Abstract:
There are provided various embodiments of medical instruments to perform knee surgery. In one embodiment a finned platform for mounting a cutting block is provided. The finned platform can be used on either a femur or tibia to allow for the proper cuts when performing a knee surgery. In another embodiment, a tibial trial is shown having a fin. The fin is useful to reinforce the bone to reduce the risk of fracture during bone preparation. In another embodiment, a reamer is provided having a plurality of cutting flutes. It may be desirable to utilize a guide with the reamer to allow the reamer to cut a noncircular portion of the tibial bone. In yet another embodiment, a plurality of fixation pegs are provided on the tibial implant to allow for easy removal of such implant if a revision surgery becomes necessary.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This present application is a U.S. National Phase of International PCT Application No. PCT/US2011/047542 filed on Aug. 12, 2011, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/373,709 filed on Aug. 13,2010, the contents of each application hereby incorporated by reference in its entirety. 
    
    
     RELATED FIELDS 
     Orthopaedic implants and methods involving the same, such as, but not limited to, orthopaedic implants and methods for the proximal tibia, such as tibial trays that may include one or more of a keel and/or a stem and methods for revising the same. 
     BACKGROUND 
     There are several factors that are potentially relevant to the design and performance of orthopaedic implants. In the example of a tibial tray, a non-exhaustive list of such factors includes the implant&#39;s flexibility (or the flexibility of certain portions of the implant or its flexibility about certain axes or other constructs), which may indicate the degree to which the tray will conform to the potentially uneven resected surfaces of a proximal tibia; the implant&#39;s rigidity (or the rigidity of certain portions of the implant or its rigidity about certain axes or other constructs), which may indicate the degree to which stresses or other forces imposed by the bony and other anatomy associated with the knee joint will be transmitted to the peripheral hard cortical shell of the proximal tibia; the implant&#39;s resistance to rotation; the amount of bone preserved; and/or other potentially relevant factors. In some instances, accommodation of these or other factors may require trade-offs to balance competing factors. In some instances, one or more of these factors will not be considered or given a high level of importance to the design of an orthopaedic implant. 
     Some known tibial trays include a fin or a keel that may increase the strength of the implant while also helping to prevent rotation relative to the bone. In some instances, such fins or keels may present certain drawbacks. For instance, in some cases, the fin or keel may impede the visualization of the implant and surrounding anatomy using x-ray or other imaging technologies. For instance, it may be desirable in some cases to visualize the implant and its surrounding anatomy, including the surrounding bony anatomy, by taking one or more x-rays in planes such as coronal and sagittal planes or in other planes to assess whether the implant may be loosening over time. Such loosening might be Indicated by lucent lines appearing in the x-ray image around portions of the implant or other indications that the bone has receded from the implant or otherwise has become loose. In some instances, a fin or keel of the implant may obstruct the ability to view such lucent lines or may otherwise hinder the evaluation of the image. Other orthopaedic components might feature these or other structures similarly impairing visualization of the implant in the bone and other anatomy. 
     Some known tibial trays are difficult to remove or revise. For some revision procedures, it is necessary to cut around the existing implant or otherwise position instrumentation about the implant to loosen it from the surrounding bone and/or other anatomy before removal. In some instances, particularly, for instance, some instances where the implant is a tibial tray having a keel, it may be difficult to cut around certain portions of the keel or otherwise access certain areas of the bone-implant interface to loosen the implant. It may be particularly difficult, for instance, to access certain areas of the bone-implant interface depending on the surgical approach taken. For instance, if an anterior-medial incision is used to access the knee joint, the keel structure may impede a surgeon&#39;s access to posterior-lateral portions of the bone-implant interface. In such instances, removal of the implant may undesirably require excessive or unintended bone removal as well. 
     In some instances, stability or fixation of the implant, such as a tibial tray or other implant, in the bone may be of some significance. For instance, the distribution of “hard” versus “soft” bone is not always uniform or predictable, and, in some instances, during bone preparation a punch, drill or other instrument may penetrate the bone at an undesired angle or position since it may tend to follow the path of least resistance into softer bone. Moreover, in some instances, such as some tibial cases, distal metaphyseal bone may tend to be spongier and softer than proximal metaphyseal bone. In some implant cases, it may be difficult to achieve adequate fixation or other stability in the distal metaphyseal bone. Moreover, with some implants, including some tibial implants, there may be a tendency over time for the implant to subside or migrate. 
     SUMMARY 
     There are provided various embodiments of medical instruments to perform knee surgery. In one embodiment a finned platform for mounting a cutting block is provided. The finned platform can be used on either a femur or tibia to allow for the proper cuts when performing a knee surgery. In another embodiment, a tibial trial is shown having a fin. The fin is useful to reinforce the bone to reduce the risk of fracture during bone preparation. In another embodiment, a reamer is provided having a plurality of cutting flutes. It may be desirable to utilize a guide with the reamer to allow the reamer to cut a non-circular portion of the tibial bone. In yet another embodiment, a plurality of fixation pegs are provided on the tibial implant to allow for easy removal of such implant if a revision surgery becomes necessary. In yet another embodiment, various rasp type instruments are shown to properly prepare the tibia for a tibial implant. In some embodiments, the tibial trial is provided with a rasp feature to allow the trial to be used to properly prepare the tibia for the tibial implant. 
     Some of the non-limiting embodiments of tibial trays described herein include one or more fins or keels that include or define holes, openings, recesses, areas formed or filled with different materials, or other structures or features. Some of the non-limiting embodiments of tibial trays described herein may additionally or alternatively include a monolithic, modular or otherwise connected fluted stem. The present application is not limited to tibial trays; however, and one of skill in the art will recognize that at least some of the concepts presented herein could be applied to other orthopaedic implants. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a top plan view of one non-limiting example of a tibial tray. 
         FIG. 2  is a rear elevation view of the tibial tray of  FIG. 1 . 
         FIG. 3  is a side elevation view of the tibial tray of  FIG. 1 . 
         FIG. 4  illustrates a modular stem that may optionally be used with the tibial tray of  FIG. 1 . 
         FIG. 5  is a distal view of the modular stem of  FIG. 4 . 
         FIG. 6  is a cross-section of the stem of  FIG. 4  taken along line  6 - 6  shown in  FIG. 5 . 
         FIG. 7  is a cross-section of the stem of  FIG. 4  taken along line  7 - 7  shown in  FIG. 5 . 
         FIG. 8  illustrates a distal view of an alternative embodiment of fluting useable with a modular stem such as the modular stem of  FIG. 4 . 
         FIGS. 9-14  illustrate schematically an alternative embodiment of a tibial tray with a modular stem. 
         FIGS. 15-18  illustrate a finned platform for mounting a cutting block. 
         FIGS. 19-22  illustrate tibial trays having a fin. 
         FIGS. 23-26  illustrate a rotatable reamer. 
         FIGS. 26-29  illustrate fixation pegs. 
         FIGS. 30-34  illustrate instruments for tibial surface preparation. 
         FIGS. 35-39  illustrate a tibial trial for tibial surface preparation. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 through 3  illustrate a non-limiting example of a tibial component  100 . As shown in  FIGS. 2 and 3 , the tibial component  100  includes support member  110  defining a pair of openings  112 . In some, although not necessarily all, embodiments, these openings may be sized, positioned, oriented and otherwise constructed to: (1) reduce by a certain degree the stiffness of the implant while maintaining a certain degree of strength; (2) facilitate the visualization (such as through x-ray imaging or other techniques) of lucent lines or other signs that the implant is loosening; (3) facilitate the loosening of the tray from the bony anatomy in the event resection is necessary, such as by facilitating the movement of cutting or other types of instrumentation through and to the far side of the keel/stem portion that would not otherwise be accessible to the cutter or other instrumentation; and/or (4) facilitate bony-ingrowth or otherwise enhance the stability of the implant in the bone. In some embodiments, the openings may not feature all of these benefits or may provide other beneficial features. 
