Ligament Attachment Method and Apparatus

1. Field of the Invention

This invention relates to surgical implants and more particularly, to surgical procedures and appliances for intraarticular anterior and posterior ligament reconstruction.

2. Prior Art

It is well known by anyone who has participated in athletics that the human knee is injury prone, particularly from lateral forces applied thereto. Where the knee joint is considered by most laymen to be essentially a hinged joint, in reality it provides a complicated mechanical movement that would be nearly impossible to duplicate with present technology. In operation, the human knee joint permits movement of flexion and extension in certain positions and even provides for a slight inward and outward rotation. Considering only movement of flexion and extension, the mechanical actions that take place in such movement include a certain amount of gliding and rotation along with the hinge action such that the same part of one articular surface of the distal fem ur or proximal tibia will not always be applied to the same part of the other articular surface, and the axis of motion is not fixed. In fact, if the knee joint is examined while a condition of extreme flexion, the posterior part of the articular surfaces of the tibia will be found to be in contact with the fem ur posterior around the extremities of the condyles. Whereas, if the movement was simple hinge like movement, the axis around which the revolving movement of the tibia would occur should be in the back part of the condyle. With the same leg brought forward into a position of semi-flexion, the upper surface of the tibia will seem to glide over the condyle of the fem ur, such that the middlepart of the articular facets are in contact, and the axis of rotation is therefore shifted forward to near the center of the condyle. When the leg is brought into the extended position, still further gliding takes place as does a further shifting forward of the axis of rotation. Knee joint flexure and extension is therefore not a simple movement but is accompanied by a certain amount of outward rotation around a vertical axis drawn through the center of the head of the tibia. This rotation is due to the greater length of the internal condyle, and to the fact that the anterior portion of its articular surface is inclined obliquely outward. In consequence, toward the close of the movement of extension, just before complete extension, the tibia will glide obliquely upward and outward over the oblique surface of the inner condyle, and the leg will be necessarily rotated outwardly. In flexation of the joint, the converse of these movements takes place, the tibia gliding backwardly around the end of the fem ur, at the commencement of which movement, the tibia is directed downward and inward along the oblique curve of the inner condyle, thus causing an inward rotation to the leg.

The above sets out a brief summary of knee joint functioning that takes place in knee flexure and extension. It is provided to show that this functioning is far more than a hinge movement and involves inward and outward rotation. It should be apparent therefore that in a repair of one or more ligaments of the knee, particularly in an intraarticular anterior and posterior ligament reconstruction that involves the cruciate ligaments, it is of significant value that the replacement ligaments, either a graft or proshetic ligament, be fitted so as to, as nearly as possible, duplicate the positioning of the natural ligament. Heretofore, procedures and devices for use in preparing damaged ligaments, particularly the cruciate ligaments, have generally involved attaching the ligament device across the knee at the juncture of the distal fem ur and proximal tibia surfaces. Where an attempt has been made to replace a cruciate ligament that involves securing the replacement ligament ends to the points on the opposing bone surfaces where that natural ligament was attached, such procedure has involved extensively opening the patient's knee area and/or forming intersection tunnels through the respective tibia and fem ur ends and positioning a ligament therebetween. An example of such surgical technique and an implant device is shown in a patent by Hunt, et al., U.S. Pat. No. 4,590,928. This patent is directed to an implant and kit therefore but does not, as does the present invention, provide an arrangement that is a near duplication for the patient's natural ligament. Rather, the Hunt, et al. patent is devoted to connectors and an implant that incorporates carbon fibers and, where tunnels are shown formed in the respective bones, such are apparently formed where access is convenient. As the tunnels are not aligned and each is open to without the fem ur and tibia surfaces, their formation involves extensive opening of the knee to provide access to the bone surfaces. Unlike the Hunt, et al. patent procedure, the present invention provides for ligament reconstruction using essentially an arthroscopic technique where a single incision only is made to the bone below the tibia tuberosity. Form that point, a tunnel is formed into the bone that passes through the respective points of connection of a cruciate ligament between the proximal tibia and distal fem ur and into the fem ur cortex. The fem ur cortex is then prepared to receive a ligament end coupling fitted therein to secure one ligament end.

