Microfracture instrument

[0001] This application claims the benefit of U.S. Provisional Application No. 61/164,732, filed Mar. 30, 2009, the entire disclosure of which is incorporated by reference herein.

[0002] The present invention is directed to surgical instruments and, more particularly, to a device for treating chondral defects of the knee.

[0003] Treatment of articular cartilage defects is typically accomplished by the microfracture procedure. This procedure is performed arthroscopically. Although articular cartilage defects may occur in any joint, the microfracture procedure is typically performed in the knee or shoulder. The surgeon visually assesses the defect and performs the procedure using special instruments that are inserted through small incisions around the joint. Unstable and loose cartilage is removed from the exposed bone so that there is a stable edge of cartilage surrounding the defect. Multiple holes (also called microfractures) are then made in the exposed bone about 3 to 4 mm apart. Bone marrow cells and blood from the holes combine to form a “super clot” that completely covers the damaged area. This marrow-rich clot is the basis for the new tissue formation. The microfracture technique produces a rough bone surface to which the clot adheres more easily. This clot eventually matures into firm repair tissue that becomes smooth and durable.

[0004] The instruments currently used to make the microfractures are manual instruments such as curved picks and/or nitinol wires and guides. One powered option is a subchondral drill which is a straight drill covered by an outer sheath. The outer sheath covers the drill tip until it contacts bone and then the drill tip advances axially into the bone. The manual instruments are undesirable in that they typically require two hands to use since a mallet is used to drive the instruments into the bone. In addition, the impact loading of the mallet may cause the pick to slide or gouge the target site rather than puncture the site perpendicular to the axis of the trocar tip. The straight drill power instrument does not provide adequate accessibility or visibility to the site which is typically in a joint space.

[0005] An instrument that can form the microfractures quickly and at pre-determined angles with repeatability is needed. Also needed is an instrument that allows the surgeon to quickly place the microfractures in the desired position using only one instrument attached to power, and with improved accessibility and visibility to the site.

[0006] The present invention provides an instrument for forming microfractures quickly and at pre-determined angles. The instrument takes less time and replaces the use of multiple manual instruments. The instrument attaches to a power system such as that used for shavers and burrs to quickly drill small diameter holes at pre-determined angles into bone. The instrument is provided with a flexible trocar tip and a curved outer sheath. The shaft of the flexible trocar tip connects to the hand piece. The outer sheath protects the sharp trocar tip during insertion and is retracted once positioned to expose the sharp trocar tip. The instrument allows the surgeon to quickly place the microfractures in the desired position using only one instrument attached to power.

[0007] These and other features and advantages of the invention will be more apparent from the following detailed description that is provided in connection with the accompanying drawings and illustrated exemplary embodiments of the invention.

[0026] The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art.

[0027] The present invention provides a microfracture instrument for forming small diameter holes in bone. The microfracture instrument of the present invention is designed to attach to a power system (such as one used for shavers and burrs, for example) to quickly drill small diameter holes at pre-determined angles into bone. The microfracture instrument is provided with a flexible trocar tip and a curved outer sheath. The shaft of the flexible trocar tip connects to the hand piece. The outer sheath protects the sharp trocar tip during insertion and is retracted once positioned to expose the sharp trocar tip. The instrument allows the surgeon to quickly place the microfractures at the desired position using only one instrument attached to power.

[0028] The present invention also provides a method of drilling a hole in a bone by inter alia: providing a shaft with a flexible end, the flexible end being coupled to a drill tip; providing a cannulated sheath with a distal end and a proximal end, the distal end of the sheath being curved and housing the drill tip; and retracting the sheath to cause the drill tip to extend beyond the distal end of the sheath.

[0029] Referring now to the drawings, where like elements are designated by like reference numerals, FIGS. 1-12 illustrate an exemplary microfracture instrument 100 of the present invention for forming small diameter holes in bone.

[0030] The microfracture instrument 100 of the present invention may be employed during a microfracture procedure, which is conducted arthroscopically to treat articular cartilage defects, for example, chondral defects of the knee. The surgeon visually assesses the defect and performs the procedure using special instruments that are inserted through small incisions on the knee. After assessing the cartilage damage, any unstable or loose cartilage is removed from the exposed bone, leaving a stable edge of cartilage around the defect.

[0031] Multiple holes (or microfractures) are then made in the exposed bone about 3 to 4 mm apart. Bone marrow cells and blood from the holes combine to form a “super clot” that completely covers the damaged area. This marrow-rich clot is the basis for the new tissue formation. The microfracture technique produces a rough bone surface that the clot adheres to more easily. This clot eventually matures into firm repair tissue that becomes smooth and durable. Similar microfracture procedures are used in other surgical sites to treat similar bone and cartilage defects, such as Hill-Sachs lesions in the shoulder.

[0032] As illustrated in FIGS. 1-12, microfracture instrument 100 of the present invention includes an outer assembly 20 and an inner assembly 50. The microfracture instrument 100 connects to a shaver hand piece (not shown) for power.

[0033] As illustrated in more detail in FIGS. 2 and 7, the outer assembly 20 includes an outer sheath 29 having a cannulated shaft provided with a distal 25 and proximal end 27. In an exemplary embodiment, the distal end 25 of the sheath 29 is curved (FIG. 1). The angle of curvature may be between about 5 to about 80 degrees, preferably between about 30 to about 60 degrees. As also illustrated in FIG. 2, the outer assembly 20 also includes an outer hub 21 with a retaining ring 25. The outer hub 21 is designed to receive the inner assembly 50 through a most proximal opening 28 (FIG. 9).

