US20080058949A1 - Implants with Transition Surfaces and Related Processes - Google Patents

Abstract

Implants, and processes for installing them, which replace the medial condyle and portions of the patellofemoral channel but preferably not portions of the lateral condyle that articulate relative to the tibia. Processes are provided which allow proper location and orientation of an anterior resection and a distal resection on the femur, which make use of a transition point which can be designated on the bone, for navigating proper positioning of such implants. Proper positioning of the implant relative to the femur for insuring a smooth transition between lateral portions of the implant and the lateral condyle is thus reduced to determining proper medial/lateral location of the implant on the anterior and distal resections. Such implants and processes can allow, among other things, for controlled location and orientation of an implant on the bone which saves lateral compartment bone, which eliminates the need to sacrifice the anterior and posterior cruciate ligaments, and which is adapted for minimally invasive surgery with its attendant benefits.

Description

• This application claims the benefit of the following U.S. Provisional Applications Ser. No. 60/828158, filed Oct. 4, 2006, titled Instrumentation for Bicompartmental Knee; Ser. No. 60/824696, filed Sep. 6, 2006, titled Instrumentation for Bicompartmental Knee; and Ser. No. 60/825533 filed Sep. 13, 2006, titled Variable Transition Referencing Guide, the entire contents of each of which are hereby incorporated by reference.
FIELD OF THE INVENTION
• The invention relates to implants and processes for use in joint surgery, particularly knee replacement surgery. In certain embodiments, methods are provided for locating and using a transition point on the femur for proper positioning of resections that are intended to receive a femoral component during a surgical procedure. Implants are provided according to certain embodiments that replace the medial condyle and part of the patellofemoral channel of the femur, but preferably do not replace portions of the lateral condyle that articulate with respect to the tibia. According to certain embodiments, a resection guide that includes a guide surface for performing a transition resection can be positioned relative to the resections on the bone formed using the transition point. The resection guide can then be moved on the resection surfaces to position the transition resection guide surface to form a transition resection that allows implant external surfaces to transition smoothly to portions of the lateral condyle that articulate with respect to the tibia.
BACKGROUND
• Knee arthritis and trauma in various forms can cause loss of joint cartilage, including for example, osteoarthritis, excessive wear or sudden trauma, rheumatoid arthritis, or infectious arthritis. When joint cartilage is worn away, the bone beneath the cartilage is left exposed, and bone-on-bone contact can be very painful and damaging. Other types of problems can occur when the bone itself becomes diseased. One conventional solution for these types of joint problems takes the form of total knee replacements. In a total knee replacement (TKR), the proximal end of the tibia is replaced with a tibial component, the distal end of the femoral bone is replaced with a femoral component, and the patella is replaced with a patellar component. Such procedures often require sacrifice of the anterior and posterior cruciate ligaments.
• However, many patients who develop knee arthritis experience issues isolated to the medial (inner) compartment and the patellofemoral (knee cap) part of the joint, while the lateral (outer) compartment of the joint remains healthy. The conventional treatment for such patients is either the combination of a unicompartmental knee in conjunction with a patellofemoral implant or the use of a total knee implant, which requires removal of the healthy lateral condyle. However, one recent solution is a hybrid femoral component that preserves the healthy lateral condyle as well as the anterior and posterior cruciate ligaments, and only replaces the medial compartment and patellofemoral joint. (Such a hybrid femoral component may be used in conjunction with a unicompartmental tibial tray, which only requires resurfacing of part of the tibia as well). A hybrid femoral component requires a smaller incision and preserves ligaments that can help the knee retain its natural kinematics. It can be implanted using a procedure called a bicompartmental knee replacement.
• A bicompartmental knee replacement is a procedure that replaces only the medial (inner) parts of the femoral and tibial components. It does not resurface or resect the lateral parts of the knee (including the distal femoral articular cartilage), and as such, can allow the anterior and posterior cruciate ligaments to be retained. Bicompartmental knee replacements have a number of advantages over total knee replacements. Because the outer lateral portion of the joint is not resurfaced, the incision made may be smaller, resulting in less pain, quicker recovery time, and less blood loss. Also, because certain ligaments do not need to be sacrificed, a greater stability of the knee can be maintained.
• The femoral component used in such a replacement is often called a monolithic implant. It has an anterior portion and a medial condyle portion, without a lateral condyle portion (again, because as much of the lateral bone as possible is retained). As with most typical femoral implants, the component may be made of titanium, stainless steel, cobalt-chrome, zirconium, oxinium, any combination thereof, or any other appropriate material that has sufficient strength and biocompatibility for use in knee replacement surgery.
• While performing bicompartmental knee replacement with a monolithic implant, it is necessary to locate the implant on the bone properly, in order, among other things, to achieve proper articulation in both the medial and lateral compartments of the knee between femur and tibia, as well as proper articulation between the patella and the femur or femoral component interface. For example, the surgeon wants to retain as much healthy bone as possible while removing the diseased bone, but also needs to consider the depth of the medial condyle portion of the implant in order to ensure that there is a smooth transition from the implant to the bone and to maintain proper performance of the reconstructed knee in flexion and extension.
• With conventional patellofemoral replacements, one popular current method for preparing the bone to receive an implant is to use an osteotome in conjunction with a trochlea trial to mark the boundary of the transition between the implant and the bone. However, there is no known solution or method for marking the boundary for bicompartmental knee replacement. Accordingly, such surgeries are conventionally performed using traditional total knee replacement instrumentation, without any additional components that help identify certain reference points. For example, recessing the implant to the cartilage on the lateral side is important, and without specific instrumentation or techniques for this type of procedure, the surgeon is left to estimate the cuts that are needed.
SUMMARY
• Implants and processes for installing them are provided for replacing the medial condyle of the femur and portions of the patellofemoral channel, preferably without replacing portions of the lateral condyle which have not been subject to degradation. According to some such processes, instrumentation may be used which allows for an anterior resection and a distal resection of the femur that are properly located and oriented so that proper positioning of the implant to ensure smooth transition between bone and implant on lateral outer surfaces of the femur, as well as proper functioning of the reconstructed knee in flexion and extension, can be reduced to determining the proper medial/lateral position of the implant on those resections.
