Flipping-type graft fixation device and method with low flipping distance

A graft retention device has an elongated body with first and a second ends, and a midpoint therebetween. A pair of elongated slots through the body defines a tang therebetween. At least one of the slots have an open first end into the body at the body first end such that the first end is closed via a retention line between the tang and the body. A graft retention loop disposed over the tang is slidable therealong from a first position closer to the body first end and a second position closer to the midpoint.

BACKGROUND

This application relates to graft fixation, and more particularly to graft tissue fixation employing flipping-type fixation devices.

Flipping-type fixation devices, such as disclosed in U.S. Pat. Nos. 5,306,301 and 5,645,588 which are incorporated herein by reference, allow a simple procedure to be used for fixing tissue such as in an Anterior Cruciate Ligament (ACL) reconstruction. Such device comprises an elongated bar having a central suture loop depending therefrom. A tunnel is prepared in the femur from a position at or near the patellar surface up through a portion of the femur and exiting through the side of the femur at a superior location. A graft is looped over the loop attached to the elongated bar. The bar is able to pass in one direction up through the tunnel. After exiting the superior end of the tunnel, the bar is flipped approximately 90 degrees so that it will not pass back through the tunnel and is positioned against the femur with the loop and graft hanging down into the tunnel therefrom. Tension on the graft keeps the bar in place against the bone surface.

To initiate the flipping, however, the bar must be passed completely outside of the tunnel. When it is then placed down against the bone the suture loop falls back into the tunnel by the amount that it was pulled free of the tunnel, about 50% of the length of the bar. This decreases the contact of the graft with the bone in the tunnel. Also, longer loop lengths have the potential to increase motion of the graft within the tunnel, thus potentially slowing the healing process in which the graft attaches to the bone.

U.S. Patent Publication No. 20130204366, incorporated herein by reference, provides a bar in which the graft retention loop is able to move axially along the bar thereby reducing the distance the graft is pulled out of the tunnel during the flipping procedure.

SUMMARY OF THE INVENTION

A graft retention device according to the present invention comprises an elongated body having a first end and a second end, a midpoint therebetween, and an upper surface and a lower surface. A first elongated slot and a second elongated slot through the body from the upper surface to the lower surface define tang therebetween. At least one of the first and second slots have an open first end into the body at the body first end such that the first end is closed via a retention line between the tang and the body. A graft retention loop disposed over the tang is slidable therealong from a first position closer to the body first end and a second position closer to the midpoint.

Preferably, each of the first slot and second slot has an open first end and each has a separate retention line or a single retention line which encloses both the first slot and the second slot.

Preferably, at least a portion of the retention line extends longitudinally beyond the first end of the body.

In one aspect of the invention, the retention line comprises a flexible material. The retention line can comprise an elastic material. The retention line can comprise a metal wire.

Preferably, a leading line connects to the body at the second end.

Preferably, the tang slopes downwardly away from the first end.

Preferably, the graft retention device is provided in a sterile condition.

Preferably, the second position is located near the midpoint such as within a central 25% of a length of the elongated body between its first end and its second end.

In one aspect of the invention, a trailing line connects to the body adjacent the slots and extends therefrom, when the graft retention loop is in the first position, through the graft retention loop toward the first end such that tension applied to the trailing line will thus tend to urge the graft retention loop away from the first position and toward the second position.

A method according to the present invention provides for fixing a graft ligament into a bone tunnel. The method comprises the steps of: a) forming a graft construct by disposing the graft ligament over a loop slidably disposed upon a tang formed between two elongated slots of an elongated fixation buckle, the loop being slidable along the tang from a first position nearer a first end of the buckle to a second position nearer a midpoint of the buckle; b) pulling the graft construct up through the bone tunnel with a second end of the buckle leading and the loop in the first position; c) retaining the loop in the slots and on the tang in the first position via a retention line between the tang and a body forming the buckle at the first end of the buckle; and d) after the buckle has been pulled through the tunnel, reorienting the buckle to be crosswise to the tunnel on the bone adjacent the tunnel with the loop depending into the tunnel from the second position on the buckle.

Preferably, a portion of the retention line extends longitudinally beyond the first end of the buckle body when the loop is in the first position. Preferably, the graft is moved no further upwards during the performance of step c) from its final position after step d) than 3.5 mm. More preferably, the graft is moved no further upwards during the performance of step c) than its final position after step d). Most preferably, the bone tunnel comprises a lower graft channel and an upper passing channel, with the graft channel having a width exceeding a maximum width of the passing channel thereby forming an end surface of the graft channel where it meets the passing channel and wherein the method further comprises the step of holding the graft in compression against the end surface of the graft channel after step d).

