Patent Publication Number: US-2010114102-A1

Title: Femoral cutting block

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 11/642,355, filed on Dec. 20, 2006, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present application relates generally to the implant of prosthetic joints and pertains, more specifically, to the preparation of the distal femur for the implantation of a femoral knee prosthesis, utilizing a femoral cutting block to assist in establishing the surfaces necessary for locating and securing the prosthesis in place on the femur. 
     The implant of a prosthetic knee joint requires that the distal femur be prepared to receive the femoral component of the knee prosthesis by cutting the bone of the femur to establish accurately located surfaces. Upon implantation, the femoral component will rest on these surfaces. 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. 
     Various cutting blocks are available to the surgeon for assisting in guiding a saw blade to make the femoral cuts which establish the desired surfaces. These guides usually have guide surfaces for making four resections and are located and secured on the distal femur, upon an already resected transverse surface on the distal femur. Typically, surfaces are provided for guiding the saw blade during the execution of an axially directed anterior femoral cut, an axially directed posterior femoral cut, an anterior chamfer and a posterior chamfer, all specifically related to the size of the femoral knee prosthesis to be implanted and to the position and orientation of the femoral knee prosthesis on the distal femur. A four-in-one cutting block is a single cutting block for making the four cuts. A four-in-two cutting block comprises two separate blocks for making the four cuts. However, such conventional cutting blocks may exhibit various disadvantages. For example, the two blocks of a conventional four-in-two cutting block are used separately and do not interlock to each other. That is, the first block is used making a first set of cuts comprising the anterior and posterior chamfer cuts and the second block is used for making a second set of cuts comprising the anterior and posterior cuts. The first set of cuts is loosely correlated to the second set of cuts which may decrease the accuracy of the cuts. In addition, these cutting blocks are made of metal which may increase the cost of manufacture. Moreover, because of the high cost of such blocks, they are typically reused for additional surgical procedures. However, this may require sterilization of the blocks which may be costly and inconvenient. 
     SUMMARY OF THE INVENTION 
     The present application discloses a cutting block that may help overcome some of the above-mentioned disadvantages. The cutting block of the present application is a four-in-two (4-in-2) cutting block assembly which may improve the accuracy in the preparation of the distal femur for the implantation of a knee prosthesis. The cutting block assembly comprises a first block for making the anterior and posterior chamfer cuts and a second block for making the anterior and posterior cuts. The first and second blocks interlock which helps correlate the four cuts and improve the accuracy of the cuts. The second block includes extended cutting surfaces which may further help improve the accuracy of the anterior and posterior cuts. In addition, the second block provides a visual indication of the accuracy of the anterior and posterior chamfer cuts before the anterior and posterior cuts are made. Moreover, the cutting block can be made of polymeric material which may help reduce the cost of making the block. In addition, because polymeric material is relatively lightweight compared to metal, the cutting block may be relatively lightweight which may improve the handling of the cutting block during a surgical procedure. 
     An aspect of the present application is a cutting block assembly comprising interlocking first and second blocks for resecting a distal femur. The first block has a first surface for providing a guiding surface for making an anterior chamfer cut on the femur and a second surface for providing a guiding surface for making a posterior chamfer cut on the femur. The second block is adapted to detachably couple to the first block. The second block has a first surface for providing a guiding surface for making an anterior cut on the femur and a second surface for providing a guiding surface for making a posterior cut on the femur. 
     Another aspect of the present application is a method of resecting a distal femur. The method includes attaching a first block to the distal femur, the first block having a first surface providing a guiding surface for making an anterior chamfer cut on the femur, a second surface providing a guiding surface for making a posterior chamfer cut on the femur, and making anterior and posterior chamfer cuts on the distal femur. The method further includes attaching a second block to the first block, the second block having a first surface providing a guiding surface for making an anterior cut on the femur, and a second surface providing a guiding surface for making a posterior cut on the femur, and making anterior and posterior cuts on the distal femur. 