• In some cases, an anterior resection instrument can be used to form an anterior resection that is properly located in the anterior/posterior dimension and in interior/exterior rotation relative to the femur. A transition point can then be chosen, which can correspond if desired to the distal-most point on a lateral portion of the anterior resection, for proper proximal/distal or superior/inferior location and valgus/varus rotation of a distal resection. A distal resection guide, of a type which can be used with cutting devices such as saws, or of a type which can be used with milling devices, or a type which can be used with both, and which can be positioned and oriented relative to the transition point may be used to perform this distal resection of the medial condyle. Alternatively, a single such instrument can be used to perform the anterior resection and the distal resection.
• In some cases, an additional resection guide can be used which can be positioned properly on the anterior resection and the distal resection and then slid or otherwise manipulated medially or laterally to determine proper location of a transition resection which will help form the transition between implant and bone on outer surfaces of lateral portions of the femur. Alternatively, one or more of the transition resection guide surface, the distal resection guide surface, and also the anterior resection guide surface can be included in one instrument or resection guide.
• In some cases, implants adapted to be installed on such resected femurs feature a transition surface which corresponds to the transition resection that has been controllably located and oriented relative to the femur as mentioned above. Such a transition when properly located aims to create a smooth transition from implant surface to bone surface by, among other things, reducing surface discontinuity such as implant and/or bone overhang. Preferably, the transition between bone and implant in such cases is located so that only anatomical lateral condyle surfaces articulate relative to the tibia in the knee joint in which the implant has been installed.
BRIEF DESCRIPTION
• FIG. 1 is a front view of an implant according to certain embodiments of the invention.
• FIG. 2A is a front view of the implant ofFIG. 1 in place on a model of a human knee.
• FIG. 2B is a navigational rose showing translational and rotational axes which may constitute useful references in positioning and orienting body parts, instruments and implants of certain embodiments of the invention.
• FIG. 2C is a front view corresponding generally toFIG. 2A with the knee shown in approximately full extension.
• FIG. 2D is a front view of the knee ofFIGS. 2A and C with the knee shown in approximately ninety degrees flexion.
• FIG. 2E is a perspective lateral view of an implant according to one embodiment of the invention made for a left knee.
• FIG. 3 is a front view of a human femur on which has been performed an anterior resection according to one embodiment of the invention.
• FIG. 4 is a perspective view of an anterior resection guide according to one embodiment of the invention in place on a patient's femur to perform an anterior resection such as shown inFIG. 3.
• FIG. 5 is a perspective view of the anterior resection guide ofFIG. 4 in place where the anterior resection has been performed.
• FIGS. 6A-6F are schematic distal and front views of human femurs on which anterior resections according to one embodiment of the invention have been performed, and which show effect of depth of the anterior resection on its shape and size.
• FIGS. 7A-7F are schematic distal and front views of human femurs on which anterior resections according to one embodiment of the invention have been performed, and which show effect of internal/external rotation of the anterior resection on its shape.
• FIG. 8A is a front view of a distal resection guide according to one embodiment of the invention in place on a human femur, to perform a distal resection on the medial condyle according to one embodiment of the invention.
• FIG. 8B is a front view of a distal resection guide according to one embodiment of the invention in place on a human femur, with a shim, to perform a distal resection on the medial condyle according to one embodiment of the invention.
• FIG. 9 is a front view of a human knee, with the femur in approximately ninety degrees flexion, showing the distal part of the femur after a distal resection to the medial condyle according to one embodiment of the invention has been made.
• FIG. 10 is a perspective front view of an anterior/posterior resection guide according to one embodiment of the invention.
• FIG. 11 is a perspective medial view showing the resection guide ofFIG. 10 in place on a human femur, in contact with the anterior resection and the medial condyle distal resections, so that it can be positioned (as by sliding) medially or laterally on the femur in contact with those resections, to position the transition cutting surface of the resection guide in order to yield a smooth transition between implant and bone on the lateral side of the knee.
• FIG. 12 is a perspective posterior view of the resection guide ofFIGS. 10 and 11 in place on a human femur.
• FIG. 13 is a perspective medial side view of the resection guide ofFIGS. 10-12 in place on a human femur.
• FIG. 14 is a perspective medial front view of a resection guide according to another embodiment of the invention positioned on a human femur.
• FIG. 15 is a perspective top view of the resection guide ofFIG. 14 positioned on a human femur.
• FIG. 16 is a perspective lateral front view of the resection guide ofFIG. 14 positioned on a human femur.
• FIG. 17 is a perspective medial front view showing a human femur on which anterior, distal, chamfer and transition resections have been made according to one embodiment of the invention, using resection guides according to certain embodiments of the invention.
• FIG. 18 is a perspective medial front view showing an implant according to one embodiment of the invention in place on a femur.
• FIG. 19 is a front view of a resection guide according to an alternate embodiment of the invention, for use with milling devices for forming resections on the femur.
• FIG. 20 is a superior view of the guide ofFIG. 19 showing certain milling devices.
• FIG. 21 is a superior view of the guide ofFIG. 19 without an intramedullary rod.
• FIG. 22 is another superior view of the guide ofFIG. 19.
• FIG. 23 is a side view of the guide ofFIG. 19.
• FIG. 24 is a perspective view of the guide ofFIG. 19.
• FIG. 25 is a side perspective view of the guide ofFIG. 19.
• FIG. 26 is a superior view of a guide according to another alternate embodiment of the invention.
• FIG. 27 is a perspective view of the guide ofFIG. 26.
• FIG. 28 is a superior view of the guide ofFIG. 26.
• FIG. 29 is a superior view of the guide ofFIG. 26.
• FIG. 30 is a superior view of the guide ofFIG. 26.
• FIG. 31 is a side view of the guide ofFIG. 26.
• FIG. 32 is a perspective view of the guide ofFIG. 26.
• FIG. 33 is a side view of a guide according to another alternate embodiment of the invention.
• FIG. 34 is a perspective view of the guide ofFIG. 33.
• FIG. 35 is a superior view of the guide ofFIG. 33.
• FIG. 36 is a superior view of the guide ofFIG. 33.
• FIG. 37 is a perspective view of the guide ofFIG. 33.
• FIG. 38 is a perspective view of a milling guide used with a milling apparatus which rotates about a medial/lateral axis according to an alternate embodiment of the invention.
• FIG. 39 is a perspective view of acollet182 for use in connection with aguide180 according to another alternate embodiment of the invention.
• FIGS. 40A and B are side and front views, respectively, of the collet ofFIG. 39.
• FIG. 41 is a perspective view of a resection guide according to another alternate embodiment of the invention.
• FIG. 42A andFIG. 42B are side and front views, respectively, of the guide ofFIG. 41.
• FIG. 43 is a perspective view of the guide ofFIG. 41.
• FIGS. 44A and 44B are front and side views of the guide ofFIG. 41.
• FIG. 45 is a perspective view of the guide ofFIG. 41.
• FIGS. 46A and 46B are front and side views of the guide ofFIG. 41.
• FIGS. 47A and 47B are side views of the guide ofFIG. 41.
• FIGS. 49A and 49B show a femur resected using the guide ofFIG. 41.
DETAILED DESCRIPTION