DETAILED DESCRIPTION

FIGS. 1 and 2show a graft fixation device10according to the present invention. It comprises an elongated bar or buckle12having a graft receiving loop14depending therefrom. The buckle12comprises a first end16and second end18, and an upper surface20and lower surface22. The terms “upper” and “lower” and related terms such as “upwards” are used herein with reference to the surfaces of the buckle12just defined, with the lower surface22being that surface which will face a bone (not shown inFIG. 1) when the buckle12is employed.)

A pair of longitudinal slots32penetrates the buckle12from the upper surface20to the lower surface22and extends from a first end34adjacent the buckle first end16to a second end36at a midpoint38of the buckle12. The slots32define a retention tang40therebetween. An upper surface42of the retention tang slopes downwardly from the first end34of the slots32to the second end36to encourage the loop14to migrate toward the midpoint38at implantation. The loop14is received through the slots32and slides along the retention tang upper surface42.

A first hole24penetrates the tang40laterally adjacent the first end16and a second hole26penetrates the buckle12at the second end18, passing from the upper surface20to the lower surface22. The first hole24receives a trailing line28and the second hole26a leading line30for guiding the buckle12during implantation. As best seen inFIG. 2, when the loop14is toward the first end34it overlaps the first hole24. When the trailing line28is tightened upwardly during the flipping portion of implantation it will tend to push the loop14away from the first end34. Placement of the hole24inboard of the first end34also allows the first end34of the slots32to be closer to the first end16of the buckle12and thereby reduce the flipping distance.

The trailing line28and leading line30are preferably formed of ORTHOCORD #2 suture available from Ethicon, Inc. of Somerville, N.J. The leading line30may experience higher stress than the trailing line28while placing the fixation device10as will become apparent as the placement procedure is described. The second hole26is shown slightly larger than the first hole24(although they could be made the same size) and the leading line30can be a higher strength suture such as with a larger diameter than the trailing line28. This difference can be used to differentiate the leading line30and trailing line28. They can also be differentiated in some other fashion such as via varying colors or visual patterns.

Preferably, the vertical dimension of the retention tang40remains constant from the first end34to second end36to enhance its strength and rigidity, with the retention tang40thus depending slightly below the buckle lower surface22at the midpoint38. The tang40is shown with a slope below the upper surface20of 13.6 degrees but could be anywhere from zero to about 45 degrees. It could also vary in slope, such as getting progressively steeper toward the midpoint38to encourage the loop to stay at the midpoint38after implantation.

Preferably, for an ACL repair the buckle12is approximately 12 mm long, 4 mm wide and 1.5 to 2.5 mm thick, with the thickest portion being the midpoint38where the tang40depends. The tang40is approximately 1.5 mm thick. The buckle12is preferably formed of a biocompatible material such as 6 Al-4V Ti alloy. Preferably, the loop14is woven of ultra-high molecular weight polyethylene, such as DYNEEMA, and polyester. The material of the loop14is preferably about 2 mm in diameter, preferably being in a range of from #2-0 up through about 4 mm, and the loop14is preferably between about 8 mm and 60 mm long. The loop14can be woven onto the buckle12to form a continuous loop without knots. U.S. Pat. No. 6,352,603 to Bryant, incorporated herein by reference, illustrates one method for achieving such a construct.

Turning also now toFIG. 3, a graft construct44comprises a tissue graft46looped over the loop14of the fixation device10and is show in place in a patient's leg48. A tunnel50in the leg's femur52comprises a larger diameter inferior portion or socket54sized to accommodate the graft46and a smaller diameter superior portion or passing channel56sized to accept the buckle12in a lengthwise orientation. The buckle12sits against the femur52in a sideways orientation with the loop14depending down through the passing channel56and into the socket54in which is placed the graft46. An opposite end of the graft46is placed into a tibial tunnel58in the leg's tibia60and held in place with an anchor62such as the INTRAFIX® anchor available from DePuy Mitek Inc. of Raynham, Mass.

Turning also now toFIGS. 4A to 4Dthe process of passing the buckle12up through the tunnel50and especially the passing channel56will be described. At the start of the procedure, the graft tissue46is threaded through the loop14. A longitudinal axis60of the buckle12is oriented coaxially with a longitudinal axis62of the tunnel50, with the loop14depending from the first end34of the slots32(FIG. 4A). Tension on the leading line30pulls the second end18of the buckle12upwardly out of the passing channel56until the first end16is free of the passing channel56(FIG. 4B). Preferably, the loop14and the passing channel56are dimensioned so that if the graft construct44is pulled up until the graft tissue46abuts an end55of the socket54the first end16of the buckle12has just cleared the end of the passing channel56thus providing tactile feedback to the surgeon that the buckle12is properly positioned to be rotated. The graft46shown inFIGS. 4A to 4Dis not to scale and is shown as a thin line so as to better illustrate the construction of the socket54. In reality the graft46would be fatter such that it entirely fills the width of the socket54. Contact between the graft46and the bone forming the socket54allows the graft to grow into and merge with the bone to form a permanent repair.