     Yet another aspect of the present application is a method of resecting a distal femur. The method includes attaching a first block to the distal femur, the first block having a first surface providing a guiding surface for making an anterior chamfer cut on the femur, a second surface providing a guiding surface for making a posterior chamfer cut on the femur. The method further includes attaching a second block to the first block, the second block having a first surface providing a guiding surface for making an anterior cut on the femur, and a second surface providing a guiding surface for making a posterior cut on the femur. The method further includes making anterior and posterior cuts on the distal femur, detaching the second block from the first block, and making anterior and posterior chamfer cuts on the distal femur. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of the bone cutting blocks in an un-assembled configuration, in accordance with an embodiment of the present application. 
         FIG. 2  is an isometric view of the cutting blocks of  FIG. 1  from a different angle. 
         FIG. 3  is a detailed isometric view of a first block of the cutting block assembly of  FIG. 1 . 
         FIG. 4  is a detailed partial isometric view of a second block of the cutting block assembly of  FIG. 1 . 
         FIG. 5  is an isometric view of the cutting block assembly of  FIG. 1 , in an assembled configuration. 
         FIG. 6  is a detailed partial isometric view of the cutting block assembly of  FIG. 5 . 
         FIG. 7  is a detailed cross-sectional view of the cutting block assembly of  FIG. 5  taken along lines A-A. 
         FIG. 8A  is an isometric view and  FIG. 8B  is a medial view of a distal femur after a distal cut has been made on the surface of the distal femur. 
         FIG. 9A  is an isometric view and  FIG. 9B  is a medial view showing the first block of the cutting block of  FIGS. 1-7  being attached to the distal femur of  FIGS. 8A-8B . 
         FIG. 10A  is an isometric view and  FIG. 10B  is a medial view showing the first block attached to the distal femur of  FIGS. 9A-9B  in preparation for making anterior and posterior chamfer cuts on the surface of the distal femur. 
         FIG. 11A  is an isometric view and  FIG. 11B  is a medial view showing the distal femur of  FIGS. 10A-10B  after the anterior and posterior chamfer cuts have been made. 
         FIG. 12A  is an isometric view and  FIG. 12B  is a medial view showing the distal femur of  FIGS. 11A-11B  with the second block being attached to the first block. 
         FIG. 13A  is an isometric view and  FIG. 13B  is a medial view showing the first and second blocks being interlocked to form a cutting block assembly for making anterior and posterior cuts on the surface of the distal femur of  FIGS. 12A-12B . 
         FIG. 14A  is an isometric view and  FIG. 14B  is a medial view showing the distal femur of  FIGS. 13A-13B  after the anterior and posterior cuts have been made on the surface of the distal femur. 
         FIG. 15  is a medial view showing the distal femur of  FIGS. 14A-14B  after the cutting block assembly has been removed. 
         FIG. 16  is an isometric view of the bone cutting blocks in an un-assembled configuration, in accordance with another embodiment of the present application. 
         FIG. 17  is a side view of the cutting blocks of  FIG. 16 . 
         FIG. 18  is an isometric view of the second block of the cutting block assembly of  FIG. 16 . 
         FIG. 19  is an isometric view of the cutting blocks of  FIG. 16  in an assembled configuration. 
         FIG. 20  is another view of the cutting block assembly of  FIG. 19 . 
         FIG. 21  is a medial view of the cutting block assembly of  FIG. 16  being attached to a distal femur. 
         FIG. 22  is a medial view showing the cutting block assembly attached to the distal femur of  FIG. 21  in preparation for making anterior and posterior cuts on the surface of the distal femur. 
         FIG. 23  is a medial view showing the distal femur of  FIG. 22  after the anterior and posterior cuts have been made. 
         FIG. 24  is a medial view showing the distal femur of  FIG. 23  with the second block of the cutting block assembly being removed. 
         FIG. 25  is a medial view showing the distal femur of  FIG. 24  with the second block removed in preparation for making posterior and anterior chamfer cuts on the surface of the distal femur. 
         FIG. 26  is a medial view showing the distal femur of  FIG. 25  after the anterior and posterior chamfer cuts have been made on the surface of the distal femur. 
