US 8157867 B2
A trochlear groove implant includes a body having a first side with an articular surface and an opposing second side with a bone apposition surface, the articular surface and the bone apposition surface each extending between a proximal end and an opposing distal end of the body. An elongated channel is recessed on the articular surface and longitudinally extends between the opposing ends of the body. An elongated ridge outwardly projects from the bone apposition surface and longitudinally extends between the opposing ends of the body.
1. A trochlear groove implant for articulating with a patella, the trochlear groove implant comprising:
a body having a first side with an articular surface, an opposing second side with a bone apposition surface, and a substantially uniform thickness between the articular surface and the bone apposition surface such that, at all locations at least 2 mm in from a perimeter edge of the body, the thickness of the body between the articular surface and the bone apposition surface does not vary by more than 20%, the articular surface and the bone apposition surface each extending between a proximal end and an opposing distal end of the body;
an elongated channel recessed on the first side of the body and longitudinally extending between the proximal end and the opposing distal end of the body, at least a first portion of the articular surface having a substantially smooth convex curvature extending between the proximal end and the distal end of the body, a second portion of the articular surface being at least one of flat and convexly curved in a direction transverse to the elongated channel, wherein the patella rides both in the elongated channel and against the second portion of the articular surface during normal articulation; and
an elongated ridge outwardly projecting on the second side of the body and longitudinally extending between the proximal end and the opposing distal end of the body, at least a portion of the bone apposition surface having a substantially smooth concave curvature extending between the proximal end and the distal end of the body.
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a bearing plate having the articular surface and an opposing bottom surface, a pocket being formed on the bottom surface of the bearing plate; and
an inlay of porous bone ingrowth material secured within the pocket.
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a bone anchor; and
means for securing a portion of the first line to the bone anchor.
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24. A trochlear groove implant for articulating with a patella, the trochlear groove implant comprising:
a body having a first side with an articular surface, an opposing second side with a bone apposition surface, a proximal end, an opposing distal end, a lateral side, a medial side, and a perimeter edge, the articular surface of the body having a centroidal location, a maximum radius extending from the centroidal location to the perimeter edge, and a minimum radius extending from the centroidal location to the perimeter edge, the minimum radius not being less than 80% of the maximum radius;
an elongated channel recessed on the first side of the body and longitudinally extending between the proximal end and the opposing distal end of the body, at least a portion of the articular surface having a substantially smooth convex curvature extending between the proximal end and the distal end of the body, the elongated channel having a bottom that is substantially centrally located between the lateral side and the medial side of the body; and
an elongated ridge outwardly projecting on the second side of the body and longitudinally extending between the proximal end and the opposing distal end of the body, at least a portion of the bone apposition surface having a substantially smooth concave curvature extending between the proximal end and the distal end of the body.
This application is a continuation-in-part of U.S. patent application Ser. No. 10/901,941, filed Jul. 28, 2004, which claims priority to U.S. Provisional Application Ser. No. 60/586,706, filed Jul. 9, 2004, which applications are incorporated herein by specific reference.
1. The Field of the Invention
The present invention relates to instruments and methods for preparing an orthopedic joint articulation surface to receive a bearing implant.
2. The Relevant Technology
The human body has a variety of movable orthopedic joints such as the knee joint, hip joint, shoulder joint, and the like. These joints are formed by the intersection of two bones. The intersecting end of each bone has smooth articular surface that is comprised of cartilage. As a result of injury, wear, arthritis, disease or other causes, it is occasionally necessary to replace all or part of an orthopedic joint with an artificial implant. This procedure is referred to as a joint replacement or arthroplasty. For example, a total knee arthroplasty comprises cutting off or resecting the articular surfaces at both the distal end of the femur and the proximal end of the tibia. Complementary artificial implants are then mounted on the distal end of the femur and the proximal end of the tibia. Where only a portion of a joint is damaged, a partial joint arthroplasty can be performed. In this procedure, one or more artificial implants replace only a portion of a joint.
Although joint replacement is now a common procedure that has met with popular success, conventional implants and related mounting techniques have significant shortcomings. One significant drawback of many joint replacements is the extended and painful patient recovery. For example, a traditional knee replacement requires an open procedure wherein a relatively large incision is made which severs a portion of the muscle bounding the femur. The large incision is made so as to fully expose the respective ends of the femur and tibia.
This exposure is necessary when using conventional techniques to resect the femur and tibia and to mount the implants. For example, some conventional tibial implants are screwed directly into the resected end face of the tibia. Mounting such screws requires exposure of the resected end face. In yet other embodiments, the implants are formed with posts projecting therefrom. The posts are received within sockets formed on the resected end face of the tibia and femur. Again, forming of the sockets and inserting the posts into the sockets requires substantially full exposure of the resected end face of the tibia and femur.
In general, the more invasive the surgery, the more painful, difficult, and time consuming the patient recovery. This is largely due to the significant amount of scar tissue produced by the incision and resection of various soft tissues. Furthermore, such open and invasive surgeries have a greater risk of infection.
Another problem with conventional joint implants and related techniques for mounting is that it can be difficult to fit, adjust, and/or exchange different implants during the fitting stage. That is, implants come in a variety of different sizes, shapes, and configurations. During the joint replacement procedure, the surgeon may often test a variety of different sized implants to determine the best fit and alignment. As conventional implants are screwed into or pounded onto the bone during placement, the fitting, adjustment, and/or replacement of different conventional implants can be difficult and potentially damaging to the bone. Likewise, it can often be difficult to replace worn or damaged implants.
