Abstract:
A method of preparing a distal femur for implantation of a femoral implant is described. The distal femur is resected to accommodate placement of a trial implant thereon. The trial implant is then placed against the resected distal femur to locate an optimal position for the femoral implant. The trial implant comprises one or more apertures through which holes are drilled in the distal femur and into which trial pegs are inserted into the distal femur to secure the trial implant to the distal femur. The surgeon then evaluates whether the holes in the femur are located appropriately to securely implant the femoral implant onto the femur. The trial implant is ultimately removed in favor of a final implant.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The human knee joint is a hinge joint formed by the cooperation of the distal end of the femur and the proximal end of the tibia, as well as the cooperation of various tendons, ligaments, and cartilage surfaces with each other and/or the femur and tibia. Because of its natural anatomical configuration and the constant pressure it is put under, the knee joint is highly susceptible to the development of defects, whether caused by injury or natural wear and tear. These defects can cause long-term or even permanent pain to patients. Often times, a person suffering from such ailments will be unable to put much, or in some cases, any, weight on the injured knee, making it difficult or impossible to walk. As such, many surgical procedures have been developed to repair defects of the knee joint. 
         [0002]    One type of knee ailment, which can result from trauma to the knee or from natural wear and tear, is the deterioration or other damage of the cartilage located on one or both of the femoral condyles. This cartilage provides an articulation surface that allows for the fluid movement of the distal end of the femur and the proximal end of the tibia (which also includes cartilage surfaces) with respect to each other. Cartilage defects may result on one or both femoral condyles. In the case of the former, unicondylar knee procedures have been developed to replace the cartilage surfaces (and portions of bone) on the single femoral condyle and corresponding cartilage surface (and portions of bone) of the tibia. In the case of the latter, total knee procedures have been developed to replace the cartilage surfaces (and portions of bone) on both femoral condyles and corresponding cartilage surfaces (and portions of bone) of the tibia. 
         [0003]    Both unicondylar and total procedures involve the resection of at least one of the condyles of the femur to accept a femoral implant and the portion of the tibia corresponding to the femoral condyle(s) to accept a tibial implant. These implants are designed to replicate the articular surfaces formed by the original anatomy. Of course, depending upon patient size and/or other anatomical features, the size, location, and orientation of the femoral and tibial implants may widely vary. As such, much care must be given to properly implanting the implants so that the natural movement of the knee joint is restored. To aid in achieving this goal, trial implants, which essentially amount to provisional versions of the final implants, are often utilized. In addition to the tools utilized in making the bone cuts and for use in implanting the final implants, tools are often required to place the trial implants. The overwhelming number of implants, trial implants and tools required or desirable for a single knee surgery necessarily increases costs and overall time associated with the surgery. 
         [0004]    Therefore, there is a need for an effective way of properly preparing the distal femur and proximal tibia to receive implants during a surgical knee procedure, through the use of less implants and tools. 
       SUMMARY OF THE INVENTION 
       [0005]    A user prepares a distal femur for implantation of a femoral implant by resecting a condyle of the distal femur and placing a trial femoral implant with at least one aperture against the resections. The user then inserts a pin into the femur through a pin aperture of the trial implant to hold the trial implant in place. Using a drill guide and drilling apparatus, the user then drills trial peg holes into the femur through the drill guide and the apertures in the trial implant. The user then uses an insertion tool to couple with a trial peg and insert the trial peg into a trial peg hole of the femur through an aperture of the trial implant to secure the implant to the femur. The user then removes the pin from the femur and the trial implant. The user then tests the mobility of the knee joint with the trial implant in place to verify whether the size, position, and orientation of the trial implant are appropriate for a femoral implant. Next, the user uses the insertion tool to remove the trial peg from the femur and the trial implant, and then removes the trial implant from the femur. 
         [0006]    Based on the user&#39;s verification whether the size, position, and orientation of the trial implant were appropriate for a femoral implant, the user either implants a femoral implant at the same position and orientation, or revaluates the knee joint. The latter may include beginning the process again with a new trial implant and may involve the re-drilling of larger peg holes in the femur. 