         FIG. 27  is a medial view showing the distal femur of  FIG. 26  after the first cutting block of the cutting block assembly has been removed and the four cuts have been made. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-7 , shown is a cutting block assembly generally denoted as  10  comprising a first block  12  capable of interlocking with a second block  14  to form a four-in-two (4-in-2) cutting block for resecting a portion of a bone such as a distal femur. Referring to  FIGS. 1-2 , the first block  12  is a generally triangular shaped block forming an anterior-chamfer cutting surface  16 , a posterior-chamfer cutting surface  18 , a contact surface  20  and side surfaces  22 . The anterior-chamfer cutting surface  16  provides a guiding surface for making an anterior-chamfer cut on a femur (not shown). The posterior-chamfer cutting surface  18  provides a guiding surface for making a posterior-chamfer cut on the femur. The contact surface  20  includes protrusions  26  adapted to fit into holes in the distal femur to detachably couple the first block  12  to the distal resected surface of a distal femur (not shown), as explained below in further detail. In one embodiment, the protrusions  26  are shown as cylindrical posts but can have other shapes such as square. In one embodiment, the first block  12  also may include angled pin holes  28  extending outwardly from the contact surface  20  to the side surfaces  22 . The pin holes  28  are adapted to receive pins (not shown) to more firmly secure the first block  12  to the distal resected surface of the distal femur. The cutting surfaces  16 ,  18  of the first block  12  form a generally V-shaped portion  13  for coupling to the second block  14 , as explained below. 
     The second block  14  is a generally trapezoidal shaped block with V-shaped portion  15  sized to receive the V-shaped portion  13  of the first block  12 . The second block  14  forms an anterior cutting surface  30 , a posterior cutting surface  32 , contact surfaces  34 ,  36  and side surfaces  38 . The anterior cutting surface  30  provides a guiding surface for making an anterior cut on the femur. The posterior cutting surface  32  provides a guiding surface for making a posterior cut on the femur. The contact surfaces  34 ,  36  of the second block  14  form the generally V-shaped open-faced portion or channel  15  which is complementary to the generally V-shaped portion  13  formed by the surfaces  16 ,  18  of the first block  12 . In this manner, as explained above, the portion  13  of the first block  12  is capable of fitting within the portion  15  of the second block  14 . 
     One possible feature of the cutting block assembly  10  is an interlocking mechanism for detachably securing the blocks  12 ,  14  to each other. In a preferred embodiment, the interlocking feature is a slidable coupling mechanism comprising holes  24  of the first block  12  adapted to receive protrusions  44  of the second block  14 . Two protrusions  44  extend outwardly from the surface  34  of the second block  14  and one protrusion  44  extends outwardly from the surface  36 . In a complementary manner, two holes  24  extend through the surface  16  of the first block  12  and one hole  24  extends through the surface  18  of the first block. The protrusions are adapted to slide into and fit within the holes  24  to form an interlocking feature to detachably couple or interlock the first block  12  to the second block  14 . Such an arrangement may provide various advantages. For example, as explained above, the first block  12  provides for anterior and posterior chamfer cuts and the second block  14  provides for anterior and posterior cuts. By using the interlocking feature to interlock the first block  12  with the second block  14 , the cutting block assembly  10  allows the four distal femur cuts (anterior-chamfer, posterior-chamfer, anterior, posterior) to be tightly correlated to each other which may help increase the accuracy of the cuts. 
     Another possible feature of the cutting block assembly  10  is that it provides a mechanism to verify the accuracy of the posterior and anterior chamfer cuts before the anterior and posterior cuts are made. For example, in one embodiment, the second block  14  includes extended portions  30   a ,  32   a  which extend beyond the contact surface  20  and cutting surfaces  16 ,  18  of the first block  12 , as best shown in  FIG. 7 . The extended portions  30   a ,  32   a  include extended portions of contact surfaces  34 ,  36 , respectively, and extended portions of cutting surfaces  30 ,  32 , respectively. As explained below in detail, because the extended cutting surfaces  30 ,  32 , which are part of extended portions  30   a ,  32   a , provide increased cutting surface area for making the anterior and posterior cuts which may help improve the accuracy of the anterior and posterior cuts. In addition, the contact surfaces  34 ,  36 , which are part of portions  30   a ,  32   a , extend onto the chamfer cuts which may allow a user to verify the anterior and posterior chamfer cuts made with the first block before making the anterior and posteriors cuts with the second block. 