• FIGS. 1 and 2A are front views of animplant10 according to an embodiment of the invention.Implant10 is adapted to be installed on thedistal portion12 of ahuman femur14. The femur can be that of a human or other being with appropriate hinge joints.FIG. 2A shows animplant10 placed on a sawbones model of ahuman femur14. Anatomically, thefemur14 cooperates with thetibia16 to form the knee joint18. Thedistal portion12 of thefemur14 includes two condyles, amedial condyle20 and alateral condyle22. These condyles articulate (move in gross motion, whether rotational or translational or both) relative to thetibial plateau24 which is a surface on theproximal portion26 oftibia16. Not shown is a patella which is connected to a patella tendon, also not shown, which in turn inserts on the tibia and attaches to the head of quadricep muscles to apply traction for extension of the knee joint. The patella tracks, as by sliding, in thepatellofemoral channel30.Patellofemoral channel30 ofimplant10 shown inFIG. 2A replicates the patellofemoral channel in the anatomical knee, which is a channel on anterior and distal surfaces of the femur betweencondyle20 andlateral condyle22 for tracking of the patella during flexion and extension of theknee18. Ordinarily, thefemur14 andtibia16 do not contact each other but instead each bear against menisci (not shown) which are interposed betweencondyles20,22 on the one hand andtibial plateau24 on the other hand. An anterior cruciate ligament (not shown) and a posterior cruciate ligament (not shown) are among two of the ligaments which are connected to both thefemur14 and thetibia16. One of the primary purposes of these ligaments is to control translation of thefemur14 and thetibia16 relative to each other and in an anterior/posterior direction. These two ligaments in particular are important for knee stability and it is often preferred to preserve them if possible during knee surgery.
• FIG. 2B is a navigational rose that corresponds toFIG. 2A. It shows the three degrees of translational freedom and the three degrees of rotational freedom that define the six degrees of potential freedom of motion in a knee such as the one shown inFIG. 2A. Translationally, the degrees of freedom are lateral/medial, anterior/posterior and superior/inferior. Rotationally, the degrees of freedom are flexion/extension, internal/external and varus/valgus. In that respect,FIGS. 2C AND 2D show aknee18 with animplant10 according to an embodiment of the invention installed on the femur with the knee at essentially zero degrees of flexion, and approximately 90 degrees of flexion, respectively.
• FIG. 1 shows animplant10 according to an embodiment of the invention together with atibial implant38 and acorresponding insert40 which together form a prosthesis for reconstructing a portion of theknee18. Theimplant10 preferably does not replace some portions of thelateral condyle22 that articulate against the menisci in thelateral compartment42, and thus indirectlytibia16. However, it does replace portions of theknee18 such as those discussed above that are often found to be more prone to osteoarthritis—the portions of themedial condyle20 that articulate against medial compartment menisci and thus indirectly against tibia16 (for the prostheses installed) and thepatellofemoral channel30. Such a structure is beneficial for a number of reasons, including that thelateral compartment42 of the knee18 (which includes portions of thelateral condyle22 and lateral portions of tibia16) is preserved with multiple beneficial effects. In addition to improved kinematics and greater stability, such partial knee replacements can reduce contact of soft tissue connecting thefemur14 and thetibia16 or lateral and medial sides of the knee with theimplant10, and thus lesser wear, particularly on the lateral side ofknee18. Additionally, the implant can be installed using minimally invasive surgical procedures to shorten the hospital stay, simplify the surgical procedure, and improve therapy prospects and long-term results, among other benefits. Furthermore, the implant can be installed without sacrificing the anterior cruciate ligament34 and the posterior cruciate ligament36 (not shown).
• Implant10 andtibial implant38 may be made of conventional metallic or other materials conventionally used for knee prosthetics, including without limitation cobalt-chrome alloys, alloys which have been treated with zirconium oxide or other treatments, stainless steel materials and other metals or materials.Insert40 may be formed of conventional ultra high molecular weight polyethylene of the sort conventionally used to form inserts in knee prosthetics, or it may be formed of any desired material.
• FIG. 2D is a front view of the anterior portion oftibia16 withknee18 in approximate 90 degrees of flexion. The distal portion offemur14 is evident, withlateral condyle22 intact and theimplant10 replacing portions of themedial condyle20 and thepatellofemoral channel30. (Thefemoral head50, which forms part of the hip socket, can also be seen in this view and can give some degree of intuitive appreciation for why it may be thatmedial compartment52 of the knee is sometimes more prone to osteoarthritis and other wear than islateral compartment42.)
• As shown inFIG. 2D,distal portion54 ofimplant10 generally corresponds to the portion of theimplant10 between theanterior portion44 and the posteriormedial condylar portion56 ofimplant10. It also corresponds generally to distal regions of themedial condyle20 andpatellofemoral channel30 of thefemur14. On the medial side of theknee18, portions of distal articulatingsurfaces58 ofimplant10 articulate againsttibial insert40 which itself is positioned relative totibial implant30 on proximal portions of thetibia16 where thetibial implant38 and insert40 are used. (In circumstances where the tibial components are not used, distal articulatingsurfaces58 ofimplant10 can articulate against menisci and tibial plateau24). On the lateral side of the knee,FIG. 2D makes evident a beneficial result ofimplant10, that the lateral distal surfaces of thefemur14 and thetibia16 remain in place to articulate relative to each other. According to this embodiment, the lateral compartment of theknee42 is left in place so that theimplant10 does not articulate with thetibia16 in that compartment. Rather, thetransition62, discussed below, between theimplant10 and the lateral articulating surfaces of thefemur14 is angled and is located sufficiently anterior on the lateral side of thefemur14 to reduce chances of such articulation, while yet providing sufficient replacement of portions of thepatellofemoral channel30 of thefemur16 which often suffer arthritic or other degradation when themedial condyle20 does.
• As shown inFIG. 2D, posterior medial articulatingsurfaces60 ofimplant10 articulate againstinsert40 at greater degrees ofknee18 flexion. In circumstances whereimplant38 and insert40 are not used, the posterior medial articulatingsurfaces60 articulate against menisci and thustibia16 indirectly.
• FIG. 2D shows, on the lateral side of theknee18, a transition portion ofimplant10 of this disclosed embodiment of the invention which includestransition62. The structure of thisimplant10 aims to create a smooth transition from the naturalbone lateral condyle22 material to theimplant10 material. Atransition62 can be considered smooth if it does not sufferundue implant10 or bone surface overhang or discontinuity betweenimplant10 and bone. Additionally, thetransition62 with its angled resection of bone does not require any resection of the anterior cruciate ligament or posterior cruciate ligament. The reasons for this include that resections required forimplant10 do not require cutting of those tissues during minimally invasive surgery or otherwise, and that no portions of theimplant10 interfere with those tissues when theimplant10 is inserted into theknee18 and positioned on thefemur14 during minimally invasive surgery. Other advantages of the structure and shape ofimplant10 are evident to a person of ordinary skill in the art fromFIG. 2D (as well as other figures and other portions of this document) and bearing in mind how theimplant10 is installed during surgical procedure. Additionally, as mentioned above, thetransition62 feature provides animplant10 structure where the lateral meniscus preferably does not come into contact with the femoral implant, but rather articulates preferably only against natural bone of thelateral condyle22.
