Soft tissue attachment device

Methods and devices are disclosed for the attachment of a soft tissue structure (e.g., tendon or ligament) to bone or a prosthetic implant. In one form, the device includes a clamp having a convex tissue engaging surface. A fastener compresses the soft tissue between the tissue engaging surface and the bone or the prosthetic implant. In another form, the device includes a second clamp comprising a porous metallic material. The second clamp has a first surface, a concave tissue engaging surface opposite the first surface, and a throughhole for a fastener. The second clamp is placed adjacent the bone, the soft tissue is placed adjacent the second clamp, and the first clamp is placed adjacent the soft tissue. The soft tissue is compressed between the convex tissue engaging surface of the first clamp and the concave tissue engaging surface of the second clamp using the fastener.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to methods and devices for the attachment of a tendon or ligament structure to bone and/or a prosthetic implant (such as a joint replacement device). In particular, the methods and devices use a clamping strategy employing soft tissue healing to a porous metal clamp.

2. Description of the Related Art

Surgical techniques in which a tendon is fixed directly to bone have been successful in achieving a strong tendon-bone attachment in selected circumstances. However, when tendon is directly fixed to metallic implants, weak fixation and mechanical failure under physiologic loading have been observed.

It has been shown that porous tantalum can function as a soft-tissue attachment and repair biomaterial. In “Direct Tendon Attachment and Healing to Porous Tantalum: An Experimental Animal Study”,The Journal Of Bone And Joint Surgery,2007; 89:1000-9, an animal model was used to demonstrate the potential utility of porous metals to achieve healing of tendon directly to a porous metallic device. Example ligament attachment devices can also be found in U.S. Pat. No. 7,208,222 and U.S. Patent Application Publication No. 2007/0162022.

Still, there exists a need for improved methods and devices for the attachment of a tendon or ligament structure to bone or a prosthetic implant.

SUMMARY OF THE INVENTION

The present invention addresses the foregoing needs by providing porous metal (such as tantalum or titanium) devices to attach (via screw or screws) soft tissue (tendons or ligaments) to bone or to prosthetic implants. Porous metal allows the ingrowth of soft tissue. The attachment devices of the invention can allow varying degrees of soft tissue compression due to the difference in curvature of (i) a first convex clamp and (ii) a second concave clamp, or a concave depression in bone or an implant. Compression of a tendon or ligament between a concave porous ingrowth surface on one side, and a convex surface of smaller radius of curvature on the other allows for varying degrees of compression. In other words, the gap between the concave porous ingrowth surface on one side and the convex surface on the other side gets bigger near the outer edge of the clamp or depression and is smallest centrally.

Because tendons and ligaments are of different thicknesses and have different requirements for clamping tension, having varying degrees of compression in the invention increases the likelihood that at some point along the curvature of the clamp(s), the level of compression would be optimal for ingrowth of soft tissue and implant success rates would increase. Also, compression across the soft tissue-clamp interface at varying degrees negates needing to find perfect tension. As a result, soft tissue ingrowth into metal is achieved because compression is just right. Furthermore, the soft tissue is flat in the center of the clamp.

In one aspect, the invention provides a device for attaching soft tissue to a bone or a prosthetic implant. The device includes a clamp and a fastener. The clamp comprises a porous metallic material, and the clamp includes a first surface, a convex tissue engaging surface opposite the first surface, and a throughhole extending from the first surface to the convex tissue engaging surface. The fastener is dimensioned for placement in the throughhole, and the fastener is dimensioned to engage the first surface, the soft tissue and the bone or the prosthetic implant such that the soft tissue is compressed between the tissue engaging surface and the bone or the prosthetic implant.

In one form, the convex tissue engaging surface of the clamp has a first curvature, the bone or the prosthetic implant includes a depression of a second curvature, and the first curvature is greater than the second curvature. The convex tissue engaging surface of the clamp can be dome shaped. A grommet can be arranged in the throughhole. The convex tissue engaging surface of the clamp can include a raised section around the throughhole. The clamp can include a second throughhole for receiving a second fastener. Various shapes are suitable for the clamp. For example, the clamp can include a periphery having a shape selected from circular, rectangular, elliptical and oval.