[0034] The outer hub 21 is also provided with an actuator mechanism 35 (FIG. 9) for moving the sheath 29 along a longitudinal axis of the microfracture instrument 100. The proximal end 27 of the sheath 29 connects to the actuator mechanism 35. In an exemplary embodiment only, the actuator mechanism 35 is a lever, but one skilled in the art will recognize alternate embodiments such as a button or a ratchet for moving the shaft along the longitudinal axis.

[0035] The outer assembly 20 is further illustrated in more detail in FIG. 12. The outer assembly 20 includes the outer sheath 29, the actuator 35, the spring 56, the outer hub 21, and a cap 90. The cap 90 is shown in greater detail in FIG. 11.

[0036] The inner assembly 50 of the microfracture instrument 100 is illustrated in more detail in FIGS. 3-6 and 8. As illustrated in FIG. 3, inner assembly 50 comprises an inner shaft 70 extending from a proximal end 77 to a distal end 75. The distal end 75 of the inner shaft houses a drill tip or trocar tip 60 for creating small diameter holes in bone. Details of trocar tip 60 are illustrated in FIG. 8, although the drill tip could have other geometries and could be fluted or in the form of a bur, for example. As shown in FIG. 3, the inner assembly 50 further includes an inner hub 53, a thrust washer 54, a spring 56, and a corresponding spring retainer 57.

[0037] The proximal end 77 of the inner shaft 70 connects to the inner hub 53 (FIG. 3). In turn, inner hub 53 connects to a shaver hand piece for power to drive the trocar tip 60 into bone. The inner shaft 70 has a flexible portion 55 (a flex coil 55 shown in FIG. 5) allowing the inner assembly 50 to conform to the curvature of the distal end 25 of the outer sheath 29 of the outer assembly 20.

[0038] When inserted into the joint space, the outer sheath 29 of the microfracture instrument 100 covers the trocar tip 60 protecting the surrounding anatomy. Once the desired location for creating the microfracture is located through the scope, the surgeon can manipulate the lever/actuator 35 to retract the sheath 29 thereby exposing the trocar tip 60. Once the tip 60 is exposed, the surgeon may turn on the power to create the hole in the bone. This technique provides the surgeon with more accessibility to the bone in the joint space due to the curvature of the outer sheath. The profile of the instrument 100 is also reduced since the tip is retracted during insertion resulting in better placement of the instrument in the joint space. An additional safety feature is the protection of the surrounding anatomy from an exposed tip during insertion of the instrument prior to drilling.

[0039] An exemplary method of preparation and insertion of the instrument 100 of the present invention (shown in use in FIG. 13) is detailed below with reference to specific steps:

[0040] The damaged articular cartilage area is prepared in the standard fashion.

[0041] The instrument 100 is then attached to a handpiece 110 with the trocar tip 60 retracted safely within the outer sheath 29.

[0042] Next, the instrument 100 is passed into the joint space 140 through a cannula or percutaneously 130.

[0043] The actuator mechanism 35 is then actuated to laterally move outer sheath 29, thereby exposing the trocar tip 60 so that the trocar tip 60 extends out of the outer sheath 29.

[0044] Next, the trocar tip 60 is placed in the appropriate location for forming a hole 122.

[0045] The handpiece 110 is energized to rotate the trocar tip 60 and the trocar tip 60 is pushed into bone 120 until the outer sheath 29 contacts bone 120, thereby forming a 1.5 mm hole 122 approximately 3 mm deep in the bone 120.

[0046] The instrument 100 is retracted while the handpiece 110 is still energized and the trocar tip 60 is rotating.

[0047] The above steps are repeated as needed on different locations of the damaged cartilage as needed until the micro-drilling procedure is complete.

[0048] Thereafter, the trocar tip 60 is retracted by raising the actuator 35 so that the trocar tip 60 is housed in outer sheath 29 and the instrument 100 is removed from the joint space.

[0049] The instrument 100 is also an ideal tool for marking the femoral tunnel location in ACL reconstructive procedures by following the above steps and using the trocar tip 60 to mark a tunnel location within the femoral notch. Using the laser mark 12 (shown in FIG. 2) on the sheath 29, the approximate tunnel location can be determined through the medial portal by placing the end of the sheath 29 at the over-top-position.

[0050] The trailing edge of the laser mark 12, which is the edge of the mark 12 farthest from the end of the sheath 29 from which the trocar tip 60 extends, is used to reference the center of the tunnel in a Single Bundle ACL technique.

[0051] The leading edge of the laser mark 12, which is the edge of the mark 12 nearest to the end of the sheath 29 from which the trocar tip 60 extends, is used to reference the center of the posterior tunnel in a Double Bundle ACL technique. After marking its position, the same measurement method is used to reference the center of the anterior tunnel referenced from the previously marked posterior tunnel position. Further, the leading and trailing edges of the laser mark 12 may be used to measure osteochondral defects.

[0052] In one embodiment, the laser mark 12 is 2 mm wide, the leading edge is 5 mm from the end of the sheath 29 from which the trocar tip 60 extends and the trailing edge is 7 mm from the end of the sheath 29 from which the trocar tip 60 extends. In other embodiments, different widths and distances may be used.

[0053] Although the present invention has been described in connection with preferred embodiments, many modifications and variations will become apparent to those skilled in the art. While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting.