Abstract:
An apparatus for aligning a cutting instrument during a surgical procedure includes a guide having an elongated slot adapted to receive a cutting instrument for resecting a patient&#39;s bone during the surgical procedure. The apparatus includes a translational assembly and first and second rotational assemblies. The translational assembly is coupled to a housing adapted for effecting distal-proximal adjustment of the guide. The first rotational assembly is also coupled to the housing adapted for effecting varus-valgus adjustment of the guide. The first rotational assembly is releasably coupled to the guide. The second rotational assembly is also coupled to the guide and adapted for effecting flexon-extension adjustment of the guide.

Description:
CROSS REFERENCES TO THE RELATED APPLICATIONS  
       [0001]     The present application claims priority of U.S. Provisional Application No. 60/444,891, entitled Apparatus for Aligning an Instrument During a Surgical Procedure, filed Feb. 4, 2003, the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates in general to an apparatus for use in aligning medical instruments which are adapted for use during various surgical procedures, and more particularly, to an apparatus for aligning a resection guide for use in arthroplastic surgery of a patient&#39;s knee.  
         [0003]     Arthroplasty is a known surgical procedure for replacing the knee joint which has been damaged due to disease or trauma. Total knee arthroplasty involves the replacement of portions of the patellar, femur and tibia with an artificial knee prostheses. In particular, a distal portion of the femur and proximal portion of the tibia are cut away, i.e., resected, and replaced with artificial knee components. As use herein, when referring to bones or other body parts, the term “proximal” means closest to the heart and the term “distal” means more distant from the heart.  
         [0004]     There are several types of knee prostheses known in the art. One type is commonly referred to as a resurfacing type. In these prostheses, the articular surface of the distal femur and proximal surface of the tibia are resurfaced with respective metal and plastic condylar-type articulate bearing components. The femoral component is often a metallic alloy construction which provides medial and lateral condylar bearing surfaces of multi-radius design of similar shape and geometry as the natural distal femur or femoral-side of the knee joint. The tibial component usually includes a distal metal base component and a proximal interlocking plastic component or insert. The plastic tibial plateau bearing surfaces are of concave multi-radius geometry to more or less match the articular geometry of the mating femoral condyles. These knee prostheses components, which provide adequate rotational and translational freedom, require minimal bone resection to accommodate the components within the boundaries of the available joint space.  
         [0005]     The surgical implant of a prosthetic knee joint requires that the distal femur and proximal tibia be prepared to receive the femoral and tibial components by cutting the bone of the femur and tibia to establish accurately located surfaces. Various guides are available to the surgeon for assisting in guiding a medical instrument such as a cutting blade for marking the femoral and tibial cuts which establish the desired resected surfaces. One important feature of these guides is the ability to align the cutting blade accurately when resurfacing the femur and tibia to accommodate the prosthetic knee components. To this end, there is known resection guides suitable for use in total knee arthroplasty from U.S. Pat. Nos. 6,090,114; 5,788,700; and 4,892,093; as well as pending application Ser. No. 09/811,318 entitled Apparatus Used in Performing Femoral and Tibial Resection in Knee Surgery, filed on Mar. 17, 2001, assigned to the same assignee of the present application.  
         [0006]     The present invention is specifically directed to an alignment guide intended for any medical condition in which the use of computer-aided surgery may be appropriate, and where a reference to rigid anatomical structures can be identified. More particularly, the present invention is directed to an alignment guide which provides improvements in accurately aligning the cutting blade for resection of bone, for example, the distal femur and proximal tibia during arthroplastic knee surgery.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     In accordance with one embodiment of the invention, there is described An apparatus for aligning an instrument during a surgical procedure, the apparatus comprising a guide adapted for guiding an instrument during the surgical procedure; and alignment means coupled to the guide for aligning the guide along a translational path and first and second rotational paths.  
         [0008]     In accordance with another embodiment of the invention, there is described an apparatus for aligning an instrument during an arthroplastic surgical procedure, the apparatus comprising a guide adapted for guiding an instrument during the arthroplastic procedure; a first assembly coupled to the guide adapted for positioning the guide along a translational path in controlled increments upon operation of the first assembly; a second assembly coupled to the guide adapted for positioning the guide along a first rotational path in controlled increments upon operation of the second assembly; and a third assembly coupled to the guide adapted for positioning the instrument guide along a second rotational path in controlled increments upon operation of the third assembly, whereby the guide is maintained in fixed position along the translational path and the first and second rotational paths upon termination of the operation of the first, second and third assemblies.  
