The present invention relates generally to total knee arthroplasty. More specifically, the present invention relates to cutting blocks for use in preparing the distal femur to accept a femoral component of a prosthetic knee joint during knee joint replacement surgery.
During knee joint replacement surgery, the distal femoral surface of a patient's knee is often replaced with a femoral component of a prosthetic knee joint in the form of a curved metallic prosthesis. Such a femoral component may have a generally smooth and continuous outer curvature that faces a corresponding tibial component which is attached to the patient's tibia. The inner surface (i.e., the side abutting the femur) of this type of femoral component of the prosthetic knee joint is typically provided with a number of intersecting flat surfaces. A common femoral component provides five intersecting flat surfaces on its inner surface. One of the flat surfaces is adapted to face the posterior surface of the femur. A second flat surface is adapted to engage the anterior cortical surface of the femur. A third flat surface is adapted to engage the distal end of the patient's femur. Additionally, a pair of flat chamfer surfaces form diagonally extending surfaces which form an interface between the distal surface and the respective anterior and posterior surfaces.
Accordingly, surgery to implant a prosthetic knee joint requires that the distal femur be prepared to receive the femoral component of the prosthetic knee joint. Preparation of the distal femur involves cutting the femur to establish accurately positioned flat surfaces against which the femoral component of the prosthetic knee joint can rest after implantation. For the common prior art femoral component mentioned above, five saw cuts must be made to the distal femur corresponding to the five flat surfaces on the inner surface of the femoral component in order to prepare the distal femur to accept the femoral component.
An initial cut is made to provide a flat surface at the distal end of the femur, commonly referred to as the “distal cut”. Once the distal cut is made, an “anterior femoral cut” is made to provide a flat surface on the anterior of the femur, a “posterior femoral cut” is made to provide a flat surface on the posterior of the distal femur, an “anterior chamfer cut” is made to provide a diagonally extending surface between the cut distal surface and the cut anterior surface, and a “posterior chamfer cut” is made to provide a diagonally extending surface between the cut distal surface and the cut posterior surface.
Various prior art cutting guides, typically referred to as cutting blocks, have been developed for assisting a surgeon in guiding a saw blade when making the five cuts to establish the desired flat surfaces on the distal femur. Typically, one cutting block may be positioned on the distal femur for making the distal cut. After making the distal cut, another block may be positioned on the cut distal surface for making the remaining four cuts. Such a cutting block is referred to as a 4-in-1 cutting block and has four guide slots for making the four remaining cuts.
The 4-in-1 cutting block is positioned and secured upon a flat transverse surface established initially on the distal femur by the distal cut in order to guide the saw blade during the execution the anterior femoral cut, the posterior femoral cut, the anterior chamfer cut and the posterior chamfer cut. Such a 4-in-1 cutting block is disclosed in, for example, U.S. Pat. No. 4,892,093 to Zarnowski (Zarnowski).
U.S. Pat. No. 5,417,694 to Marik (Marik) discloses a distal femoral cutting block. Marik also discussed several prior art patents that describe various types of prior art devices for use in preparing the distal femur to accept a prosthetic knee joint.
When using a typical prior art 4-in-1 cutting block of the type described in Zarnowski, it is necessary to make a relatively large incision in the area of the distal femur to allow for the positioning and securing of the cutting block and for carrying out the four saw cuts.
Techniques have been developed to reduce the size of the incision required when using a typical 4-in-1 cutting block, in an attempt to make the knee joint replacement surgery less invasive. However, when making a smaller incision, the available operation field also becomes smaller. In order to compensate for the smaller operating field resulting from a smaller incision, the knee must be bent several times over the course of the operation, in order to enable access to different portions of the femur in the small operation field, so that the five different cuts may be made. In particular, in order to make the posterior femoral cut (also referred to as the dorsal condylar cut) using a 4-in-1 cutting block, the patient's leg must be brought to approximately 90 degrees of flexion, since preparation of the dorsal condyles from the front of the femur (i.e., the posterior femoral cut) is otherwise prevented by the tibia.