The device can include a second clamp comprising a porous metallic material. The second clamp can include a first part and a mating second part wherein the soft tissue is compressed between the first part and the second part. In one form, the first part comprises a first channel, the second part comprises a second channel, and the soft tissue is compressed between an inner surface of the first channel of the first part and an inner surface of the second channel of the second part. The first part and the second part can form a frustoconical shape when mated together.

In another aspect, the invention provides a device for attaching soft tissue to a bone or a prosthetic implant. The device includes a first clamp, a second clamp, and a fastener. The first clamp comprises a porous metallic material. The first clamp includes a first surface, a convex tissue engaging surface opposite the first surface, and a throughhole extending from the first surface to the convex tissue engaging surface of the first clamp. The convex tissue engaging surface of the first clamp can be dome shaped. The second clamp comprises a porous metallic material. The second clamp includes a first surface, a concave tissue engaging surface opposite the first surface, and a throughhole extending from the first surface to the concave tissue engaging surface of the second clamp. The fastener is dimensioned for placement in the throughhole of the first clamp and the throughhole of the second clamp. The fastener is dimensioned to engage the first surface of the first clamp, the soft tissue and the bone or the prosthetic implant such that the soft tissue is compressed between the convex tissue engaging surface of the first clamp and the concave tissue engaging surface of the second clamp.

In one form, the convex tissue engaging surface of the first clamp has a first curvature, the concave tissue engaging surface of the second clamp has a second curvature, and the first curvature is greater than the second curvature. The first clamp can include a periphery having a shape selected from circular, rectangular, elliptical and oval, and the second clamp can include a periphery having a shape selected from circular, rectangular, elliptical and oval. In one use of the device, a depression is formed in a bone, and the second clamp is received in the depression of the bone. The porous metallic material of the first clamp can be tantalum, and the porous metallic material of the second clamp can be tantalum.

In yet another aspect, the invention provides a method for attaching soft tissue to a bone. The method uses a clamp comprising a porous metallic material wherein the clamp includes a first surface, a convex tissue engaging surface opposite the first surface, and a throughhole extending from the first surface to the convex tissue engaging surface. The soft tissue is placed adjacent the bone, and the clamp is placed adjacent the soft tissue opposite the bone. A fastener is inserted through the throughhole, through the soft tissue and into the bone such that the soft tissue is compressed between the tissue engaging surface and the bone. The convex tissue engaging surface of the clamp can have a first curvature, and the method can further comprise forming a depression of a second curvature in the bone, wherein the first curvature of the convex tissue engaging surface of the clamp is greater than the second curvature of the depression. The soft tissue is placed in the depression such that the soft tissue is compressed between the convex tissue engaging surface and the bone.

In still another aspect, the invention provides a method for attaching soft tissue to a prosthetic implant. The method uses a clamp comprising a porous metallic material. The clamp includes a first surface, a convex tissue engaging surface opposite the first surface, and a throughhole extending from the first surface to the convex tissue engaging surface. The soft tissue is placed adjacent the prosthetic implant, and the clamp is placed adjacent the soft tissue opposite the implant. A fastener is inserted through the throughhole, through the soft tissue and into the prosthetic implant such that the soft tissue is compressed between the tissue engaging surface and the prosthetic implant. The convex tissue engaging surface of the clamp can have a first curvature, and the prosthetic implant can further comprise a depression of a second curvature in the prosthetic implant, wherein the first curvature of the convex tissue engaging surface of the clamp is greater than the second curvature of the depression. The soft tissue is placed in the depression such that the soft tissue is compressed between the convex tissue engaging surface and the prosthetic implant.