• Accordingly,FIG. 2D shows a distal view of a femoral implant which differs from implants such as conventional implants used in bicompartmental knee arthroplasty, because (among other things) it omits lateral condylar distal and proximal portions and instead truncates the lateral structure withtransition62.
• FIG. 2E shows a perspective view of theimplant10 ofFIG. 1 from another perspective which is helpful in understanding thetransition62 and other geometric and navigational aspects and features of certain embodiments of the invention. Among other things, the inner surfaces of theimplant10 are shaped and oriented in a manner that allows precise and accurate positioning ofimplant10 onfemur14 in order, among other things, to replicate motion of the natural knee and optimize the benefits of maintaining natural bone in thelateral condyle22 usingtransition62 or similar constructs and related geometry and structures, while producing a smooth transition from bone to implant acrosstransition62.
• FIG. 2E shows a navigational rose which is helpful in understanding the orientation of various surfaces ofimplant10. Anterior articulatingsurfaces46, distal articulatingsurfaces58 and posterior medial articulatingsurfaces60 are evident. A transition portion ofimplant10 includingtransition62 is also evident. A number of surfaces are shown inFIG. 2E as cooperating to form inner surfaces ofimplant10. As is known to those who design and install femoral implants, these surfaces are formed with a view to fitting to distal areas of thefemur14 which have been resected to correspond to the surfaces. Some or all of the surfaces may be cemented to the bone or may contain bone in-growth material such as sintered beads or wires or other porous or similar material which enhances growth of bone into the surface of the implant, or they may feature any desired surface characteristics. In the particular implant shown inFIG. 2E, all of these surfaces on the inner side ofimplant10 are substantially planar, that is generally flat in the shape of a plane but including the possibility of discontinuities such as bone ingrowth material, indentations, raised areas, pegs, openings and other surface discontinuities which could otherwise technically be said to remove a surface from the strict category of being substantially in a plane or being planar. However, implants according to the invention can also feature one or more interior surfaces which are curved, to fit resected surfaces which have been formed by resection guides of the present invention that resect curved surfaces onto bone as by using milling, grinding, routing, machining, or similar apparatus which is capable of forming curved surfaces on materials (hereinafter “milling” devices or apparatus).
• In theparticular implant10 shown inFIG. 2E, anteriorinner surface64, distalinner surface66,posterior chamfer surface68 and posteriorinner surface70 are intended substantially to abut corresponding portions of resected bone or shims or inserts which are interposed between bone and implant to compensate for undue bone loss or for other reasons. Anteriorinner chamfer surface72 is disposed between distalinner surface66 and anteriorinner surface64 to intersect, preferably as a line, anterior intersection line74.
• Additionally,transition surface76 which is also preferably but not necessarily substantially planar, extends along lateral portions ofimplant10 to intersect anteriorinner chamfer surface72, preferably in a line, thelateral intersection line78. In this particular structure of this embodiment of the invention shown inFIG. 2E, the anteriorinner surface64, anteriorinner chamfer surface72, andtransition surface76 intersect at a point on lateral portions of theimplant10, theconvergence point80. As a corollary in this construct, anterior intersection line74 andlateral intersection line78 intersect atconvergence point80. In a similar fashion, planes of the anteriorinner surface64,transition surface76 and distalinner surface66 intersect atimplant point83.Implant point83 in some embodiments is located laterally, when theimplant10 is installed onfemur14, totransition point82.
• In the particular implant shown inFIG. 2E,transition surface76, like other inner surfaces, is planar, although it can be curved in other implants according to other embodiments of the invention. A primary aim of some embodiments of the invention is to define and use a reference or navigation point on the bone for positioning and orienting resections and therefore implant10. So long as a navigational point such as a transition point on the bone can be designated to properly form resections that will permit an implant to be properly positioned and oriented on the femur for good knee kinematics and performance, the particular shape of the resected surfaces and corresponding implant surfaces, whether curved or planar, and how the resections are formed, whether by sawing, milling or otherwise, matter less and can be accommodated within the principles of the invention.
• FIG. 3 is a front view of distal portions of afemur14 which shows ananterior resection84 and atransition point82 designated on the bone that can be used to position and orient a distal resection100 (discussed below) of thefemur14 that, in combination with the anterior resection, ultimately allow positioning of an implant such as shown inFIGS. 1 and 2 on the bone. Accordingly, among other things, the implant can be located and oriented properly relative to mechanical axes of the anatomy and otherwise for proper flexion/extension and other kinematics and functioning of the knee, and also to allow the transition from bone toimplant10 acrosstransition62 to be smooth, so that for instance it suffers minimal discontinuities such as overhang of implant or bone.
• In thefemur14 shown inFIG. 3, anterior portions of thefemur14 have been resected to formanterior resection84 using instrumentation that corresponds to the implant shown inFIGS. 1 and 2, as discussed more fully below.Anterior resection84 will correspond to anterior portioninner surface64 ofimplant10 when theimplant10 is installed onfemur14.Anterior resection84 is often hourglass in shape with alateral lobe86 and amedial lobe88. Thetransition point82 can be chosen as the distal-most point of lateral portions ofanterior resection84, which in the drawing ofFIG. 3 is the distal-most point on thelateral lobe86 ofanterior resection84. What point is distal-most for purposes of determining the location of thetransition point82 on the bone can be considered as intersection of a line that is parallel to a line connecting distal-most portions of the medial andlateral condyles20,22.
• Alternatively, location oftransition point82 can be at another location inside or outside of anterior resection, or at any other desired point on the bone. What matters primarily isanterior resection84 be formed properly on thefemur14 in the anterior/posterior dimension and in internal/external rotation (seeFIGS. 6A-6F) and that a transition point can be designated relative to which a distal resection100 (discussed below) can be formed properly in the superior/inferior dimension relative to theanterior resection84 and oriented properly in varus/valgus rotation. Proper positioning of animplant10 with corresponding surfaces can then be achieved so that among other things, the implant can be located and oriented properly relative to mechanical axes of the anatomy and otherwise for proper flexion/extension and other kinematics and functioning of the knee, and also to allow the transition from bone toimplant10 acrosstransition62 to be smooth, so that for instance it suffers minimal discontinuities such as overhang of implant or bone.