These techniques are referred to as “moving window” techniques, since flexing the leg to different degrees enables access to different portions of the femur in the same operation field or window. Although such moving window techniques allow for a smaller surgical incision, various amounts of tension are placed on the soft tissue of the leg and knee when it is bent to different angular positions. Such tension may impart trauma to the soft tissue of the leg and knee, lengthening recovery time and possibly weakening the leg and/or implanted knee prosthetic.
It would therefor be advantageous to provide methods and apparatus that enable the use of a small incision and field of operation, while minimizing the amount of soft tissue trauma to the leg and knee during knee joint replacement surgery. It would be further advantageous to provide methods and apparatus that do not require bending of the leg to 90 degrees for making the posterior femoral cut, thereby reducing soft tissue trauma to the leg and knee. It would also be advantageous to reduce the amount of space taken up in the operation field by prior art 4-in-1 cutting blocks.
The methods, systems, and cutting blocks of the present invention provide the foregoing and other advantages.
The present invention relates to cutting blocks for use in preparing the distal femur to accept a femoral component of a prosthetic knee joint in knee joint replacement surgery, and methods for using these cutting blocks.
The cutting blocks provided in accordance with the present invention are designed for use after the distal femur has been initially prepared by making a distal femur cut to provide a resected distal end of the femur.
In accordance with an example embodiment of the present invention, two cutting blocks are provided, which may be used together as a system for preparing a femur for total knee arthroplasty.
A first cutting block comprises a block body positionable on a resected distal end of the femur. A first slot, which passes through the block body, is provided for guiding a saw blade when making an anterior femoral cut. A second slot, which passes through the block body, is provided for guiding a saw blade when making an anterior chamfer cut. A third slot, which passes through the block body, is provided for guiding a saw blade when making a posterior chamfer cut. The second cutting block comprises a block body positionable on the resected distal end of the femur after making the anterior femoral cut, the anterior chamfer cut, and the posterior chamfer cut. A slot, passing through the block body of the second cutting block, is provided for guiding a saw blade when making a posterior femoral cut.
The block body of the first cutting block may be positionable on the resected distal end of the femur during approximately 45 degrees of knee flexion. The block body of the second cutting block may be positionable on the resected distal end of the femur during approximately 90 degrees of knee flexion.
In one example embodiment, the block body of the first cutting block may be adapted to abut against a planar surface resulting from resection of the distal femur. In such an example embodiment, the block body of the first cutting block may comprise a vertical surface for abutting the planar surface resulting from the resection of the distal femur. The second and third slots of the first cutting block may pass through the vertical surface. The block body may further comprise a top portion extending above the vertical surface, with the first slot passing through the top portion. The block body of the first cutting block, when positioned on the resected distal femur, may extend approximately from above a top portion of the resected distal femur to a point between a midpoint of the resected distal femur and a bottom portion of the resected distal femur.
In a further example embodiment, the block body of the second cutting block may be adapted to abut against four planar surfaces obtained from making the anterior femoral cut, the anterior chamfer cut, and the posterior chamfer cut at the resected distal end of the femur. In such an example embodiment, the block body of the second cutting block comprises an upward sloping surface for abutting the planar surface resulting from the anterior chamfer cut and a downward sloping surface for abutting the planar surface resulting from the posterior chamfer cut. The block body of the second cutting block may further comprise a vertical surface disposed between the upward and downward sloping surfaces for abutting the planar surface resulting from resection of the distal end of the femur and a horizontal surface extending from an upper end of the upward sloping surface for abutting the planar surface resulting from the anterior femoral cut.
At least one fixing means may be provided for fixing the first cutting block or the second cutting block in position on the resected distal end of the femur.
