Dovetail meniscal allograft technique and system

[0001] This application claims the benefit of U.S. Provisional Application Ser. No. 60/403,438, filed Aug. 15, 2002, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to the field of surgery reconstruction and, in particular, to a meniscal allograft technique and system using a meniscal allograft having a dovetail notch.

[0003] A known method of performing an anatomical reconstruction of the meniscus is the so-called meniscal allograft “keyhole” technique using instrumentation sold by Arthrex, Inc. of Naples, Fla. In this technique, the bone block of a meniscal allograft is formed in the shape of a keyhole plug, to match a corresponding keyhole groove prepared through the cortical and cartilagenous surface of the tibial plateau. The bone plug for the meniscal allograft is then fed into the keyhole groove, such that the meniscal allograft is mounted on the tibial plateau and secured without transosseous sutures.

[0004] Although the above-described technique is a vast improvement over prior meniscal allograft technique, the “keyhole” shape of the allograft implant is difficult to reproduce and necessitates a long preparation time, typically about 45 minutes. Thus, although the “keyhole” technique described above is a vast improvement over prior meniscal allograft techniques, it would be desirable to provide a meniscal transplant system and technique that is quicker, easier and more reproducible.

[0005] The present invention overcomes the disadvantages of the “keyhole” technique by providing a meniscal allograft technique using a meniscus allograft having a trapezoidal shape in cross-section, as opposed to a “keyhole” shape. The trapezoidal shape is more easily reproducible than a “keyhole” shape. Preferably, the dovetail meniscus allograft has a trapezoidal shape with a 90 degree angle and is formed as a pre-cut meniscal allograft.

[0006] The dovetail meniscus allograft of the present invention is advanced into a same-size dovetail groove of a bone by impaction. The dovetail groove is formed initially using drill bits. Dilators are used to increase the size of the drilled openings. The orthogonal corner at the bottom of the groove is shaped using a rasp. A smooth dilator compacts the bone in the acute angle at the bottom of the groove opposite the orthogonal corner to create the final dovetail shape.

[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.

[0040] The present invention provides a meniscal allograft technique for forming a longitudinal groove in a bone, the groove having a trapezoidal or dovetail cross-section, and providing a pre-cut meniscal allograft also having a trapezoidal or dovetail cross-section. The trapezoidal shape of the pre-cut meniscal allograft is more easily reproducible than a “keyhole” shape.

[0041] Referring now to the drawings, where like elements are designated by like reference numerals, FIGS. 1–17 illustrate an exemplary embodiment of a dovetail meniscal allograft implant 100 (FIGS. 15–17) fabricated according to the present invention, while FIGS. 18–31 illustrate the formation of a longitudinal dovetail tibial groove 99 (FIG. 31) that accommodates the dovetail meniscal allograft implant 100. FIG. 32 illustrates the dovetail meniscal allograft implant 100 of FIGS. 15–17 inserted into the dovetail tibial groove 99 of FIG. 31.

[0042] The dovetail meniscus implant 100 can be machined from allograft cortical bone using known techniques, and is preferably a single piece of harvested material with the meniscus on a bone block. Alternatively, the implant can be formed of a synthetic material, preferably a synthetic cortical bone material. A preferred synthetic bone material is tricalcium phosphate (TCP) and/or hydroxyapatite (HA), or a biodegradable polymer, preferably a polylactide, such as PLLA.

[0043] FIG. 1 illustrates a meniscus 10 formed of allograft cortical bone. As shown in FIG. 1, meniscus 10 is first mounted on a graft workstation, where bone block 14 is marked and trimmed to a length “L” corresponding to the longitudinal length of dovetail tibial groove 99 (the formation of which will be described in more detail below with reference to FIGS. 17–30). Referring to FIG. 2, any additional bone that is anterior or posterior to the sides of horns 12 of meniscus 10 is removed. FIG. 3 shows the marking of dovetail configuration A onto both the anterior and posterior facets of the bone block 14, so that the horns 12 are centered on side A₄ of the trapezoid or dovetail configuration A. The dovetail configuration A is a cross-sectional trapezoidal shape with four edges A₁ (height), A₂ (base), A₃ and A₄ (small base), edges A₁ and A₂ forming a ninety degree angle and edges A₂ and A₃ forming an acute dovetail angle α, as shown in FIG. 3. The acute dovetail angle α is about 25 degrees to about 75 degrees, more preferably about 45 degrees.

[0044] FIGS. 4 and 5 illustrate meniscus 10 secured between two grafting holding posts and positioned upside down. As shown in FIGS. 4 and 5, meniscus 10 hangs freely and away from the bone block 14, so that the edge A₁ of the dovetail configuration A is aligned with the holding posts. As also illustrated in FIG. 4, base A₂ is aligned with the bottom of the holding posts.

[0045] Referring now to FIGS. 6–8, a first cutting jig 21 is aligned (FIGS. 6, 7) to the edge A₁ of the of the meniscus 10, so that bone from the bone block 14 is vertically cut (FIG. 8) along the edge A₁ of the dovetail configuration A. A second cutting jig 22 (FIG. 9) is then aligned with the flat base A₂ so that bone from the block 14 is horizontally cut along the base A₂ of the dovetail configuration A of the bone block 14, as shown in FIG. 10. The length of the edge A₁ of the dovetail configuration A is of about 8 mm to about 12 mm, more preferably of about 10 mm. The length of the base A₂ of the dovetail configuration A is of about 8 mm to about 12 mm, more preferably of about 10.5 mm.