Earlier ligament replacement procedures have involved an extensive opening of the knee and have included forming passages or tunnels in the tibia and fem ur from the bone surfaces wherethrough are pulled a natural or artificial ligament, the ends of which ligament are bent and secured as with staples to the bone surfaces. Unlike such earlier procedures and arrangements, the present invention provides for both fitting a ligament to extend across the knee so as to most nearly duplicate the natural ligament positioning and provides for internal coupling the one ligament within a bone cortex. Additionally, the present invention provides a convenient arrangement for adjusting the implanted ligament tensioning to most nearly duplicate a natural condition. The present invention therefore provides both a unique surgical approach and attachment devices to produce and implant that most nearly duplicates the patient's natural ligament arrangement tham has heretofore been possible.

It is therefore a primary object of the present invention to provide an arthroscopic system or technique for replacing with an allograft or prosthetic ligament a ruptured ligament of the knee, preferably a cruciate ligament.

It is another of the present invention to provide an arthroscopic procedure that employs a single incision only that is made medial to the patient's tibial tuberosity and at this point tunneling through the bone, across the distal fem ur and proximal tibial surfaces and into the fem ur cortex, the tunnel to pass through the points of connection of the ligament ends to the bone of either the anterior or posterior cruciate ligament.

It is another object of the present invention to provide for forming the tunnel to end in the femoral cortex just beyond the medullary channel and to prepare it to receive a connector that is turned or expanded therein so as to positively lock a ligament end within that bone cortex. It is another object of the present invention to provide a procedure for tunneling through the patient's tibia across the proximal tibial and distal fem ur surfaces and into the fem ur cortex that involves opening the patient's knee at a single point or location only on the tibial tuberosity and for closely controlling the tunnel formation through a use of fluoroscopic and/or arthroscopic procedures to form a passage that is essentially straight and intersects the connection points of the ruptured cruciate ligament on the bone surfaces so as to receive an allograft or prosthetic ligament that is fixed on one end within the fem ur cortex and extends from the tunnel end at the tibial tuberosity.

Still another object of the present invention is to provide an end coupling for the prosthetic ligament to secure it at the tunnel entrance at the tibial tuberosity and adjusting the ligament tensioning.

Still another object of the present invention is to provide a surgical procedure for replacing a torn or damaged cruciate ligament with an allograft or prosthetic ligament that requires minimal patient trauma and minimizes the time required for healing.

Still another object of the present invention is to provide an allograft or prosthetic ligament for replacement of a ruptured or damaged ligament that includes connectors made of a biodegradable material for maintaining the ligament in place and will be absorbed by the body in the healing process.

In accordance with the above objects, the present invention is in an arthroscopic surgical procedure for installation of an allograft or prosthetic ligament as a replacement for a ruptured knee ligament, preferably either an anterior or posterior cruciate ligament. In a practice of the procedure, a patient's lower leg is maintained in approximately a ninety degree (90.degree.) angle to their upper leg and a longitudinal incision is made medial to the tibial tuberosity, which incision is made to the bone. At that incision, a stainless steel guidewire is driven in the anterior medial tibia at a point that is approximately two (2) centimeters distance to the medial tibial plateau. Guidewire insertion is conducted under flurorscopic and arthroscopic control. The guidewire, after insertion, is thereby visualized as it is forced through the joint of the distal fem ur and proximal tibia, crossing the intercondylar notch area of the knee to engage the posterior and lateral femoral condyle. The preferred point of fem ur entry is deep within the inter-condylar notch, as identified under fluoroscopic visualization, approximately four (4) millimeters anterior to the junction of the fem ur posterior cortex and the inter-condylar seam as would be seen in a true lateral x-ray film of the distal fem ur. Guidewire travel is continued to pass through the fem ur cancellous bone, the medullary channel and into the anterior lateral cortex so as to be just proxim al to the metaphysical flare of the distal fem ur. So installed, the guidewire is then used to direct drill points of increasing drill sizes along its course, the drilling operation to sequentially increase the passage or tunnel diameter from the tunnel entry at the tibial tuberosity.