In yet another aspect, the invention provides a method for attaching soft tissue to a bone. The method uses a first clamp comprising a porous metallic material and a second clamp comprising a porous metallic material. The first clamp includes a first surface, a convex tissue engaging surface opposite the first surface, and a throughhole extending from the first surface to the convex tissue engaging surface. The second clamp includes a first surface, a concave tissue engaging surface opposite the first surface, and a throughhole extending from the first surface to the concave tissue engaging surface. The second clamp is placed adjacent the bone, and the soft tissue is placed adjacent the second clamp opposite the bone. The first clamp is placed adjacent the soft tissue opposite the second clamp, and a fastener is inserted through the throughhole of the first clamp, through the soft tissue, through the throughhole of the second clamp and into the bone such that the soft tissue is compressed between the convex tissue engaging surface of the first clamp and the concave tissue engaging surface of the second clamp. The convex tissue engaging surface of the first clamp can have a first curvature, and the concave tissue engaging surface of the second clamp can have a second curvature, wherein the first curvature is greater than the second curvature.

It is therefore an advantage of the invention to provide improved methods and devices for the attachment of a tendon or ligament structure to bone or to a prosthetic implant.

Like reference numerals will be used to refer to like parts from Figure to Figure in the following description of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Looking first atFIG. 1, there is shown an example application of an attachment device10according to the invention in a human knee. This is shown for illustrative purposes, and the attachment device is not limited to knee surgery. The attachment device10can be used to attach any soft tissue (such as tendons and ligaments) to any bone. InFIG. 1, the knee joint12is shown with femur14, tibia16, tibial tunnel18and femoral tunnel20. The tibial tunnel18and the femoral tunnel20can be prepared using standard techniques. A ligament replacement22is arranged in the tibial tunnel18and the femoral tunnel20. A top end24of the ligament replacement22is attached to the femur14using the attachment device10and a bottom end26of the ligament replacement22is attached to the tibia16using the attachment device10.

Turning toFIGS. 2 and 3, the attachment device10is shown in greater detail. The attachment device10includes a clamp30having a domed (convex) tissue engaging surface32, a circular periphery34, a bottom surface36, and a central throughhole38. A tubular grommet40is arranged in the throughhole38. The side wall42of the grommet40can engage the inner surface of the throughhole38and a flange44extends outwardly from an end of the side wall42. The grommet40is optional, but can be advantageous as the grommet40can prevent the ligament replacement22at the apex of the clamp30from being totally flattened. The attachment device10also includes a fastener such as screw46that is inserted through the grommet40, through the ligament replacement22, and into the tibia16. The screw46compresses the ligament replacement22between the clamp30and the tibia16. Note inFIG. 2how the gap between the convex porous ingrowth surface32on one side and the concave surface of the depression48on the other side gets bigger near the periphery34of the clamp30and is smallest centrally near screw46.

In an alternative embodiment, the grommet40is omitted and the convex tissue engaging surface32includes a raised section around the throughhole38. This raised section can have an annular shape equivalent to the flange44of the grommet40. This raised section can prevent the ligament replacement22at the apex of the clamp30from being totally flattened.

The tissue engaging surface32of the clamp30has a first curvature which can be calculated as the inverse of the radius from a point P (which is on the central axis of the throughhole38and which is in the plane of the bottom surface36) to various points on the tissue engaging surface32. The ligament replacement22is secured between the tissue engaging surface32and a depression48that can be formed in the tibia16. The depression48has a second curvature which can be calculated as the inverse of the radius from point P (which is on the central axis of the throughhole38aand which is in the plane of the bottom surface36) to various points on the inner surface of the depression48. Also, the depression48can be prepared with a depth such that the flat bottom surface36of the clamp30can be counter-sunk into the tibia16if desired.

The clamp30and the grommet40may comprise a material that promotes soft tissue ingrowth from the ligament replacement22into the clamp30and the grommet40. One non-limiting example material is a porous metallic material, also known as metal foam, which can be produced with interconnective porosity coupled with a regular pore shape and size. One such material that is currently commercially available for a variety of orthopedic implants involves the elemental metal tantalum fabricated with >80% interconnective porosity with use of a metal vapor deposition technique (Trabecular Metal from Zimmer, Warsaw, Ind., USA). This material is also described in U.S. Pat. No. 5,282,861 which is incorporated herein by reference. While tantalum is one example porous metallic material, other non-limiting example porous metallic materials include titanium alloys, cobalt-chromium alloys, stainless steel alloys, tantalum alloys, and niobium alloys. The screw46is preferably formed from a non-porous metallic material such as a titanium alloy or a stainless steel alloy.

