will cause similar relative motion between sheath  302  and handle  304 . In the exemplary embodiment of  FIG. 12 , sheath  302  will be moved distally (relative to handle  304 ) when actuator  356  is moved distally (relative to handle  304 ). Additionally, sheath  302  will be moved proximally (relative to handle  304 ) when actuator  356  is moved proximally (relative to handle  304 ). 
         [0079]    In  FIG. 12 , implant expander  320  is shown residing outside of lumen  308  defined by sheath  302 . In  FIG. 12 , implant expander  320  is shown assuming an unstressed configuration. Implant expander  320  can be selectively urged to assume a compact configuration, for example, by placing implant expander inside lumen  308  defined by sheath  302 . Implant expander can be placed inside lumen  308 , for example, by advancing sheath  302  over implant expander  320 . 
         [0080]      FIG. 13  is a plan view illustrating an exemplary assembly in accordance with the present detailed description. The assembly of  FIG. 13  includes a sheet-like implant  50  and an implant expander  520 . Implant expander  520  of  FIG. 13  comprises a central portion  522  and a plurality of leg portions  524  radiating from central portion  522 . In the embodiment of  FIG. 13 , a sheet-like implant  50  is trapped between implant expander  520  and a target tissue  538 . With reference to  FIG. 13 , it will be appreciated that implant expander  520  includes a plurality of retainers  558 . In the embodiment of  FIG. 13 , retainers  558  engage sheet-like implant  50  so that sheet-like implant  50  moves when implant expander  520  is moved and may aid in imparting lateral stress of the legs into lateral stress within the implant. 
         [0081]      FIG. 14  is a plan view illustrating an exemplary assembly in accordance with the present detailed description. The assembly of  FIG. 14  includes a sheet-like implant  50  and an implant expander  720 . Implant expander  720  of  FIG. 14  comprises a central portion  722  and a plurality of leg portions  724  radiating from central portion  722 . In the embodiment of  FIG. 14 , a sheet-like implant  50  is trapped between implant expander  720  and a target tissue  738 . With reference to  FIG. 14 , it will be appreciated that sheet-like implant  50  includes a plurality of pockets  762 . In the embodiment of  FIG. 14 , each pocket  762  is dimensioned to receive the end of a leg portion  724  of implant expander  720 . When this is the case, implant expander  720  engages pockets  762  so that sheet-like implant  50  moves when implant expander  720  is moved. 
         [0082]      FIG. 15A  through  FIG. 15F  are a series of stylized plan views illustrating an exemplary method in accordance with the present detailed description.  FIG. 15A  through  FIG. 15F  may be referred to collectively as  FIG. 15 . A proximal direction is illustrated with an arrow P in  FIG. 15 . A distal direction is illustrated with another arrow D in  FIG. 15 . The exemplary method of  FIG. 15  may be used, for example, to fix a sheet-like implant  50  to a surface of a target tissue  138 . 
         [0083]      FIG. 15A  is a stylized plan view of illustrating a shoulder  22  of a patient. Shoulder  22  of  FIG. 15A  has been inflated to create a cavity  62  therein. In the exemplary embodiment of  FIG. 15A , a fluid supply  64  is pumping a continuous flow of saline into cavity  62 . This flow of saline exits cavity  62  via a fluid drain  66 . 
         [0084]    In  FIG. 15A , a sheath  102  of a delivery system  60  is shown positioned near a shoulder  22 . Delivery system  60  also comprises a delivery aid  130  including an implant expander that is fixed to the distal end of a control rod  132 . In the embodiment of  FIG. 15A , a sheet-like implant  50  is overlaying the implant expander of delivery aid  130 . In the embodiment of  FIG. 15A , delivery aid  130  includes a projection  148  extending distally from the implant expander. In the exemplary embodiment of  FIG. 15A , projection  148  comprises a spike  150  having a generally cone-like shape. Spike  150  can be seen extending through sheet-like implant  50  in  FIG. 15A . Spike  150  may be used to temporarily center sheet-like implant  50  on a target location. Once sheet-like implant  50  has been fixed to target tissue  138 , spike  150  can be withdrawn from target tissue  138  and sheet-like implant  50 . 
         [0085]    Delivery aid  130  can be used to insert sheet-like implant  50  into cavity  62  formed in shoulder  22 . Delivery aid  130  can also be used to hold the sheet-like implant against a target tissue  138 . In some embodiments, the sheet-like implant is folded into a compact configuration when inside the lumen of the sheath. When this is the case, delivery aid  130  may be used to unfold the sheet-like implant into an expanded shape. 
