Abstract:
A system and surgical methods for repairing tears in meniscal tissue using meniscal darts. In a preferred embodiment, the system includes a cannulated insertion sheath, a meniscal dart, and a disposable dart driver preloaded with a meniscal dart at its distal end. The insertion sheath is located near a meniscal tear, and sharp prongs on the tip of the sheath are used to secure and position the central fragment of the torn meniscus. The dart driver with a preloaded dart is advanced through the cannulation of the insertion sheath such that the preloaded meniscal dart at the distal end of the driver is inserted through the meniscal tear.

Description:
This application claims the benefit of U.S. Provisional Application Ser. No. 60/350,029, filed Jan. 23, 2002, the entire disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to apparatus and techniques for meniscal repair using meniscal darts. 
     BACKGROUND OF THE INVENTION 
     The menisci are crescent-shaped structures of fibrocartilaginous tissue located in the knee between the condyles of the tibia and the femur. The menisci, which are actually extensions of the tibia, serve to deepen the tibial plateau to better accommodate the opposing curvature of the articulating surface of the femoral condyle. 
     A typical injury to the knee is a meniscal tear, which can occur, for example, when the meniscus is displaced and caught between the femoral and tibial condyles during a sudden change of movement of the knee involving a combined flexion-rotation or extension-rotation motion. Meniscal tears were originally treated by removing the meniscus in an operation called a meniscectomy. However, results showed that removing the meniscus, either entirely or even partially, resulted in degenerative arthritis and instability in the knee. 
     As a result of the above-described complications, surgeons began treating torn meniscus tears with suturing techniques to retain as much of the meniscus as possible. However, suturing of a meniscal tear, like a meniscectomy, was originally an open technique, requiring a large incision and consequently longer periods of rehabilitation and recovery. Advances in instrumentation ultimately led to arthroscopic meniscal repair using long needles for passing suture through the tear. 
     More recently, various tacks and screws have been developed for meniscal repair, which can be used arthroscopically and simplify the surgery by eliminating the need for suturing altogether. See, for example, U.S. Pat. Nos. 4,873,976; 4,884,572; 4,895,148; 4,924,865; 4,976,715; 5,059,206; 5,125,906; 5,562,672; and 5,569,252. The known tacks and associated surgical methods have various disadvantages, such as the need for special preparation of the meniscus prior to insertion. 
     SUMMARY OF THE INVENTION 
     The present invention provides improved systems and surgical techniques for repairing a soft tissue defect, with particular application to defects in the meniscus of a knee. 
     In one aspect, the present invention provides a disposable meniscal repair assembly comprising a meniscal insertion sheath and a dart stick driver with a preloaded meniscal dart. The disposable dart stick driver is provided with a slit-tube tip for tightly engaging and securing a truncated conical protrusion at the proximal end of the meniscal dart. The dart stick driver is placed within the meniscal insertion sheath and the meniscal dart is manually inserted through an incision in the knee in the proximity of a meniscal tear. 
     In another aspect, the invention provides a non-disposable meniscal repair assembly comprising a non-disposable joystick handle, a non-disposable insertion sheath attached to the joystick handle and a disposable dart driver having a preloaded dart at one end. The disposable dart driver is provided with a slit-tube tip for tightly engaging and securing a truncated conical protrusion at the proximal end of the meniscal dart. The dart driver with the preloaded dart is placed within the insertion sheath for manual insertion of the dart through an incision in the knee and in the proximity of a meniscal tear. 
     Alternatively, a non-disposable dart driver may be employed with a non-disposable joystick handle and a non-disposable insertion sheath attached to the joystick handle. According to this embodiment, a meniscal dart is selected and removed from a sterile dart retainer and inserted into the non-disposable insertion sheath. The non-disposable dart driver is then placed within the non-disposable insertion sheath, and the dart is manually inserted through an incision in the knee in proximity of a meniscal tear. 
     In yet another aspect, the invention provides a method of surgical repair of a soft tissue, such as knee meniscus. An incision is first made in the knee to enable the dart to be arthroscopically positioned proximal and perpendicular to a tear in the meniscus. A meniscal insertion sheath provided with a pointed tip is then inserted through a dart cannula into the joint proximal and perpendicular to the meniscal tear. The central fragment of the torn meniscus is positioned and secured with the pointed tip of the insertion sheath. Either a non-disposable joystick driver or a disposable dart stick driver is then inserted through the insertion sheath. Meniscal repair is accomplished by placing the insertion sheath into the joint. The driver, with the dart in place, is placed into the proximal end of the sheath and advanced until the dart is inserted into the meniscus. The driver is then removed, leaving the dart in place. 
