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TRIPLANAR KNEE RESECTION SYSTEM
This is a division of my co-pending application Ser. No. 317,875, filed Nov. 3, 1981, now U.S. Pat. No. 5 4,487,203.
The invention relates generally to knee surgical techniques and, more particularly, to apparatus and method 10 for resection of the knee joint for a knee prosthesis.
Replacement of a knee joint with a prosthesis involves a comprehensive surgical procedure, as is known to those skilled in the art. The surgical procedure is complicated by the fact that only a relatively small area IS of the patient's leg, namely the knee, is exposed during the operation. The remainder of the patient's leg, as well as most of his body, is covered with sterile drapes. The R.M.C. Tm Total Knee System technique manual published by Richards Manufacturing Company, Inc., 20 1450 Brooks Rd., Memphis, Tenn. 38116 illustrates this aspect of the surgical procedure. The surgical procedure is further complicated by the presence of the muscle and skin tissue which surrounds the knee joint.
Once the knee joint is exposed by known techniques, 25 the distal femur and proximal tibia must be prepared to enable implantation of the prosthesis. Such preparation includes resection of the anterior and posterior distal femoral condyles, the proximal tibia, and the distal femur. In order to achieve proper stability of the knee 30 prosthesis when implanted, the aforementioned resections must be accurately aligned relative to an imaginary axis extending through the hip joint, knee joint, and ankle joint.
It is necessary for the distal femoral condylar resec- 35 tions to be parallel to the proximal tibial resection when the knee is in flexion and for the proximal tibial resection when the knee is in extension. These "triplanar" resections should be made to provide equal flexion and extension gaps, i.e., the distance between the posterior 40 femoral condylar resection and the proximal tibial resection with the knee in flexion (the flexion gap) should be equal to the distance between the distal femoral resection and the proximal tibial resection with the knee in extension (the extension gap). Furthermore, the re- 45 sected proximal tibia and resected distal femur should be perpendicular to the above-referenced imaginary axis when the knee is extended.
The necessity of accurately making the triplanar resections has led to the development of relatively com- 50 plicated instrumentation to aid the orthopedic surgeon. Illustrative of such instrumentation are the Howmedica @ Universal Tm Total Knee Instrument System as shown in the catalogue published by Howmedica, Inc., Orthopaedics Division, 359 Veterans Blvd., Ruth- 55 erford, N.J. 07070 and the Insall/Burstein surgical instrument system as designed by John Insall, M.D. and Albert H. Burstein, Ph.D. and shown in the publication entitled "Knee Replacement Using the Insall/Burstein Total Condylar Knee System." 60
Although providing some guidance to the orthopedic surgeon, these prior instrument systems utilize long alignment rods which have proved to be less than satisfactory under sterile operating room conditions, as described previously. Furthermore, such instrument sys- 65 tems include numerous components which still require much manual manipulation and which are cumbersome to use.
In accordance with the present invention, an improved triplanar knee resection system, free of many disadvantages of the prior art, is provided. The triplanar knee system includes a single guide member for use in making the proper bone resections. The guide member includes an alignment opening for cooperating with a guide rod. The guide rod has a 90° angle bend and is adapted to be inserted into the femur for use in aligning the guide member. In one aspect of the present invention, the guide rod is designed such that it remains inserted in the femur during the surgical procedure, thereby establishing a common reference point for the bone resections.
The guide member includes three pairs of parallel guide slots which are utilized in making the triplanar bone resections. The guide member cooperates with the guide rod to enable resection of the knee joint with the knee always in flexion.
A second identical guide rod is provided along with a tibia adapter and a tibia bar for use with the guide member in resecting the proximal tibia. A femur bar is provided for use with the guide member and femur guide rod in making the resection of the distal femur.
In a second aspect of the present invention, the femur guide bar is designed to compensate for the appropriate valgus angle of the femur relative to an imaginary axis extending through the hip joint, knee joint, and ankle joint. In another aspect of the present invention, the triplanar knee system achieves equal flexion and extension gaps of the resected knee joint. In still another aspect, the triplanar knee system ensures proper alignment of the distal femoral resection and the proximal tibial resection although these two resections are independently aligned.
In a method aspect of the invention, a common reference is established for resecting the anterior and posterior distal femoral condyles and the distal femur. This common reference is used to provide equal flexion and extension gaps.
In another aspect of the method, the alignment of the guide member for resecting the distal femur is accomplished without the use of any "eyeball" techniques.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other advantages and features of the present invention will become apparent from the following detailed description considered in connection with the appended drawings in which like parts are given identical reference numerals and in which:
FIG. 1A is an illustrative view of a triplanar guide member cooperating with a guide rod for making the distal femoral condylar resections in accordance with the present invention;
FIG. IB is an illustrative view, partially cut away for detail, of the rear side of the triplanar guide member of FIG. 1A;
FIG. 2A is a side view of the guide member cooperating with a second guide rod, a tibia adaptor, and a tibia bar for resecting the proximal tibia in accordance with the present invention;
FIG. 2B is an illustrative view of the tibia adaptor of FIG. 2A;
FIG. 2C is an illustrative view of the tibia bar of FIG. 2A;
FIG. 2D is a cross section of the tibia guide rod taken along section line 2D—2D in FIG. 2A;
FIG. 2E is an illustrative view of the rear side of the triplanar guide member of FIG. 2A, partially cut away for detail;
FIG. 3 is an illustrative view of the femoral guide rod being used to determine the flexion gap in accordance 5 with the present invention;
FIG. 4 is a top view of the femoral guide member being used to establish an extension gap equal to the flexion gap in accordance with the present invention;
FIG. 5A is a top view of the guide member cooperat- 10 ing with the femoral guide rod and a femur bar for proper positioning of the guide member with the knee extended in accordance with the present invention;
FIG. 5B is an illustrative view of the femur bar of FIG. 5A; 15
FIG. 6 is a side view of the guide member cooperating with the femoral guide rod and femur bar with the knee in flexion in accordance with the present invention;
FIG. 7A is an illustrative view of a modified femur 20 bar;
FIG. 7B is an illustrative view of a pointer for use with the modified femur bar of FIG. 7A;
FIG. 7C is a schematic diagram of the modified femur bar cooperating with the pointer and the guide member 25 to establish the proper valgus angle in accordance with the present invention; and
FIG. 8 is an illustrative view of a modified tibia bar for use with the pointer of FIG. 7B.