The present invention also includes methods for preparing a femur for total knee arthroplasty using the first and second cutting blocks described above. In an example embodiment of such a method, the distal end of the femur is resected and the first cutting block is positioned on the resected distal end of the femur. With the first cutting block in place, an anterior femoral saw cut may be made through a first guide slot in the first cutting block, an anterior chamfer saw cut may be made through a second guide slot in the first cutting block, and a posterior chamfer saw cut may be made through a third guide slot in the first cutting block. These cuts may be made in any order. After these cuts are completed, the first cutting block may be removed from the resected distal end of the femur. Next, the second cutting block is positioned on the resected distal end of the femur, and a posterior femoral saw cut is made through a guide slot in the second cutting block. Once this final saw cut is completed, the second cutting block may be removed from the resected distal end of the femur. The femoral component of the prosthetic knee joint may now be fixed to the distal femur.
The knee may be brought into approximately 45 degrees of flexion prior to the positioning of the first cutting block and into approximately 90 degrees of flexion prior to the positioning of the second cutting block.
The first and second cutting blocks may be fixed in position prior to making the saw cuts through the guide slots of the first and second cutting blocks.
The features of the first and second cutting blocks used with the above-described method correspond to the first and second cutting blocks of the system described above.
Further, the present invention also covers various embodiments of the first and second cutting blocks as described above.
The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like reference numerals denote like elements, and:
The ensuing detailed description provides exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description of the exemplary embodiments will provide those skilled in the art with an enabling description for implementing an embodiment of the invention. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention as set forth in the appended claims.
In accordance with an example embodiment of the present invention, a cutting block system for preparing a femur for total knee arthroplasty is provided. The system comprises two cutting blocks for use in preparing the distal femur to accept a femoral component of a prosthetic knee joint. The two cutting blocks are used in succession and enable completion of the knee arthroplasty using a smaller than normal surgical incision and resulting smaller than normal surgical window than that which can be achieved using a typical prior art 4-in-1 cutting block. Such results are achieved with the present invention by the reduction in size and the overall outer geometry of the two cutting blocks when each is compared to that of a typical 4-in-1 cutting block. In other words, by dividing the 4 saw cuts required after resection of the distal femur and making three of the cuts using one cutting block and the last of the cuts using a different cutting block, the present invention allows each of these two separate cutting blocks to be smaller than a typical 4-in-1 cutting block. Thus, with the present invention, the joint replacement can be carried out with a smaller surgical incision and in a smaller surgical field. Further, the cutting blocks of the present invention enable the surgery to proceed in this smaller surgical field without the need to flex the patient's leg to more than 45 degrees before the first cutting block is positioned, thereby minimizing soft tissue damage to the leg and knee joint.
An example embodiment of a first cutting block 10 in accordance with the present invention is shown in
The first cutting block 10 comprises a block body 12 positionable on a resected distal end of the femur. The first cutting block 10 may be considered to be a 3-in-1 cutting block, as it comprises three slots 14, 16, and 18 for making three of the 4 remaining cuts after resection of the distal femur. A first slot 14, which passes through the block body 12, is provided for guiding a saw blade when making an anterior femoral cut. A second slot 16, which passes through the block body 12, is provided for guiding a saw blade when making an anterior chamfer cut. A third slot 18, which passes through the block body 12, is provided for guiding a saw blade when making a posterior chamfer cut.
An example embodiment of a second cutting block 50 in accordance with the present invention is shown in
The second cutting block 50 comprises a block body 52 positionable on the resected distal end of the femur after making the anterior femoral cut, the anterior chamfer cut, and the posterior chamfer cut using the first cutting block 10. A single slot 54, which passes through the block body 52 of the second cutting block, is provided for guiding a saw blade when making a posterior femoral cut.