     These and other features and advantages of the invention will become apparent from the following detailed description that is provided in connection with the accompanying drawings and illustrated exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a planar view of a straight meniscal dart insertion sheath according to a first embodiment of the present invention. 
         FIG. 1B  illustrates a cross-sectional view of the straight meniscal dart insertion sheath of  FIG. 1A . 
         FIG. 1C  illustrates a detailed view of the distal end of the straight meniscal dart insertion sheath of  FIG. 1A . 
         FIG. 2A  illustrates a planar view of a 15° meniscal dart insertion sheath according to a second embodiment of the present invention. 
         FIG. 2B  illustrates a cross-sectional view of the 15° meniscal dart insertion sheath of  FIG. 2A . 
         FIG. 2C  illustrates a detailed view of the distal end of the 15° meniscal dart insertion sheath of  FIG. 2A . 
         FIG. 3A  illustrates a side view of a 12 mm meniscal dart according to the present invention. 
         FIG. 3B  illustrates a side view of the 12 mm meniscal dart of  FIG. 3A  rotated 90 degrees. 
         FIG. 3C  illustrates a detailed view of the proximal end of the 12 mm meniscal dart of  FIG. 3A . 
         FIG. 3D  illustrates atop view of the proximal end of the 12 mm meniscal dart of  FIG. 3A . 
         FIG. 4A  illustrates a planar view of a meniscal dart stick driver according to the present invention. 
         FIG. 4B  illustrates a cross-sectional view of the meniscal dart stick driver of  FIG. 4A . 
         FIG. 4C  illustrates a detailed view of the distal end of the meniscal dart stick of  FIG. 4A . 
         FIG. 5  illustrates a meniscal repair system of the present invention including a meniscal insertion sheath, a preloaded meniscal dart and a dart driver. 
         FIG. 6A  illustrates a non-disposable joystick handle for attachment of a meniscal insertion sheath according to the present invention. 
         FIG. 6B  illustrates a non-disposable insertion sheath which is attachable to the joystick handle of  FIG. 6A . 
         FIG. 6C  illustrates a detailed view of the distal end of the insertion sheath of  FIG. 6B . 
         FIG. 6D  illustrates a meniscal dart driver insertable in the insertion sheath of  FIG. 6B . 
         FIG. 6E  illustrates a detail of the insertion sheath of  FIG. 6B , with a trocar protruding from the distal end. 
         FIG. 7A  illustrates a schematic three dimensional view of a knee meniscus undergoing a meniscal repair procedure employing a meniscal repair system of the present invention. 
         FIG. 7B  illustrates the meniscus of  FIG. 7A  at a stage of meniscal repair subsequent to that shown in  FIG. 7A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following detailed description, reference is made to various specific embodiments in which the invention may be practiced. These embodiments are described with sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be employed, and that structural and logical changes may be made without departing from the spirit or scope of the present invention. 
     Referring now to the drawings, where like elements are designated by like reference numerals,  FIGS. 1A-1C  illustrate a disposable meniscal dart insertion sheath  66 , according to one embodiment of the present invention, and which comprises a proximal end  63 , an elongate body  60  and a distal end  61  (shown in greater detail in  FIG. 1C ). The meniscal dart insertion sheath  66  also comprises an applicator handle  62  located at the proximal end  63  of the elongate body  60 , for grasping and insertng the insertion sheath through a dart cannula into a joint. 
     As depicted in  FIG. 1B , which is a cross-sectional view of the insertion sheath  66  of  FIG. 1A , distal end  61  comprises a pointed tip  65  for shifting and positioning meniscal tissue from above or below the meniscus prior to the insertion of the dart of the present invention.  FIG. 1C  depicts in side view the orientation of the pointed tip  65  located on a beveled edge  69 . Preferably, the pointed tip  65  comprises two pointed prongs having a pyramidal or tetrahedral configuration, among others, and located symmetrically to each other relative to the longitudinal axis of the insertion sheath  66 . 