• FIG. 4 shows ananterior resection instrument90 according to one embodiment of the invention for performing ananterior resection84 onfemur14 to accommodate theimplant10 ofFIGS. 1 and 2.Instrument90 is coupled to anintramedullary rod92 which has been inserted into thedistal portion12 offemur14. An extramedullary rod can be used instead of the intramedullary rod. Beforeinstrument90 is coupled tointramedullary rod92, a template or other device may be employed to mark geometry on thefemur14, such as the anterior-posterior line and/or a line perpendicular to it. Theinstrument90 may be coupled to the intramedullary rod and aligned with such indicia to ensure thatanterior resection84 is properly oriented and located. Theinstrument90 shown inFIGS. 4 and 5 includes abody94 to which may be connected in sliding fashion for adjustment in the anterior-posterior direction, an anteriorresection guide surface96.Body94 may be connected tointramedullary rod92 or extramedullary rod with a collar or other desired structure to allow for translational and/or rotational freedom as desired. In the embodiment shown inFIG. 4,body94 can be controllably constrained from rotating in any direction relative to the rod, although the rod itself may be rotated in bone to align thebody94 with the indicia marked on thefemur14. However,body94 can move in the anterior-posterior direction relative to the rod, and theguide surface96 can move relative tobody94 in the same direction.Body94 is also able to slide relative to the rod in the superior/inferior direction. In the particular embodiment shown inFIGS. 4 and 5, thebody94 is constrained from translating in the medial/lateral direction, although that need not necessarily be the case. Apaddle98, with or without other components connected tobody94, can be used to determine the appropriate size ofimplant10 and thus, in some aspects of the invention, in some cases, size of certain instrumentation which will be used to install theimplant10. Once theinstrument90 and particularlybody94 and anteriorresection guide surface96 have been properly positioned, guidesurface96 may be used to createanterior resection84.
• FIGS. 6A-F show effects of moving theguide surface96 in the anterior-posterior direction to perform theanterior resection84.FIGS. 6A and 6B show ananterior resection84 made with theguide surface96 position in a “neutral” anterior-posterior position. If theguide surface96 is positioned posteriorly to that “neutral” position,FIG. 6D shows how the shape and size ofanterior resection84 changes and enlarges, respectively. If theguide surface96 is positioned more anterior to the “neutral” position,FIG. 6F shows that theanterior resection84 diminishes in size and changes shape. Although the shape of each of the particularanterior resections84 shown inFIGS. 6B,6D and6F are hourglass and featurelateral lobes86 andmedial lobes88, it is possible that at some point the shape could be other than hourglass such as if theguide surface96 is positioned sufficiently posterior of the “neutral” position to make it more heart shaped, or if it is positioned sufficiently anterior of the “neutral” position to cause theanterior section84 to take the form of two ovals or other rounded closed areas.
• FIGS. 7A-F show effects of internal and external rotation of theguide surface96 relative to intramedullary orextramedullary rod92 to perform the resection.FIG. 7B shows theanterior resection84 formed when theguide surface96 is positioned in a neutral internal-external rotational orientation.FIG. 7D shows theanterior resection84 when theguide surface96 has been positioned with two degrees of internal rotation relative tointramedullary rod92. The size of thelateral lobe86 has diminished and the size themedial lobe88 has increased. As shown inFIG. 7F, two degrees of external rotation of theguide surface96 relative tointramedullary rod92 to form theanterior resection84 causes the opposite effect: thelateral lobe86 increases in size and themedial lobe88 decreases in size.
• FIGS. 6 and 7 show that positioning of the anteriorresection guide surface96 and the anterior-posterior translational and the internal-external rotational direction can change the size and shape of theanterior resection84 and therefore in some embodiments the location of thebone transition point82 that is employed to create the rightdistal resection100/anterior resection84 location and orientation to allow proper positioning ofimplant10 as shown inFIGS. 1 and 2.
• After theanterior resection84 has been performed using this particular embodiment of the invention,instrument90 may be removed from theintramedullary rod92 and adistal resection instrument102 coupled to thatintramedullary rod92 for performing adistal resection100 on the medial condyle of thefemur14.FIGS. 8A and 8B show one suchdistal resection instrument102 according to this embodiment of the invention.
• Distal resection instrument102 shown inFIGS. 8A and 8B includes a distalresection guide surface104 and structure for connecting it to theintramedullary rod92. Preferably, that structure allowsdistal resection guide104 to be adjusted in at least varus/valgus rotational and superior/inferior translational directions relative to therod92. The structure connecting the distalresection guide surface104 and theintramedullary rod92 can include, for example, acollet106 and abody108. Thecollet106 can be positioned on theintramedullary rod92 in sliding relationship and connected directly or indirectly tobody108 which can be connected directly or indirectly to resectionguide surface104. For example, guidesurface104 can be connected in sliding relationship tobody108 so that it can move relative tobody108 in anterior/posterior direction but be constrained in the other degrees of freedom with respect tobody108.Collet106 can include indicia to select and/or indicate magnitude of rotation ofguide104 in the varus/valgus direction. One form ofsuch indicia110 can be seen on the top surface ofcollet106 andFIG. 8B. Alternately, a series of collets can be provided for selection by the surgeon to accommodate various angles of varus/valgus. Distalresection guide surface104 can also contain a plurality ofopenings112 to receive pins for pinning it to the bone when properly positioned, for example by pinning it to theanterior resection84.
• Adistal resection100 can be performed on themedial condyle20 such as by usinginstrument102 as follows. Other instrumentation can also be used, and can suffice if it allows a distal resection to be made to themedial condyle20 which substantially passes through or is navigated relative totransition point82 and is correctly oriented in the varus/valgus direction. With reference toFIGS. 8A and 8B,distal resection instrument102 can be placed onintramedullary rod92 and positioned by sliding so thatbody108 is positioned correctly to locate distalresection guide surface104 so that it can be positioned and oriented relative to thebone transition point82 and rotated in varus/valgus so that adistal resection100 may be made usingresection guide surface104 which passes through, near or suitably relative to,transition point80 and is properly oriented in varus/valgus. It may be desirable to position theresection guide surface104 so that thedistal resection100 can pass proximal to thetransition point82 or, if desired, distal to it. Once the distalresection guide surface104 has been properly positioned relative to intramedullary, extramedullary orother rod92, it can be pinned toanterior resection84, if desired, to perform thedistal resection100. Accordingly, therod92,body108 andcollet106 can be removed from the bone to leave distalresection guide surface104 retained in place by the pins. Resection can also be performed without pins if desired, by relying onrod92 and the other structure ofinstrumentation102 to retain theresection guide surface104 in place whileresection100 is being performed.
• To serve as a distalresection guide surface104index114, a portion of the flat surface of theresection guide surface104 can be employed to visually align the distalresection guide surface104 with thetransition point82, or to place this portion of theresection guide surface104 near, such as proximal or distal relative to, thetransition point82 so thatdistal resection100 will pass through, near or suitably relative to,transition point82. Alternatively,index114 can include a physical indicium (not shown) such as a mark, engraving, raised portion, or other desired indicium on any portion of the distalresection guide surface104.
• After thedistal resection100 has been performed, distalresection guide surface104 can removed from the bone (ascan instrumentation102 andintramedullary rod92 if they were left in place).