Rotation is approximately 90 degrees and can occur by applying tension to the trailing line28(FIG. 4C). The final orientation depends upon the angle at which the tunnel50penetrates the femur52. As the buckle12is rotated, opposing tension supplied by the graft tissue46tends to cause the loop14to slide along the retention tang40leaving it depending down into the passing channel56from the midpoint38of the buckle12. This occurs with a distinct snapping motion that can be felt by the surgeon through the trailing line28to provide tactile feedback that the migration has occurred properly. The trailing line28and leading line30are then removed and tension from the graft tissue46pulls the buckle12lower surface22firmly against the femur52(FIG. 4D). The crosswise orientation of the buckle12versus the passing channel56and the loop14depending from the midpoint38of the buckle12prevent the buckle from migrating back into the passing channel56thus providing secure fixation of the graft tissue46.

The slope of the tang upper surface42assists in urging the loop14toward the midpoint38. Its angle on the femur52versus the tunnel50also tends to pull the loop14across the buckle12to sit at the slot second ends36and the buckle12. Locating the ends36at the midpoint38thus helps keep the loop14seated at the midpoint38. In terms of final seating of the loop14the term “midpoint” can be broadly construed. Seating at the exact middle of the buckle12provides an equal amount of buckle to each side thereof to minimize any chance that the buckle12can slip along the bone in such a fashion that and end thereof could fall back into the passing channel56. In practical terms the loop14can be seated in other locations yet still be safely situated to prevent the buckle12from falling back into the passing channel56. Preferably, the loop14is seated somewhere in the middle 50% of the length of the buckle12and more preferably within the middle 25%.

The flipping distance is representative of the gap between the graft46and the end of the socket54. Ideally this gap is zero and the graft46extends all the way to the end of the socket54.

FIG. 5illustrates a further embodiment of a buckle100according to the present invention. It comprises a body102having first and second ends104and106with holes108and110for trailing and leading lines107and109respectively. It also has slots112forming a tang114for supporting a graft support loop115. The slots112extend from a midpoint116to the first end104rather than being enclosed by the body102at the first end104as in the previous embodiment. To retain the loop on the tang114a retaining line118is provided through aperture120in the tang114and adjacent apertures122in the body102.

The retaining line118can be a suture, wire or other material with sufficient tensile strength to retain the loop. It can be flexible, stretchable or rigid. As shown inFIG. 5it bows outwardly124between the tang114and adjacent body102to further minimize the flipping distance, but it could be made straight with no bowing. The bowing124can be present in a resting state such as being formed in a wire, or may by dynamically formed under force of the loop115against the retaining line118if the line118is formed of an elastic material which stretches to form the bowing124. For instance the line118could be formed of a suture with a lower than average modulus of elasticity such as PDS (Polydioxanone) or Prolene and multiple lengths of such suture could be employed to form the line118with sufficient strength. Rubber or silicone materials, as for instance silicone tubing, of an implantable grade could are other possibilities for an elastic material. The bowing124could be formed by the line118being flexible, such as a suture, with sufficient slack as to form the bowing124especially when the loop presses against it.

Fixation of the line118in the apertures122can be effected by providing knots126the ends of the line118, particularly if it is formed of suture, such that the knots126cannot pass through the apertures122. Other methods for fixation include welding, adhesives, interference screws etc.

With sufficient bowing124the buckle100could have a flipping distance of zero or even a negative value allowing the graft to be seated to the end55of the graft socket54(not shown inFIG. 5). With sufficient bowing124and a negative flipping distance, the graft will reach the end55of the graft socket54as the buckle100is flipped. After the flipping is completed and the buckle100is seated against the bone the loop115would be pulled upwards versus its position during flipping such that a tension in the loop115would pull the graft into contact with the end55of the socket54with a contact force thereagainst thereby maximizing the bone to graft contact area of the completed repair. In prior devices this bone surface55is wasted as they do not allow the graft to contact it sufficient to achieve ingrowth between the graft and the bone.

The loop115is preferably a continuous closed loop. Formation of such a structure through weaving etc. is made more difficult if it must be formed around the tang114. With the design ofFIG. 5the loop115can be formed alone which is much easier and then slipped onto the tang114prior to placing the line118onto the buckle100. This simplifies manufacturing.

Refinements and variations to the buckle could include slots which extend to both sides such that the second side mirrors the first, and the retention tang sloping down from both ends toward the center. This would allow a surgeon to pull the buckle up through the tunnel50by either end. Also, the upper surface of the retention tang could be rounded to provide a better surface for the loop14to ride over and lessen chafing of the loop14.

Provision can be made to discourage the loop14from moving away from the midpoint38, such as by providing barbs (not shown) along the upper surface42or other areas of the buckle12where they may engage the loop14as it slides along the slots32. The tang can have a pronounced dip to capture and retain the loop14at the midpoint.

The buckle is particularly suited to ACL repair, but can be useful in other repairs such as for example reattachment of a biceps brachii tendon.