Accordingly, what is needed are implants and related methods and systems for preparing an articular surface of a joint and mounting an implant thereat which minimizes the length of incision, the amount of bone resection, and/or the impact on soft tissue. What is also needed are implants and related methods and systems which enable easier fitting, alignment, testing, and/or replacement of implants.
Various embodiments of the present invention will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope.
The present invention relates to methods and apparatus for preparing an articulation surface of an orthopedic joint to receive an implant, implants for mounting at an articulation surface of an orthopedic joint, anchoring systems for securing an implant at an articulation surface of an orthopedic joint, and related methods and instruments. As used in the specification and appended claims, the terms “articulation surface” and “natural articulation surface” are broadly intended to include all natural articular surfaces of a bone forming a portion of an orthopedic joint and all articulation wear surfaces of a bone forming a portion of an orthopedic joint which are produced as a result of ware, trauma, disease, or other causes which remove all or a portion of the natural articular surface.
The implants, anchoring systems, instruments, and methods of the present invention can be used in combination to mount an inventive implant or can be used separately or in combinations with other conventional implants, anchoring systems, instruments and/or methods. It is appreciated that the implants, anchoring systems, instruments, and methods of the present invention can be used for mounting an implant on virtually any articulation surface of any orthopedic joint in a human or other mammal. By way of example and not by limitation, the implants, anchoring systems, instruments, and methods of the present invention can be used in association with resurfacing an articulation surface of a knee joint, ankle joint, hip joint, shoulder joint, elbow joint, wrist joint, interphalangeal joint, or other joints. As such, the implants can be mounted on the proximal end and distal end of the femur, tibia, humerus, radius, and ulna, and on the articular surfaces of the scapula, pelvis, bones within the foot and hand, and other bone articular surfaces. Likewise, the implants, anchoring systems, instruments, and methods of the present invention can be used in facilitating a partial joint arthroplasty or a total joint arthroplasty.
In one embodiment, the implants, anchoring systems, instruments, and/or methods of the present invention are designed so that an articulation surface of a joint can be prepared and an implant mounted thereon using procedures that are minimally invasive. As a result, recovery time is significantly improved while the damage to soft tissue if decreased and the risk of infection minimized. Also in one embodiment of the present invention, the implants, anchoring systems, instruments, and/or methods are designed so that the implant can be selectively adjusted, tightened, and/or loosened after the implant is positioned on the articulation surface. This ability allows for greater ease in adjustment and fitting of an implant at the time of initial placement and for greater easy in replacement of an implant.
Set forth below are several embodiments of the present invention used in association with preparing an articulation surface at a proximal end of a tibia and mounting a condylar implant at the proximal end of the tibia. It is again noted that these embodiments are only given by way of example and that one skilled in the art based on the teaching provided herein would be able to use corresponding implants, methods, and instruments to prepare and/or mount an implant on other joint articulation surfaces.
Although tibia 12 shown in
In one embodiment, to facilitate mounting of a condylar implant on medial condyle 21, conventional arthroscopic procedures are used to resect the posterior portion of the medial meniscus. Once the posterior portion of the medial meniscus is removed, a vertical or horizontal incision, generally in a range between about 2 cm to about 6 cm, is formed over the anterior side of the medial meniscus. Following retraction of the surrounding tissue, the anterior side of the medial meniscus is resected. A coarse rasp is then inserted between the medial condyle of the femur and medial condyle 21 of tibia 12. The rasp is used to remove approximately 1-2 mm of articular cartilage on medial facet 24 of tibia 12. Removal of the meniscus and the articular cartilage provides increased access to medial facet 24 of tibia 12.
Tunnel 400 is typically formed using a drill in combination with one of a variety of different types of guide assemblies. Alternative methods and techniques for forming tunnel 400 are disclosed in U.S. patent application Ser. No. 10/901,941, filed Jul. 28, 2004 which is incorporated herein by specific reference (hereinafter “the '941 application”).
Using the above-referenced methods and instruments, tunnel 400 can be formed by procedures that are minimally invasive to the patient. Once tunnel 400 is formed, tunnel 400 can then be used to assist in the resection of medial fact 24 and/or the mounting of a condylar implant on the resected medial facet 24. Furthermore, by using tunnel 400 the resection of medial facet 24 and the mounting of the condylar implant can also be performed using procedures that are minimally invasive.
As will be discussed below in greater detail, a bone anchor is secured within first end 402 of tunnel 400. The bone anchor requires a larger opening than what is necessarily needed for a line or fastener to pass through tunnel 400. Accordingly, where tunnel 400 is minimized to limit bone removal, first end 402 of tunnel 400 can be counter bored with a larger drill so as to enable proper placement of the bone anchor. In one embodiment, tunnel 400 can be counter sunk so as to have a diameter in a range between about 4 mm to 8 mm. Again, other dimensions can also be used.
In general, condylar implant 300 has a top articular surface 306 and an opposing bone apposition surface 303. In one embodiment, top articular surface 306 has a generally concave contour that continuously curves front to back and side to side so as to mate with a corresponding femoral condyle. Alternatively, articular surface 306 can be substantially flat. Bone apposition surface 303 has a generally convex contour that continuously curves front to back and side to side and that is configured to mate with pocket 194 (
In alternative embodiments, bone apposition surface 303 can be substantially flat. As a result, implant 300 can be mounted directly on flat resected surface 234. In this embodiment, however, contouring of articular surface 306 would result in the opposing ends of implant 300 being thicker than the middle. Again, however, depending on the size of the patient and the portion of the bone being replaced, implant 300 can have an array of different sizes and configurations.