     Another possible feature of the cutting block assembly is that it can be made of relatively lightweight material which may provide various advantages. In one embodiment, the blocks  12 ,  14  are made of a polymeric material such as plastic which may help reduce the complexity and cost of manufacturing the block. Moreover, because the blocks are made of a polymeric material, the blocks can be discarded after being used instead of having to sterilize the blocks for subsequent use. However, the blocks  12 ,  14  can be made of other materials, such as metal, or other materials well known to one skilled in the art. In a preferred embodiment, the cutting surfaces  16 ,  18 ,  30 ,  32  are generally planar and smooth. In another embodiment, the surfaces  16 ,  18 ,  30 ,  32  can be non-smooth with grooves or ridges on the surfaces. In a preferred embodiment, the contact surfaces  34 ,  36  of the second block  14  are formed with ribs  42  extending into the interior of the block which may help reduce the amount of material and thus improve manufacturability and reduce the cost of manufacture. In addition, the use of less material and/or polymeric material may help make the cutting block more lightweight which may make the cutting block easier to use or manipulate during a surgical procedure. 
     Another possible feature of the cutting block assembly is that it provides a “keyed” mechanism to help ensure that the blocks are interlocked in a proper manner. In one embodiment, the number and arrangement of the protrusions  44  and holes  24  provide a locking mechanism which requires the blocks  12 ,  14  to be oriented and coupled to each other in only a single configuration. The first block  12  includes two holes  24  disposed over a single hole  24 . In a complementary manner, the second block  14  includes two protrusions  44  disposed over a single protrusion. In this manner, the blocks  12 ,  14  can be coupled to each other in only one orientation. That is, the anterior surfaces  16 ,  30  are required to be aligned to each other and the posterior surfaces  18 ,  32  are required to be aligned to each other. This feature may help reduce the possibility of error during a surgical procedure. However, the number, size and arrangement of the protrusions  44  and holes  24  can be implemented in other ways. For example, the arrangement can be reversed, with one protrusion disposed over the two protrusions and the holes  24  configured in a similar manner. 
     Referring to  FIGS. 3 and 4 , shown are detailed views of the first block  12  and second block  14  respectively of  FIGS. 1-2 . As explained above, the protrusions  44  of the second block  14  are adapted to fit within the holes  24  of the first block  12  to form an interlocking feature to detachably couple or interlock the blocks  12 ,  14  to each other. The protrusions  44  and the corresponding holes  24  are shown as generally square shaped but can have other shapes, such as cylindrical, as long as they are complementary to provide a relatively secure interlock between the blocks. The protrusions  44  have generally square shaped ramps  44   a  on bottom surfaces of the protrusions. In a complementary manner, the holes  24  have generally square shaped ramps  24   a  on bottom surfaces of the holes. The protrusions  44  are slightly yieldable to accommodate the ramps  24   a  of the holes, as explained below. 
     Referring to  FIGS. 4 ,  5 ,  6 , shown are detailed views of the first block  12  and second block  14  of  FIG. 1  in an assembled configuration. To assemble the blocks  12 ,  14  to form assembly  10 , the blocks  12 ,  14  are advanced toward each other to permit the protrusions  44  of the second block  14  to be inserted into the holes  24  of the first block  12 . The blocks  12 ,  14  are further advanced toward each other such that the ridges  44   a  of the second block  14  contact the ramps  24   a  of the first block  12 . As the blocks  12 ,  14  are further advanced toward each other, the protrusions  44  yield upward and away from the ramps  24   a  and the ridges  44   a  pass beyond the surface of the ramps  24   a  and return to their original position. Once the ridges  44   a  are positioned behind the surfaces of the ramps  24   a , the protrusions  44  are held in place in the holes  24  to provide a secure detachable coupling or interlock between the blocks  12 ,  14 . To detach the blocks  12 ,  14  from each other, the blocks are moved away from each other with sufficient force to cause the ridges  44   a  to slide over and away from the ramps  24   a  thereby freeing the blocks from each other. 