         [0007]    A first aspect of the present invention is a method of preparing a distal femur for implantation of a femoral implant. In accordance with certain embodiments of this first aspect, the method includes the steps of making at least one resection in the distal femur, selecting a trial femoral implant to be implanted on the distal femur, the trial implant including a first aperture, placing the trial implant on the resected distal femur, drilling a first peg hole in the femur through the first aperture, and inserting a trial peg through the first aperture and into the first peg hole formed in the distal femur. 
         [0008]    In other embodiments, the method may include the further step of drilling a second peg hole in the femur through a second aperture in the trial implant. The drilling step may include drilling through a drill guide placed adjacent the first aperture, with the drill guide including an elongate tube having a passage aligned with the first aperture. The first aperture may include a countersink and a shoulder, the elongate tube placed within the countersink and against the shoulder. The drilling step may include drilling through a drill guide placed adjacent the first and second apertures. Alternatively, or additionally, the drill guide may include a first elongate tube having a first passage aligned with the first aperture and a second elongate tube having a second passage aligned with the second aperture. The inserting step may include coupling and uncoupling the trial peg with an insertion device. The method may include the further step of removing the trial peg from the distal femur, where the removing step includes coupling the trial peg with an insertion device. The method may also include the step of verifying the position and orientation of the trial implant on the distal femur. The method may also include the step of removing the trial implant from the femur and implanting a femoral implant having a first peg, the first peg disposed in the first peg hole when the femoral implant is implanted. The trial peg may include a head and a shank and the the first aperture may include a countersink and shoulder, where the head of the trial peg is smaller than the countersink and larger than the shoulder. The method may also include the step of evaluating the spacing of a knee joint, where the evaluating step includes contacting and moving the trial femoral implant with a tibial trial implant. 
         [0009]    A second aspect of the present invention is another method of preparing a distal femur for implantation of a femoral implant. In accordance with one embodiment of this second aspect, the method may include the steps of making at least one resection in the distal femur, selecting a trial femoral implant to be implanted on the distal femur, the trial implant including a first aperture having a first countersink and a first shoulder, placing the trial implant on the resected distal femur, placing a drill guide in the first countersink of the first aperture, drilling a first peg hole in the femur through the drill guide and the first aperture, and inserting a trial peg through the first aperture and into the first peg hole formed in the distal femur, the trial peg including a head dimensioned smaller than the first countersink and larger than the first shoulder and a shank dimensioned smaller than the first countersink and first shoulder. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A more complete appreciation of the subject matter of the present invention and the various advantages thereof can be realized by reference to the following detailed description with reference to the accompanying drawings in which: 
           [0011]      FIG. 1  is a side perspective view of the bones of a knee joint with resections made on both the distal femur and proximal tibia. 
           [0012]      FIG. 2  is a front perspective view of the knee joint shown in  FIG. 1  with a trial femoral implant placed on the distal femur. 
           [0013]      FIG. 3  is a side perspective view of the knee joint shown in  FIG. 2 . 
           [0014]      FIG. 4  is a perspective view of the knee joint shown in  FIG. 1  with trial implants placed on both the distal femur and proximal tibia. 
           [0015]      FIG. 5  is a perspective view similar to that of  FIG. 4  with a drill guide, insertion tool used to place the drill guide, and a drilling apparatus for drilling through the drill guide and the trial femoral implant shown. 
           [0016]      FIG. 6  is a perspective view similar to that of  FIG. 4  with a pin and an insertion tool for inserting the pin into the femur through a pin aperture of the trial femoral implant shown. 
           [0017]      FIG. 7  is a perspective view of the pin shown in  FIG. 6 . 
           [0018]      FIG. 8  is a perspective view of the insertion tool shown in  FIGS. 5 and 6 . 
