Dovetail meniscal allograft technique and system

A meniscal allograft with a bone block having a trapezoidal shape in cross-section and a technique for using a meniscus allograft having a trapezoidal shaped bone block are disclosed. A groove is formed initially in the bone using drill bits. Dilators are used to increase the size of the drilled groove. 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 trapezoid shape of the bone groove. A meniscal allograft having a bone block of corresponding trapezoidal shape is prepared using a workstation and three cutting jigs to make three corresponding cuts. The trapezoidal bone block of the meniscal allograft is then installed within the bone groove.

FIELD OF THE INVENTION

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.

BACKGROUND OF THE INVENTION

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.

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.

SUMMARY OF THE INVENTION

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.

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.

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.

DETAILED DESCRIPTION OF THE INVENTION

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.

Referring now to the drawings, where like elements are designated by like reference numerals,FIGS. 1–17illustrate an exemplary embodiment of a dovetail meniscal allograft implant100(FIGS. 15–17) fabricated according to the present invention, whileFIGS. 18–31illustrate the formation of a longitudinal dovetail tibial groove99(FIG. 31) that accommodates the dovetail meniscal allograft implant100.FIG. 32illustrates the dovetail meniscal allograft implant100ofFIGS. 15–17inserted into the dovetail tibial groove99ofFIG. 31.

The dovetail meniscus implant100can 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.

FIG. 1illustrates a meniscus10formed of allograft cortical bone. As shown inFIG. 1, meniscus10is first mounted on a graft workstation, where bone block14is marked and trimmed to a length “L” corresponding to the longitudinal length of dovetail tibial groove99(the formation of which will be described in more detail below with reference toFIGS. 17–30). Referring toFIG. 2, any additional bone that is anterior or posterior to the sides of horns12of meniscus10is removed.FIG. 3shows the marking of dovetail configuration A onto both the anterior and posterior facets of the bone block14, so that the horns12are centered on side A4of the trapezoid or dovetail configuration A. The dovetail configuration A is a cross-sectional trapezoidal shape with four edges A1(height), A2(base), A3and A4(small base), edges A1and A2forming a ninety degree angle and edges A2and A3forming an acute dovetail angle α, as shown inFIG. 3. The acute dovetail angle α is about 25 degrees to about 75 degrees, more preferably about 45 degrees.

FIGS. 4 and 5illustrate meniscus10secured between two grafting holding posts and positioned upside down. As shown inFIGS. 4 and 5, meniscus10hangs freely and away from the bone block14, so that the edge A1of the dovetail configuration A is aligned with the holding posts. As also illustrated inFIG. 4, base A2is aligned with the bottom of the holding posts.

Referring now toFIGS. 6–8, a first cutting jig21is aligned (FIGS. 6,7) to the edge A1of the of the meniscus10, so that bone from the bone block14is vertically cut (FIG. 8) along the edge A1of the dovetail configuration A. A second cutting jig22(FIG. 9) is then aligned with the flat base A2so that bone from the block14is horizontally cut along the base A2of the dovetail configuration A of the bone block14, as shown inFIG. 10. The length of the edge A1of the dovetail configuration A is of about 8 mm to about 12 mm, more preferably of about 10 mm. The length of the base A2of the dovetail configuration A is of about 8 mm to about 12 mm, more preferably of about 10.5 mm.

FIGS. 11–14illustrate cutting of bone from the bone block14along edge A3of the dovetail configuration A using a third cutting jig23, to define the length of the edge or small base A4and to complete the fabrication of body15of the dovetail meniscal allograft implant100. The length of the small base A4is of about 5 mm to about 10 mm, more preferably of about 7 mm. As illustrated inFIGS. 15,16and17, which are more detailed illustrations of the dovetail meniscal allograft implant100fabricated as described above, body15is defined by the four edges (A1, A2, A3and A4) of the dovetail or trapezoid configuration A, with the horns12of the meniscus10attached to the surface defined by the small base A4and the length L of the body15.

A method of forming longitudinal dovetail tibial groove99(FIG. 30) is now described with reference toFIGS. 18–31and by using known techniques of drilling through the tibia50, shown inFIG. 18. The longitudinal tibial groove99of the present invention has a dovetail configuration and a size that accommodates the insertion of the dovetail meniscal allograft implant100fabricated as described above.

Osteotome55and alignment guide53are assembled, as shown inFIG. 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 rod54(FIG. 19) is then positioned in an anterior to posterior plane, entered through the anterior and posterior horns57and58, respectively, of the tibial meniscus.FIG. 20illustrates osteotome55and alignment rod54positioned so that the osteotome55can advance into the proximal side of tibia50through the horns57,58so that the top of the osteotome55is flush with tibial plateau51and stops at the posterior horn58, as shown inFIG. 21.

The handle of osteotome55is then removed, leaving its blade55ainto position. A first Drill Guide60is subsequently positioned over the blade55a, flush to the anterior tibia, as shown inFIG. 22. Using a 6 mm drill bit61(FIG. 23), the tibial plateau51is cut through and drilled through the first Drill Guide60, from the anterior horn57to the posterior horn58for a distance “L” which illustrates the length of the dovetail meniscal implant100(FIG. 17).FIG. 24illustrates the 6 mm drill bit61cutting through the plateau channel and advancing through into the tibia under direct visualization until it contacts the posterior tibial cortex.

The first Drill Guide60that accommodates the 6 mm drill bit61is then removed from the osteotome55, so that a second Drill Guide70is attached to the osteotome55, as shown inFIG. 25. The second Drill Guide70accommodates an 8 mm drill bit71(FIG. 25) to drill through the tibial plateau51from the anterior horn57to the posterior horn58, in a way similar to that using the 6 mm drill bit61. A curette may be optionally used to further debride the groove subsequent to the drilling operation.FIG. 26illustrates tibial groove90formed within tibia50at the end of the drilling operation with both the 6 mm drill bit 61 and 8 mm drill bit71.

A rasp75is subsequently used to create the orthogonal angle of the dovetail configuration A (FIGS. 15,16and17) into the tibial groove90, as shown inFIG. 27. The rasp75must 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 dilatator80(FIGS. 28,29) may be also inserted in the tibial groove90to increase the size of the drilled channel and to form the dovetail acute angle α of the dovetail configuration A (FIGS. 15,16and17), using gentle taps of a mallet if necessary, and to complete the formation of the longitudinal dovetail tibial groove99, as shown inFIGS. 30 and 31.

The longitudinal dovetail tibial groove99has a size and a length “L” that accommodate the dovetail meniscal allograft implant100fabricated as described above. By placing a ruler inside the prepared tibial groove99, the length L is properly measured and then transferred onto the allograft bone block14ofFIG. 1, to prepare the formation of the dovetail meniscal allograft implant100, as described above with reference toFIGS. 15–17.

Finally, the dovetail meniscal allograft implant100is passed into the recipient dovetail tibial groove99, as shown inFIG. 32, and the dovetail groove is cleared of any remaining bone debris in the posterior portion of the tibia. As the dovetail meniscal allograft implant100is delivered to the tibial groove99, the graft passing suture attached to the meniscal allograft implant100is 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 implant100into the dovetail tibial groove99.

As described above, the invention provides an improvement over the “keyhole” technique in that the shapes of the dovetail meniscal allograft implant100and of the corresponding longitudinal dovetail tibial groove99are 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 implant100, in about 5 to 8 minutes, as opposed to about 45 minutes required for the fabrication of the “keyhole” allograft structure.

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.

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.