As depicted in
Inlay 320 is secured within pocket 316 of body 301 so as to encircle stem 304. Inlay 320 is comprised of a porous bone ingrowth material such as porous tantalum. Other conventional porous bone ingrowth materials can also be used. Inlay 320 is secured within pocket 316 using conventional techniques such as press fit, welding, adhesive, sintering, and the like. Inlay 320 can also be mechanically connected to body 301 such as by screws, fasteners, rivets, or the like. In alternative embodiments, pocket 316 can be eliminated and inlay 320 can be secured to the bottom surface of body 301 using various techniques. Inlay 320 has an exposed bottom surface 322 that, as discussed above, can be arched, substantially flat, or can have any other desired configuration. In this embodiment, bottom surface 322 of inlay 320 comprises substantially all of bone apposition surface 303 of base plate 301.
In contrast to having a single pocket 316 in which a single inlay 320 is positioned, it is appreciated that body 301 can be formed having a plurality of pockets each adapted to receive a separate inlay. For example, depicted in
Similarly, depicted in
In still other embodiments, it is appreciated that the inlay of porous bone ingrowth material can be eliminated. In this embodiment, the condylar implant can comprise a single integral member. For example, depicted in
In one embodiment, a flexible line is used to secure the implants to tibia 12. As used in the specification and append claims, the term “line” is broadly intended to include wire, cable, cord, suture, braded line, combinations thereof or any other type of flexible filament. The line can be made of metal, alloys, synthetics, composites, or any other desired material. In one embodiment of the present invention the line comprises braded filaments of a cobalt chrome alloy having a diameter in a range between about 0.25 mm to about 5 mm with about 0.5 mm to about 3 mm being more common and about 0.5 mm to about 2 mm being most common. Other dimensions can also be used. The line can be of any desired length.
In one embodiment, the line can also be defined in that for an unsupported length of line of 4 cm, the line has substantially no compressive strength. In yet other embodiments, for an unsupported length of line of 4 cm, the line fails under buckling when an axial compressive load of 0.25 Newtons (N), 1 N, 2 N, 5 N, 20 N, or 50 N is applied. That is, different lines can be used that fail under different loads. Stiffer lines can also be used.
It is also appreciated that the line can be static or resiliently stretchable. In one embodiment where the line is resiliently stretchable, the line can be comprised of a material have shape memory of pseudo elastic properties. One example of such a material is a nickel titanium alloy sold under the name Nitinol. In yet other embodiment, it is appreciated that sections of the line could be replaced with a spring member such as a coiled spring or rubber or bungee type member.
In one embodiment of the present invention, means are provided for connecting flexible line 438 to implant 300. By way of example and not by limitation, stem 304 is provided with a threaded socket 312. Slidably disposed on line 438 is a tubular retainer 444. Retainer 444 comprises a body 445 having one or more helical threads 446 mounted on the exterior surface thereof. Threads 446 are configured to engage with threaded socket 312. A channel 448 longitudinally extends through body 445. Channel 448 constricts toward the distal end of body 445 so that the channel 448 thereat is larger than the diameter of line 438 but smaller than the diameter of head 442. The proximal end of channel 448 is enlarged and has a polygonal transverse cross section. As a result, first end 439 of line 438 can be passed through channel 448 of body 445 distal to proximal. Line 438 can then be pulled through retainer 444 until head 442 is stopped by the constricted section of channel 448. The first end of line 438 can then be advanced through a central channel in a tubular driver (not shown) having a free end adapted to fit within channel 448 of retainer 444 at the proximal end thereof. The driver can thus be used to screw retainer 444 into threaded socket 312, thereby securing line 438 to implant 300.
In the embodiment depicted in
Furthermore, by connecting line 438 to implant 470 at two spaced apart locations, the implant is secured in a more stable configuration that prevents unwanted sliding or rotation on the bone. In other embodiments, it is appreciated that line 438 can be connected to only a single projection 474. It is also appreciated that a first line can be connected to projection 474A while a second line is connected to projection 474B. In like manner, it is appreciated that in all embodiment disclosed herein, two or more discrete lines can be connected two each of the implants using any of the methods disclosed herein. It is also appreciated that there are still a large number of other ways in which line 438 can be secured to an implant. For example, the line can be welded, press fit, or attached by a variety of different types of fasteners such as bolts, rivets, or clamps. Examples of still other condylar implants having a line connected thereto are also disclosed in the '941 application.
As depicted in
Projecting from second end 850 of body 846 are a plurality of flexible fingers 856. As depicted in
As depicted in
Second driver 816 also comprises a tubular shaft 867 having a proximal end 868 and an opposing distal end 870. A tubular handle 872 is mounted proximal end 868. As such, a passage 874 extends the length of second driver 816 so that line 438 can extend completely therethrough. Distal end 870 of shaft 867 terminates at a tip 875. Tip 875 has a configuration complementary to channel 840 at proximal end 836 of lock 813. As such, second driver 816 can be selectively coupled with lock 813 for selective rotation of lock 813.
Line 438 is continually pulled through tunnel 400 to remove all slack. With the slack removed, condylar implant 300 is slid onto resected surface 234 so as to fit within pocket 194. Here it is noted that because condylar implant 300 has a relatively low profile, condylar implant 300 can be easily passed through the relatively small incision that was originally formed over the medial meniscus. This is in contrast to other conventional procedures where larger incisions must be made to either allow placement of an implant having a large stem that is embedded within the bone for securing or to provide access room to enable securing the implant by passing screws down through the top of at least a portion of the implant.