In the passage or tunnel form ation the increasing size drills are stopped in the medullary channel. As a final step in the tunnel formation, the tunnel end is drilled beyond the medullary channel into the fem ur anterior cortex where the guidepin has been lodged. This final hole is made in preparation for turning either a tap therein forming threads or a flaring drill to widen that tunnel end. In one embodiment the ligament femoral end connection is a threaded component to be turned into the threaded tunnel end. In another embodiment the ligament femoral end connector is arranged to be expanded or outwardly flared to fill the widened tunnel end.

After tunnel formation, the ligament is inserted to where its end is secured in the fem ur cortex as by either turning or expanding the connector end therein. The ligament thereby extends from its cortex end to where it exits the tunnel at the tunnel point of entry on the tibial tuberosity. Where the ligament is an allograft, the ligament end can be bent at the tunnel end across the bone and stapled thereto. Where the ligament is a prosthetic ligament, a preferred end coupling involves forming threads in the ligament end to receive a flat disk that is center tapped and slopes outwardly from one face to the other around the circumference, the small diameter face to nest in the tunnel end. This connector arrangement provides a capability for ligament length adjustment to achieve a desired ligament tensioning. In both embodiments, the respective connectors can be formed of a biodegradable material, such as a polylactic acid that will be absorbed by the body during the healing process, the bone growing to either the prosthetic or allograft ligaments.

Utilization of the above-described ligament and preferred connector installing procedure provides for ligament positioning to most nearly duplicate a damaged ligament and for setting a desired tensile stress in the ligament.

In the drawings that illustrate that which is presently regarded as the best mode for carrying out the invention:

FIG. 1 shows a patient's leg with their lower leg maintained at approximately a ninety (90.degree.) angle to the upper leg, which positioning is to be maintained throughout a surgical procedure of the present invention;

FIG. 2 is an enlarged side elevation view exposing the proximal tibia and distal fem ur ends of the leg of FIG. 1, which distal fem ur is shown as having had a section removed to the bone cortex, exposing a tunnel formed therein that contains one embodiment of a prosthetic ligament and end connectors therefore of the present invention;

FIG. 3 is a front elevation view of the distal fem ur and proximal tibia ends of FIG. 2 showing a portion of the fem ur cortex removed exposing the tunnel with the prosthetic ligament end secured therein;

FIG. 4 shows an enlarged side elevation view of the prosthetic ligament of FIGS. 2 and 3 removed from the patient's knee, and shows the ligament femoral and tibial attachment ends as they appe ar before installation;

FIG. 5A is an enlarged end view of the femoral attachment end of the prosthetic ligament of FIG. 4;

FIG. 5B is a view like FIG. 5A except that it shows the femoral attachment end having been expanded to the flared configuration shown in FIGS. 2 and 3;

FIG. 6 shows another embodiment of a prosthetic ligament that incorporates a deep threaded end as the femoral attachment end and includes the threaded tibial attachment end that is like shown in FIGS. 2 through 4;

FIG. 7 is a side elevation view of a distal fem ur showing a section removed so as to expose the bone cortex and shows the ligament femoral attachment end of FIG. 6 turned into a tapped tunnel end;

FIG. 8 shows a profile perspective view of a threaded cylindrical allograft ligament end connector that is for turning into a tapped tunnel end in the fem ur cortex;

FIG. 9 shows a sectional view taken along lines 9--9 of the end connector of FIG. 8;

FIG. 10 shows the end connector of FIG. 9 being sewn onto the end of an allograft ligament and shows a hex-sided driver fitted into a like sided longitudinal hole in that end connector with the allograft ligament wrapped therearound; and

FIG. 11 shows a front elevation view of a fem ur that has a tunnel formed into the base cortex, showing a section of the bone removed to expose the end connector of FIGS. 8 through 10 turned therein.