Still referring toFIGS. 2 and 3, it can be seen that the first curvature of the convex tissue engaging surface32of the clamp30is greater than the second curvature of the depression48in the tibia16. Stated in another way, the radius curvature of the convex tissue engaging surface32of the clamp30is smaller than the radius of curvature of the depression48in the tibia16. This allows for varying degrees of ligament replacement22compression due to the difference in curvature of the first curvature of the convex tissue engaging surface32of the clamp30and the second curvature of the depression48in the tibia16. As tendons and ligaments are of different thicknesses and have different requirements for tension between the clamp30and the tibia16, having varying degrees of compression between the clamp30and the tibia16increases the likelihood that at some point along the convex tissue engaging surface32of the clamp30, the level of compression would be optimal for ingrowth of soft tissue and therefore implant success rates increase.

Turning toFIG. 4, an alternative embodiment of the clamp of the attachment device is shown. The clamp30ahas a generally rectangular periphery34a, and two throughholes38aand39a, which allow for the use of two screws and optionally two grommets. The use of two screws for compressing the ligament replacement22between the clamp30aand the tibia16can increase compression force on the ligament replacement22. The rectangular periphery34aof the clamp30acan provide for increased surface area for soft tissue ingrowth. The clamp30acan comprise the porous metallic materials mentioned above. The convex tissue engaging surface of the clamp30acan have a radius curvature similar to the radius of curvature of the convex tissue engaging surface32of the clamp30shown inFIG. 2.

Turning toFIG. 5, another alternative embodiment of the clamp of the attachment device is shown. The clamp30bhas a generally oval periphery34b, and two throughholes38band39b, which allow for the use of two screws and optionally two grommets. The use of two screws for compressing the ligament replacement22between the clamp30band the tibia16can increase compression force on the ligament replacement22. The oval periphery34bof the clamp30bcan provide for increased surface area for soft tissue ingrowth. The clamp30bcan comprise the porous metallic materials mentioned above. The convex tissue engaging surface of the clamp30bcan have a radius curvature similar to the radius of curvature of the convex tissue engaging surface32of the clamp30shown inFIG. 2.

Looking now atFIG. 6, there is shown another embodiment of an attachment device110according to the invention. The attachment device110includes a first clamp130having a domed (convex) tissue engaging surface132, a circular periphery134, a bottom surface136, and a central throughhole138. The attachment device110also includes a second clamp141having a concave tissue engaging surface142in a well, a circular periphery143, a bottom surface144, and a central throughhole145. The attachment device110also includes a fastener such as screw146that is inserted through the throughhole138, through the ligament replacement22, through the throughhole145, and into the tibia16. The screw146compresses the ligament replacement22between the first clamp130and the second clamp141, which can be inserted in a circular depression148formed in the tibia16. While the first clamp130shown has a circular periphery134and the second clamp141shown has a circular periphery143, the periphery of each of the first clamp130and the second clamp141can have different shapes such as shown inFIGS. 4 and 5.

The tissue engaging surface132of the first clamp130has a first curvature which can be calculated as the inverse of the radius from a point (which is on the central axis of the throughhole138and which is in the plane of the bottom surface136) to various points on the tissue engaging surface132. The concave tissue engaging surface142of the second clamp141has a second curvature which can be calculated as the inverse of the radius from a point (which is on the central axis of the throughhole138and which is in the plane of the bottom surface136) to various points on the concave tissue engaging surface142of the second clamp141.