Once implant 300 is positioned, bone anchor 812 is fed onto line 438. Specifically, with lock 813 partially inserted into bone anchor 812, as discussed above with reference to
First driver 814 is then used to screw bone anchor 812, having lock 813 therein, into first end 402 of tunnel 400. Bone anchor 812 is advanced until proximal end 822 passes into tibia 12. In one embodiment, a tap, not shown, is used to initially thread the interior surface of tunnel 400 at first end 402. Alternatively, bone anchor 812 can be self-tapping.
Next, a tensioner 878 is used to tension line 438. As depicted in
Positioned on clamp arm 890 is a stop plate 892. An eccentrically mounted cam 894 is rotatably mounted to clamp arm 890 and is spring biased against stop plate 892. A handle 895 projects from cam 894. Depressing handle 895 causes cam 894 to rotate away from stop plate 892. Line 438 can then be placed between cam 894 and stop plate 892. When handle 895 is released, cam 894 spring biases against stop plate 892 causing line 438 to be secured therebetween. Because cam 894 is eccentrically mounted, the more tension on line 438 toward first driver 814, the greater the force applied by cam 894 to secure line 438 in place.
A force measuring device, such as a transducer, can be coupled with tensioner 878 for measuring the tension force applied to line 438. In turn, the tension force on line 438 is the same force used to bias implant 300 against tibia 12. When a sufficient tension force is applied to line 438, handle 872 of second driver 872 is rotated, thereby causing lock 813 to secure line 438 within bone anchor 812. In one embodiment, the tension force applied to line 438 is in a range between about 25 pounds (110 N) to about 300 pounds (1,335 N) with about 150 pounds (670 N) to about 250 pounds (1,110 N) being more common. Other forces can also be applied.
Once lock 813 is secured in place, tensioner 878, second driver 816 and first driver 814 are removed. One of the unique features of this embodiment of the present invention is that should the surgeon wish to make some modification to the implant or related anchor system, lock 813 can simply be loosened using second driver 816 to allow the desired movement or adjustment. The above process can then be repeated to resecure implant 300 in place. Once properly position and secured, line 438 is severed just proximal of lock 813. Even after line 438 is severed, however, further tension can be applied to line 438 by backing bone anchor 812 back toward first end 402 of tunnel 400 using first driver 814. Closing procedures for the tissue are then performed.
It is appreciated that many of the mounting steps can be modified or performed in an alternative order. For example, in one method condylar implant can be positioned in pocket 194 prior to having line 438 connected thereto. As previously discussed with regard to
In one embodiment of the present invention means are also provided for securing line 438 to bone anchor 812. One example of such means comprises lock 813. In alternative embodiments lock 813 can have a variety of different configurations or be replaced with a variety of different structures. For example, any number of different wedges, cleats, or cams can be placed in bone anchor 812 so that line 438 can be pulled one way through bone anchor 812 but is prevented from being pulled back. In yet other embodiments, once line 438 is tensioned, a lock can be crimped or otherwise secured to line 438. The lock would then bias against bone anchor 812 to prevent line 438 from being pulling back through bone anchor 812. Examples of various locks which can be used are disclosed in U.S. Pat. No. 5,702,397, issued Dec. 30, 1997 and U.S. patent application Ser. No. 09/970,559, filed Oct. 3, 2001. The bone anchors with related line locking structures disclosed in U.S. Pat. No. 5,702,397 and application Ser. No. 09/970,559 are incorporated herein by specific reference.
In still other embodiments, it is appreciated that bone anchor 812 can have a variety of different configurations. For example, depicted in
Bone anchor 980B is similar to bone anchor 980A except that helical threads 825 have been completely removed. In this embodiment, exterior surface 821 extending between proximal end 822 and distal end 823 is smooth. Bone anchor 980B is designed to be slid or wedged within the bone tunnel and held in place by the taper along the length thereof and/or the enlarged head 982. By increasing the exterior taper of bone anchor 980B, it is also appreciated that enlarged head 982 can be removed. Because bone anchor 980B is not threaded into the bone, socket 430 at proximal end 416 need not be polygonal to engage a driver but can be round. In alternative embodiment, the interior or exterior surface of head 982 can have a polygonal or other non-circular configuration so as to facilitate positive engagement with a driver.
To secure implant 470 to tibia 12, first end 439 of line 438 is passed proximal to distal through channel 826 in first bone anchor 812A. First end 439 is then passed up through first tunnel 400A, though passages 475 on implant 470 (
It is appreciated that first bone anchor 812A can be replaced with a variety of alternative structures that prevent second end 440 of line 438 from being pulled through first tunnel 400A. For example, the first bone anchor can simply comprise an enlarged washer that captures enlarged head 442 but is too big to pass through tunnel 400A. In yet other embodiment, the first bone anchor can simply comprise an enlarged tubular wedge that wedges into tunnel 400A but cannot pass therethrough. In still other embodiments, line 438 can be formed without enlarged head 442. In this embodiment, lock 813 or other wedging or locking type structure can be used to secure second end 440 of line 438 to the first bone anchor. Where two separate lines 438 are connected to an implant, each line is extended through a corresponding tunnel. The process discussed with regard to
Line 438 and anchor assembly 810 is one embodiment of means for securing an implant to a bone. It is appreciated, however, that other anchoring techniques can also be used. For example, another system for securing an implant to a bone is disclosed in U.S. patent application Ser. No. 10/798,665, filed Mar. 11, 2004 which is incorporated herein by specific reference.
