FIELD OF THE INVENTION

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

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 inFIG. 1the 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.

The four muscles of the rotator cuff arise from the scapula12. The distal tendons of the rotator cuff muscles splay out and interdigitate to form a common continuous insertion on the humerus14. The subscapularis16arises from the anterior aspect of the scapula12and attaches over much of the lesser tuberosity of the humerous. The supraspinatus muscle18arises 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 tuberosity11. The infraspinatus muscle13arises from the infraspinous fossa of the posterior scapula and attaches to the posterolateral aspect of the greater tuberosity11. The teres minor15arises from the lower lateral aspect of the scapula12and attaches to the lower aspect of the greater tuberosity11.

The mechanics of the rotator cuff muscles10are complex. The rotator cuff muscles10rotate the humerus14with respect to the scapula12, compress the humeral head17into 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.

The rotator cuff muscles10are 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.

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 supraspinatus tendon19is schematically depicted inFIG. 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 tendon19and 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 inFIG. 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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

Further aspects of the present invention will become apparent upon review of the Detailed Description with reference to the following drawings.