         [0009]     In accordance with another embodiment of the invention, there is described an apparatus for aligning a surgical cutting instrument during a surgical procedure along a translational path and first and second rotational paths, the apparatus comprising an instrument guide having an opening adapted for receiving the instrument; and an alignment guide having first, second and third assemblies coupled to the instrument guide for aligning the opening in controlled increments along the translational path and the first and second rotational paths; wherein the first, second and third assemblies each include a rotational component adapted for manipulating the instrument guide along the translational path and the first and second rotational paths upon rotation of the rotational component.  
         [0010]     In accordance with another embodiment of the invention, there is described an apparatus for aligning an instrument during a surgical procedure, the apparatus comprising an instrument guide adapted for guiding the instrument during the surgical procedure; a first assembly adapted for aligning the instrument guide along a first rotational path, the first assembly including an internally threaded sleeve rotationally coupled to the instrument guide, a first pair of spaced apart rods slideably coupling a cross-member to the instrument guide, and a threaded first rod rotationally coupled at one end thereof to the sleeve and attached at another end thereof to the cross-member, whereby rotation of the sleeve effects translation of the cross-member thereby effecting manipulation of the instrument guide along the first rotational path; a second assembly adapted for aligning the instrument guide along a second rotational path, the second assembly including a housing supporting a rotatable plate including a first portion having a first gear and a second portion coupled to the instrument guide, and a rotatable second gear coupled to the first gear, whereby rotation of the second gear effects rotation of the plate thereby effecting manipulation of the instrument guide along the second rotational path; and a third assembly adapted for aligning the guide instrument along a translational path, the third assembly including a yoke, a second pair of spaced apart rods slideably coupling the yoke to the housing, and a second threaded rod rotatably coupled to the yoke and threadingly coupled to the housing, whereby rotation of the second threaded rod effects translation of the instrument guide relative to the yoke.  
         [0011]     In accordance with another embodiment of the invention, there is described an apparatus for aligning a cutting instrument during a surgical procedure, the apparatus comprising a guide having an elongated slot adapted to receive a cutting instrument for resecting a patient&#39;s bone during a surgical procedure; a housing; a translational assembly coupled to the housing adapted for effecting distal-proximal adjustment of the guide; a first rotational assembly coupled to the housing adapted for effecting varus-valgus adjustment of the guide; the first rotational assembly is adapted to be releasably coupled to the guide and a second rotational assembly coupled to the guide adapted for effecting flexon-extension adjustment of the guide.  
         [0012]     In accordance with another embodiment of the invention, there is described a method for aligning an instrument during a surgical procedure using an alignment apparatus comprising an instrument guide adapted for guiding the instrument during the surgical procedure; a first assembly adapted for aligning the instrument guide along a first rotational path, the first assembly including an internally threaded sleeve rotationally coupled to the instrument guide, a first pair of spaced apart rods slideably coupling a cross-member to the instrument guide, and a threaded first rod rotationally coupled at one end thereof to the sleeve and attached at another end thereof to the cross-member; a second assembly adapted for aligning the instrument guide along a second rotational path, the second assembly including a housing supporting a rotatable plate including a first portion having a first gear and a second portion coupled to the instrument guide, and a rotatable second gear coupled to the first gear; and a third assembly adapted for aligning the guide instrument along a translational path, the third assembly including a yoke, a second pair of spaced apart rods slideably coupling the yoke to the housing, and a second threaded rod rotatably coupled to the yoke and threadingly coupled to the housing; the method comprising rotating the sleeve to effect translation of the cross-member and manipulation of the instrument guide along the first rotational path, rotating the second gear to effect rotation of the plate and manipulation of the instrument guide along the second rotational path, and rotating the second threaded rod to effect translation of the instrument guide relative to the yoke. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The above description, as well as further objects, features, and advantages of the present invention will be more fully understood with reference to the following detailed description of an apparatus for aligning an instrument during a surgical procedure, when taken in conjunction with the accompanying drawings, wherein:  
         [0014]      FIG. 1  is a perspective view of an unassembled resection guide adapted for aligning a cutting blade for resecting the distal femur;  
         [0015]      FIG. 2  is a perspective view of an unassembled resection guide adapted for aligning a cutting blade for resecting the proximal tibia;  
         [0016]      FIG. 3  is a perspective view of a partially assembled resection guide adapted for aligning a cutting blade for resecting the distal femur;  
         [0017]      FIG. 4  is a top plan view of one component of an assembly for varus-valgus alignment of the resection guide;  
         [0018]      FIG. 5  is a cross-sectional view of a portion of the resection guide taken along line  5 - 5  in  FIG. 3  illustrating cannulated wheels in a first orientation;  
         [0019]      FIG. 6  is a cross-sectional view of a portion of the resection guide taken along line  6 - 6  in  FIG. 3  illustrating the cannulated wheels in a second orientation;  
         [0020]      FIG. 7  is a side elevational view of a femoral fixation plate;  
         [0021]      FIG. 8  is a perspective view of an assembled resection guide adapted for aligning a cutting blade for resecting the distal femur;  
         [0022]      FIG. 9  is a perspective view of an assembled resection guide adapted for aligning a cutting blade for resecting the proximal tibia;  
         [0023]      FIG. 10  is a side elevational view of the tibial fixation plate; and  
         [0024]      FIG. 11  is a top-plan view of a tibial fixation plate. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     In describing the preferred embodiments of the subject matter illustrated and to be described with respect to the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected and is to be understood that each specific term includes all technical equivalence which operate in a similar manner to accomplish a similar purpose.  