The present invention is in a surgical process or system whereby, from a single incision only made in a patient to their tibial tuberosity, a straight passage or tunnel is formed that will cross the proximal and distal fem ur surfaces and extend into the fem ur cortex. The tunnel is for receiving a ligament, either allograft or prosthetic, that is secured therein by one of several ligament end attachment embodiments of the invention. The process is primarily directed to but should be understood is not limited to replacement of a patient's damaged anterior or external cruciate ligament. The present procedure is described herein with respect to a replacement of the amterior cruciate ligament that is the ligament that is attached on its one end to the depression in front of the spine of the tibia and is part of the external semi-lunar fibrocartilage and is arranged to pass obliquely upwardly as well as backwardly and outwardly therefrom. The other ligament end is joined onto the inner and back part of the fem ur outer condyle. The anterior cruciate ligament, during leg rotation, is in a semi-flexed condition, and opposes inward rotation. It is this ligament that, in athletic play where the knee is subjected to an inward force, such as football, is most often dam aged. Heretofore, repair of the anterior cruciate ligament has involved an extensive surgical opening of the knee along with a release of the outer ligaments and cartilage that surround the tibia to effectively lay open the knee. Whereafter, the ruptured ligament has been repaired, if possible or replaced with an allograft or prosthetic ligament. Where replacement is in order, the procedure has involved tunneling through the fem ur and tibia, the tunnel exiting both bone surfaces, and a stapling of the ligament ends of the bone surfaces. Such procedure has required that the patient's leg be immobilized for an extended period of time to allow for healing, and, generally a full restoration of the patient's knee has not been obtained. Even in the best of circumstance, after a long restorative or healing period, extensive physical therapy is necessary to restore the knee to proper functioning. Unique to such former procedures the present invention provides a reconstructive procedure for arthroscopic insertion of either an allograft or prosthetic ligament that involves a single sm all incision only and provides, with a successful completion of the procedure, a ligament that is essentially ready for use.

FIG. 1 shows that in a practice of the arthroscopic procedure of the present invention for replacement of the amterior cruciate ligament, the patient's leg 10 is preferably maintained at approximately a ninety degree (90.degree.) angle between the fem ur and tibia. W ith the leg 10 so maintained, a longitudinal incision of approximately five (5) centimeters is made in the lower leg just below the external semi-lunar fibrocartilage to open the skin to the tibial tuberosity. At this exposed bone section, the end of a stainless steel guidewire, not shown, is positioned on a point of the tibial tuberosity that is approximately two (2) centimeters distal to the medial tibial plateau. The guidewire is then urged into that bone mass at that point by an application of a force thereto as by hammering the opposite guidewire end, or the like. This insertion process is made under fluoroscopic control to allow a surgeon to follow the guidewire progress through the bone so as to ensure that it will exit a point on the proximal tibia surface where the anterior crucial ligament is connected to the tibia and is blended with the semi-lunar fibrocartilage. This point will be approximately two (2) centimeters posterior to the most anterior border of the tibial plateau. Guidewire travel to verify its positioning as it enters the joint after piercing the tibial connection of the anterior cruciate ligament can also be visualized arthroscopically through an opening made in the knee cap area.

