US20140142697A1 - Fixation screw, graft ligament anchor assembly, and method for securing a graft ligament in a bone tunnel - Google Patents

Abstract

A fixation screw, graft ligament anchor assembly, and method for fastening a graft ligament in a bone tunnel. The screw comprises an elongated shank having a distal end and a proximal end, and a central axis extending from the distal end to the proximal end. Screw threads are disposed on the shank and extend from the distal end to the proximal end. The proximal end defines an end plane disposed transversely to the axis and at an angle thereto other than a normal angle.

Description

FIELD OF THE INVENTION
• This invention relates to medical apparatus and methods in general, and more particularly to apparatus and methods for reconstructing ligaments.
BACKGROUND OF THE INVENTION
• Ligaments are tough bands of tissue which serve to connect the articular extremities of bones, or to support and/or retain organs in place within the body. Ligaments are typically composed of coarse bundles of dense white fibrous tissue which are disposed in a parallel or closely interlaced manner, with the fibrous tissue being pliant and flexible but not significantly extensible.
• In many cases ligaments are torn or ruptured as a result of accidents. Various procedures have been developed to repair or replace such damaged ligaments.
• For example, in the human knee, the anterior and posterior cruciate ligaments (i.e., the “ACL” and “PCL”) extend between the top end of the tibia and the bottom end of the femur. The ACL and PCL cooperate, together with other ligaments and soft tissue, to provide both static and dynamic stability to the knee. Often, the anterior cruciate ligament (i.e., the ACL) is ruptured or torn as a result of, for example, a sports-related injury. Consequently, various surgical procedures have been developed for reconstructing the ACL so as to restore substantially normal function to the knee.
• In many instances, the ACL may be reconstructed by replacing the ruptured ACL with a graft ligament. More particularly, in such procedures, bone tunnels are generally formed in the top end of the tibia and the bottom end of the femur, with one end of the graft ligament being positioned in the femoral tunnel and the other end of the graft ligament being positioned in the tibial tunnel. The two ends of the graft ligament are anchored in place in various ways well known in the art so that the graft ligament extends between the bottom end of the femur and the top end of the tibia in substantially the same way, and with substantially the same function, as the original ACL. This graft ligament then cooperates with the surrounding anatomical structures so as to restore substantially normal function to the knee.
• In some circumstances, the graft ligament may be a ligament or tendon which is harvested from elsewhere in the patient; in other circumstances, the graft ligament may be a synthetic device. For the purposes of the present invention, all of the foregoing are collectively referred to as a “graft ligament”.
• It has been found that in securing graft tendons to tibias, because of the surface configuration of the tibia bone it often is necessary to advance a fixation screw well into a bone tunnel in the tibia, often so far that for one side of the screw to be substantially flush with the bone tunnel opening, the other side of the screw will have advanced past the outer dense hard cortical bone and entered the inner and softer cancellous bone.
• It has further been found that to refrain from advancing the fixation screw to the aforementioned location (that is, to leave a portion of the screw in cortical bone all around the screw) requires that a proximal portion of the screw remain outside the bone tunnel and project from the tibia.
• Thus, there is a need for a fixation screw, graft ligament anchor assembly and method which affords full advancement of a fixation screw, but at the same time permits the screw to be engaged all around in the cortical portion of the tibia or other bone.
OBJECTS OF THE INVENTION
• An object of the invention is to provide a fixation screw configured for disposition in cortical bone portions, so as to strengthen the retention of the screw in the bone.
• Another object of the invention is to provide a fixation screw which, when the screw is fully implanted, substantially conforms to a surrounding bone surface at a proximal end of the screw.
• A further object of the invention is to provide a graft ligament anchor assembly for improved retention in a bone, such as a tibia, and which in operative position conforms to a surrounding bone surface.
• A still further object is to provide a method for securing a graft ligament in a bone tunnel so as to improve retention of the graft ligament in the bone, and so as to provide for conformance of a graft ligament anchor and fixation screw to a surface of surrounding hone.