           [0019]      FIG. 9  is a side perspective illustration of the bones of the knee joint with trial implants placed on both the distal femur and proximal tibia and the range of motion of the joint being tested. 
           [0020]      FIG. 10  is a perspective view similar to that of  FIG. 4  with a final femoral implant and final tibial implant implanted on the distal femur and proximal tibia, respectively. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    In describing the preferred embodiments of the subject matter illustrated and to be described with respect to the drawings, specific terminology will be used for the sake of clarity. However, the invention is not to be limited to the specific term so selected, and it is to be understood that each specific term includes all technical equivalents which function or operate in a similar manner to accomplish a similar purpose. Furthermore, it is noted that while the methods and apparatus of the present invention are shown and described in connection with a unicondylar procedure, such may also apply to a total knee procedure. 
         [0022]    As used herein, when referring to bones or other parts of the body, the term “proximal” means closer to the heart and the term “distal” means more distant from the heart. The term “inferior” means toward the feet and the term “superior” means towards the head. The term “anterior” means towards the front part of the body or the face and the term “posterior” means towards the back of the body. The term “medial” means toward the midline of the body and the term “lateral” means away from the midline of the body. 
         [0023]      FIG. 1  depicts a knee joint  1  which has been prepared, so that both a distal portion of a femur  2  and a proximal portion of a tibia  3  of knee joint  1  have been resected in accordance with conventional surgical techniques for a unicondylar knee procedure. Specifically, the distal portion of one condyle of femur  2  has been resected to create resected surfaces  4   a - c  and the proximal portion of one side of tibial  3  has been resected to create a single flat resected surface  5 . Resected surfaces  4   a - c  are configured to accept and engage with like surfaces formed on a final femoral implant (as well as a trial femoral implant), and resected surface  5  is configured to accept and engage with a like surface formed on a final tibial implant (as well as a trial tibial implant). Different implants may require cooperation with differently configured resected surfaces on the femur and/or tibia. For instance, it is contemplated that a final femoral implant (and trial femoral implant) may be configured to engage five resected surfaces on the distal portion of femur  2 , as opposed to the three shown in  FIG. 1 . Likewise, although the resected surfaces are shown in the accompanying drawings as being flat, such surfaces may be of any configuration, including but not limited to curved surfaces. Moreover, although the resected surfaces are shown in the drawings as being formed in the actual bone of the femur and tibia, it is contemplated that such surfaces could be formed in cartilage surfaces in the knee joint. It is to be understood that the present invention is not limited to only those configurations shown and/or discussed in the present application. 
         [0024]      FIGS. 2 and 3  show a femoral trial implant  10  in accordance with the present invention. Specifically, trial implant  10  is shown placed on the resected distal portion of femur  2  depicted in  FIG. 1 . Trial implant  10  includes an articular surface  12  and an opposing bone contacting surface  14  (best shown in  FIG. 3 ). While articular surface  12  is a generally continuous curved surface, bone contacting surface is made up of three intersecting flat surfaces  16   a ,  16   b , and  16   c  which cooperate with resected surfaces  4   a ,  4   b , and  4   c , respectively. Trial implant  10  also includes apertures  18  and  20 , which are formed through articular surface  12  and bone contacting surface  14  so as to allow for access to femur  2  while the implant is placed on the bone. Preferably, aperture  18  includes a countersunk surface  18   a  and aperture  20  includes a countersunk surface  20   a , thereby forming shoulders  22  and  24 , respectively. In the embodiment shown in the figures, trial implant  10  further includes a pin aperture  26  (best shown in  FIG. 2 ) to allow insertion of a pin  28  (best shown in  FIG. 4 ) into femur  2  to temporarily hold trial implant  10  in place. 