       FIGS. 2A-C  depict another embodiment of the present invention, according to which meniscal dart insertion sheath  77  of the present invention is provided with an arcuate distal end that forms an angle “α” with the longitudinal axis of the insertion sheath  77 . The meniscal dart insertion sheath  77  comprises an elongate body  70 , an angled distal end  71  and an applicator handle  72  located at a proximal end  73  of the elongate body  70 . In the preferred embodiment of the invention, the angle “α” is about 15 degrees. 
       FIG. 2B  depicts the meniscal dart insertion sheath  77  of  FIG. 2A  in a cross-section view and rotated 90 degrees. As shown in Detail A of  FIG. 2C , the distal end  71  further comprises a pointed tip formed of two pointed prongs as in the straight sheath embodiment of  FIGS. 1A-1C . 
     The elongate body  60 ,  70  of the meniscal dart insertion sheath  66 ,  77  may have various cross-sectional shapes and geometries, for example, cylindrical, rectangular, or elipsoidal, among others. The elongate body may be formed of metals and metal alloys, for example, stainless steel and stainless steel alloys, platinum and platinum alloys, gold and gold alloys, nickel and nickel alloys, titanium and titanium alloys, and molybdenum and molybdenum alloys, among others. 
     If desired, the elongate body  60 ,  70  of the meniscal dart insertion sheath  66 ,  77  may be covered with, and insulated by, a dielectric material which may comprise an electrically insulating material such as epoxy, plastic, silicon-based material, ceramic, glass or compositions of these mentioned materials, among many others. The dielectric material may also comprise a perforated shield also formed of an electrically insulating material which may be porous and which may include an opening that allows the elongate body  60 ,  70  to contact the target meniscal repair. 
       FIGS. 3A-D  illustrate a  12  mm meniscal dart  20  to be employed in conjunction with the meniscal dart insertion sheath  66 ,  77  of the present invention. Dart  20  of  FIGS. 3A-D  is similar to the meniscal dart disclosed in U.S. Pat. No. 6,056,778 (the disclosure of which is incorporated herein by reference) to the extent that meniscal dart  20  comprises an elongate body  25  having a pointed distal end  23 , a proximal end  21 , a central axis  26  along the length of the elongate body  25 , and a plurality of lateral grooves  27  disposed along the sides of the elongate body  25 . Meniscal dart  20  of  FIGS. 3A-D  differs, however, from the meniscal dart of U.S. Pat. No. 6,056,778 in that the proximal end  21  is designed to matingly engage a corresponding end of a dart stick driver  50  ( FIGS. 4A-C ) provided with a slit-tube tip, as described in more detail below. As depicted in Detail A ( FIGS. 3A and 3C ), the proximal end  21  of meniscal dart  20  terminates in a truncated conical protrusion  22 ; however, it must be understood that the invention is not limited to this embodiment and contemplates a proximal end of various shapes and geometries, as desired. 
       FIG. 3B  depicts the meniscal dart  20  with lateral grooves  27  disposed along each of the opposing sides, and rotated 90 degrees from the view depicted in  FIG. 3A .  FIG. 3C  provides greater detail of the truncated conical protrusion  22 .  FIG. 3D  illustrates a top view of the truncated conical protrusion  22  of  FIG. 3D . Dart  20  of the present invention may be provided in pre-selected sizes, including but not limited to a 10 mm, 12 mm, or 14 mm length (12 mm dart is depicted in  FIGS. 3A-D ). Preferably, meniscal dart  20  of the present invention is formed of a bioabsorbable material such as PLLA or PLDLA copolymer material. Such PLDLA copolymer material can be completely absorbed within  36  weeks after insertion at a meniscal tear. 
       FIGS. 4A-C  illustrate a disposable meniscal dart driver  50  of the present invention which is employed in conjunction with the meniscal sheath  66  ( FIG. 1 ) and dart  20  ( FIG. 3 ). As shown in  FIGS. 4A-B , the meniscal dart driver  50  comprises an elongate shaft  51 , a proximal end  56  provided with an elongate section  52 , and a distal end  53 . The elongate section  52  allows a user, for example a surgeon, to maneuver and operate the dart driver within the meniscal insertion sheath  66  and into the proximity of the meniscal repair by simply using the thumb. 
       FIG. 4B  depicts the meniscal dart driver  50  rotated 90 degrees from the orientation depicted in  FIG. 4A . As illustrated in greater detail in Detail A ( FIG. 4C ), distal end  53  has a slit-tube tip  55  for tightly engaging and accommodating the truncated conical protrusion  22  of the meniscal dart  20  of  FIGS. 3A-D . 