• FIG. 9 shows a distal view of adistal resection100 of themedial condyle20 of afemur14 performed using instrumentation as shown inFIGS. 8A and 8B. At this stage, after thedistal resection100 has been performed, the position and orientation of animplant10 have been defined in at least four degrees of freedom by resecting in accordance with certain embodiments of the invention as disclosed above:
• anterior/posterior translation as defined by theanterior resection84;
• superior/inferior translation as defined by thedistal resection100;
• internal/external rotation as defined by theanterior resection84; and
• varus/valgus rotation as defined by thedistal resection100.
• Thus, essentially all that remains for determining proper location and orientation of theimplant10 on thefemur14 is medial/lateral positioning on theanterior resection84 anddistal resection100.
• For such medial/lateral positioning, atransition resection guide116 according to an embodiment of the invention as shown inFIGS. 10-13, or other desired instrument, can be used. Among other things, theresection guide116 shown in those FIGS. can be used to createtransition resection118 andanterior chamfer resection120. Essentially, any structure is sufficient to perform these resections if atransition resection118 can be performed using the instrumentation which positions properly thetransition surface76 ofimplant10 or other implant according to the invention with reference to location and orientation of bothanterior resection84 anddistal resection100.
• Resection guide116 as shown inFIGS. 10-13 can include a finger orother index122 for aligningguide116 withtransition point82.Index122 can correspond to a relevant landmark on theimplant10, such as a lateral outer extremity of theimplant10, or with a predetermined lateral/medial and/or superior/inferior offset distance, to a point located relative to the implant point81. Theindex122 may be of any particular structure or shape, including virtual if desired rather than physical. It can be connected tobody124 ofresection guide116 as by aflange126 which has, on its posterior side as seen best inFIG. 13, an anteriorresection alignment surface128. Anteriorresection alignment surface128 can be used to positionresection guide116 as by positioningalignment surface128 flat againstanterior resection84.
• Thebody124 or any other desired portion ofresection guide116 can include a distalresection alignment surface130 which can be used to positionresection guide116 as by positioning it flat againstdistal resection100.Resection guide116 may thus be positioned against thefemur14 for proper resection oftransition resection118 andchamfer resection120 by moving anteriorresection alignment surface128 onanterior resection84 and distalresection alignment surface130 ondistal resection112 while aligning orpositioning index122 medially or laterally to positiontransition resection guide134 properly for a smooth transition of bone to implant acrosstransition62 which, for instance, features minimal discontinuities such as overhang of implant or bone. One way to achieve that result using theguide116 shown inFIGS. 10-12 is to positionindex122 laterally/medially to an extent that shows the surgeon where the lateral extremity of theimplant10 will be positioned relative to the bone, if atransition resection120 is performed using transitionresection guide surface134 onguide116 withguide116 in that position. Condyle marks125 on posterior surfaces of guide116 (seeFIG. 12) corresponding, for example, to condyle width, can also be used in combination with theindex122 for this purpose.Marks125 orindex122 may be used independently, or guide116 can include any other marks or indices for helping the surgeon determine where best to position theguide116 and thus implant10 laterally/medially for performing thetransition resection118 at a location that causes minimal surface discontinuity acrosstransition62 betweenimplant10 and bone.
• Transition resection guide116 can also contain a chamferresection guide surface132 for forming an anterior chamfer surface on the bone corresponding to chamfersurface72 of the implant10 (seeFIG. 2E) and a drill guide bore136 that is tangent to chamferresection guide surface132 and transitionresection guide surface134, or otherwise corresponds to their intersection.Guide116 can if desired include a drill guide bore136 which can operate as follows: Once theresection guide116 has been properly positioned on thefemur14 as disclosed above, a drill may be aligned through drill guide bore136 to form abore138 in the bone of thefemur14 that will correspond tolateral intersection78 on the inner surface ofimplant10 that extends fromconvergence point80 in an angular fashion to help form the intersection betweentransition surface76 of the implant and anteriorinner chamfer surface72 of implant10 (seeFIG. 2E).Transition resection118 can then be performed using transitionresection guide surface134, andchamfer resection120 can then be performed using chamferresection guide surface132. These resections can be performed without using drill guide bore136 to form abore138, and drill guide bore136 can be omitted fromguide116 if desired.
• Anterior/posterior resection guide116 may also include a posteriorresection guide surface137 for forming aposterior resection139 that corresponds to posteriorinner surface70 of theimplant10. Similarly,resection guide116 can include a posterior chamferresection guide surface140 for forming aposterior chamfer resection142 on the bone that corresponds to posterior chamferinner surface68 ofimplant10. These latter resections are shown inFIG. 13.
• FIGS. 14-16 show an alternative form ofresection instrumentation144 which uses asingle instrument144 for performing both aanterior resection84 and thedistal resection100. Anteriorresection guide surface147 can be used to perform ananterior resection100 afterinstrument144 has been adjusted so that anteriorresection guide surface147 is properly located in the anterior/posterior dimension and in internal/external rotation. Distalresection guide surface146 is connected through a structure which allows it to be positioned relative to intramedullary orextramedullary rod92 so thatresection guide surface146 can be oriented correctly relative totransition point82 on the bone and oriented in varus/valgus to form thedistal resection100. Such structure in the embodiment shown inFIGS. 14-16 include acollet148 andbody150. The collet includesindicia152 to indicate desired varus/valgus orientation of theresection guide surface146. Similar to the way in whichdistal resection instrumention102 may be used, the alternate distalresection guide surface146 can be positioned in the superior/inferior direction relative tointramedullary rod92 by slidingcollet148 on the rod. It can be adjusted in varus/valgus by using the indicia on thecollet148. As in the case of distalresection guide surface104, the alternate distalresection guide surface146 surface itself, without any markings or special physical distinctions, can serve as anindex154 for positioning of the alternate distalresection guide surface146 so that thedistal resection100 passes through or near or relative as desired to thetransition point82. As with the case of distalresection guide surface104, alternate distalresection guide surface146 or other portion of alternatedistal resection instrumentation144 can contain indica (not shown) or other desired markings or features to serve as anindex154 for such proper alignment so that thedistal resection100 extends through, near or suitably relative to thetransition point82 and is correctly positioned in varus/valgus.
• Implant sizing markings156 can also be included, as shown inFIGS. 14-16 to allow thisinstrumentation144, in a manner similar toanterior resection instrument90 and/ordistal resection instrumentation102, to show or suggest to the surgeon what size ofimplant10, and what size oftransition resection guide116, will be needed.
• FIG. 17 showsdistal portion12 offemur14 with what is left ofanterior resection84 after performing atransition resection118 andchamfer resection120 according to one embodiment of the invention. This view is taken beforeposterior resection138 andposterior chamfer resection142 have been performed.
• FIG. 18 shows implant10 installed onfemur14, with the knee in approximately 65 degrees of flexion. The posterior medial articulatingsurfaces60 ofimplant10 are articulating againsttibial insert40 of themedial compartment52 of the knee, while natural bone of thelateral condyle22 of thefemur14 and thetibial plateau24, form thelateral compartment42 of theknee18.