SUMMARY OF THE INVENTION
• With the above and other objects in view, as will hereinafter appear, there is provided a fixation screw for fastening a graft ligament in a bone tunnel. The screw comprises an elongated shank having a distal end and a proximal end, and a central axis extending from the distal end to the proximal end. Screw threads are disposed on the shank and extend from the distal end to the proximal end. The proximal end defines an end plane disposed transversely to the axis and at an angle thereto other than a normal angle.
• In accordance with a further feature of the invention there is provided a fixation screw comprising an elongated shank having a generally conically-shaped distal end portion, a proximal end, and a central axis extending from the distal end portion to the proximal end. Screw threads are disposed on the shank and extend from the distal end portion to the proximal end. The proximal end comprises a generally planar end surface disposed transversely to the axis and at an angle thereto other than a normal angle.
• In accordance with a further feature of the invention, there is provided a fixation screw for fastening a graft ligament in a bone tunnel. The screw comprises an elongated shank having a generally conically-shaped distal end portion, a proximal end, and a central axis extending from the distal end portion to the proximal end. Screw threads are disposed on the shank, and extend from the distal end portion to the proximal end. The proximal end comprises a generally planar end surface disposed transversely to the axis and at an angle thereto other than a normal angle, and appropriate for positioning the end surface as generally a continuation of surrounding hone surface of a body in which the graft ligament is fastened.
• In accordance with a further feature of the invention, there is provided a graft ligament anchor assembly comprising a tubular body having a bore therethrough, and proximal and distal ends. The tubular body is adapted for placement in a bone tunnel proximate an opening thereof in a bone surface. The tubular body comprises a deferrable wall and defines, at least in part, a chamber for receiving a graft ligament therein. A fixation screw is provided for insertion into the tubular body axially of the tubular body, for impinging upon the deferrable wall so as to press the deformable wall, and hence the graft ligament received in the chamber, toward a wall of the bore, to fix the graft ligament in the bone tunnel. The screw comprises an elongated shank having a generally conically-shaped distal end portion, a proximal end, and a central axis extending from the distal end portion to the proximal end. Screw threads are disposed on the shank and extend from the distal end portion to the proximal end. The proximal end comprises a generally planar end surface disposed transversely to the axis and at an angle thereto other than a normal angle, and appropriate for positioning as generally a continuation of surrounding bone surface of a body in which the graft ligament is fastened.
• In accordance with a still further feature of the invention, there is provided a method for securing a graft ligament in a bone tunnel having an end opening in a bone surface, a free end of the graft ligament extending out of the bone tunnel end opening. The method comprises the steps of providing a fixation screw for insertion into the bone tunnel adjacent the graft ligament for impinging upon the graft ligament and a wall of the bone tunnel to fix the graft ligament in the bone tunnel. The screw comprises an elongated shank having a generally conically-shaped distal end portion, a proximal end, and a central axis extending from the distal end portion to the proximal end. Screw threads are disposed on the shank and extend from the distal end portion to the proximal end. The proximal end comprises a generally planar end surface disposed transversely to the axis and at an angle thereto other than a normal angle, and appropriate for positioning as generally a continuation of surrounding portions of the bone surface. The method further comprises the steps of pulling the graft ligament taut, inserting the screw into the bone tunnel and advancing the screw therein to threadedly engage the graft ligament and a wall of the bone tunnel to fix the graft ligament in the bone tunnel, and turning the screw until the shank proximal end surface thereof is substantially a continuation of the surrounding bone surface.