       FIG. 5  depicts a disposable meniscal repair assembly or system  100  comprising the meniscal straight insertion sheath  66  ( FIGS. 1A-C ), the meniscal dart stick driver  50  ( FIGS. 4A-C ) positioned within the insertion sheath  66  and engaging at least one preloaded meniscal dart  20  ( FIGS. 3A-D ), all in accordance with the present invention. A disposable cannula with an obturator (not shown) may also be provided for use with meniscal repair assembly  100 . Preferably, the meniscal repair assembly  100  of the present invention is provided as two pre-packed sterile packs, with five dart and driver units provided in one sterile pack, and five cannula/obturator assemblies provided in a separate sterile pack. 
     In yet another embodiment of the present invention, a non-disposable meniscal dart insertion sheath may be attached to a non-disposable joystick handle and used with a non-disposable joystick driver in lieu of the disposable dart stick driver  50  of the meniscal repair assembly  100  described above. For example,  FIGS. 6A and 6B  illustrate, respectively, a non-disposable joystick handle  88  and insertion sheath  89  for the manual insertion of the dart across a meniscal tear. The non-disposable insertion sheath  89  is preferably provided in a straight configuration, as shown in  FIG. 6B , and in curved 15° up, 15° up/30° right, 15° up/30° left configurations (not shown). The joystick handle  88  comprises a generally elongate body  80  and a top attachment module  83  which is designed to threadingly engage base  84  of the meniscal insertion sheath  89 . Detail A of  FIG. 6B  shows the pointed barbs on the tip of sheath  89  for engaging and positioning meniscal tissue. After assembly of the handle  88  and sheath  89 , a conventional dart (as disclosed in U.S. Pat. No. 6,056,778) is loaded (from a plastic retainer) into sheath  89  and advanced into the meniscus using a non-disposable joystick driver  90 , shown in  FIG. 6D . 
     If desired, a trocar  44  ( FIG. 6E ) may be inserted through the non-disposable meniscal insertion sheath  89  to create a pilot hole prior to the insertion of the darts. This embodiment is especially desirable when tough, calcified meniscal tissue is encountered during meniscal repair operations. 
     Alternatively, a disposable meniscal dart driver provided with slit-tube tip for securely engaging a meniscal dart, such as the meniscal dart driver  50  ( FIG. 4 ) engaging dart  20  ( FIG. 3 ), can be inserted into the non-disposable sheath  90  attached to the non-disposable joystick handle  89 . After insertion of the disposable meniscal dart driver, the meniscal dart is advanced into the meniscus. 
     The meniscal repair assemblies of the present invention described above with reference to  FIGS. 1-6  may be employed in various surgical medical procedures for soft tissue repair. For example the disposable meniscal repair assembly  100  of  FIG. 5  may be employed in meniscal tear repairs or repairs of any bodily tissue, such as cartilage, bone, ligaments and skin. 
     To better illustrate an exemplary surgical procedure conducted with the disposable meniscal repair assembly  100  of the present invention, reference is now made to  FIG. 7A , which illustrate a three-dimensional view of a knee meniscus  90  provided with meniscal tear  94  to be repaired. The disposable meniscal repair assembly  100  is shown in  FIG. 7A  in the proximity of the meniscal tear  94 . 
     A preferred method for surgical repair of the meniscal tear  94  according to the present invention commences with standard diagnostic arthroscopy to evaluate the location and extent of meniscal pathology. Meniscal tears located in the vascular zone can also be evaluated with the combination of arthroscopic visualization and a flexible meniscal dart measuring probe. A meniscal vascular punch may be also used to create a bleeding environment in the area of the meniscal tear prior to repair. The punch can be inserted through the tear into the periphery to create an open channel to increase clot formation within the tear. Non-vascular meniscus tears are resected using manual or power instrumentation as necessary. 
     Upon confirmation of a repairable tear, such as the meniscal tear  94  of  FIG. 7A , the peripheral and central edges of the tear may be debrided of fibrous tissue and loose fragments and prepared with a meniscal rasp, for example. This step further stimulates a healing response following dart insertion. 