Guidewire travel can thereby be observed both arthoscopically and fluoroscopically, insuring that it travels across the intercondylar notch area of the knee to engage the posterior and lateral femoral condyle at a point that is deep within the notch. This point is approximately where the opposite end of the anterior crucial ligament attaches to the fem ur at the intercondylar notch area. It is generally located approxim ately four (4) millimeters anterior to the junction of the fem ur posterior cortex and the intercondylar seam as would be seen in a true lateral x-ray film of the distal fem ur. During this procedure, as set out above and shown in FIG. 1, the knee is maintained or fixed in a ninety degree (90.degree.) position to ensure that the formed passage will be essentially straight and that points of engagement of the guidewire with the ends of the anterior crucial ligament will be optimal.

After verifying that the guidewire pointed end is properly located on the junction of the fem ur posterior cortex and the intercondylar seam, it is further forced into the bone mass. The guidewire is driven through the cancellous bone that surrounds the medullary channel to pass through that medullary channel and into the fem ur amterior lateral cortex to a point that is just proximal to the metaphysical flare. Guidewire positioning is again verified radiologically and is thereafter utilized to guide drill points of increasing sizes along the guidewire course. Such drilling begins at the entry point on the anterior medial tibia and terminates at the fem ur medullary channel before the anterior lateral cortex. The drill points that are selected for forming the tunnel to receive a prosthetic ligament preferably begin at five sixteenths of an inch (5/16") and are progressively increased in size by one sixteenth of an inch (1/16") increments to approximately seven sixteenths of an inch (7/16") in diameter. In practice, it is preferred that the tunnel is not drilled beyond the fem ur medullary channel so as not to dislodge the guidewire end lodged in the anterior cortex. For forming a tunnel to receive an allograft ligament, the above described procedure is employed, except that the preferred drill sizes begin at six (6) millimeters and progress to eight (8) millimeters as the tunnel is enlarged.

After the required diameter of hole or tunnel is formed that is suitable for the selected ligament, a final drilling step is the insertion of a one quarter of an inch (1/4") canulated drill into the tunnel to pierce the anterior lateral cortex of the fem ur. This step is in preparation for fitting a tap or flaring drill into that cortex. With this drilling step the guidewire is released and can be removed. The tunnel end in the fem ur anterior lateral cortex is then ready to be prepared to receive a femoral attachment end of either allograft or prosthetic ligament to be secured therein. For a threaded end coupling the anterior lateral cortex will preferably be tapped to approximately a three eights of an inch (1/2") diameter. While, for a skirted end coupling as will be described later herein, the tunnel end receives a flaring drill turned therein.

With the tibia maintained at a ninety degree (90.degree.) angle to the fem ur, FIGS. 2 and 3 show tunnel 11 formed between the distal fem ur and proximal tibia ends and show a section of the fem ur removed therefrom. The Figs. illustrate the positioning of the respective bone ends and show a prosthesis ligament secured therein. Tunnel 11 exits the proximal tibia at a point 14 that is approximately two (2) centimeters posterior to the most anterior border of that tibial plateau 13 and is approximately the connection point of the end of the anterior cruciate ligament to the bone surf ace. The intercondylar notch area, shown at 15 in FIG. 3, is the point of entry of tunnel 11 into the distal fem ur, the tunnel passing between the posterior and lateral femoral condyles 16 and 17. The preferred tunnel entry point is on the distal fem ur is determined radiologically and should be appropriately four (4) millimeters anterior of the juncture of the fem ur posterior cortex 18 and the intercondylar seam 19. From this point of entry the tunnel 11 passes through the cancellous bone 20 and through the medullary channel 21, as shown in broken lines, and terminates in the anterior lateral cortex 22.

A practice of the above set out procedure therefore will produce a tunnel suitable for receiving a ligament to replace the anterior cruciate ligament as shown in FIGS. 2, 3, 7, and 11, with the tunnel end that terminates in the cortex to receive a ligament end connector secured therein, as will be discussed in detail hereinbelow. It should, however, be understood that, with appropriate changes to the tunnel point of entry and angle of travel therethrough it can be formed to pass through the junctions of the posterior cruciate ligament with the respective bone surfaces within the scope of this disclosure.