• In accordance with another feature of the invention, there is provided a method for securing a graft ligament in a bone tunnel having an end opening in a bone surface, a free end of the graft ligament extending out of the hone tunnel end opening. The method comprises the step of providing a graft ligament anchor comprising a tubular body having a bore therethrough and proximal and distal ends, the tubular body comprising a deformable wall and defining at least in part a chamber, and a fixation screw. The screw comprises an elongated shank having a generally conically-shaped distal end portion, a proximal end, and a central axis extending from the distal end portion to the proximal end. Screw threads are disposed on the shank and extend from the distal end portion to the proximal end. The proximal end comprises a generally planar end surface disposed transversely to the axis and at an angle thereto other than a normal angle, and appropriate for positioning as generally a continuation of surrounding portions of the bone surface. The method includes the further steps of extending the graft ligament free end through the chamber, placing the tubular body in the end opening and in the bone tunnel, pulling the graft ligament taut, inserting the screw into the tubular body and advancing the screw therein to press the deformable wall, and hence the graft ligament received in the chamber, toward the wall of the bore, to fix the graft ligament in the bone tunnels and turning the screw until the proximal end surface thereof is substantially a continuation of the bone surface therearound.
• The above and other features of the invention, including various novel details of construction and combinations of parts and method steps will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular devices and method steps embodying the invention are shown by way of illustration only and not as limitations of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
• These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which are to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein:
• FIG. 1 is a perspective view of one form, of a fixation screw for fastening a graft ligament in a bone tunnel, illustrative of an embodiment of the invention;
• FIG. 2 is a side elevational view of an alternative embodiment of fixation screw;
• FIG. 3 is a diagrammatic illustration of the screw ofFIG. 1 in operation;
• FIG. 4 is a diagrammatic illustration of a graft ligament anchor assembly including the screw ofFIG. 1 and illustrating an anchor assembly in operation; and
• FIG. 5 is a diagrammatic illustration of still another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring toFIG. 1, it will be seen that anillustrative fixation screw10 includes anelongated shank12 having adistal end portion14, which may be generally conically-shaped, as shown inFIG. 1, and have a generally pointeddistal end16. Theshank12 is further provided with aproximal end18 defining an end plane b-b. A central axis a-a extends from thedistal end16 to theproximal end18. The plane b-b is disposed transversely to the axis a-a and at an angle c thereto, the angle c being other than a normal angle, and preferably of about 40°-55°. Theproximal end18 may comprise a generallyplanar surface22, as illustrated inFIG. 1. Screw threads28 are disposed on theshank12 and extend from thedistal end16 to theproximal end18.
• Referring toFIG. 2, it will be seen that thefixation screw10 may be of tubular structure and provided withapertures24 extending throughsidewalls26 thereof, facilitating ingrowth of bone to further secure the screw in place over time. Further, as shown inFIG. 2, thedistal end portion14 of thescrew10 may be other than conical, such as generally cylindrical, and thedistal end16 of thescrew10 may be other than pointed, such as defining a plane normal to the axis a-a.
• inFIG. 3, there is illustrated a manner in which thefixation screw10 ofFIG. 1 orFIG. 2 may be used to secure agraft ligament30 in abone tunnel32 having anend opening34 in abone surface36. InFIG. 3, the bones shown for illustrative purposes are major bones of a knee joint, including afemur38 andtibia40. The invention presumes that oneend42 of theligament30 has been secured in the femur in accordance with known methods and that anotherend portion44 extends from theend opening34.
• In the method illustrated inFIG. 3, an operator pulls theligament30 taut by manipulation of the exposedligament end portion44. Thescrew10 is then inserted into thebone tunnel32, by way of theend opening34. Thescrew10 is advanced into thebone tunnel32, threadedly engaging theligament30 and awall46 of thebone tunnel32, to secure theligament30 in thebone tunnel32. As thescrew10 advances to nearly full insertion, the screw is turned until the shankproximal end surface22 is disposed so as to be substantially flush with, and form substantially a continuation of, the surroundingbone surface36.
• Thus, threaded portions of thescrew10 are engaged throughout 360° withcortical portions48 of thetibia40, or other selected bone, to securely retain the screw in place. With thescrew10 in place, the exposedligament end portions44 may be snipped off alonglines50, shown inFIG. 3 (the “snipped off” portions ofligament end portions44 are shown in phantom inFIG. 3). As noted above, when the embodiment of fixation screw shown inFIG. 2 is used, over time material from thebone wall46 will migrate through theapertures24, to further lock the screw in place.