By using the above discussed implants and anchor assemblies with the corresponding methods and instruments, it is appreciated that the implants can be securely mounted to tibia 12 using procedures that are minimally invasive. Furthermore, because the implants are only secured in place after they are positioned on the proximal end of the tibia, the surgeon can easily switch out different sizes of implants when trying to determine an appropriate fit. Likewise, because the anchoring assemblies are operated through the first end of the tunnel which is remote from the implant, the inventive anchoring assemblies enable the surgeon to easily adjust the placement of the implant during initial positioning and to subsequently remove the implant should a replacement be required at a later date.
Furthermore, as a result of using a flexible line to secure the implants, the surgeon can select the best location for forming the tunnel and mounting the bone anchor at the time of the operation. That is, the surgeon is not limited to forming the tunnel at a predefined location based on structural limitations imposed by the implant. In addition, because the line can be relatively small, the size of the required tunnel can be minimized, thereby minimizing the amount of bone that needs to be removed when forming the tunnel. Replacement of a worn or damaged implant is also relatively easily achieved by cutting the line.
Because the inventive implants, anchor assemblies, tissue preparation instruments, and corresponding methods each produce independently unique benefits, it is appreciated that theses various features can be used independently with other conventional apparatus and techniques. For example, in one embodiment a larger incisions can be made at the knee of a patient and the proximal end of tibia 12 resected using conventional resection techniques. In this embodiment, tunnel 400 can be formed either before or after the resection of tibia 12. Once the tibia is resected and the tunnel formed, the above procedure can then be used to secure condylar implant 300. In another alternative, tunnel 400 can be formed and tibia 12 resected as discussed above. However, once tibia 12 is resected, a conventional implant can be mounted on tibia 12 using conventional techniques.
The above discussed embodiments relate to mounting a condylar implant on tibia 12. As previously mentioned, however, the present invention can also be used to mount other types of implants on other articulation surface so as to achieve one or more of the same benefits. For example, the '941 application also discloses a full tibial implant and methods for mounting.
Features of the present invention can also be used for mounting a femoral implant on the distal end of a femur. Like elements between different embodiments are identified by like reference characters. For example, depicted in
Mounted on medial condyle 537 is a guide template 900. Guide template bounds an elongated opening 902 that extends therethrough and which is configured to closely fit over a predefined portion of an articulation surface of medial condyle 537. Opening 902 bounds the area where the bone is to be resected and a condylar implant mounted. Guide template is curved and comes in a variety of different sizes and shapes so that a proper fit can be made on medial condyle 537. Once a proper sized and fitting guide template 900 is positioned, guide template 900 is secured in place by spaced apart screws 904 that are screwed through mounting holes in guide template 900 and into the medial side of femur 530.
In one embodiment, a milling head 906 is used to facilitate resection of medial condyle 537 bounded by guide template. Milling head 906 has a substantially hour-glass configuration and has an elongated handle 908 projecting from one side and a stem 909 projecting from the other. Milling head 906 is positioned within opening 902 in a medial-lateral orientation with handle 908 projecting from medial side 540 of femur 530. In this orientation, milling head 906 is rapidly rotated and then selectively moved within opening 902 anterior-posterior. This movement is guided by the sides of guide template 900 bounding opening 902. Milling head 906 grinds away the bone bounded within opening 902 until handle 908 and stem 909 rest against guide template 900, thereby preventing milling head 906 from descending further into the bone.
Because guide template 900 is curved anterior-posterior, the milled pocket formed by milling head 906 is outwardly arched anterior-posterior. Likewise, because milling head 906 is curved lateral-medial, the milled pocket is also outwardly arched lateral-medial. As such, the recessed pocket produced by milling head 906 is arched anterior-posterior and lateral-medial. Again, this pocket configuration enables the formation of a low profile implant having substantially uniform thickness and strength. Furthermore, the pocket formation produces a stable platform for the implant having a complementary configuration. In alternative embodiments, it is again appreciated that milling head 906 can have a variety of different configurations.
As depicted in
Once the recessed pocket is finished, a tunnel guide can be used to form tunnel 400 extending from lateral side 542 of femur 530 to the recessed pocket. Examples of such tunnel guides and corresponding method of use are disclosed in the '941 application. Alternatively, tunnel 400 can be drilled starting at the recessed pocket and extending to the lateral or medial side of the femur. Because it is less critical where tunnel exits on the lateral or medial side, a tunnel guide is not required but could, if desired, still be used. This process can also be used on the tibial side.
Once tunnel 400 is formed, a femoral condylar implant 928 is then positioned within the recessed pocket. As depicted in
A pair of pockets 934A and B are formed on bottom surface 932 and are separated by a bridge 935. Disposed within each pocket 934A and B is an inlay 936A and B of porous bone ingrowth material. Bridge 935 and inlays 936A and B substantially comprise a bone apposition surface 938. Bone apposition surface 938 can have a configuration complementary to the formation of the recessed pocket formed on medial condyle 537. Bone apposition surface 938 can also have a configuration complementary to articular surface 931. In one embodiment, bone apposition surface 938 can have a continuous concave curvature which extends between opposing sides 500 and 502 and a continuous concave curvature which extends between opposing ends 504 and 506. As a result, condylar implant can have a substantially uniform thickness along its length.
Connected to bridge 935 is line 438. It is appreciated that the various alternatives as previously discussed with regard to the tibial condylar implants and the methods for connecting line 438 thereto are also applicable to femoral condylar implant 928.