FIGS. 2 and 3 illustrate a first embodiment of an expandable cone 26 as a femoral attachment end for a prosthetic ligament 25. The expandable cone 26 is cylindrical in shape and preferably includes longitudinal slots 27 formed at spaced intervals therearound. So arranged, the cone end can be expanded to the attitude shown in FIGS. 2 and 3 when an expansion anchor 33 is pulled therein, the cone end breaking at longitudinal slots 27 to form a skirt. To accommodate the cone 26 that has been flared into a skirt, as shown also in FIG. 5B, the femoral end of tunnel 11 must also be outwardly flared at its most distant point. From the flared portion, the tunnel to taper a lesser radius or circumference that is essentially the ligament radius. For forming such outwardly flared tunnel end portion, a drill that is shown in an earlier application for U.S. patent application, Ser. No. 845,929, that the present inventor is a coinventor of, is preferred. Such drill includes sissoring blades that, at a certain depth of penetration of the drill end relative to a guide sleeve thereof, will pivot apart. With the sissoring blades flaring outwardly, the drill will then cut an inverted skirt shaped hole at the tunnel end to accommodate the prosthetic ligament expandable cone 26 after it has been flared outwardly therein. While a drill like that described in the aforesaid earlier application for U.S. patent is preferred, it should be understood that other drill arrangements for forming an inverted skirt or like enlarged femoral end of tunnel 11 can be so used within the scope of this disclosure.

FIGS. 2, 3, and 4 show the prosthetic ligament 25, shown to be preferably formed from a braided fabric and includes as the femoral attachment end, the expandable cone 26. The expandable cone 26 is preferably attached to the prosthetic ligament 25 in the manufacturing process. The opposite end of ligament 25 is shown threaded therealong at 29 for receiving, as a tibial attachment end, a flattened cone 30. Flattened cone 30 is holed and threaded longitudinally therethrough to be turned over the threaded prosthetic ligament tibial end 29. The flattened cone outer circumference is shown to appear outwardly from the edge of one face to the edge of the other face with the lesser diameter cone face to wedge in tunnel 11 open end. To provide for expanding cone 26, as shown best in FIG. 4, the prosthetic ligament 25 includes a longitudinal passage that is open therethrough and receives an inner shaft 31 telescoped to slide therein. The inner shaft 31, as illustrated best in FIGS. 5A and 5B, included a threaded end 32 that is for turning into a threaded central opening in a flat face of an expansion anchor 33. The expansion anchor 33 is shown to have, opposite to the flat face, a cylindrical nose and is flared or tapered outwardly back from the nose end into a cylindrical center section 34. Back therefrom the anchor tapers inwardly from an end edge 35 into a saddle 36 and then flares outwardly from 37 to terminate in a rear edge 38. The anchor rear edge 38 is aligned with the expanding cone 26 open end to travel therein. The cone 26 is tapered inwardly from a widest point at its open end, the opening therethrough reducing in diameter, as illustrated in broken lines at 26a in FIGS. 5A and 5B to a continuous groove 39 formed around the cone inner circumference at approximately the closed ends 27a of longitudinal slots 27. As shown best in FIG. 5B, pulling the expansion anchor 33 into the expandable cone 26 causes that cone end to expand outwardly, flaring the cone at longitudinal slot ends 27a. With continued travel of the expansion anchor therein the anchor rear edge 38 will engage and seat in groove 39 having flared the cone 26, as shown in broken lines in FIG. 5B, locking the expansion anchor therein. Shaft 31 travel to so move expansion anchor 33 into the expandable cone 26 is shown by the arrow B in FIG. 5B. So arranged, travel of the anchor within the expandable cone 26 causes it to break at the slot 27 end 27a flaring the cone end outwardly into a flattened cone. The expandable cone 26 is thereby erected to have to its greatest diameter at its rearmost point the tunnel 11, that cone flared portion filling the tunnel end and permanently seating therein. This coupling has been found in pull-out tests performed thereon to resist separation at forces in excess of 1300 neutrons that is estim ated to be a maximum force as could reasonably be expected to be exerted on the ligament.