• InFIG. 4, there is shown a graft ligament anchor60 in atibia40. The anchor60 includes thescrew10, as described hereinabove, and atubular body62 having abore64 therethrough and having distal and proximal ends66,68. Thetubular body62 is adapted for placement in thebone tunnel32 proximate the end opening34 thereof in thebone surface36. A deformable wall70 is disposed in the tubular body, defining at least in part achamber72 for receiving thegraft ligament30 therein.
• In the anchor assembly60 shown inFIG. 4, thetubular body62 itself forms a deformable wall70. In pending prior U.S. patent application Ser. No. 09/248,523, filed Feb. 9, 1999 by Joseph H. Sklar for GRAFT LIGAMENT ANCHOR AND METHOD FOR ATTACHING A GRAFT LIGAMENT TO A BONE, which pending prior patent application is hereby incorporated herein by reference, there are disclosed several ligament anchor assemblies having tubular bodies with alternative arrangements of deformable walls and appropriate for use in the anchor assembly presented herein.
• In use of the graft ligament anchor assembly, theligament end portions44 are extended through thetubular body chamber72 by an operator. Thetubular body62 is inserted in the end opening34 of thebone tunnel32. Theligament30 is pulled taut by the operator. Thefixation screw10 is then inserted into thetubular body62 and advanced to press thegraft ligament30 and deformable wall70 toward thewall46 of thebone tunnel32, to fix the ligament to thebone tunnel wall46. As theproximal end18 of thescrew10 draws near thebone surface36, thescrew10 is turned until the screwproximal end surface22 is disposed so as to be flush with, and substantially a continuation of, thebone surface36 therearound.
• Thetubular body62 and theligament end portions44 may then be snipped off to provide a relatively smooth surface in the area of the closed opening34 (the “snipped off” portions oftubular body62 and theligament end portions44 are shown in phantom inFIG. 4).
• In the embodiment shown inFIG. 4, thethreads20 of thescrew10 do not directly engage thecortical bone48; however, thethreads20 force thetubular body62 into engagement with thecortical bone48, providing stronger fixation than if similarly engaged with acancellous portion74 of thebone40.
• There is thus provided an improved fixation screw, graft ligament anchor assembly and methods for fixing ligaments in bone tunnels.
• In the aforementioned U.S. patent application Ser. No. 09/248,523, which patent application has already been incorporated herein by reference, there are also disclosed bone tunnel liners for lining the wall of a bone tunnel prior to securing a graft ligament therein.
• Looking now atFIG. 5, there is shown abone tunnel liner100 which may be positioned within abone tunnel32 of abone40.Bone tunnel liner100 includes acentral bore102 extending from itsdistal end104 to itsproximal end106. The outer surface ofbone tunnel liner100 includesscrew threads108 and preferably includesopenings110. In use,bone tunnel liner100 is positioned inbone tunnel32 inbone40, the graft ligament's end portions are extended throughchambers72 oftubular body62,tubular body62 is inserted intobone tunnel liner100, andfixation screw10 is inserted into the central bore oftubular body62 and advanced distally so as to press the tubular body's deferrable walls, and hence the graft ligament, towardbone tunnel liner100, whereby to secure the graft ligament in the bone tunnel.
• In accordance with the present invention, theproximal end106 ofbone tunnel liner100 is preferably formed with an end surface which is set at an angle to the longitudinal axis of the bone tunnel liner, whereby the proximal end of the bone tunnel liner may be disposed flush with, and substantially a continuation of, thebone surface36 therearound.
• It is to be understood that the present invention is by no means limited to the particular construction and method steps herein disclosed and/or shown in the drawings, but also comprises any modification or equivalent within the scope of the claims. For example, it will be apparent that the particular inclination of the proximal end plane to the shank central axis is selected to match thebone surface36. The angle is determined by the application site morphology.

Claims (2)

1.-24. (canceled)

25. A bone tunnel liner for lining the wall of a bone tunnel which is to have a graft ligament fastened therein, said bone tunnel liner comprising;

a tube having a distal end and a proximal end, and a central axis extending from said distal end to said proximal end; and

screw threads disposed on said tube and extending from said distal end to said proximal end;

wherein said proximal end defines an end plane disposed transversely to the central axis and at an angle thereto other than a normal angle.

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