     A disposable meniscal dart cannula and obturator (not shown) may be inserted into the anteromedial or anterolateral portal to allow atraumatic insertion of the meniscal repair system  100  of  FIG. 5 . The flexible cannula and obturator allows the surgeon to accomplish atraumatic arthroscopic insertion of the tip of the insertion sheath  66  into the joint without obstruction by soft tissue. Although the meniscal repair method of the present invention will be described below with reference to a straight mensical insertion sheath, such as the insertion sheath  66  of  FIGS. 1 and 5 , it must be understood that the invention also contemplates employing a curved insertion sheath, such as the curved insertion sheath  77  of  FIG. 2 . 
     Once the insertion sheath  66  has been inserted through the dart cannula, the obturator is removed and a meniscal dart probe is inserted to measure the ideal angle of approach of the dart insertion instrumentation. The probe also measures the meniscus  90  to determine the proper length of the dart  20 . Multiple markings located on the meniscal probe serve to determine the appropriate length of the dart  20  necessary to repair the tear  94  in the meniscus  90 . The probe is marked at 10, 12 and 14 mm with respect to the corresponding dart sizes available. Thus, the actual size of the dart  20  to be employed in the meniscus repair depends upon the variable width of the meniscus tissue to be repaired. The length of the dart  20  must be also selected such that, when inserted, the dart  20  is entirely contained within the meniscus. The insertion sheath  66  is then positioned to provide recommended meniscal dart placement parallel to the surface of the tibial plateau and perpendicular to the tear  94 . 
     The central fragment of the torn meniscus is secured with the pointed tip  65  of the insertion sheath  66  and positioned into the correct anatomic position for fixation. Care is taken to position the insertion sheath 4 to 6 mm from the tear  94 , to provide maximum fixation and apposition of the meniscus once the device is deployed. The dart  20  securely engaged at the tip of the driver  50  is subsequently pushed into the meniscus  90  until the dart is placed beneath the surface of the meniscus and in the meniscal tear  94 , as shown in  FIG. 7B . Dart placement may be carried out on the femoral or tibial meniscus surfaces as necessary. If desired, multiple darts  20  may be deployed perpendicular to the tear  94 , depending on the length of the tear. 
     A probe is inserted to confirm apposition of the meniscus tear  94  and the complete insertion of the dart  20  ( FIG. 7B ) within the body of the meniscus tissue. If the dart is not completely inserted, the insertion sheath  66  may be repositioned over the end of the dart and re-driven to complete full insertion of the dart. Final inspection of the meniscus  90  should confirm complete apposition of the tear with no portion of any implant exposed outside of the meniscus. The knee is stabilized in a post-op brace in full extension and patients are instructed to avoid full weight bearing for a minimum of 4 weeks post operatively. 
     Alternatively, if non-disposable instrumentation is employed, such as the instrumentation shown in  FIGS. 6A-6E , then the non-disposable insertion sheath  89  is first secured to the non-disposable joystick handle  88 , and then either a disposable meniscal dart driver with an attached dart, such as the meniscal dart driver  50  of  FIG. 4  and dart  20  of  FIG. 3 , or the non-disposable meniscal dart driver  90  of  FIG. 6D  with a separate conventional dart may be employed. If the non-disposable meniscal dart driver is employed, then the proper meniscal dart is selected and inserted from a sterile dart retainer (not shown) into the sheath. 
     At this stage, fluid flow from the source (pump or gravity flow system) should be preferably stopped to prevent the dart from being inadvertently pushed out of the insertion sheath. While applying sufficient forward pressure and compression of the reduced meniscus tear, the dart driver is then slid through the insertion sheath, and the dart  20  is pushed into the meniscus  90  until the dart bridges the tear in the meniscus. The handle  88  and insertion sheath assembly are then removed. 
     Prior to dart insertion, a trocar, such as the trocar  44  of  FIG. 6E , may be introduced through the non-disposable insertion sheath and into the meniscus, creating a pilot hole into which dart  20  is deployed. This additional step is performed when it is determined that the meniscus tissue is too rigid to receive a dart without first creating a pilot hole. 
     Following insertion of an initial dart, the insertion sheath is repositioned, reloaded and the next dart deployed as needed until the meniscus tear is securely repaired. Additional darts are preferably inserted in 5 mm increments over the entire length of the tear. Final inspection of the meniscus should confirm complete apposition of the tear with no portion of any implant exposed outside of the meniscus. 
     The above description and drawings illustrate preferred embodiments which achieve the objects, features and advantages of the present invention. It is not intended that the present invention be limited to the illustrated embodiments. Any modification of the present invention which comes within the spirit and scope of the following claims should be considered part of the present invention.