         [0086]    In  FIG. 15B , sheath  102  is shown extending into shoulder  22 . A distal opening of sheath  102  has been placed in fluid communication with cavity  62  in the embodiment of  FIG. 15B . By comparing  FIG. 15A  and  FIG. 15B , it will be appreciated that sheet like implant  50  has been advanced distally so that a central portion of sheet like implant  50  is contacting a surface of target tissue  138 . The central portion of sheet like implant  50  is trapped between implant expander  120  and the surface of target tissue  138  in the embodiment of  FIG. 15B . 
         [0087]    In  FIG. 15C , implant expander  120  of delivery aid  130  is shown assuming a deployed configuration. By comparing  FIG. 15C  and  FIG. 15B , it will be appreciated that sheath  102  has been retracted in a proximal direction P. Implant expander  120  of  FIG. 15  comprises a central portion  122  and a plurality of leg portions  124  radiating from central portion  122 . In the embodiment of  FIG. 15B , implant expander  120  is assuming a deployed configuration. Implant expander  120  is fixed to the distal end of control rod  132  in the embodiment of  FIG. 15 . 
         [0088]    Sheet like implant  50  is shown overlaying an outer surface of target tissue  138  in  FIG. 15C . In the embodiment of  FIG. 15C , sheet like implant  50  is generally conforming to the shape of target tissue  138 . Implant expander  120  is holding sheet-like implant  50  against target tissue  138  in the embodiment of  FIG. 15C . 
         [0089]    Some exemplary methods in accordance with this detailed description include the steps of inflating a shoulder to create a cavity therein and placing a distal opening of a sheath in fluid communication with the cavity while the sheath is surrounding a delivery device disposed inside a lumen thereof and the sheath is maintaining the delivery device in a first compact configuration. A central portion of the sheet-like material may be placed in contact with a surface of a target tissue. The sheath may be withdrawn from around the delivery device so that the delivery device is free to assume a deployed configuration inside the cavity. The delivery device may be used to hold the sheet-like material against a surface of the target tissue while the delivery device is assuming the deployed configuration. The sheet-like implant  50  may be fixed to the target tissue while sheet-like implant  50  is held against the surface of the target tissue. The delivery device may be urged to assume a second compact configuration as the delivery device is removed from the cavity. 
         [0090]    In  FIG. 15D , a fixation tool shaft  72  of a fixation tool  70  is shown extending into shoulder  22 . In  FIG. 15D , a distal end of fixation tool shaft  72  is disposed proximate an edge of sheet like implant  50 . One or more staples may be disposed inside fixation tool shaft  72 . Fixation tool  70  may apply staples to fix sheet like implant  50  to target tissue  138  while sheet like implant  50  is held in place by implant expander  120 . 
         [0091]    Various attachment elements may be used to fix sheet like implant  50  to target tissue  138  without deviating from the spirit and scope of this detailed description. Examples of attachment elements that may be suitable in some applications include sutures, tissue anchors, bone anchors, and staples. In the exemplary embodiment of  FIG. 15E , sheet like implant  50  is fixed to target tissue  138  by a plurality of staples  74 . In some exemplary methods, a plurality of staples may be applied using a fixation tool. The fixation tool may then be withdrawn from the body of the patient. In the exemplary embodiment of  FIG. 15E , delivery aid  130  may be used to hold sheet like implant  50  against target tissue  138  while staples  74  are applied using fixation tool  70 . 
         [0092]    With reference to  FIG. 15F , it will be appreciated that delivery aid  130  has been withdrawn from shoulder  22  and retracted into lumen  108  defined by sheath  102 . Implant expander  120  of delivery aid  130  has been urged to assume a second compact configuration in the embodiment of  FIG. 15F . Implant expander  120  comprises a central portion  122  and a plurality of leg portions  124  radiating from central portion  122 . With reference to  FIG. 15F , it will be appreciated that the free end of each leg portion is disposed distally of central portion  122  when implant expander  120  is assuming the second compact configuration. 
         [0093]      FIG. 16  is a stylized depiction of a kit  123 . In the exemplary embodiment of  FIG. 16 , kit  123  comprises a sheet-like implant  50  and a number of tools that may be used in conjunction with sheet-like implant  50 . The tools of kit  123  may be used, for example, for delivering sheet-like implant  50  to a target location within the body of a patient. These tools may also be used, for example, for fixing sheet-like implant  50  to a target tissue. 