     Referring to  FIGS. 8A-8B  to  14 A- 14 B, a description is provided of a surgical procedure for resecting a distal femur  52  of a femur bone  50  using the cutting block assembly  10  of  FIGS. 1-7  in accordance with an embodiment of the present application. Referring to  FIGS. 8A-8B , the distal femur  52  has an anterior portion  52   a , a medial portion  52   b , a posterior portion  52   c , and a lateral portion  52   d . In an initial step of the surgical procedure, a distal cut is made which involves the resection or removal of a distal bone portion (not shown) from the distal femur  52  leaving behind a generally flat resected distal surface  56 . A cutting device (not shown) can be used to remove the distal bone portion using conventional techniques. The cutting device can be a bone cutter such as an oscillating saw or other bone cutting device well-known to one skilled in the art. Once the distal cut has been made, pilot holes  54  can be drilled into the distal surface  56  in precise location and orientation as known to one skilled in the art to accommodate the protrusions  26  of the first block  12  as shown in  FIGS. 9A-9B  and described below. 
       FIG. 9A  is an isometric view and  FIG. 9B  is a medial view showing the first block  12  of the cutting block assembly  10  of  FIGS. 1-7  being attached to the distal femur of  FIGS. 8A-8B . The first block  12  is advanced toward the distal femur  52  with the contact surface  20  of the first block  12  oriented to face the distal surface  56  of the distal femur. The first block  12  is also oriented with the protrusions  26  of the first block being aligned with the holes  54  of the distal surface  56 . In addition, the first block  12  is oriented with the cutting surface  16  (labeled “Anterior”) generally facing the anterior portion  52   a  of the distal femur  52 . The first block  12  is advanced toward the distal surface  56  until the protrusions  26  enter the holes  54  of the distal surface  56  and the contact surface  20  of the first block  12  is flush with the distal surface  56 , as shown in  FIGS. 10A-10B  and described further below. 
       FIG. 10A  is an isometric view and  FIG. 10B  is a medial view showing the first block  12  attached to the distal femur  52  of  FIGS. 9A-9B  in preparation for making anterior and posterior chamfer cuts on the surface of the distal femur  52 . The first surface  16  of the first block  12  provides a guiding surface for making an anterior-chamfer cut along an anterior-chamfer plane  62 . To make the anterior-chamfer cut, a bone cutting device such as a saw (not shown) is applied to the surface  16  of the first block  12  and advanced toward the distal surface  56  along the plane  62  until an anterior-chamfer bone portion  64  is removed. In a similar manner, the second surface  18  of the first block  12  provides a guiding surface for making a posterior-chamfer cut along a posterior-chamfer plane  66 . To make the posterior-chamfer cut, a cutting device is applied to the surface  18  of the first block  12  and advanced toward the distal surface  56  along plane  66  until a posterior-chamfer bone portion  68  is removed. In one embodiment, holes (not shown) can be made to the distal surface  56  through which pins (not shown) could be inserted through holes  28  of the first block  12  and into the holes of the surface  56 . In another embodiment, self-drilling bone pins (not shown) can be used which don&#39;t require holes to be predrilled into the surface  56 . In both cases, the first block can be more firmly secured to the distal surface  56  which may reduce the possibility of movement of the first block during the cutting process. As explained above, the anterior-chamfer cut is made and then the posterior-chamfer cut is made. However, the sequence of cuts could be reversed with the posterior-chamfer cut being made first and the anterior-chamfer cut being made second. 
       FIG. 11A  is an isometric view and  FIG. 11B  is a medial view showing the distal femur of  FIGS. 10A-10B  after the anterior and posterior chamfer cuts have been made. Once the anterior-chamfer cut has been made, an anterior-chamfer surface  70  remains. Likewise, once the posterior-chamfer cut has been made, a posterior-chamfer surface  72  remains. The distal femur  52  is now ready to have the second block attached to the first block  12  and to have the anterior and posterior cuts made as shown in  FIGS. 12A-12B  and explained below. 
       FIG. 12A  is an isometric view and  FIG. 12B  is a medial view showing the distal femur of  FIGS. 11A-11B  with the second block  14  being attached to the first block  12 . The second block  14  is advanced toward the first block  12  with the contact surface  34  of the second block facing the cutting surface  16  of the first block and the contact surface  36  of the second block  14  facing the cutting surface  18  of the first block. The second block  14  is oriented with the protrusions  44  of the second block being aligned with the holes  24  of the first block  12 . The second block  14  is then advanced toward the first block  12  until the protrusions  44  of the second block  14  enter the holes  24  of the first block  12  and the blocks interlock, as shown in  FIGS. 13A-13B  and described further below. 