         [0025]    Similar to  FIGS. 2 and 3 ,  FIG. 4  depicts trial implant  10  placed on the resected distal portion of femur  2 . Pin  28  is placed through pin aperture  26  so as to hold trial implant  10  in place during drilling procedures that will be discussed more fully below.  FIG. 4  also depicts a tibial trial implant  30  placed on resected surface  5  of tibia  3 . Any suitable tibial trial implant can be used in connection with the present invention. As will be discussed more fully below, implants  10  and  30  are meant to emulate final implants (shown in  FIG. 10 ) that are implanted during the surgical procedure, but are provided to allow the surgeon to confirm the size and fit of the final implants and evaluate the movement of the femur and tibia with respect to each other prior to final implantation (see  FIG. 9 ). As will be discussed more fully below, trial implant  10  is also provided to allow for further preparation of femur  2 . 
         [0026]    The placement of a final femoral implant requires that such be fixed to femur  2  in some fashion. In accordance with the present invention, it is contemplated to utilize an implant having two pegs meant to engage holes formed in the distal portion of femur  2 . These holes are preferably formed prior to the implantation of the final implant, through the use of trial implant  10  of the present invention. Specifically, aforementioned apertures  18  and  20  are meant to cooperate with a drill guide  32  (best shown in  FIG. 5 ) to guide a drill  34  to prepare holes in the distal femur  2 . Apertures  18  and  20  are essentially sized and configured on implant  10  so as to directly correspond to the peg of the final femoral implant. Likewise, drill guide  32  includes two elongate drill tubes  36  and  38  which are sized and configured to fit within countersinks  18   a  and  20   a  and abut shoulders  22  and  24  of apertures  18  and  20 . These tubes provide a guide for the elongate drill  34 , which is utilized in making the two necessary peg holes in distal femur  2 . Drill guide  32  also preferably includes an aperture  40  (shown as a third elongate tube in the drawings) that is capable of being removably coupled with an insertion/extraction tool  42  (discussed more fully below). It is noted here that drill guide  32  may include a single drill tube that would require the separate placement of the guide within apertures  18  and  20  to prepare the necessary peg holes. It is also noted that drill guide  32  may be formed integral with an insertion handle, or tool  42  may be left connected with drill guide  32  during a surgical procedure. However, the removable nature of tool  42  from drill guide  32  may allow for the tool to be removed prior to the drill procedure, thereby providing the surgeon with a clearer view of the surgical area. 
         [0027]    In use, after trial implant  10  is placed on the resected distal end of femur  2  (and optionally pinned by pin  28 ), drill guide  32  is engaged with insertion tool  42  and tubes  36  and  38  are guided into apertures  18  and  20 , respectively. The tubes are preferably inserted until a portion of tube  36  abuts shoulder  22  and a portion of tube  38  abuts shoulder  24 . Because the tubes are sized to be slightly smaller than countersinks  18   a  and  20   a , they are somewhat retained within apertures  18  and  20 . Thus, insertion/extraction tool  42  can be disengaged from guide  32 . Alternatively, tool  42  can be left in place. Regardless, the surgeon can then move drill  34  through each of tubes  36  and  38  to form the peg holes discussed above. When complete, tool  42  can be re-engaged with drill guide  32  (if it had been previously disengaged) and the assembly can be removed from the surgical area. As trial implant  10  is designed to emulate a final implant, and apertures  18  and  20  are so situated, femur  2  is now provided with the necessary peg holes to accept pegs of a final implant. 