FIG. 6 shows another embodiment of a prosthetic ligament 40 that includes, as a femoral attachment end, deep threads 41 that are formed in the ligament femoral end. These threads are preferably formed during the fabrication thereof as are smaller machine threads 42 that are formed in the ligament tibial attachment end. Threads 41, as illustrated, are preferably cut deep and wide to bite deeply into the tunnel femoral anterior cortex end, which threads are cut or formed therein, as set out hereinabove, as a last step in the tunnel formation process. As with the description of prosthetic ligament 25, the machine threads 42 that are formed as the tibial attachment end are to receive a flattened cone 43 turned thereover. In the prosthetic ligament 25 and 40 embodiments the tibia attachment component is preferably the flattened cone shaped collar that is longitudinally center threaded therethrough for turning over the threaded prosthetic ligament threaded end such that the cone lesser diameter end will travel into the tibia tunnel 11 end. Flattened cone 43 turning is preferably accomplished by fitting a tool, not shown, into a hole or holes 43a that extend through the cone to the greater diameter face thereof, and turning the collar with that tool. This arrangement provides for adjusting ligament tension by appropriately turning the collar on the ligament to engage the tibia tunnel end.

As set out hereinabove, the tunnel 11 femoral end, after it has been tapped or otherwise machined to form threads therein, accommodates the threaded end 41 of prosthetic ligament 40 turned therein. This tapping or threading can be accomplished by insertion of the canulated drill into the fem ur anterior lateral cortex end of tunnel 11, as described hereinabove, followed by a tap turned therein. Such tap is inserted along the prepared tunnel 11 and is turned to tap that fem ur anterior cortex at 44, as illustrated in FIG. 7. Whereafter, the prosthetic ligament 40 of FIG. 6 is turned into the tunnel end 44, as illustrated in FIG. 7, to where the ligament end butts against the tunnel end, locking the ligament therein. Thereafter, prosthetic ligament length and tension adjustment is accomplished, as set out above, by turning the flattened cone 43 on the prosthetic ligament thread end 41, to where it engages the tibia end of tunnel 11. Setting prosthetic ligament tension is preferably accomplished while maintaining the patient's leg 10 in the attitude shown in FIG. 1.

FIG. 10 shows a threaded cylinder 50 that is a preferred configuration of a femoral attachment for an allograft ligament 49 for securing a ligament end in the femoral anterior cortex end of tunnel 11. Cylinder 50 is shown to have the appearance of a set screw, in that it is threaded at 51 along its entire length, as shown in FIG. 8 and 9, and includes a center hex-sided cavity 53. Additionally, the cylinder 50 preferably includes longitudinal holes 5-2 that are radially formed therethrough around the center hex-sided cavity 53. The cavity 53 is formed in a ligament attaching end of cylinder 50 that is preferably dished below a circumferential lip 54. The cylinder 50 is preferably fabricated of a biodegradable material such as a polylactic acid plastic or like material, to be absorbed by the body in the healing process. FIG. 10 shows an end of allograft ligament 49 being attached to cylinder 50 by passing a suture 56 at spaced intervals around the ligament end, which suture is also selectively threaded through longitudinal passages 52 using a needle 57. The ligament end is then drawn tightly against the cylinder 50 dished out portion, fitting below the circumferential lip 54. Shown in FIGS. 10 and 10 A, for installation, the allograft ligament is unrolled and is wrapped around a hex-sided driver 58, which drive should be long enough to be turned from without the tunnel 11. The allograft ligament has an overlapping layered appearance, as shown in the sectional view of FIG. 10A. To install the hex-sided driver 58 the allograft ligament is unwrapped so as to loosen it as the center wherethrough the hex-sided driver if fitted. The ligament and driver are then fitted into tunnel 11 and the cylinder 50 threads 51 are turned into a tapped fem ur end 60 of tunnel 11. After seating of the cylinder, the hex-sided driver 58 is removed and the allograft ligament 49 stretched out, as illustrated in FIG. 11. The cylinder threads 51, are preferably machine type threads, as shown in FIGS. 8 through 11, and therefore thread 51 depth is not as great as is the depth of threads 41 of the prosthetic ligament 40 of FIG. 6. It should, however, be understood that the threaded femoral attachment end of the prosthetic ligament 40 and cylinder 50 can have the same or different depth of thread within the scope of this disclosure.