Finally, turning to
The present invention can also be used for mounting a trochlear implant on femur 530. For example, depicted in
Extending through body 952 between top surface 954 and bottom surface 956 is an enlarged opening 966. Opening 966 is configured to overlay the bone which is to be removed so as to form a pocket in which the trochlear implant is received. The portion of the bone that is removed includes all or a portion of the bone forming trochlear groove 539 and, optionally, additional surrounding bone. In one embodiment, opening 966 has or covers an area in a range between about 3 cm2 to about 20 cm2 with about 9 cm to about 16 cm2 being more common. Other dimensions can also be used.
It is appreciated that opening 966 can have a variety of different configurations. In the embodiment depicted, opening 966 is bounded by an interior surface 968. As perhaps best depicted in
Turning again to
Because the area surrounding trochlear groove 539 has an irregular configuration, the use of three supports 978-980 provides a stable platform that can be easily designed so as to rest in a stable fashion on a plurality of differently sized and shaped femurs. In alternative embodiments, it is appreciated that the supports can be positioned at different locations on body 952 and can have a variety of different sizes and shapes. Furthermore, fewer or more supports can also be used. For example, guide template 950 can be designed with two supports so that the two supports and a portion of body 952 rest directly against femur 930. In yet other embodiments, four or more supports can be formed projecting from body 952.
As depicted in
The present invention also includes means for securing body 952 to femur 530. By way of example and not by limitation, spaced apart mounting holes 988 are formed on or extend through body 952. Screws 990 or other fasteners can be passed through mounting holes 988 so as to secure guide template 950 to femur 930 once guide template 950 is positioned in the desired location. In the embodiment depicted, three mounting holes and screws are used to secure guide template 950. As in prior embodiments, however, alternative numbers of screws and mounting holes or other types of fastening techniques can also be used. Furthermore, the mounting holes 988 can be positioned at a variety of different locations on body 952 and can have a variety of different orientations so as to better stabilize body 952 when the screws are received therein. Likewise, mounting holes 988 are positioned and oriented so that screws 990 only enter the bone outside of the articulation surface, i.e., articular cartilage or on a non-function peripheral edge thereof.
Projecting from contact face 1010 of slide rest 1008 is a cutting mount 1016. Cutting mount 1016 comprises a cutting surface 1018 formed by a plurality of cutting teeth 1020. (It is noted that in
As depicted in
During operation as depicted in
Once slide rest 1008 reaches top surface 954, the bone has been removed to the desired depth. Here it is noted that the curvature of top surface 954 causes rasp 994 to move in a curved path as slide rest 1008 slides along top surface 954. Rasp 994 is then removed so as to reveal, as depicted in
Due to the configuration of cutting mount 1016, a rounded, elongated channel 948 is recessed along floor 944 in substantial alignment with where trochlear groove 539 was previously disposed. That is, channel 948 extends between opposing ends 953 and 955. Floor 944 also has a convex curvature that extends between opposing ends 953 and 955. As will be discussed below in greater detail, the configuration of recessed pocket 942 enables the formation of a low profile trochlear implant having substantially uniform thickness. Furthermore, the formation of pocket 942 produces a stable platform for the implant having a complementary configuration.
In one alternative embodiment, it is appreciated that recessed pocket 942 can be formed by using two or more different rasps. For example, instead of trying to remove all of the bone material using a single rasp, a smaller rasp can initially be used to form channel 948 within recessed pocket 942. By way of an illustrated example, depicted in
Cutting surface 1040 substantially comprises a surface of rotation which curves between proximal end 1044 and distal end 1046 about a common rotational axis 1056. Of course, the surface of rotation has some variation due to the fact that it is formed from the plurality of teeth 1042. In one embodiment, cutting surface 1040 can extend about axis 1056 over an angle greater that 300°. More commonly however, cutting surface 1040 extend over an angle in a range between about 15° to about 180° with about 25° to about 100° being more common. Other angles can also be used.
Cutting surface 1040 is also depicted as having a non-linear contour when viewed in a plane extending between side faces 1048 and 1050 and intersection with rotational axis 1056 along the length thereof. Specifically, cutting surface 1040 has a rounded, outwardly projecting ridge 1054 which extends between opposing ends 1044 and 1046 substantially centrally between opposing side faces 1048 and 1050. Ridge 1054 is used to form channel 948 of recessed pocket 942. It is appreciated that rasp 1034 can be used to form recessed pockets for other types of implants and that in such alternative uses, the contour of cutting surface 1040 can have a variety of different configurations.
Rasp 1034 is configured so that cutting mount 1038 can be disposed within opening 966 of guide template 950 so that as rasp 1034 is reciprocated, cutting surface 1040 reciprocates against the bone surface. In turn, teeth 1042 on cutting surface 1040 progressively resect the bone surface until slide rests 1052 bear against top surface 954 of guide template 950. Rasp 1034 can thus also be used to form recessed pocket 942 having channel 948. One of the benefits of rasp 1034 is that because of the unique configuration of cutting surface 1040, cutting surface 1040 can be rotated or positioned at any desired angle about axis of rotation 1056 and still produce recessed pocket 942 having the same contour. As a result, the operator of rasp 1034 is able to selectively position or repeatedly position the orientation of handle 996 for the most convenient orientation of reciprocating without jeopardizing the desired configuration for recessed pocket 942.