         [0094]    In the exemplary embodiment of  FIG. 16 , kit  123  comprises a locating guide  125 , a locating guide removal tool  127 , a fixation tool  70 , and a delivery aid  129 . In some useful embodiments, locating guide  125  includes a temporary fixation mechanism proximate its distal end. A method in accordance with the present detailed description may include temporarily fixing the distal end of locating guide  125  to a target tissue and advancing sheet-like implant  50  over locating guide  125  for delivering the sheet-like implant to the target location. In some applications, delivery aid  129  may be used for advancing sheet-like implant  50  over locating guide  125  and urging sheet-like implant  50  against a target tissue. Fixation tool  70  of kit  123  may be used, for example, for fixing sheet-like implant  50  to the target tissue. Locating guide removal tool  127  may be used to remove locating guide  125  after sheet-like implant  50  has been fixed to the target tissue. In the embodiment of  FIG. 16 , fixation tool  70  includes a fixation tool shaft  72 . 
         [0095]      FIG. 17A  is an enlarged plan view illustrating delivery aid  129  shown in the previous Figure.  FIG. 17B  is a partial cross-sectional perspective view further illustrating delivery aid  129 .  FIG. 17A  and  FIG. 17B  may be collectively referred to as  FIG. 17 . A distal direction is illustrated with an arrow D in  FIG. 17 . 
         [0096]    In the exemplary embodiment of  FIG. 17 , delivery aid  129  includes an implant expander  133  fixed to a distal end of a control rod  135 . Implant expander  133  of  FIG. 17  has a central portion  137  and an outer portion  139  extending radially from central portion  137 . In the embodiment of  FIG. 17 , no external forces are acting on implant expander  133  and implant expander  133  is free to assume an unstressed configuration. With reference to  FIG. 17B , it will be appreciated that a distal surface  143  of implant expander  133  comprises a generally concave surface  145  when the implant expander is assuming an unstressed configuration. With continuing reference to  FIG. 17 , it will be appreciated that an outermost edge  147  of outer portion  139  is disposed distally of central portion  137  when implant expander  133  is assuming the unstressed configuration. 
         [0097]      FIG. 18A  through  FIG. 18I  are a series of stylized plan views illustrating an exemplary method in accordance with the present detailed description.  FIG. 18A  through  FIG. 18I  may be referred to collectively as  FIG. 18 . A proximal direction is illustrated with an arrow P in  FIG. 18 . A distal direction is illustrated with another arrow D in  FIG. 18 . The exemplary method of  FIG. 18  may be used, for example, to fix a sheet-like implant  50  to a surface of a target tissue  138 . 
         [0098]    In  FIG. 18A , a cannula  149  is shown extending into a shoulder  22 . Cannula  149  defines a lumen  153 . A distal end of cannula  149  is located proximate a target tissue  138 . The distal end of cannula  149  defines a distal opening that fluidly communicates with lumen  153 . 
         [0099]    In  FIG. 18B , a locating guide  125  is shown extending through lumen  153  defined by cannula  149 . Some methods in accordance with the present disclosure may include the step of advancing the distal end of a locating guide through a cannula. In the embodiment of  FIG. 18B , a distal portion of locating guide  125  is disposed in target tissue  138 . In some useful embodiments, the distal portion of locating guide  125  includes a barb. When this is the case, the barb may help maintain the position of the distal end of locating guide  125  in the target tissue. 
         [0100]    In  FIG. 18C , a sheet-like implant  50  is shown disposed about locating guide  125 . Some methods in accordance with the present disclosure may include the step of inserting a locating guide through a sheet-like implant. Some of these methods may also include the step of advancing the sheet-like implant over the locating guide toward a target tissue. 
         [0101]    In  FIG. 18D , a delivery aid  129  is shown disposed about locating guide  125 . Some methods in accordance with the present disclosure may include the step of inserting the proximal end of a locating guide  125  into a distal aperture of a delivery aid  129 . When this is the case, the delivery aid  129  may be advanced over locating guide  125  for urging a sheet-like implant  50  toward a target tissue (e.g., target tissue  138 ). In this way, delivery aid  129  may be used to urge sheet-like implant  50  in a longitudinal direction along locating guide  125 . In some applications, delivery aid  129  may also be used to hold sheet-like implant  50  against a target tissue. 