With cylinder 50 seated as described and the allograft ligament 49 stretched thereform, to complete the ligament reconstruction, the allograft ligament 49 is pulled tight so as to achieve a certain tensile loading thereon. The ligament tibial end is then secured to the tibia as by bending the ligament 49 tibial end across the bone surface from the tunnel 11 entry and is fixed thereat as by driving staples into the bone that span the ligament. Of course, a tibial attachment device such as a collar arrangement, that could be pinched around the ligament, not shown, or the like, can be used for attaching the allograft ligament tibial end to the tibia within the scope of this disclosure.

The above sets out the preferred end connector arrangements and system for their use for ligament reconstructive surgery as particularly applicable to a replacement of the anterior cruciate ligament with a prosthetic or allograft ligament. It should, however, be understood that the described procedures is and/or the devices described herein can be appropriately modified to be used to surgically replace the posterior cruciate ligament and/or other knee ligaments, within the scope of this disclosure. It should also be understood that any or all of the described ligament end connectors can be fabricated from a material or materials such as a polylactic acid plastic, or the like, to be absorbed by the body during the healing process. Obviously, however, the described connectors can be manufactured from an appropriate metal to remain in the bone after the healing process has taken place.

The present disclosure has, of course, been directed to both prosthetic and allograft ligaments. Within present technology, a prosthetic ligament manufactured by Zimmer U.S.A. is believed to be suitable for the described application. Approval for this ligament for use as an implant is currently being sought from the Food and Drug Administration for human implant. It should, however, be understood that the present invention is not limited to use with such particular prosthetic ligament only and that the end connection devices set out herein can be used with other prosthetic ligaments as may be now available or as may be developed in the future within the scope of this disclosure. Of course, allograft ligaments from cadavers are presently available for human implant.

The above described configurations of an allograft femoral device, shown as cylinder 50 in FIGS. 8 through 11, has been laboratory tested as set out in Table I hereinbelow. Table I shows the pull out strength of the femoral attachment component, the cylinder 50 that incorporates three (3) sutures 56 each threaded through and back through passage 52, securing the ligament end to the cylinder end. Each suture was capable of sustaining a twenty (20) pounds tensile load. The test standard thereby being that the attachment device, cylinder 50 and its suture connection would sustain at least a pull-out tensile stress of sixty (60) pounds. The test data in Table I shows that this criterior was met, the minimum sustained load shown as sixty seven (67) pounds. Additionally, it should be noted that all tests were performed using bones that came from specimens that were older than sixty (60) years at the time of death. The advanced age of the bone specimens used, it can be assumed, increases the chances that the bones will be softer and more porous, greatly reducing the bone strength. Test performed on younger bones, it can reasonably be assumed, would likely show greater failure strengths. Even using the aged specimens, the tests demonstrated the utility of the connector as the minimum load sustained of sixty seven (67) pounds was still greater than the combined suture strength of sixty (60) pounds, with the other tests for the different thread configurations showing much greater failure strength.

Herein has been set out a preferred surgical procedure or system and ligament end attachement devices. It should, however, be understood that the present disclosure is made by way of example only and that variations to the procedure or system and the described ligament end connectors are possible without departing from the subject matter coming within the scope of the following claims, which claims we regard as our invention.