     The support member  110  shown in  FIGS. 2 and 3  includes a stem portion  114  and two arms  116  extending therefrom. In this particular example, the support member  110  is attached to an underside of a tibial tray  118  at three points forming a tripod-like construct. The stem portion  114  shown includes a lower cylindrical portion  120  and an upper portion  122  that is blended to the arms  116 . In the depicted embodiment, the stem portion  114  slants at an angle α and in an anterior-posterior direction as it extends away from an inferior surface  124  of the tray  118 ; however, in other embodiments, the stem portion  114  may have other geometries. The stem portion  114  of this particular tibial component  100  is located anteriorly on the tray  118 , although other locations are also possible. The arms  116  shown in  FIGS. 2 and 3  extend posteriorly and outwardly from a mid-point of the stem  114  and curve to connect to the underside of the tibial tray  118 . In other embodiments, other numbers of arms and/or stems in other configurations and geometries can be employed. 
     The arms  116  and stem portion  114  of the support member  110  shown in  FIGS. 2 and 3  define two openings  112  abutting the inferior surface  124  of the tibial tray  118 . In other embodiments, different numbers, configurations, shapes, orientations, and positionings of the openings may be possible. As discussed below, in some embodiments, the openings  112  of the support member  110  may not be “openings” at all in the traditional sense, but may be areas where other materials or components are located, or in which the material forming the tibial component  100  has different properties or characteristics. 
     In some embodiments, the openings  112  formed in the support member  110  increase certain flexibility characteristics of the tibial component  100  while not overly impinging on a desired strength characteristic of the component. In some embodiments, the openings  112  can be sized and shaped so that the remaining solid material is relatively uniform in shape. In some embodiments, the remaining solid material is uniform in shape in the regions of highest stress at the most peripheral edges of the arms  116 . In some embodiments, the opening size can be configured to be short enough to allow a sawblade to easily clear material away from the sides while being tall enough to allow a thin and narrow osteotome to pass through in order to facilitate revision surgery. In other embodiments, the openings  112  may be configured to only permit a sawblade or an osteotome, but not both. In some embodiments, such as, for example, where revisability is not a primary goal, taller and deeper openings may be used to facilitate maximal ingrowth through and around the openings. 
     In some embodiments, the openings  112  formed in the support member  110  provide for better visualization of the tibial component  100 , the bone surrounding the tibial component, and the interface or interfaces between the bone and the tibial component  100 . The openings  112 , in some embodiments, may act as “windows” facilitating the visualization of lucent lines or other visual indications on the imaging data, which may suggest or indicate that the tibial component is loosening or provide other information for evaluating other issues or concerns. In some embodiments, the size, shape, placement and/or orientation of the openings  112  can be optimized to facilitate visualization of bone-implant interfaces and other areas of interest for future visualization of the implant after installation. For instance, as shown in the Figures, the openings  112  are primarily oriented in a coronal plane, although, in other embodiments, they could be primarily oriented in a sagittal plane or other orientations. In some embodiments, a wider attachment region with a less abrupt thickness change may be used to provide for lower stress in the region. In some embodiments, a more narrow attachment region may be used to increase visibility by lessening the amount of material that could block a user&#39;s view. 
     In some embodiments, the openings  112  are not physical openings extending through the support member  110  or other portion of the tibial component, but may instead be components or areas that do not completely or partially impair visualization such as by x-ray technologies or other visualization technologies. For instance, in some embodiments, the “openings” may be filled or may be comprised of materials of lower density (such as materials for facilitating bony in-growth or other materials) or that are otherwise semi or completely radio-lucent. 