         [0026]     Turning now to the drawings, wherein like reference numerals represent like elements, there is shown in  FIG. 1  an alignment guide generally designated by reference numeral  100  adapted for femoral resection. The femoral alignment guide  100  includes an adjustment assembly  102 , a femoral resection cutting guide  104  and a femoral fixation plate  106 . As shown in  FIG. 1 , the components of the guide  100  are illustrated in an unassembled relationship. In this regard, the resection guide  104  and fixation plate  106  are to be releasably coupled to the adjustment assembly  102  during the arthroplastic surgery. As will be described hereinafter, the tibial alignment guide incorporates the use of the adjustment assembly  102 , which is coupled to left-right tibial resection guides and a tibial fixation plate. Accordingly, the femural and tibial resection guides and femoral and tibial fixation plates may be interchangeably coupled to the common adjustment assembly  102 .  
         [0027]     The femoral alignment guide  100  is provided with three assemblies to separately accommodate varus-valgus adjustment, resection level (distal-proximal) adjustment and flexion-extension adjustment. Specifically, the adjustment assembly  102  includes a varus-valgus adjustment assembly  108  and a resection level adjustment assembly  110 , while a flexion-extension adjustment assembly  112  is coupled to the femoral and left-right tibial resection guides. Although the adjustment assemblies  108 ,  110 ,  112  are to be described as manually operated, it is contemplated that the adjustment assemblies can be coupled to a servo-motor and operated by a programmed computer.  
         [0028]     Referring to  FIGS. 1 and 3 , the varus-valgus adjustment assembly  108  includes an enclosed housing  114  having a front wall  116 , a rear wall  118  and a pair of sidewalls  120 ,  122 . The front wall  116  is provided with an elongated opening  124  which communicates with the interior of the housing  114  while extending into a portion of the sidewalls  120 ,  122 . The rear wall  118  is provided with an opening  126  which opposes opening  124  in communication therewith. The sidewalls  120 ,  122  are each provided with a circular opening  128 ,  130  in longitudinal alignment with each other, while communication with the interior of the housing  114 .  
         [0029]     An elongated worm  132  is received within the housing  114  opposing opening  126 . The ends of the worm  132  are rotationally journalled within openings  128 ,  130  provided in the sidewalls  120 ,  122 . The ends of the worm  132  are provided with an engagement member  134  which enables rotation of the gear about its longitudinal axis within the housing  114 . The engagement member  134 , as shown, is in the nature of a polygonal shaped stud which can be received within a similarly shaped hand tool or coupled to a servo-motor to effect rotation of the worm  132 .  
         [0030]     The varus-valgus adjustment assembly  108  further includes an L-shaped mounting bracket  136  as best shown in  FIG. 4 . The bracket  136  includes a planar front wall  138  and rearwardly extending planar bottom wall  140  arranged transverse thereto. The bottom wall  140  includes an arcuate-shaped leading edge  142  provided with a plurality of teeth  144 . The teeth  144  are dimensioned so as to mesh with the worm  132 . An arcuate-shaped opening  146  is provided in the bottom wall  140  of the bracket  136  adjacent edge  142 , generally having the same radius of curvature. A bore  148  is provided extending through a central portion of the front wall  138 .  