The first curvature of the convex tissue engaging surface132of the clamp130is greater than the second curvature of the concave tissue engaging surface142of the second clamp141. Stated in another way, the radius curvature of the convex tissue engaging surface132of the clamp130is smaller than the radius of curvature of the concave tissue engaging surface142of the second clamp141. This allows for varying degrees of ligament replacement22compression due to the difference in curvature of the first curvature of the convex tissue engaging surface132of the clamp130and the second curvature of the concave tissue engaging surface142of the second clamp141. Note inFIG. 6how the gap between the convex porous ingrowth surface132on one side and the concave tissue engaging surface142of the second clamp141on the other side gets bigger near the periphery134of the clamp130and is smallest centrally near screw146. As tendons and ligaments are of different thicknesses and have different requirements for tension between the first clamp130and the second clamp141, having varying degrees of compression between the first clamp130and the second clamp141increases the likelihood that at some point along the convex tissue engaging surface132of the first clamp130and the concave tissue engaging surface142of the second clamp141, the level of compression would be optimal for ingrowth of soft tissue and therefore implant success rates increase.

The first clamp130and the second clamp141may comprise a material that promotes soft tissue ingrowth from the ligament replacement22into first clamp130and the second clamp141The first clamp130and the second clamp141can comprise the porous metallic materials mentioned above for clamp30.

Turning now toFIGS. 7 and 8, the knee joint12is shown with femur14, tibia16, tibial tunnel18and femoral tunnel20. The tibial tunnel18and the femoral tunnel20can be prepared using standard techniques. A ligament replacement22is arranged in the tibial tunnel18and the femoral tunnel20. A top end of the ligament replacement22is attached to the femur14in the femoral tunnel20using the another attachment device210according to the invention. The bottom end26of the ligament replacement22is attached to the tibia16using the attachment device10as described above. The attachment device210as shown inFIG. 8forms a two-part frustoconical clamp230. The clamp230includes a first curved channel232having a wall233that terminates in a first longitudinal edge234and a second longitudinal edge236. The wall233has a first semicircular end237and a second semicircular end238of greater radius than the first semicircular end237. The clamp230also includes a second curved channel242having a wall243that terminates in a first longitudinal edge244and a second longitudinal edge246. The wall243has a first semicircular end247and a second semicircular end248of greater radius than the first semicircular end247. When the first edge234and the second edge236of the first channel232are brought into mating contact with the first edge244and the second edge246of the second channel242respectively, the clamp230has a hollow frustoconical shape. The first channel232and the second channel242can comprise the porous metallic materials mentioned above for clamp30.

To use the attachment device210, the ligament replacement22is positioned between the first channel232and the second channel242, and the first edge234and the second edge236of the first channel232are brought near the first edge244and the second edge246of the second channel242respectively. The clamp230is then inserted into the femoral tunnel20with the first semicircular end237and the first semicircular end247going in first. The first channel232and the second channel242clamp the ligament replacement22, and are wedged against the inner surface19of the femoral tunnel20. The compression of the ligament replacement22allows for ingrowth of soft tissue into the first channel232and the second channel242and therefore the implant success rate increases.

Referring now toFIG. 9, there is shown a prior art femoral prosthesis310that may be implanted in a resected femur as part of a hip replacement procedure. The prosthesis310includes a body312having a neck portion313, a femoral head314and a collar315. The femoral head314is received in an acetabular component (not shown) that is mounted in a patient's pelvis as is well known in the art. Extending away from the body312of the prosthesis310is a generally cylindrical or tubular stem316that is inserted within the intramedullary canal of the femur14. The stem316has an upper lateral corner317. The femoral prosthesis310may be formed from a metal alloy such as titanium alloys (e.g., titanium-6-aluminum-4-vanadium), cobalt-chromium alloys, stainless steel alloys and tantalum alloys; nonresorbable ceramics such as aluminum oxide and zirconia; nonresorbable polymeric materials such as polyethylene; or composite materials such as carbon fiber-reinforced polymers (e.g., polysulfone).