     In some embodiments, the openings  112  allow a cutting device or other instrument to physically pass through one or more of the openings  112  to facilitate cutting or otherwise loosening the tibial component from the bone in the event a revision procedure is necessary. In the embodiment shown in  FIGS. 2 and 3 , the openings  112  are oriented such that posterior-lateral portions of the bone-implant interface can be accessed by a surgical cutter or other instrument if an anterior-medial approach to accessing the joint space is used. The openings  112  shown in  FIGS. 2 and 3  also may allow this and other portions of the bone-implant interface to be accessed from other approaches or directions. In other embodiments, the position, orientation, size, shape and number of openings  112  could be altered to facilitate access to remote portions of the bone-implant interface depending on the particular implant involved, the expected surgical approach or approaches that may be utilized, and/or other factors (e.g. the size and shape of the instrument(s) that might need to pass through the opening). In some embodiments, the “openings” are not necessarily physical openings through the support member  110  but are areas that are frangible or otherwise capable of being relatively-easily penetrated by a surgical instrument to access the remote portions of the bone-implant interface if necessary. In some embodiments, the opening(s) could be designed to function as guides for the instrumentation passing through them, which, in some uses, might control depth and/or direction of insertion of the instrument (e.g. to lessen chance of damaging surrounding anatomy, such as postero-lateral nerves or arteries) or other aspects of the procedure. In some embodiments, openings  112  can be configured for improved visibility and an ability to approach from anterior to posterior. In some embodiments, the opening(s)  112  could be designed to accommodate surgical cutting instruments such as reciprocating or oscillating planar saw blades having cutting edges on either or both of a distal end or one or both sides, milling bits and other types of rotating cutting devices, chisels, other osteotomes, prying devices, or any other type of surgical instrument that might be used for a revision procedure. 
     As mentioned above, in some embodiments, the openings  112  could be filled with a porous structure or material or otherwise define in-growth surfaces. In some embodiments, the porous structure or material could be formed from the same material as the rest of the support member  110  but having a different porosity, density or other characteristics than other portions of the support member  110 . In some embodiments, the porous structure is not necessarily confined to the opening  112  and could occupy geometric volumes outside of and around other portions of the support member  110 . Indeed, in some embodiments, the support member  110  could function as an internal scaffolding for a volume of bone in-growth material(s) that completely or at least in portions encompass the support member  110 . In other embodiments, other materials or structures may fill the openings  112  and a porous structure or treatment is not necessary. In some embodiments, the filling material or structure may be intended to facilitate anti-rotation aspects of the implant. 
       FIG. 1  shows a superior surface  126  of the tibial tray  118 , which includes attachment feature  128  for receiving and/or securing one or more articular inserts (not shown) to the tibial tray  118 , such inserts designed to contact and articulate with a femoral orthopaedic implant (not shown) in use. In the depicted embodiment, the attachment feature  128  is a shaped channel to receive and lock-in the articular insert. In other embodiments, the tibial tray  118  itself may include articular surfaces and does not require separate articular inserts. The tibial tray  118  shown in  FIGS. 1 through 3  includes a posterior notch  130 , which may be designed to allow preservation of the attachment site of a posterior cruciate ligament, although, in other embodiments, the tibial tray  118  may or may not include this or other notches or gaps for preserving one or both of the cruciate ligaments. In other words, the tibial tray, in some embodiments, may be for use in a cruciate sacrificing procedure, a posterior cruciate preserving procedure, or a bi-cruciate preserving procedure. In some embodiments, the tibial tray  118  may be used for a mobile bearing knee joint or a fixed bearing knee joint. It will be appreciated that a variety of upper surface and peripheral shapes are possible according to various embodiments and that such shapes can be influenced, at least in part, by strength requirements for the tray. For example, in some embodiments, a cruciate notch or dovetail mechanism may be used, but may also act as a stress-riser. 
     The tibial component  100  shown in  FIGS. 1 through 3  may be part of a set of tibial trays of various standard sizes, or may be a patient-matched tibial tray with certain geometries and/or other aspects of the tray customized for a particular patient&#39;s anatomy. The tibial component  100  shown in  FIGS. 1 through 3  may be formed from bio-compatible materials typically used to manufacture orthopaedic implants or may be formed from other materials. The tibial component  100  shown in  FIGS. 1 through 3  may be formed using any desired or appropriate methodologies or technologies. 