During the rasping process, it is noted that the rasp can cause slight vibration or movement of guide template 950 which is typically formed from a metal or other rigid material. In turn, this movement can cause supports 978 and 979, which are typically integrally formed with by 952, to wear against the articulation surface. To prevent unwanted wear, flexible pads can be positioned between supports 978 and 979 and the articulation surface. In other embodiments, all or portions of the supports 978 and 979 can be formed from a flexible material that will not damage the articulation surface. Such flexible materials can comprise a polymeric or rubber material. In yet other embodiments as discussed below in greater detail, the supports can be removed during the rasping process to as to avoid damage to the articulation surface.
Once recessed pocket 942 is finished, the rasp is removed and tunnel 400 is formed extending from pocket 942 to a location spaced apart from the articulation surface, such as the lateral or medial side of femur 530. As disclosed in various a embodiments depicted in the '941 application, guide template 950 can be used in association with a centering template and tunnel guide to facilitate formation of tunnel 400. In an alternative embodiment, it is again appreciated that the centering template and tunnel guide can be eliminated. That is, tunnel 400 can be drilled after removal of guide template 950 by starting at recessed pocket 942 and extending to the lateral or medial side of the femur 530. Because it is less critical where tunnel exits on the lateral or medial side, a tunnel guide is not required but could, if desired, still be used.
Once tunnel 400 is formed, a trochlear implant is then secured within the recessed pocket 942. Depicted in
In one embodiment viewed in a plane extending between sides 1076 and 1078 (
As depicted in
Ridge 1094 is typically aligned with channel 1080 so that trochlear implant 1064 can have a substantially uniform thickness. For example, in one embodiment bone apposition surface 1092 can be substantially complementary to articular surface 1068 so that implant 1064 has a substantially uniform thickness between surfaces 1068 and 1092. In other embodiments, implant 1064 may be slightly tapered along perimeter edge 1071. Thus, at all locations at least 2 mm in from the perimeter edge 1071, body 1066 has a thickness extending between the bone apposition surface 1092 and the articular surface 1068 that does not vary by more than 30%, 20%, or more commonly 15%. Other percentages can also be used. The actual thickness depends on the desired implant and is typically in a range between about 3 mm to about 10 mm.
Ridge 1094 is also configured to be complementarily received within channel 948 formed on recessed pocket 942. Bone apposition surface 1092 thus also has a continuous concave curvature extending between opposing ends 1072 and 1074. Because of the unique method in which pocket 942 can be formed, bone apposition surface 1092 can be formed having a smooth surface with no stepped shoulders or corners as required in many conventional implants. Implant 1064 can also be modified in the same manner as the other implants disclosed herein. For example, spikes or other forms of projections can be formed projecting from bone apposition surface 1092.
Because implant 1064 is configured to fit within pocket 942, implant 1064 has an outer perimeter having an asymmetrical configuration. In one embodiment, articular surface 1068 of implant 1064 has a centroidal location. Articular surface 1068 has a maximum radius extending from the centroidal location to perimeter edge and a minimum radius extending from the centroidal location to the perimeter edge, the minimum radius not being less than 70% and more commonly not being less than 80% of the maximum radius. Other dimensions can also be used. It is also appreciated that the alternatives as previously discussed with regard to implant 300 are also applicable to implant 1064.
Base 1102 comprises body 952, as previously discussed, having support 980 projecting from proximal end 958. First guide rail 982 has been eliminated but second guide rail 984 still upwardly projects from top surface 952 at side 964. As will be discussed below in greater detail, three mounting holes 988 are formed on side 964 while one mounting hole 988 is formed at distal end 960. A coupling hole 1103 (
As depicted in
In the above assembled configuration, guide template 1100 is positioned onto the distal end of femur 530 in substantially the same orientation as previously discussed with regard to
Each screw 990 comprises an elongated shaft 1132 having a first end 1134 and an opposing second end 1136. Threads 1138 are formed on second end 1136 while an enlarged head 1139 is formed at first end 1134. In the embodiment depicted, enlarged head 1139 comprises a flange 1140 that encircles and radially outwardly projects from first end 1134. An engagement head 1142 extends above flange 1140 and has a polygonal or non-circular cross section so that a driver can be connected to engagement head 1142 for selective rotation of screw 990. It is appreciated that enlarged head 1139 of screw 990 can come in a variety of different configuration. For example, enlarged head 1139 can be formed with a socket, slot(s) or other engaging surfaces to engage with other types of drivers. Each screw 990 is configured so that second end 1136 can be received within and slid through a corresponding passage 1128 of a guide sleeve 1120. Enlarged head 1139 is larger than passage 1128 and thus functions as a stop.
During mounting of guide template 1100, guide template 1100 with mount 1104 secured to base 1102 is positioned on the distal end of femur 530 in the same orientation as depicted in
Furthermore, each mounting hole 988 has a central longitudinal axis 989 along with each screw 990 is intended to extend. Mounting holes 988 are oriented at different angles relative to each other so that merely screwing screws 990 into femur 530 through guide sleeves 1120 positioned within mounting holes 998 causes guide template 1100 to be locked in place. That is, it is not necessary for screws 990 to directly bias guide template 1100 against femur 530. Due to the off-set angles of screws 990 and thus the off-set angles of guide sleeves 1120, it is sufficient if screws 990 merely secure guide sleeves 1120 in place to lock guide template 1100 in place.
Once guide sleeves 1120 are properly positioned, screws 990 are passed down through guide sleeves 1120 and screwed into femur 530. Screws 990 are advanced until flange 1140 biases against first end 1124 of each guide sleeves 1120, thereby securely fixing each guide sleeve 1120 to femur 530. It is noted that flange 1130 of guide sleeves 1120 need not bias against body 952 bounding mounting holes 988. Flanges 1130 primarily function to prevent guide sleeves 1120 from falling through mounting holes 988 during placement of guide template 1100, and in alternative embodiments flanges 1130 can be eliminated.