• FIGS. 19-25 show aresection guide158 according to an alternate embodiment of the invention, which can resect bone so thatimplants10 having one or move curved inner surfaces can be installed. Accordingly, ananterior resection84, which may be flat or curved, can be formed using any desired resection device or guide, such as those discussed above, or milling apparatus with appropriately positioned guide. As in the devices discussed above, abone transition point82 which may be designated as desired, including the distal most point on the lateral portion ofanterior resection84. Upon designation of thetransition point82, guide158 may be positioned on the distal portion offemur12. In the structure shown inFIGS. 19-25, guide158 features ananterior paddle160 which may be substantially flat or curved as appropriate to correspond toanterior resection84. The paddle or other portion of theguide158 can also include atransition point index162 for helping locateguide158 relative totransition point82.Transition point index162 can be any desired physical or other marker or structure onguide158 as desired. Also, helping position guide158 relative tofemur14 is acollet164 which is connected, preferably in adjustable relationship, to an intramedullary orextramedullary rod166.Collet164 could also be in the form of an adjustable structure with indica as can be the case with resection guides discussed above, or a series ofcollets164 each corresponding to a particular desired varus/valgus angle, may be employed, one of thecollets164 being selected for a particular application. Thus, guide158 can be properly navigated and located relative to distal portion offemur12 using thetransition point82 to help regulate the depth of the distal resection or distal surface to be formed by a milling device operating relative to guide158, and proper navigation and location in varus/valgus and otherwise to causeguide158 properly to guide milling or other resection devices to form curved surfaces, straight surfaces, or combinations, in proper orientation and position for proper kinematics of the reconstructed knee.
• FIG. 20 shows guide158 properly located onfemur14 to form a curveddistal resection112 andposterior resection139, together with transition resection118 (not shown inFIGS. 20-25, but similar in location and orientation to thetransition resection118 discussed in connection with resection guides disclosed above.) As shown inFIGS. 20-23, one or more medialcondyle milling devices168 can be guided byguide158 to formdistal resection112 andposterior resection139, both of which are curved and preferably meet in curved continuous fashion in the particular embodiment shown inFIGS. 20-23.Guide158 can be constructed to use only one medialcondyle milling device168, multiple such devices, or as otherwise desired.Guide158 can also be structured to allow thedevices168 to be positioned in order to rotate about a medial/lateral axis rather than as shown inFIGS. 20-23. A transitionresection milling device170 can be used to track withinguide158 to form thetransition resection118.FIGS. 24 and 25 show ashim172 which may be coupled to guide158 to help position guide158 relative tomedial condyle20.
• FIGS. 26-32 show a version of theguide158 with apaddle160 adapted to correspond to a curvedanterior resection84.
• FIGS. 33-38 show aguide174 according to another embodiment of the invention adapted to be navigated relative to thetransition point82 on a flat or curvedanterior resection84, and for forming aflat posterior resection139 onmedial condyle20.Guide174 can be navigated relative to thefemur14 using thetransition point82 on thefemur14 which has been designated as disclosed above, and relative to an intramedullary orextramedullary rod166 using acollet176. Thecollet176 can be of the same sort as disclosed above in connection withguide158. Once theguide174 has been properly navigated and located, including if desired, likeguide158, being pinned to the bone in conventional fashion, thedistal resection112 can be formed using medial condyle milling devices in a fashion similar to that disclosed in connection withguide158. Alternatively, surfaces ofguide174 can be used to guide a milling device whose rotational axis is in the medial lateral direction, as shown inFIG. 38 by way of example. Medial/lateralrotational milling device176 can be wider than that shown inFIG. 38, if desired, and used with aguide174 which uses slots or other desired structure to allowmilling device176 to rotate against bone on themedial condyle20 to shape it appropriately, and fordevice176 to be guided by and manipulated relative to guide174. Atransition milling device170, not shown, may be used as in theguide158, to formtransition resection118.
• Guides158 or174 may be configured and structured as desired in order to guide one or more medialcondyle milling devices168 or176 to formdistal resection112 and/orposterior resection139 in a continuous curved fashion, with or without flat portions, or as otherwise desired.Guide174 likeguide158 can be used in connection with flat or curvedanterior resections84 which resections may be formed using cutting blocks or milling guides.
• FIGS. 39-49 show aresection guide180 according to another alternate embodiment of the invention. Such a guide can incorporate functionality for forming not only thedistal resection112,transition resection118 andposterior resection139, but alsoanterior resection84. Theparticular guide180 shown in these figures is adapted to be positioned on a generallytubular collet182.Collet182 can be located and positioned on intramedullary orextramedullary rod92 so thatcollet182 and guide180 may be properly positioned and then locked in place as desired relative to therod92. Any other collet can be used, whether or not adjustable or provided in a series to accommodate various angles of varus/varus. In the particular structure shown in theseFIGS. 39-49, guide180 can slide and then be locked in place relative to collet180 in an anterior/posterior direction, as well as rotated and then locked into place relative to collet182 to adjustguide180 in a varus/valgus rotation as desired relative tofemur14. Accordingly, guide180 can be positioned relative to intramedullary orextramedullary rod92 in a varus/valgus and interior/exterior rotational direction, and in a superior/inferior and anterior/posterior translational direction, and then locked in place as desired in each of these rotations or translations.Guide180 contains an anteriorresection guide surface184, a distalresection guide surface186, a posteriorresection guide surface188, a transitionresection guide surface190, an anteriorchamfer guide surface192 and a posteriorchamfer guide surface194. Ashim196 can be used to help position guide180 for proper distal and other resections.Shim196 is shown inFIG. 43.
• In use, intramedullary orextramedullary rod92 is placed and theguide190 ofFIGS. 39-49 properly positioned relative to it oncollet182 to form ananterior resection84 in accordance with the principles discussed in connection with the embodiment shown inFIGS. 5-8.Transition point82 is then designated and apositioner198 as shown inFIG. 43 can be connected to guide190 to abutanterior resection84 or otherwise referenced to it, and also referencepositioner198 and guide180 relative totransition point82 so that adistal resection112 can be formed at proper depth to achieve proper flexion extension of the reconstructed knee.Positioner198 can also contain the distalresection guide surface186 for formingdistal resection112.Guide180 andpositioner198 are shown properly navigated and located into place on thefemur14 for forming thedistal resection112. The other resections, includingtransition resection118,posterior resection139,anterior chamfer resection120,posterior chamfer resection142 can be formed using the respective guide surfaces188,190,192, and194.FIGS. 49A and B show the resections formed on the bone using guide180:anterior resection84;distal resection112,posterior resection139,anterior chamfer resection120 andposterior chamfer resection142 andtransition resection118.
• An implant such as that shown inFIGS. 1 and 2 can be installed on thefemur14 so resected.