     In some embodiments, the tibial component  100  may be manufactured using Selective Laser Sintered technologies (“SLS”) or other free-form fabrication technologies, such as one or more of the EOS Laser-Sintering systems available from EOS GmbH of Munich, Germany. For instance, in some embodiments, the entire tibial component  100  may be formed as a monolithic implant (including any porous or other in-growth promoting surfaces or materials). In other embodiments, portions of the tibial component  100  may be formed using SLS technology and then additional in-growth materials, surfaces, and/or treatments could be added or applied to the implant. In other embodiments, electron beam melting methods or methods that use lasers to subtract or remove select portions of material from an initially solid fin may be used. In other embodiments, portions or all of the tibial component can be formed using casting or other technologies or methods. In some embodiments, a non-porous implant such as a tibial component may be formed using SLS technologies and subsequently that implant may be subjected to acid etching, grit blasting, plasma spraying (e.g. of titanium oxide or another metal to promote in-growth) or other treatments. 
       FIGS. 4 through 8  illustrate a modular stem  200  that may be used with the tibial component  100  of  FIGS. 1 through 3  in some, although not necessarily all, embodiments. Indeed, in some embodiments, the tibial component of  FIGS. 1 through 3  will be used without any modular stem or otherwise incorporating any of the features or constructs of the modular stem shown in  FIGS. 4 through 8 . The modular stem  200  may connect to the stem portion  114  of the support member  110  of the tibial component of  FIGS. 1 through 3  via a taper fit mechanism (which may be further secured by a screw or other fastener in some embodiments). In other embodiments, other mechanical attachment mechanisms may be employed, or, in still other embodiments, the stem is not modular but an integral part of the tibial component. 
     The embodiment of the modular stem  200  shown in  FIGS. 4 through 8  includes an inner core  210  from which a plurality of flutes  212  extend. In some embodiments, the inner core  210  has a tapered, conical or press fit geometry positioned and oriented for where it is most likely (at least in some cases) to encounter “harder” bone, and the flutes  212  are positioned where they are most likely to encounter “softer” bone. In some embodiments the general shape of the modular stem  200  facilitates implantation in a relatively close orientation and position to a pre-defined orientation and position. 
     As shown in  FIG. 6 , the inner core  210 , in some embodiments, may be slightly tapered and/or define a somewhat conical shape. Conical features such as this one (whose axes, at least in some embodiments, may be directed generally parallel to the direction of load application) may be beneficial because, in some uses, they may convert what otherwise would be a purely compressive load into a compressive load that also has a transverse component (i.e. a direction of which could be characterized, at least in some embodiments, as orthogonal to the direction of the compressive load). In some embodiments, this may be beneficial in preventing bone immediately adjacent to the implant from being shielded from loading, at least for some of the time. In some cases, bone that is shielded from loading could remodel, resorb or otherwise degrade, resulting in a poor quality bone-implant interface. The tapered or conical shape of the modular stem  200  may also facilitate the prevention of subsidence or migration. The tapered or conical nature of the inner core  210  may also facilitate a press-fit type interface between the implant and bone. In the embodiment shown, a distal tip  214  of the inner core is rounded. 
     As shown in  FIGS. 4, 5, and 7 , several flutes  212  extend radially from the inner core  210  of the modular stem  200 . In the particular embodiment shown, the flutes  212  extend in a radially symmetric pattern such that the apexes of the flutes  212  are parallel to a central axis CA of the inner core  210 . In other words, although the inner core tapers, the apexes of the flutes extend along a virtual cylinder. In other embodiments, the apexes of the flutes may also taper as they extend towards the distal tip of the stem; although, in at least some of these embodiments, the flutes do not taper as much as the inner core. Because, at least in some embodiments, the inner core tapers to a greater degree than the apex of the flutes, the flutes will “protrude” from the stem to a greater extent at distal portions of the stem than at proximal portions of the stem. Accordingly, in some embodiments, such a design may pose less of a risk of fracturing the hard bone that is located proximate the proximal portions of the stem while still achieving fixation (rotational and/or translational) in the soft bone located proximate the distal portions of the stem. Additionally, in some embodiments, there may be less of a risk of deflection or mal-orientation or mal-position due to lack of or lessening of press-fit between the flutes and the hard bone. 