       FIG. 13A  is an isometric view and  FIG. 13B  is a medial view showing the first block  12  and second block  14  being interlocked to form a cutting block assembly for making anterior and posterior cuts on the surface of the distal femur  52 . As explained above, the cutting assembly  10  has an interlocking feature which allows the blocks  12 ,  14  to be interlocked to each other and to correlate the four distal femur cuts (anterior-chamfer, posterior-chamfer, anterior, posterior) to each other. In this manner, the accuracy of the cuts may be increased. The anterior cutting surface  30  of the second block  14  provides a guiding surface for making an anterior cut along an anterior plane  74 . In a similar manner, the posterior cutting surface  32  of the second block  14  provides a guiding surface for making a posterior cut along a posterior plane  78 . 
     As explained above, the cutting block assembly  10  has a cutting surface verification feature which provides the ability to verify the accuracy of the posterior and anterior chamfer cuts before the anterior and posterior cuts are made. Thus, before the anterior and posterior cuts are made, the second block  14  can be used to check or verify the accuracy of the anterior and posterior chamfer cuts previously made by the first block  12 . For example, as explained above, the second block  14  has extended portions  30   a ,  32   a  which extend beyond the contact surface  20  and cutting surfaces  16 ,  18  of the first block  12  and onto the chamfer surfaces  70 ,  72 . The extended portions  30   a ,  32   a  provide a user with a visual indication of whether the chamfer surfaces have been properly cut. If any of the chamfer surfaces  70 ,  72  have been improperly cut, for example, having uneven or skewed surfaces, then a gap or space will be present between the chamfer surfaces and the extended portions  30   a ,  32   a  indicating that cuts have been improperly made. In this case, a user can proceed to take remedial action such as reapplying the saw to the chamfer surfaces to attempt to fix the imperfections. 
     However, if the chamfer surfaces  70 ,  72  have been properly cut, then no gap or space will be present between the chamfer surfaces and the contact surfaces of the extended portions  30   a ,  32   a  indicating that the cuts have been properly made. In this case, a user can proceed to make the anterior and posterior cuts using the second block  14 . To make the anterior cut, a bone cutting device is applied to the surface  30  of the second block  14  and advanced toward anterior bone portion  76  and along plane  74  until the anterior bone portion  76  is removed. To make the posterior cut, a cutting device such as a saw is applied to the surface  32  of the second block  14  and advanced toward a posterior bone portion  80  and along surface  78  until the posterior bone portion  80  is removed. In one embodiment, the anterior cut can be made first and the posterior cut can be made second. However, in another embodiment, the posterior cut can be made first and the anterior cut can be made second. 
       FIG. 14A  is an isometric view and  FIG. 14B  is a medial view showing the distal femur of  FIGS. 13A-13B  after the anterior and posterior cuts have been made on the surface of the distal femur. As explained above, the extended cutting surfaces  30 ,  32 , which are part of extended portions  30   a ,  32   a , provide increased cutting surface area for making the anterior and posterior cuts. As a result, the accuracy of the anterior and posterior cuts may be improved. Once the anterior cut has been made, an anterior surface  82  remains. Likewise, once the posterior cut has been made, a posterior surface  84  remains. At this point in the surgical procedure, the four cuts (anterior-chamfer, posterior-chamfer, anterior, posterior) have been made and the cutting block assembly  10  can be removed as a single unit from the distal femur as shown in  FIG. 15  and explained further below. 
       FIG. 15  is a medial view showing the distal femur  52  after the four cuts have been made and the cutting assembly has been removed. The distal femur  52  shows the four cuts (anterior-chamfer  70 , posterior-chamfer  72 , anterior  82 , posterior  84 ) and the distal cut  56  made by the cutting block assembly of the present application. The distal femur  52  is now ready for further procedures including the implantation of a knee prosthesis using conventional techniques. 