         [0031]     The bracket  136  is assembled into the housing  114  by inserting the bottom wall  140  through opening  124  until the teeth  144  mesh with worm  132 . The bracket  136  is rotationally fixed within the housing  114  by a pair of spaced apart pins  150  which extend through the housing  114  and through the opening  146  in the bottom wall  140 .  
         [0032]     In the assembled relationship, the front wall  138  of the bracket  136  is positioned overlying the front wall  116  of the housing  114 . As shown in  FIG. 3 , the front wall  116  slopes rearwardly towards the side walls  120 ,  122  at an angle from the central line of the front wall. This creates a space for the front wall  138  which allows the bracket  136  to pivot or rotate about its centerline to provide varus-valgus adjustment without interference with the housing  114 .  
         [0033]     The resection level adjustment assembly  110  includes a yoke  152  formed from a pair of spaced apart lower side arms  154 ,  156  and an upper solid connecting member  158 . A plurality of transverse rods  160  are connected between the side arms  154 ,  156  at various spaced apart locations. The connecting member  158  supports a pair of ears  162  each having an opening into which there is fixed an elongated cylindrical shaft  164 . As will become apparent, the shafts  164  need not be cylindrical, for example, other shapes such as square, polygonal, rectangular and the like are contemplated. Each of the shafts  164  are slidingly received within an opposing bore  166  of corresponding shape to the shaft  164  formed through the upper portion of the housing  114 . A threaded adjustment rod  168  is provided with a circular flange  170  at one end thereof from which there extends an engagement member  134  which can be coupled to a hand tool or servo-motor. Flange  170  is rotationally captured between a pair of spaced apart aligned grooves  172  formed within the opposing inner sides of the ears  162 . The threaded end of the adjustment rod  168  is threadingly received within a threaded bore  174  within the housing  114 . As to be explained hereinafter, rotation of the adjustment rod  168  will affect resection level adjustment of the resection guide  104 .  
         [0034]     The resection guide  104  includes an enclosed housing  176  having a rear wall  178 , a top wall  180 , a bottom wall  182  and a front wall  184 . A shelf  186  extends outwardly from the front wall  184 . A narrow elongated slot  188  is formed extending longitudinally through the housing  176  adjacent rear wall  178 . The slot  188  is adapted to receive a cutting instrument such as a surgical saw blade. The housing  176  includes a pair of spaced apart rectangular cutouts  190  into which there is rotationally mounted a cannulated wheel  192  each having a through bore  194  having an axis aligned with the diameter of the wheel.  
         [0035]     As shown in  FIGS. 5 and 6 , each of the cannulated wheels  192  are provided with a cutout  196  along a circumferential portion thereof. A pin  198  is attached to the housing  176  projecting into the cutouts  190  in operative alignment with cutouts  196  within the cannulated wheels  192 . Accordingly, each wheel  192  may be rotated in a clockwise and counterclockwise direction limited by the extent of the cutout  196 . As the wheels  192  are rotated, the angular orientation of each of the through bores  194  can be manipulated between a vertical position as shown in  FIG. 5  and an angular position as shown in  FIG. 6 . As explained hereinafter, the bores  194  are sized to receive a fixation pin (not shown).  
         [0036]     The flexion-extension adjustment assembly  112  is coupled to the shelf  186  of the resection guide  104 . The shelf  186  is provided with a forward elongated opening  200  having aligned grooves  202  formed within opposing sidewalls  204 . The flexion-extension adjustment assembly  112  includes an elongated internally threaded sleeve  206  having an engagement member  134  at one end thereof which can be coupled to a hand tool or servo-motor. A pair of guide rods  208  are slidingly received within bores  210  extending through shelf  186  adjacent the sidewalls  204  forming the opening  200 . One end of each of the rods  208  is provided with an enlarged stop member  212  having a size larger than that of the bore  210 . The other end of the rods  208  are attached to an elongated cross-member  214  having a semi-circular cross-section. A threaded rod  216  has one end secured to the cross-member  214  between the guide rods  208 . The other end of the rod  216  is threadingly received into the internally threaded sleeve  206 . A circular flange  218  is attached to the sleeve  206 , or integrally formed therewith, having a circumferential portion captured within the grooves  202 . Accordingly, rotation of the sleeve  206  by means of the engagement member  134  effects longitudinal translation of the threaded rod  216  within the sleeve, which in turn, advances the cross member  214  while being guided by rods  208 .  