     As shown best in  FIG. 8 , in addition to the flutes  212  described in the previous paragraph, the inner core of the modular stem may also include secondary/smaller fluting  212 ′ extending therefrom. In some embodiments, the secondary fluting  212 ′ may be rounded or sharp, and may further facilitate a tight fit with the surrounding bone, while, because they are smaller, lessening the chance of tibial pain. In some embodiments, the fluting is radially symmetric and facilitates insertion of the stem  200  to follow a pilot hole.  FIG. 8  shows fluting useable in some embodiments of modular stems in which the stem  200  has fluting (or at least primary fluting) that is spaced 120 degrees apart. 
     In some embodiments, the fluting is not radially symmetrical, but instead exhibits planar symmetry. Planar symmetry may allow, in some embodiments, matching of the fluting to the support member geometry of a tibial component. In some embodiments, the fluting is not radically symmetrical and is instead “handed” and specific for left or right tibias to accommodate particular or expected locations of hard and soft bone. In some embodiments, patient matched technologies could be employed to customize the fluting to the hard vs. soft bone distribution of the specific patient. 
     In some embodiments, the fluting may be tapered. In some embodiments, the “soft bone flutes” may be designed in such a way that over small sections, they may be lower than the “hard” bone flutes. In some embodiments, the “soft” bone flutes could be parallel to the “hard” bone flutes but become tangentially wider to increase their effectiveness in soft bone. In some embodiments, the flutes could be discontinuous. In some embodiments, the flutes could be made of a material different than that of the rest of the stem. In some embodiments, portions of the stem could be porous coated or have surface finishes applied. 
       FIGS. 9-11  illustrate alternative possible support member shapes. For example, in  FIGS. 9 and 10 , there are two branches  310  (or arms or wings) of the support member  300 . In  FIG. 9 , the branches  310  are angled relative to one another, but in  FIG. 10  the branches  310  are substantially aligned with one another. In  FIGS. 11 and 12 , the support member  300  has three branches or arms  312 . Fewer or greater numbers of branches are possible. 
     As illustrated in  FIGS. 12, 13 and 14 , the tibial tray  410  and support member  420  may be modular and may have a male/female arrangement. Although in the figures the stem portion  420  is shown to have a female portion and the tibial tray  410  is shown to have a male portion, these could be reversed. In the embodiment depicted in  FIG. 13 , the tibial tray  410 ′ has a shoulder  430  that engages a ledge  440  of the stem portion  420 ′. The shoulder/ledge arrangement allows force to be transferred from the tibial tray  410 ′ to the stem portion  420 ′. The shoulder  430  also may provide a porous surface area for bone in-growth. As best seen in  FIG. 13 , the stem portion  420 ′ may engage in a taper lock with a portion of the tibial tray  410 ′. 
       FIGS. 15-18  illustrate a finned platform  500  for mounting a cutting block  502 .  FIG. 15  illustrates a state of the art cutting block  502  having a spike  504  that is used to hold the block temporarily in place. The spike has certain drawbacks. For example, the cutting block may shift with an applied load as a surgeon tries to keep even contact between a sawblade  506  and the cutting surface  508 . This may result in uneven or mal-rotated, poorly positioned cuts. 