         [0028]    With the peg holes having been formed, the surgeon then utilizes trial implants  10  and  30  to evaluate the fit of the implants and the spacing of knee joint  1 . However, because it extends from articular surface  12  of trial implant  10 , pin  28  (if inserted) must be removed. In order to ensure that trial implant  10  remains attached to femur  2 , it is affixed in another manner. As is shown in  FIG. 6 , in accordance with the present invention, a trial peg  44  is provided and is preferably capable of cooperating with insertion/extraction tool  42 , or a similar tool. Trial peg  44  includes a head  46 , an elongated spike  48 , and a shank  50  connecting the head and the spike (shown in more detail in  FIG. 7 ). Head  46  is preferably dimensioned to pass through countersink  20   a , but abut shoulder  24 . When placed within aperture  20 , head therefore sits below articular surface  12 . This allows the surgeon to move trials  10  and  30  with respect to each other without any interference from trial peg  44 , or any other component. Spike  48  and shank  50  are preferably sized and configured to fit entirely through aperture  20  and the already prepared peg hole in femur  2 . However, spike  48  preferably extends far enough from shank  50  to extend into bone situated below the already prepared peg hole, so as to allow the spike to engage unprepared bone in the femur  2 . This allows trial peg to act to fix trial implant  10  to femur  2  much in the way a screw or nail would in a wood substrate. The trial peg also preferably includes an aperture  52  that extends through head  46  and partially into shank  50  for engagement with insertion tool  42 . While discussed above as only being placed within aperture  20 , it is noted that in other embodiments, peg  44  could be designed to be placed within aperture  18 , or in both apertures. 
         [0029]    In use, prior or subsequent to removing pin  28 , trial peg  44  is coupled with insertion/extraction tool  42  which the surgeon utilizes to guide the peg through aperture  20  of implant  10 . Trial peg  44  is pushed through aperture  20  until head  46  abuts shoulder  24  and spike  48  is inserted into some unprepared bone. The surgeon may perform this insertion merely by hand or could utilize an impaction instrument to ensure the pin is properly placed. With the peg so placed, tool  42  can be removed. The surgeon can then evaluate knee joint  1 . This may include moving the implants  10  and  30  with respect to each other, so that the femur and tibia are moved through a full range of motion. The fact that trial peg  44  is completed disposed below articular surface  12  allows for this entire motion. When satisfied with the fit and movement of the joint, the surgeon can then re-engage tool  42  with trial peg  44  and remove the peg. Again, the surgeon may perform this step merely by hand or through the use of an additional instrument such as a grip or the like. Trial implants  10  and  30  can then be removed from knee joint  1  and the final implants can be implanted (see  FIG. 10 ). 
         [0030]    Insertion/extraction tool  42  is preferably meant to cooperate with both drill guide  32  and trial peg  44 . While many different insertion/extraction tools can be utilized, with each using different methods to connect with guide  32  and peg  44 ,  FIG. 8  illustrates in more detail one embodiment tool  42  in accordance with the present invention. The tool shown in that figure includes a barrel  52  and a handle  54  which are connected to each other. At one end of barrel  52  is an actuator  56  (shown as a depressible button), and at the other end is a spring detent tip  58 . Tip  58  is preferably dimensioned to couple with both aperture  40  of drill guide  32  and aperture  52  of trial peg  44 . Likewise, tip  58  preferably includes a spring detent meant to cooperate with a corresponding structure formed on drill guide  32  and trial peg  44 . For instance, both drill guide  32  and trial peg  44  includes apertures formed near their respective tool engaging apertures for acceptance of a ball or other structure of the spring detent. In use, depression of actuator  56  causes the spring detent to move thereby allowing for the attachment and removal of tip  58  from either aperture  40  or aperture  52 . Actuator  56  may be spring actuated so as to allow for the actuator to be biased in an engagement position absent a force applied thereto. It is also contemplated to provided one tool for use in inserting drill guide  32  and trial peg  44 , and a separate tool for use in extracting such components. Moreover, specific tools may be provided for cooperation with only one of guide  32  and peg  44 . 
         [0031]    The description provided herein is intended to be exemplary, and the present invention is not limited to the embodiment disclosed herein. It is acknowledged that other embodiments or variations of the present embodiments will become obvious to those skilled in the art, and the present application intends to encompass all such embodiments. For example, while the present disclosure describes a trial implant including two trial peg holes for use with two trial pegs, a number of different quantities of pegs and peg holes could be used without deviating from the scope and spirit of the present invention. Similarly, although the present embodiment discloses a trial implant having three flat posterior surfaces and resections creating three surfaces for engagement therewith, a trial implant and resections having a different number of surfaces would not deviate from the scope and spirit of the present invention. 
         [0032]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.