The block body 12 of the first cutting block 10 may be positionable on the resected distal end of the femur during approximately 45 degrees of knee flexion. The block body 52 of the second cutting block 50 may be positionable on the resected distal end of the femur during approximately 90 degrees of knee flexion. Approximately 90 degrees of flexion is necessary to prevent the saw blade from contacting the tibia when making the posterior femoral cut, which would prevent the saw blade from moving freely. At approximately 90 degrees of flexion, the sawing plane for the posterior femoral cut is parallel to the upper side of the tibia and the saw blade will be able to move freely in the gap between the tibia and the femur.
In one example embodiment, the block body 12 of the first cutting block 10 may be adapted to abut against a planar surface resulting from resection of the distal femur. In such an example embodiment, the block body 12 of the first cutting block 10 may comprise a vertical surface 20 (
In a further example embodiment, the block body 52 of the second cutting block 50 may be adapted to abut against four planar surfaces of the distal femur obtained from making the anterior femoral cut, the anterior chamfer cut, and the posterior chamfer cut at the resected distal end of the femur. In such an example embodiment, the block body 52 of the second cutting block 50 comprises an upward sloping surface 56 for abutting the planar surface resulting from the anterior chamfer cut and a downward sloping surface 58 for abutting the planar surface resulting from the posterior chamfer cut. The block body 52 of the second cutting block 50 may further comprise a vertical surface 60 disposed between the upward and downward sloping surfaces 56 and 58 for abutting the planar surface resulting from resection of the distal end of the femur and a horizontal surface 62 extending from an upper end 64 of the upward sloping surface 56 for abutting the planar surface resulting from the anterior femoral cut.
At least one fixing means may be provided for fixing the first cutting block 10 or the second cutting block 50 in position on the resected distal end of the femur. For example, as can be seen from
The present invention also includes methods for preparing a femur for total knee arthroplasty. An example embodiment of such a method is shown in
b shows the resected distal end 114 of the femur 100 after the distal cut is made. The distal cutting block 110 can then be removed.
As shown in
As shown in
e shows the planar surfaces resulting from the distal cut 114, the anterior femoral saw cut 116, the anterior chamfer saw cut 118, and the posterior chamfer saw cut 120 after removal of the first cutting block 10.
Next, as shown in
As shown in
The distal end of the femur 100 is now prepared for accepting a femoral component of a prosthetic knee joint. Such a prosthesis may have a generally smooth and continuous outer curvature that faces a corresponding tibial component which is attached to the patient's tibia. The inner surface (i.e., the side abutting the femur) of such a femoral component of the prosthetic knee joint is provided with five intersecting flat surfaces which correspond to the planar surfaces resulting from the distal saw cut 114, the anterior femoral saw cut 116, the anterior chamfer saw cut 118, the posterior chamfer saw cut 120, and the posterior femoral saw cut 122. An example of such a prosthetic knee joint is the e.motion® implant developed by Aesculap AG & Co. KG, the assignee of the present invention.
As discussed above, the shape of the cutting blocks enable the first cutting block 10 to be positioned and the saw cuts to be made through the first cutting block 10 with the knee in approximately 45 degrees of flexion or less. The second cutting block 50 may be positioned and the saw cuts may be made through the second cutting block 50 with the knee in approximately 90 degrees of flexion. Since the first four saw cuts have been made prior to positioning of the second cutting block 50 on the resected distal end of the femur 114, there is ample room in the knee joint to enable 90 degrees of flexion without increasing tension on the soft tissue of the knee joint.
It should now be appreciated that the present invention provides advantageous systems, methods and cutting blocks for preparing the distal end of a femur to accept a femoral component of a prosthetic knee joint. By using two separate cutting blocks for the four cuts made after the distal cut, the present invention enables total knee arthroplasty using a smaller surgical incision and resulting smaller field of operation. Further, the present invention minimizes soft tissue damage in and around the leg and knee area due to a reduction in tension on the soft tissue of the knee joint during the surgery.
Although the invention has been described in connection with various illustrated embodiments, numerous modifications and adaptations may be made thereto without departing from the spirit and scope of the invention as set forth in the claims.