In part, guide sleeves 1120 function as guides for screws 990. That is, as a result of supports 978-980, the bottom of the mounting holes 988 are spaced above femur 530. This configuration helps ensure proper fitting of guide template 1100 without interference by body 952. However, as a result of the spacing between mounting holes 988 and femur 530, there is the potential for screws 990 to become misaligned from the central longitudinal axis of each corresponding mounting hole 988 as the screw 990 is passed from mounting hole 988 to femur 530. This misalignment can cause binding of the screw 990 against guide template 1100 which in turn can cause unwanted displacement or improper securing of guide template 1100. By using guide sleeves 1120 which extend from mounting holes 988 to or adjacent to femur 530, guide sleeves 1120 help maintain proper orientation and alignment of each screw 990.
Once all of screws 990 are secured in place so that the guide sleeves 1120 are secured in place, guide template 1100 is locked in place. In this position, mount 1160 is removed from base 1102 as depicted in
Once mount 1160 is removed, a rasp 1146 as depicted in
In addition to the other benefits of the present invention previously discussed, the above apparatus and process has other improvements over the prior art. For example, by using the inventive guide template and rasp, a shallow and precise pocket can be formed to receive the implant with minimal bone removal. The precise pocket provides for improved fitting between the implant and the pocket. Minimizing bone removal simplifies the procedure, minimizes trauma to the bone, and leaves more bone which significantly simplifies subsequent procedures where it may be necessary to replace the implant or perform a full arthroplasty. Furthermore, the process allows for smaller, thinner implants which can be easily mounted and adjusted.
As depicted in
Body 1166 typically has a minimal thickness so as to minimize size and thus simplify insertion within the tissue. In alternative embodiments, however, all or portions of top surface 954 and bottom surface 956 can be substantially flat by increasing the thickness of body 1166.
Projecting from proximal end 958 is a support 1170. In contrast to support 980 of template 1100, support 1170 has a mounting hole 988 extending threrethrough. Two other mounting holes 988 are also formed on side 964. As previously discussed, in one embodiment each mounting hole 988 has a central longitudinal axis that is oriented at a different angle than the others so as to support body 1166 is a suspended position over the bone. Coupling hole 1103 is also formed on side 964 to facilitate removable coupling between base 1162 and mount 1164.
Mount 1164 comprises a brace 1172 having a generally arched, L-shape configuration. Brace 1172 has a top surface 1174 and an opposing bottom surface 1176 each extending between a proximal end 1178 and an opposing distal end 1180. Brace 1172 also has an inside edge 1182 and an opposing outside edge 1184 both extending between surfaces 1174 and 1176. An elongated guide rail 1186 projects from bottom surface 1176 along or adjacent to inside edge 1182. Also projecting from bottom surface 1176 at distal end 1180 are spaced apart supports 1188 and 1189.
Although not required, in the depicted embodiment support 1188 is projecting from the distal end of guide rail 1186. Guide rail 1186 and supports 1188 and 1189 each have an outside face 1192 that is inwardly spaced from outside edge 1184 of brace 1172. As such a portion of bottom surface 1176 extending between outside face 1192 and outside edge 1184 forms a resting surface 1194. Extending through brace 1172 at distal end 1180 at a location between supports 1188 is a mounting hole 1196. A coupling hole 1114 extends through brace 1172 at proximal end 1170.
In contrast to guide template 1100 where supports 978 and 979 are at least partially positioned outside of opening 966 bounded by base 1102 (
In the above assembled configuration, a handle, such as handle 1116 in
In the above mounted position, screws 990 or other fasteners are passed through mounting holes 988 and 1196 so as to secure guide template 1160 to femur 530. It is appreciated that a guide sleeve 1120 (
As depicted in
Cutting mount 1207 has a cutting surface 1212 having apposing sides 1214 and 1216 extending between a proximal end 1218 and an opposing distal end 1220. Cutting surface is comprised of a plurality of teeth, such as teeth 1020 shown in
By reciprocating rasp 1200 side to side within opening 966 and advancing rasp 1200 between proximal end 958 and distal end 960, recessed pocket 942 as shown in
Set forth above are several different embodiments of the present invention. Other embodiments are also disclosed in the '941 application. It is appreciated that the different features of the different embodiments can be mixed and matched to produce a variety of other embodiments within the scope of the present invention. By way of example and not by limitation, each of the different implants can be made with or without an inlay of porous bone ingrowth material on the bone apposition surface; each different implant can have one or more different lines that are connected in one or more different ways; and each different implant can be made as an integral body or two or more separate parts. For example, each implant can comprise a metal tray that is mounted to the bone and a plastic bearing plate that is mounted to the tray. It is likewise appreciated that the different methods steps for the different embodiments can also be mixed and matched and used with other techniques. For example, the guide template having supports, such as supports 978-980, that are either fixed or removable can be used for resecting any type of articulation surface on any joint. Finally, it is again noted that the implants described herein are only by way of example and not by limitation. The present invention can also be used in association with resurfacing articulation surfaces of other orthopedic joints.
Finally, the above embodiments primarily discuss mounting implants on resected articulation surfaces. On occasion, however, a sufficient portion of a natural articulation surface has been worn down or otherwise removed by events other than surgical resection so that it is not necessary to resect the wear surface which is still functioning as a natural articulation surface. On these occasions, it is envisioned that the implant can be mounted directly on the worn natural articulation surface with minimal or no surgical resection of the articulation surface.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.