Turning toFIGS. 10 and 11, another attachment device410according to the invention is shown. The prosthesis310ais similar to the prosthesis310ofFIG. 9. The prosthesis310aincludes a body312ahaving a neck portion313a, a femoral head314aand a collar315a. However, an indented section420of the upper lateral corner417of the prosthesis310ahas been removed. The attachment device410includes a clamp430having a convex tissue engaging surface432, a generally rectangular periphery434, a bottom surface436, and throughholes438and439. In the cross-section shown inFIG. 10, the clamp430has a general shape of a quadrant of an oval. The clamp430may comprise a material that promotes soft tissue ingrowth from the ligament replacement22into clamp430. The clamp430can comprise the porous metallic materials mentioned above for clamp30.

The attachment device410also includes fasteners such as screws446,447that are inserted through the throughholes438,439, respectively, through the ligament replacement22, and into the stem316aof the prosthesis310a. The screws446,447compress the ligament replacement22between the convex tissue engaging surface432of the clamp430and the concave tissue engaging surface442of the indented section420of the stem316aof the prosthesis310a. The convex tissue engaging surface432of the clamp430has a first curvature is greater than the second curvature of the concave tissue engaging surface442. This allows for varying degrees of ligament replacement22compression due to the difference in curvature of the first curvature of the convex tissue engaging surface432of the clamp430and the second curvature of the concave tissue engaging surface442. Either end of the ligament replacement22can be attached to another bone or implant.

Looking now atFIG. 12, there is shown another embodiment of an attachment device510according to the invention. The attachment device510includes a first clamp530having a domed (convex) tissue engaging surface532, a circular periphery534, a bottom surface536, and a central throughhole538. The attachment device510also includes a second clamp541having a concave tissue engaging surface542in a well, a circular periphery543, a bottom surface544, and a central throughhole545. The attachment device510also includes a fastener such as screw546that is inserted through the throughhole538, through the ligament replacement22, through the throughhole545, and into the tibia16. The screw546compresses the ligament replacement22between the first clamp530and the second clamp541, which can be inserted in a recess548formed in the tibia16.

The tissue engaging surface532of the first clamp530has a first curvature which can be calculated as the inverse of the radius from a point (which is on the central axis of the throughhole538and which is in the plane of the bottom surface536) to various points on the tissue engaging surface532. The concave tissue engaging surface542of the second clamp541has a second curvature which can be calculated as the inverse of the radius from a point (which is on the central axis of the throughhole538and which is in the plane of the bottom surface536) to various points on the concave tissue engaging surface542of the second clamp541.

The first curvature of the convex tissue engaging surface532of the clamp530is greater than the second curvature of the concave tissue engaging surface542of the second clamp541. This allows for varying degrees of ligament replacement22compression due to the difference in curvature of the first curvature of the convex tissue engaging surface532of the clamp530and the second curvature of the concave tissue engaging surface542of the second clamp541. Note inFIG. 12how the gap between the convex porous ingrowth surface532on one side and the concave tissue engaging surface542of the second clamp542on the other side gets bigger near the periphery534of the clamp530and is smallest centrally near screw546. As tendons and ligaments are of different thicknesses and have different requirements for tension between the first clamp530and the second clamp541, having varying degrees of compression between the first clamp530and the second clamp541increases the likelihood that at some point along the convex tissue engaging surface532of the first clamp530and the concave tissue engaging surface542of the second clamp541, the level of compression would be optimal for ingrowth of soft tissue and therefore implant success rates increase.

The first clamp530and the second clamp541may comprise a material that promotes soft tissue ingrowth from the ligament replacement22into first clamp530and the second clamp541The first clamp530and the second clamp541can comprise the porous metallic materials mentioned above for clamp30.

Thus, the invention provides methods and devices for the attachment of a tendon or ligament structure to bone and/or a prosthetic implant (such as a joint replacement device). In particular, the methods and devices use a clamping strategy employing soft tissue healing to a porous metal clamp.

Although the present invention has been described in detail with reference to certain embodiments, one skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which have been presented for purposes of illustration and not of limitation. Therefore, the scope of the appended claims should not be limited to the description of the embodiments contained herein.