     Referring to  FIGS. 16-20 , shown is a cutting block assembly generally denoted as  100  in accordance with another embodiment of the present invention. The cutting block assembly  100  comprises a first block  112  capable of interlocking with a second block  114  to form a four-in-two (4-in-2) cutting block assembly for resecting a portion of a bone such as a distal femur. The cutting block assembly  100  is similar to the cutting block  10  above. For example, referring to  FIGS. 16-20 , the first block  112  is a generally triangular shaped block forming an anterior-chamfer cutting surface  116 , a posterior-chamfer cutting surface  118 , a contact surface  120  and side surfaces  122 . The contact surface  120  includes protrusions  126  adapted to fit into holes in the distal femur (not shown). The first block  112  also may include angled pin holes  128  extending outwardly from the contact surface  120  to the side surfaces  122 . The second block  114  is a generally trapezoidal shaped block with V-shaped portion  115  sized to receive the V-shaped portion  113  of the first block  112 . The second block  114  forms an anterior cutting surface  130 , a posterior cutting surface  132 , contact surfaces  131 ,  133  and side surfaces  138 . The cutting block assembly  100  has many of the same features as the cutting block  10  above. For example, the cutting block assembly  100  provides an interlocking mechanism for detachably securing the blocks  112 ,  114  to each other. Also, the cutting block assembly  100  can be made of relatively lightweight material to provide many of the same advantages as in assembly  10 . 
     However, unlike the second block  14  of the cutting block assembly  10  of  FIGS. 1-7  above, the second block  114  of the cutting block assembly  100  of  FIGS. 16-20  does not include extended portions  30   a ,  32   a . Instead, the second block  114  includes an anterior contact surface  131  and a posterior contact surface  133 . The anterior contact surface  131  is adapted to make contact with the anterior portion of the distal surface of the distal femur (not shown) and the posterior contact surface  133  is adapted to make contact with the posterior portion of the distal surface of the distal femur. In addition, the cutting block assembly  100  can be used for resecting a distal femur similar to the procedure described above in the context of cutting block assembly  10  of  FIGS. 1-7 , except that the sequence of the cuts is reversed, as explained below in detail. That is, with the cutting block assembly  100 , the anterior and posterior cuts are made first and then the anterior and posterior chamfer cuts are made second. 
     Referring to  FIGS. 21-27 , a description is provided of a surgical procedure for resecting a distal femur  152  of a femur bone  150  using the cutting block assembly  100  of  FIGS. 16-20  in accordance with another embodiment of the present application. This procedure is similar to the procedure explained with reference to  FIGS. 9A-9B  to  15 A- 15 B in the context of cutting block assembly  10 , except that the order of the cuts are reversed and the cutting block assembly  100  is attached to the distal femur as a single unit, as explained below. Referring to  FIG. 21 , the distal femur  152  has an anterior portion  152   a  and a posterior portion  152   b . In an initial step of the surgical procedure, a distal cut is made which involves the resection or removal of a distal bone portion (not shown) from the distal femur  152  leaving behind a generally flat resected distal surface  156 . Once the distal cut has been made, pilot holes (not shown) can be drilled into the distal surface  156  in precise location and orientation as known to one skilled in the art to accommodate the protrusions  126  of the first block  112 . In this embodiment, the first block  112  is attached to the second block to form cutting block assembly  100 . In this regard, the cutting block assembly  100  is to be attached to the distal femur as a single unit. The contact surface  120  of the first block  112  is oriented to face the distal surface  156  of the distal femur. The first block  112  is also oriented with the protrusions  126  of the first block being aligned with the holes (not shown) of the distal surface  156 . In addition, the second block  114  is oriented with the contact surface  131  facing the anterior portion of the distal surface  156  and the contact surface  133  facing the posterior portion of the distal surface. The cutting block assembly  100  is advanced as a single unit toward the distal surface  156 , in the direction shown by arrow  188 , until the protrusions  126  enter the holes (not shown) of the distal surface  156  and the contact surface  120  of the first block  112  and the contact surfaces  131 ,  133  are flush with the distal surface  156 , as shown in  FIG. 22  and described further below. 