Claims (25)

1. A femoral implant for implantation on resected distal portions of a patient's femur, comprising:

An anterior portion which comprises an anterior medial articulating surface, an anterior lateral articulating surface, an anterior patellofemoral channel and an anterior inner surface adapted to correspond to an anterior resection on the femur;

A transition portion which comprises a transition medial articulating surface, a transition patellofemoral channel, a transition lateral articulating surface, and a transition inner surface adapted to correspond to a transition resection on the femur, the transition inner surface intersecting the transition medial articulating surface to form a truncation of the transition medial articulating surface;

A distal medial portion which comprises a distal articulating surface and a distal inner surface adapted to correspond to a distal resection on the femur; and

A posterior medial portion which comprises a posterior medial articulating surface and at least one posterior medial inner surface adapted to correspond to at least one posterior resection of the femur.

2. An implant according toclaim 1 (all elements of which are incorporated by this reference) wherein the anterior inner surface, the distal inner surface and the transition inner surface intersect at an implant point.

3. An implant according toclaim 2 (all elements of which are incorporated by this reference) adapted to be installed on a resected femur whereby the anterior resection on the femur contains a transition point, the anterior resection on the femur is oriented at a predetermined amount of internal/external rotation relative to the femur, and the distal resection on the femur substantially intersects the transition point and is oriented at a predetermined amount of varus/valgus rotation relative to the transition point.

4. An implant according toclaim 3 (all elements of which are incorporated by this reference) adapted to be installed on a resected femur wherein the location of the transition resection on the femur is determined by moving a resection guide, which contains a slot corresponding to the transition resection and which is in sliding contact with the anterior resection and the distal resection, in a medial or lateral direction on the anterior and distal resections and determining the position at which bone abutting the transition articulating lateral surface will form a smooth transition to lateral condylar articulating surfaces of the femur.

5. An implant according toclaim 1 (all elements of which are incorporated by this reference) further comprising at least one peg extending from an inner surface.

6. An implant according toclaim 1 (all elements of which are incorporated by this reference) wherein the implant is structured so that the lateral condyle of the knee rather than the implant abuts the tibia at between substantially zero and substantially ninety degrees flexion of the knee.

7. An implant according toclaim 1 (all elements of which are incorporated by this reference) wherein a patella or patella implant tracks the patellofemoral channel of the implant at between substantially zero and substantially seventy degrees flexion.

8. An implant according toclaim 1 (all elements of which are incorporated by this reference) further comprising a tibial component for attachment to a tibia and for articulating relative to the implant.

9. An instrument adapted to perform a distal resection a patient's femur comprising;

An instrument index adapted to correspond to a transition point on an anterior resection of the femur;

A distal resection guide surface and a rod connection portion, the rod connection portion adapted to adjustably connect to an intermedullary or extramedullary rod, whereby orientation of the distal resection guide surface is adjustable in varus/valgus rotation relative to the transition point on the femur by maintaining the index substantially aligned with the transition point while adjusting orientation of the instrument relative to the rod;

Whereby the distal resection guide surface is positioned and oriented properly to form a distal resection on the medial condyle of the femur when the index corresponds to the transition point and the instrument is properly oriented in varus/valgus relative to the rod.

10. An instrument according toclaim 9 (all elements of which are incorporated by this reference) wherein the instrument index is adapted to correspond to a transition point that is located at the distal-most point of a lateral portion of an anterior resection on the knee.

11. An instrument according toclaim 9 (all elements of which are incorporated by this reference) wherein the rod connection portion comprises a collet adapted to receive an intramedullary rod.

12. An instrument according toclaim 9 (all elements of which are incorporated by this reference) further comprising a transition resection guide surface for forming a transition resection positioned and oriented at an angle relative to the anterior resection and the distal resection.

13. An instrument according toclaim 9 (all elements of which are incorporated by this reference) wherein the distal resection guide surface is adapted to guide one of the following: a sawblade and a milling device.

14. A resection guide adapted to resect a patient's femur, comprising:

A distal resection abutment surface adapted to contact a distal resection on the femur;

An anterior resection abutment surface adapted to contact an anterior resection on the femur;

A transition resection guide surface for guiding a transition resection of the femur;

An index located on the resection guide at a position that corresponds to a lateral extremity of an implant that corresponds in size to the resection guide;

Whereby the transition resection guide surface is adapted to be properly positioned relative to the distal resection and the anterior resection for performing a transition resection by contacting the abutment services of the resection guide with the anterior resection and the distal resections, and moving the guide in a medial or lateral direction on the femur to a point where the index indicates proper medial/lateral alignment of the transition resection guide surface.

15. A resection guide according toclaim 14 (all elements of which are incorporated by this reference) further comprising a chamfer resection guide surface for guiding a chamfer resection.

16. A resection guide according toclaim 15 (all elements of which are incorporated by this reference) wherein the chamfer resection guide surface and the transition resection guide surface are substantially planar and intersect along a line.

17. A process for conducting knee surgery on a knee comprising a tibia and a femur, the femur in turn comprising a lateral condyle and a medial condyle, comprising:

Resecting an anterior portion of a distal portion of the femur, thereby creating an anterior resection, the anterior resection positioned at a predetermined depth and oriented at a predetermined angle relative to the femur in internal/external rotation;

Selecting a transition point relative to the anterior resection, wherein the transition point is located in the vicinity of the distal-most point of a lateral portion of the anterior resection;

Performing a distal resection on a portion of the medial condyle, the distal resection intersecting a point in the vicinity of the transition point, and oriented at a predetermined angle relative to the femur in varus/valgus rotation;

Performing a transition resection on a lateral portion of the femur at an angle relative to both the anterior resection and the distal resection, the transition resection intersecting the anterior resection and distal resection so that an implant installed on the bone does not project beyond lateral external surfaces of the femur and so that external surfaces of lateral portions of the implant form a smooth transition to lateral external surfaces of the femur; and

Installing an implant on the resected femur, the implant having inner surfaces which substantially fit the resections, which implant replaces distal articulating surfaces of the medial condyle and patellofemoral articulating surfaces, but does not replace surfaces of the lateral condyle which articulate with the tibia.

18. A process according toclaim 17 (all elements of which are incorporated by this reference) wherein the process is conducted and the implant is installed without resection of either an anterior cruciate ligament or a posterior cruciate ligament of the knee.

19. A process according toclaim 17 (all elements of which are incorporated by this reference) further comprising resecting a medial portion of the tibia and installing an implant on the resected portion of the tibia.

20. A process according toclaim 17 (all elements of which are incorporated by this reference) further comprising installing a patellar implant.

21. A process according toclaim 17 (all elements of which are incorporated by this reference) in which resecting the anterior portion of the femur creates a substantially hour-glass shaped anterior resection with two lobes, wherein the transition point is located at the distal-most point on the lateral lobe.

22. A process according toclaim 17 (all elements of which are incorporated by this reference) in which the distal resection is performed using a distal resection instrument connected to an intramedullary rod inserted in the femur.

23. A process according toclaim 17 (all elements of which are incorporated by this reference) in which the distal resection and the transition resection are formed using the same resection guide.

24. A process according toclaim 17 (all elements of which are incorporated by this reference) in which at least one of the resections is formed using a milling device.

25. A process according toclaim 17 (all elements of which are incorporated by this reference) in which at least one of the resections is curved.

Images