[0046] FIGS. 11–14 illustrate cutting of bone from the bone block 14 along edge A₃ of the dovetail configuration A using a third cutting jig 23, to define the length of the edge or small base A₄ and to complete the fabrication of body 15 of the dovetail meniscal allograft implant 100. The length of the small base A₄ is of about 5 mm to about 10 mm, more preferably of about 7 mm. As illustrated in FIGS. 15, 16 and 17, which are more detailed illustrations of the dovetail meniscal allograft implant 100 fabricated as described above, body 15 is defined by the four edges (A₁, A₂, A₃ and A₄) of the dovetail or trapezoid configuration A, with the horns 12 of the meniscus 10 attached to the surface defined by the small base A₄ and the length L of the body 15.

[0047] A method of forming longitudinal dovetail tibial groove 99 (FIG. 30) is now described with reference to FIGS. 18–31 and by using known techniques of drilling through the tibia 50, shown in FIG. 18. The longitudinal tibial groove 99 of the present invention has a dovetail configuration and a size that accommodates the insertion of the dovetail meniscal allograft implant 100 fabricated as described above.

[0048] Osteotome 55 and alignment guide 53 are assembled, as shown in FIG. 18, after debriding the remaining meniscus just to the periphery, leaving only a thin cartilaginous peripheral rim attached to the capsule. Using a high speed bur, the lateral tibial eminence is shaved down until there is a bleeding vascular bed. Removal of the tibial eminence enhances exposure and ensures proper placement of the drill guide, as described in more detail below. Alignment rod 54 (FIG. 19) is then positioned in an anterior to posterior plane, entered through the anterior and posterior horns 57 and 58, respectively, of the tibial meniscus. FIG. 20 illustrates osteotome 55 and alignment rod 54 positioned so that the osteotome 55 can advance into the proximal side of tibia 50 through the horns 57, 58 so that the top of the osteotome 55 is flush with tibial plateau 51 and stops at the posterior horn 58, as shown in FIG. 21.

[0049] The handle of osteotome 55 is then removed, leaving its blade 55a into position. A first Drill Guide 60 is subsequently positioned over the blade 55a, flush to the anterior tibia, as shown in FIG. 22. Using a 6 mm drill bit 61 (FIG. 23), the tibial plateau 51 is cut through and drilled through the first Drill Guide 60, from the anterior horn 57 to the posterior horn 58 for a distance “L” which illustrates the length of the dovetail meniscal implant 100 (FIG. 17). FIG. 24 illustrates the 6 mm drill bit 61 cutting through the plateau channel and advancing through into the tibia under direct visualization until it contacts the posterior tibial cortex.

[0050] The first Drill Guide 60 that accommodates the 6 mm drill bit 61 is then removed from the osteotome 55, so that a second Drill Guide 70 is attached to the osteotome 55, as shown in FIG. 25. The second Drill Guide 70 accommodates an 8 mm drill bit 71 (FIG. 25) to drill through the tibial plateau 51 from the anterior horn 57 to the posterior horn 58, in a way similar to that using the 6 mm drill bit 61. A curette may be optionally used to further debride the groove subsequent to the drilling operation. FIG. 26 illustrates tibial groove 90 formed within tibia 50 at the end of the drilling operation with both the 6 mm drill bit 61 and 8 mm drill bit 71.

[0051] A rasp 75 is subsequently used to create the orthogonal angle of the dovetail configuration A (FIGS. 15, 16 and 17) into the tibial groove 90, as shown in FIG. 27. The rasp 75 must remain flush to the articular surface of the tibia and may be slowly advanced with a combination of maletting and hand rasping until it reaches the posterior tibial cortex. A dilatator 80 (FIGS. 28, 29) may be also inserted in the tibial groove 90 to increase the size of the drilled channel and to form the dovetail acute angle α of the dovetail configuration A (FIGS. 15, 16 and 17), using gentle taps of a mallet if necessary, and to complete the formation of the longitudinal dovetail tibial groove 99, as shown in FIGS. 30 and 31.

[0052] The longitudinal dovetail tibial groove 99 has a size and a length “L” that accommodate the dovetail meniscal allograft implant 100 fabricated as described above. By placing a ruler inside the prepared tibial groove 99, the length L is properly measured and then transferred onto the allograft bone block 14 of FIG. 1, to prepare the formation of the dovetail meniscal allograft implant 100, as described above with reference to FIGS. 15–17.

[0053] Finally, the dovetail meniscal allograft implant 100 is passed into the recipient dovetail tibial groove 99, as shown in FIG. 32, and the dovetail groove is cleared of any remaining bone debris in the posterior portion of the tibia. As the dovetail meniscal allograft implant 100 is delivered to the tibial groove 99, the graft passing suture attached to the meniscal allograft implant 100 is lead out the posterior lateral capsule via a standard inside out meniscal suturing technique. A meniscal allograft tamp may be employed to position the meniscal allograft implant 100 into the dovetail tibial groove 99.

[0054] As described above, the invention provides an improvement over the “keyhole” technique in that the shapes of the dovetail meniscal allograft implant 100 and of the corresponding longitudinal dovetail tibial groove 99 are more easily reproducible compared to the “keyhole” structures. Further, the invention provides a method of fabricating a meniscal allograft implant, such as the dovetail meniscal allograft implant 100, in about 5 to 8 minutes, as opposed to about 45 minutes required for the fabrication of the “keyhole” allograft structure.

[0055] Variations, modifications, and other uses of the present invention will become apparent to those skilled in the art, including the following, non-limiting examples: attachment of bone to bone; attachment of soft tissue to bone; non-medical applications. Thus, although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art.

[0056] 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.