       FIG. 22  shows the cutting block assembly  100  attached to the distal femur  152  of  FIG. 21  in preparation for making anterior and posterior cuts on the surface of the distal femur  152 . In one embodiment, pins  129  could be inserted through holes of the first block  112  and into the holes of the distal surface  156  to more firmly secure the assembly  100  to the distal surface  156 . The first surface  130  of the second block  114  provides a guiding surface for making an anterior cut along an anterior plane  174 . To make the anterior cut, a bone cutting device (not shown) is applied to the surface  130  of the second block  114  and advanced toward the distal surface  156  along the plane  174  until an anterior bone portion  176  is removed. In a similar manner, the second surface  132  of the second block  114  provides a guiding surface for making a posterior cut along a posterior plane  178 . To make the posterior cut, a cutting device (not shown) is applied to the surface  132  of the second block  114  and advanced toward the distal surface  156  along plane  178  until a posterior bone portion  180  is removed. In another embodiment, the sequence of cuts could be reversed with the posterior cut being made first and the anterior cut being made second. 
       FIG. 23  shows the distal femur of  FIG. 22  after the anterior and posterior cuts have been made. Once the anterior cut has been made, an anterior surface  182  remains. Likewise, once the posterior cut has been made, a posterior surface  184  remains. The second block  114  can now be detached from the first block  112  in preparation for making the anterior and posterior chamfer cuts as shown in  FIG. 24  and explained below. 
       FIG. 24  shows the distal femur of  FIG. 23  with the second block  114  being detached from the first block  112 . The second block  114  is moved away from the first block  112 , in the direction shown by arrow  190 , with sufficient force to detach the second block from the first block but with the first block remaining attached to the distal femur. Once the second block  114  has been removed, the distal femur  152  is ready to have the anterior and posterior chamfer cuts made as shown in  FIG. 25  and explained below. 
       FIG. 25  shows the first block  112  attached to the distal femur  152  ready for making anterior and posterior chamfer cuts on the surface of the distal femur  152 . The anterior cutting surface  116  of the first block  112  provides a guiding surface for making an anterior-chamfer cut along an anterior plane  162 . In a similar manner, the posterior cutting surface  118  of the first block  114  provides a guiding surface for making a posterior-chamfer cut along a posterior plane  166 . To make the anterior-chamfer cut, a bone cutting device is applied to the surface  116  of the first block  112  and advanced toward anterior bone portion  164  and along plane  162  until the anterior bone portion  164  is removed. To make the posterior-chamfer cut, a cutting device is applied to the surface  118  of the first block  112  and advanced toward a posterior-chamfer bone portion  168  and along surface  166  until the posterior-chamfer bone portion  168  is removed. In another embodiment, the posterior-chamfer cut can be made first and the anterior-chamfer cut can be made second. 
       FIG. 26  shows the distal femur of  FIG. 25  after the anterior and posterior chamfer cuts have been made on the surface of the distal femur. Once the anterior-chamfer cut has been made, an anterior-chamfer surface  170  remains. Likewise, once the posterior-chamfer cut have been made, a posterior-chamfer surface  172  remains. At this point in the surgical procedure, the four cuts (anterior-chamfer, posterior-chamfer, anterior, posterior) have been made and the first block  112  can be detached from the distal femur by removing the pins  129  from the first cutting block and distal femur and moving the first block  112  away from the distal femur in the direction shown by arrow  192 . 
       FIG. 27  shows the distal femur  152  of  FIG. 26  after the four cuts have been made and the cutting assembly has been removed. The distal femur  152  shows the distal cut  156  and the four cuts (anterior-chamfer  170 , posterior-chamfer  172 , anterior  182 , posterior  184 ) made by the cutting block assembly  100  of the present application. The distal femur  152  is now ready for further procedures including the implantation of a knee prosthesis using conventional techniques. 
     The cutting block devices of the present application may provide various advantages. The cutting block device is a four-in-two (4-in-2) cutting block assembly which may improve accuracy in the preparation of the distal femur for the implantation of a knee prosthesis. The cutting block assembly comprises a first block for making the anterior and posterior chamfer cuts and a second block for making the anterior and posterior cuts. The first and second blocks interlock which may help improve the correlation between the four cuts and improve the accuracy of the cuts. In one embodiment, the second block includes extended surfaces which may help improve the accuracy of the anterior and posterior cuts. In addition the extended surfaces of the second block may help provide a visual indication of the accuracy of the chamfer cuts before the anterior and posterior cuts are made. Moreover, the cutting block can be made of polymeric material which may help reduce the cost of manufacture and may improve the handling of the cutting block during a surgical procedure. 
     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.