         [0037]     The femoral fixation plate  106  includes a C-shaped planar plate  220  formed by spaced apart legs  222 ,  224 . A pin reinforcement guide  226  is secured to each of the legs  222 ,  224  having a plurality of holes  228  in alignment with corresponding holes  230  in the plate  220 .  
         [0038]     As best shown in  FIG. 7 , a hook-shaped projection  232  extends outwardly from the plate  220  between the legs  222 ,  224 . The projection  232  is formed to provide an opening  234  which is restricted in size by a spring biased ball assembly  236 . The ball assembly  236  is formed by a shaft  238  having a ball end  240  extending into the opening  234 . The shaft is biased by an internal spring  242  to maintain the ball end  240  projecting outwardly to restrict the opening  234 . The ball end  240  may be depressed inwardly into the projection  232  against the biasing force of spring  242  to enlarge the opening  234 . As will be described hereinafter, the opening  234  is adapted to releasably capture one of the rods  160  on the yoke  152 .  
         [0039]     The femoral alignment guide  100  is assembled during various stages of the arthroplastic surgery. The final assembled form of the alignment guide  100  is shown in  FIG. 8 . By way of explanation, as shown in  FIGS. 1 and 3 , the femoral fixation plate  106  is rotationally coupled to the adjustment assembly  102 . In this regard, the hooked-shaped projection  232  on the femoral fixation plate  106  is forced into engagement with one of the rods  160  on the yoke  152 . The rod  160  will initially engage the ball end  240  of the ball assembly  236 , displacing same to enable passage of the rod into the opening  234 . The ball end  240  by virtue of being spring biased will retain rod  160  coupled to the hook-shaped projection  232 . The height of the adjustment assembly  102  relative to the femur can be adjusted by attaching the femoral fixation plate  106  to a selected one of the rods  160 . In the assembled relationship as shown in  FIG. 3 , the adjustment assembly  102  is rotational about the longitudinal axis of the rod  160  to which the femoral fixation plate  106  is coupled.  
         [0040]     Turning to  FIG. 1 , the mounting bracket  136  is provided with a pair of positioning pins  244  extending outwardly from the front wall  138 . The positioning pins  244  include an upper planar sloping surface  246  and an articulated bottom surface  248  having a bulbous end  250 . The connection point of the positioning pins  244  to the bracket  236  is surrounded by a ferrule-like member  258 , see  FIG. 4 .  
         [0041]     The positioning pins  244  are adapted to be received within corresponding aligned openings within the resection guide  104 . As best shown in  FIG. 3 , a circular opening  260  is spaced apart from an oblong opening  262 , respectively aligned with the positioning pins  244 . The provision of an oblong opening  262  facilitates alignment of the openings  260 ,  262  with the positioning pins  244 . Insertion of the positioning pins  244  into their respective openings  260 ,  262  is also facilitated by the sloping top surface  246  and the bulbous end  250 . The openings  260 ,  262  are sized to effectively receive the ferrule-like member  258  whereby the front wall  138  of the bracket  136  is brought into engagement with the rear wall  178  of the resection guide  104 .  
         [0042]     The adjustment assembly  102  is releasably coupled to the resection guide  104  by means of a locking assembly  264 . The locking assembly  264  includes a spring biased shaft  266  which is slidingly received within bore  148  provided in the front wall  138  of the bracket  136 . A knob  268  is attached to the extended exposed end of the shaft  266 . An arm  270  is attached to the lower end of the shaft  266  extending outwardly from the bracket  136  through an opening  272 . The free end of the arm  270  supports an upwardly extending projection  274  (See  FIG. 3 ).  
         [0043]     As shown in  FIG. 3 , the rear wall  178  of the resection guide  104  is provided with an oval-shaped opening  276  which receives the arm  270  on the locking assembly  264 . A secondary opening (not shown) is formed within the housing  176  of the resection guide  104  in communication with opening  276 . The formed opening is sized to receive the projection  274  thereby releasably attaching the adjustment assembly  102  to the resection guide  104 . By depressing knob  268  downwardly, arm  270  will also be displaced downwardly to disengage the projection  274  from the opening within the housing  176 .  