       FIG. 16  illustrates a finned platform  500 . The finned platform  500  has a head  510 , a shaft  512 , and fins  514  on the shaft  512 . The head  510  has a planar surface at its uppermost portion or may have an enlarged planar surface  526  at its uppermost portion. The finned platform  500  may be cannulated as shown at  516  to receive a spike  518  of a bone cutting block  520  as shown in  FIG. 18 . The fins may be in the form of a thread  514 ′ (finned platform  500 ′ in FIG.  16 or a plurality of ribs. The fins  514  may have a large surface to adequately engage soft, spongy bone. The fins and/or head may resist movement. The finned platform  500  may be made of metal or a polymer. In some embodiments, the finned platform  500  is removed after cutting the bone. In some embodiments, the finned platform  500  is left in after surgery to assist in mounting an implant to the bone. In some embodiments, the finned platform  500  is made from a resorbable material. In some embodiments, the finned platform  500  is made from a shape memory material. In use, the finned platform  500  is placed into bone  522 . Optionally, a pilot hole  524  may be drilled prior to placement of the finned platform  500 . A cutting block  520  with a spike  518  is engaged with the finned platform  500 . In some embodiments, the spike may extend beyond the finned platform or vice versa. Thereafter, the cutting block  520  is used as guide by a sawblade  506 , cutting tool, or other instrument. The finned platform  500  may stabilize the cutting block for more reproducible cuts. The finned platform  500  of the present invention may be used on either the femoral bone component or the tibial bone component to properly prepare the respective bone portion for receiving either a femoral knee implant or a tibial tray implant.  FIG. 16 a    shows an alternative embodiment of the finned platform  530 . The finned platform  530  is shown having a head  532 , a shaft  534  and a plurality of fins  536  extending longitudinally along the shaft  534 . There may be any number of fins  536 , however,  FIG. 16 a    shows the finned platform  530  having four equally spaced fins  536 . The finned platform  530  may also be cannulated as shown at  538  to receive the spike  518  of a bone cutting block  520  (shown in  FIG. 18 ). The benefit of the fins  514  and  536  of platforms  500  and  530  are to resist lateral movement of the cutting block as shown by arrows in  FIG. 15  depicting the prior art. 
       FIGS. 19-22  illustrate a tibial trial  550  having a fin  552 . The fin  552  may be in the form of a raised portion  554  on the underside of the tibial trial  550 . The top side of the tibial trial or implant is often called a tray  556 . The tibial trial  550  with the fin  552  may be used to reinforce bone to reduce the risk of fracture during bone preparation. The tibial trial  550  with the fin  552  may aid in securing the tray  556  during trialing. During trialing, a number of trial inserts (not shown) may be positioned on the tray  556  to determine the correct spacing of the tibial implant with respect to the femoral implant portion of the overall knee implant. The tibial trial  550  with the fin  552  may aid in securing the tray  556  during bone preparation. The tibial trial  550  with the fin  552  may provide a foundation for other instruments, such as punches, reamers, and drills (not shown). As best seen in  FIG. 20 , the fin  552  may be in the form of two arms  558  and  560 . And, as best seen in  FIG. 21 , the fin  552  may be in the form of two arms  562  and  564  with a center portion  566 . As examples, the center portion  566  may be in the form of a circle, cylinder, square, rectangle, or triangle. As best seen in  FIG. 22 , the fin  552  may be in the form of a series of protrusions  568 . For example, the fin  552  may be in the form of a series of cylinders. In use, the tibial trial  550  is placed upon bone and impacted to force the fin  552  into the bone. It would also be possible that the tibial trial has a plurality of holes placed where the protrusions  568  are shown to allow the user to drill a plurality of holes through the trial  550  and into the bone underneath the trial. It would then be easier to place the tibial tray implant into the bone without fracturing the bone site. 
       FIGS. 23-25  illustrate a reamer  600 .  FIG. 23  illustrates a reamer  600  in a first embodiment. The reamer  600  has a shaft  602 , a depth stop  604  and one or more cutting flutes  606  mounted to the shaft  602 . The shaft can be rotated and pivoted to engage the cutting flutes  606  with bone. The shaft  602  may have different shapes. In one embodiment, the shaft  602  may be circular, however the shaft  602  may also be oval (as shown in  FIG. 23 ) or otherwise have any other more complex shape. The benefit of such a reamer is the ability to cut or carve out a non-circular portion of the bone.  FIG. 24  illustrates a reamer  620  in a second embodiment. The reamer  610  has a shaft  612  and one or more cutting flutes  614  mounted to the shaft  612 . The reamer  610  can be used in conjunction with an anchor  616 . The anchor  616  would be inserted within a tibia, for example, to allow for the user to cut or carve out a portion of the bone. The anchor  616  may have a depression  618  to receive a tip  620  of the shaft  612  of the reamer  610 . The tip  620  may be rounded. The anchor  616  may be temporary or permanently positioned within the tibia. The shaft can be rotated and pivoted to engage the cutting flutes  614  with bone.  FIGS. 24 and 25  illustrate a guide  630  that can be used with the second embodiment of the reamer  610 . The guide  630  has a stator  632  with a cam opening  634 . The shaft  612  is moved along the cam opening  634  to restrict and or limit movement of the reamer within the bone. The shape of the cam opening  634  would determine the shape of the bone cutout in the tibia. 