DETAILED DESCRIPTION 30
Referring now to FIGS. 1A and IB, shown is a knee joint 20 including a distal femur 22 and proximal tibia 24 in flexion. It is to be understood that the exposure of the distal femur and proximal tibia is achieved by known 35 surgical techniques. Such known techniques may include removal of the anterior and posterior cruciate ligaments (not shown). However, the present invention is applicable in making bone resections for a cruciate sparing prosthesis as well. 40
A pair of collateral ligaments 26, which connect the distal femur 22 and proximal tibia 24, are left in place. It is to be understood that any necessary ligamentous release may be performed by known surgical techniques before making the appropriate bone resections for re- 45 placement of the knee.
In accordance with the present invention, with the knee in flexion, a first hole 28 is drilled into the end of distal femur 22, approximately centered in the medullary canal by known techniques. Likewise, a second 50 hole 30 is drilled into the end of proximal tibia 24, slightly anterior relative to the centerline extending into the medullary canal of the tibia.
A femur guide rod 32 having a longer portion 34 and a shorter, threaded portion 35 forming an L-shape is 55 inserted into a triplanar guide member 36. Guide member 36 has a generally rectangular configuration with a front surface 38, a rear surface 40, a top surface 42, a bottom surface 44, a left surface 46, and a right surface 48. Guide member 36 includes three pairs of resection 60 guide slots 50, 52, 54 which are utilized to make the appropriate bone resections. A vertical guide slot 56 is centrally located in the guide member relative to sides 46, 48. Guide slot 56 forms a guide rod recess 58 at its upper end. A vertical bore 60 extends upward from 65 guide rod recess 58 through guide member 36. Guide rod recess 58 and bore 60 are configured to matingly receive threaded portion 35 of guide rod 32 and to
stabilize the guide rod with respect to guide member 36. The guide rod is secured in place with a circular nut or cap 62, which is threaded onto threaded portion 35 of the guide rod until the nut or cap abuts top surface 42 of guide member 36.
Guide member 36 may be provided with a pair of handles 64. It is to be understood that handles 64 may be integrally formed with guide member 36 or may be threadably connected to the guide member and still remain within the contemplation of the present invention. Guide member 36 is also provided with a plurality of pins 66 protruding outwardly from rear side 40. Pins 66 are adapted to anchor the guide member into the bone to prevent the guide member from rotating during use.
As shown in FIG. 1A, femur guide rod 32 is inserted into drilled hole 28. Before pressing pins 66 into the end of distal femur 22, guide member 36 is manually oriented to obtain the proper alignment of the guide member relative to the anterior and posterior distal femoral condyles, identified as 68 and 70, respectively, as is known to those skilled in the art. When aligned, guide member pins 66 are pressed into the distal femur. Anterior distal femoral condyles 68 are resected with an oscillating saw (not shown) or the like by using upper guide slots 50. Likewise, posterior distal femoral condyles 70 are resected with an oscillating saw with the aid of bottom guide slots 54. The guide member and guide rod are then pulled partially out to disengage pins 66, and guide member 36 is then removed from guide rod 32 after removing cap 62. Preferably, femur guide rod member 32 is then pushed back into hole 28 and remains there for later resection of the distal femur. It is to be understood, however, that guide rod 32 may be removed from the femur and reinserted later for use in resecting the distal femur. Any remaining portion of the anterior or posterior distal femoral condyles, such as in the center region where the guide slots do not extend, may then be removed by using the previously resected bone portions as a leveling guide.
The proximal tibia is then subluxed to its forward position, as shown in FIG. 2A. A tibia guide rod adapter 72 is slidably disposed onto a longer portion 75 of a second guide rod 73, which is identical to the first guide rod that remains inserted in the femur during this stage of the procedure. As shown in FIG. 2B, adapter 72 has an opening 74 which cooperates with a recess 76 to stabilize guide rod 73 relative to the adapter. Tibia adapter 72 is provided with a pair of pins 78, which are pressed into the end of the proximal tibia to prevent the guide rod from rotating about the longitudinal axis extending through longer portion 75. The guide rod carrying the tibia adapter 72 is inserted into drilled hole 30, and a shorter portion 77 of guide rod 73 is manually oriented such that a plane extending through the Lshaped guide rod is parallel to the sagittal plane extending through the tibia. When properly aligned, the guide rod is pushed further into hole 30, thereby implanting tibia adapter pins 78 and preventing rotation of guide rod 73.
A tibia bar 80 having an extended threaded portion 82 and a generally rectangular base 84, as shown in FIG. 2C, is inserted into vertical guide slot 56 of guide member 36 such that threaded portion 82 extends through vertical bore 60 in the guide member. A second cap 63 is threaded partially onto the threaded portion of tibia bar 80. The rectangular base of the tibia bar has a bore 86 extending lengthwise therethrough, and a key lock