         [0102]    In the embodiment of  FIG. 18E , sheet-like implant  50  is disposed in a lumen  153  defined by cannula  149 . By comparing  FIG. 18E  and  FIG. 18D , it will be appreciated that sheet-like implant  50  has been pushed distally into lumen  153 . In the embodiment of  FIG. 18E , sheet-like implant  50  has been folded into a compact configuration. Sheet-like implant  50  is shown overlaying the implant expander of delivery aid  129  in  FIG. 18E . In the exemplary embodiment of  FIG. 18E , the implant expander is urged to assume a first compact configuration as the implant expander and sheet-like implant  50  are advanced into lumen  153 . 
         [0103]    In the exemplary embodiment of  FIG. 18F , sheet-like implant  50  is shown overlaying target tissue  138 . Some methods in accordance with the present detailed description include the step of passing a sheet-like implant through a cannula. In the exemplary embodiment of  FIG. 18F , for example, sheet-like implant  50  may be pushed through cannula  149  using delivery aid  129 . Delivery aid  129  may also be used to hold sheet-like implant  50  against target tissue  138  while a surgeon attaches sheet-like implant  50  to target tissue  138 . 
         [0104]    In  FIG. 18G , a fixation tool shaft  72  of a fixation tool  70  is shown extending through cannula  149 . In  FIG. 18G , a distal end of fixation tool shaft  72  is disposed proximate sheet-like implant  50 . One or more staples may be disposed inside fixation tool shaft  72 . Some methods in accordance with the present detailed description include the step of passing a staple through a cannula. In the exemplary embodiment of  FIG. 18G , for example, a staple may be passed through cannula  149  while the staple resides in fixation tool shaft  72 . 
         [0105]    In the exemplary embodiment of  FIG. 18H , sheet-like implant  50  is fixed to target tissue  138  by a plurality of staples  74 . In some exemplary methods, a plurality of staples may be applied to a sheet-like implant and a target tissue using a fixation tool. The fixation tool may then be withdrawn from the body of the patient. With reference to  FIG. 18H , it will be appreciated that delivery aid  129  has been withdrawn from shoulder  22  and locating guide  125  remains in the position shown in  FIG. 18H . 
         [0106]    In the exemplary embodiment of  FIG. 18I , locating guide  125  has been withdrawn from shoulder  22 . Some useful methods in accordance with the present detailed description, include the use of a locating guide including a temporary fixation mechanism located proximate its distal end. These exemplary methods may also include the use of a locating guide removal tool to aid in withdrawing the locating guide from the body of the patient. In  FIG. 18I , a plurality of staples  74  can be seen fixing sheet-like implant  50  to target tissue  138 . 
         [0107]      FIG. 19  is a plan view showing a locating guide  125 . With reference to  FIG. 19 , it will be appreciated that locating guide  125  has a point  155  at its distal end. In the embodiment of  FIG. 19 , locating guide  125  includes a barb  157  near its distal end. In  FIG. 19 , point  155  is shown pointing in a distal direction D and barb  157  is shown pointing in a proximal direction P. 
         [0108]      FIG. 20  is a plan view showing a locating guide removal tool  127 . Locating guide removal tool  127  may be used, for example, to remove a locating guide  125  from a target tissue. In the embodiment of  FIG. 20 , locating guide removal tool  127  includes a tubular body  159  that is fixed to a grip  163 . In operation, tubular body  159  is advanced over the proximal end of a locating guide so that a portion of the locating guide extends into a lumen defined by tubular body  159 . Locating guide removal tool  127  may then be used to grasp a proximal portion of the locating guide and produce relative motion between the locating guide and tubular body  159 . 
         [0109]    In the embodiment of  FIG. 20 , a lever  165  is pivotably coupled to grip  163 . Relative motion between locating guide  125  and tubular body  159  can be produced by rotating lever  165  relative to grip  163  when locating guide removal tool  127  is grasping the proximal portion of locating guide  125 . This relative motion can be used to advance tubular body  159  over the barb  157  of locating guide  125 . Locating guide  125  may be withdrawn from the body of the patient while tubular body  159  is covering barb  157 . 
         [0110]    While exemplary embodiments of the present invention have been shown and described, modifications may be made, and it is therefore intended in the appended claims and subsequently filed claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.