       FIGS. 26-29  illustrate fixation pegs  640 . The fixation pegs  640  are placed on both the tibial and femoral implant components to prevent such components from twisting once placed over the bone portion.  FIG. 26  illustrates a fixation peg  640  with a solid center  642  and a porous outer portion  644 . The shape of the solid center portion  642  provides a fixation peg  640  having portions that are thin enough such that a saw can cut through them but are still thick enough to withstand loading. This is significant as prior fixation pegs were such that a saw could not cut through without significant difficulty. Thus, the pegs shown in  FIG. 26  may be beneficial if the implant must be replaced or revised.  FIG. 27  illustrates a cap  650  (porous or solid) that can be placed over an existing solid fixation peg.  FIG. 28  illustrates a peg  660  with a cylindrical solid core  662  and a porous exterior portion  664 . The solid core  662  can be molded together with the porous exterior portion  664  or the porous exterior portion  664  can be slid over the solid core  662  during use.  FIG. 29  illustrates a modular trial  680  and punch  682 . The punch  682  can be attached to the trial  680  with a quick connect feature. The punch  682  may include a portion  684  to prepare for the lugs and a portion  686  to prepare for one or more arms (or fins). The portion  684  of the punch  682  may be in the form of spikes  688  which would pass through the trial  680  and into the bone underneath the trial. The pegs (like those shown in  FIG. 26 ) of a tibial tray implant would then be inserted into the prepared holes in the bone. 
       FIGS. 30-34  illustrate instruments for tibial surface preparation.  FIG. 30  illustrates the current state of the art wherein there remains an uneven surface after the bone surface is cut. As shown therein a trial  700  could sit unevenly on top of an improperly cut tibial bone.  FIGS. 31-33  illustrate a rasp  702  that is impacted on top of the tibial bone will produce a surface that is more planar. The rasp  702  may be struck by an impactor  704  one time or repeatedly until the rasp  702  is embedded onto the tibial bone to create an even uniform bone surface as shown in  FIG. 33 . In some cases, the bone will flow onto the teeth  706  of the rasp  702  to assist in creating an even bone surface. In some embodiments, the rasp may form a portion of or replace the trial.  FIG. 34  illustrates a multi-part rasp  710 . The rasp  720  has a center portion  712  that is struck by an impactor in the direction of the arrow. Impacting the center portion  712  forces the outer rasp portions  714  and  716  apart to cut and smooth the bone. 
       FIGS. 35-39  illustrate a tibial trial  800  for tibial surface preparation.  FIGS. 35 and 36  illustrate the state of the art. The tibial trial  800  is placed upon the prepared surface after cutting of the tibial bone. However, the prepared surface is shown uneven such that the trial  800  does not sit well upon the prepared surface  802 .  FIGS. 37-39  illustrate a trial  810  with a build-in rasp  812 . In use, the bone  814  is cut and the surface is prepared. The combination trial  810  and rasp  812  is placed upon the bone surface and moved in the directions of the arrows shown in  FIG. 37  to engage the rasp  812  with bone. For example, the combination trial  810  and rasp  812  may be rotated or moved in an A-P or M-L direction to engage the rasp  812  with bone  814  to cut and smooth the surface. Thereafter, normal trialing may be carried out and an implant can be properly mounted to the bone. 
     One of skill in the art will recognize that changes, deletions, alterations, additions and other modifications could be made to the non-limiting embodiments described above without departing from the scope or spirit of the inventions described herein.