         [0044]     The use of the femoral alignment guide  100  will be briefly described with reference to  FIG. 8 . In this regard, the alignment guide  100  is generally intended for any medical condition in which the use of computer-aided surgery may be appropriate, and where a reference to rigid anatomical structures, such as the femur or the tibia can be identified. As previously noted, one preferred application of the alignment guide  100  is in arthroplastic surgery to perform total knee replacement. The femoral alignment guide  100  is intended to be pinned to the distal portion of the femur for computer-aided alignment of the distal femoral cut. As to be described hereinafter, a tibial alignment guide is intended to be pinned to the proximal portion of the tibia for computer-aided alignment of the proximal tibia cut. However, the alignment guides can be coupled to the medial and lateral sides of the tibia and femur. In this regard, the alignment guide is modular in construction and can be used in both the femur and tibia configurations. While the adjustment assembly  102  is universal, the resection cutting guide and fixation plates are assembled depending on the bone undergoing treatment.  
         [0045]     As shown in  FIG. 8 , the femoral fixation plate  106  is pivotably attached to the adjustable assembly  102 . In turn the adjustable assembly  102  is mounted to the resection cutting guide  104 . The assembly of the femoral alignment guide  100  is accomplished in the manner as previously described. A tracker  278  is attached to the resection cutting guide  104  by means of tracker adaptor  280 . The tracker  278 , by way of example, is an electronic LED device which is visible to a camera providing two-way communication. The tracker  278  is used in conjunction with a navigation system which allows correct positioning and orientation of the implants. One such navigation system for use in arthroplastic surgery is known as the Stryker Knee Navigation System, which is available from Stryker Howmedica Osteonics of Allendale, N.J. The operation of the navigation system and tracker  278  in conjunction with the use of a femoral and tibial alignment guide is more fully described in the Stryker Navigation System User Manual, Knee Navigation V. 1.1, and incorporated in its entirety by reference.  
         [0046]     The femoral fixation plate  106  is pressed onto the distal condyles of the femur  282 . Initially, the tracker  278  is aligned with the sensors in the navigation system by rotating the tracker adapted  280  on the resection cutting guide  104 . Preferably, the femoral alignment guide  100  can be secured to the femur  282  using pins (not shown) inserted through one or more of the holes  228 ,  230  in the femoral fixation plate  106 .  
         [0047]     The varus-valgus angle, flexion extension angle and resection level are now adjusted using the assemblies  108 ,  110  and  112 . The adjustment using one of the assemblies  108 ,  110 ,  112  will not effect the alignment based on the use of another assembly. Specifically, the varus-valgus angle is adjusted by rotating worm  132  using any suitable implement which is operative for rotating the engagement member  134 . As the worm  132  is rotated within housing  114 , the varus-valgus mounting bracket  136  will rotate about its central line by virtue of pins  150  extending through the arcuate-shaped opening  146  within the bottom wall  140  thereof. As the mounting bracket  136  rotates, a corresponding rotation of the resection guide  104  will occur thereby providing varus-valgus alignment. The proper varus-valgus angle may be determined using the tracker  278  and the navigation system.  
         [0048]     The use of a meshed gear-type arrangement in the varus-valgus adjustment assembly  108  allows for the precise controlled manipulation of the resection cutting guide  104  in controlled increments. That is, for each rotation of worm  132 , a predetermined angular rotation will be imparted to the resection cutting guide  104  providing for continuously variable adjustment. By selecting the design of the worm  132  and teeth  144  on the mounting bracket  136 , precision control of aligning the resection guide for varus-valgus angle can be accomplished. Based upon the foregoing construction of the varus-valgus adjustment assembly  108 , the resection guide  104  is maintained in its proper angular orientation by the adjustment assembly once rotation of the worm  132  is terminated. Accordingly, there is no requirement for a secondary clamping or locking assembly, such as a cam lock, to maintain the proper varus-valgus angle of the resection guide  104  during any period of the adjustment process.  
         [0049]     The flexion-extension angle is adjusted using the flexion-extension adjustment assembly  112 , which is coupled to the resection cutting guide  104 . Sleeve  206  is rotated by a suitable tool which is attached to the engagement member  134 . As the sleeve  206  is rotated, the cross-member  214  which is attached to the thread rod  216  is advanced longitudinally while being guided by the spaced apart guide rods  208 , providing continuously variable adjustment. The cross member  214  will press against the femur  282  which results in rotation of the resection cutting guide  104  about the specific rod  160  to which the femoral fixation plate  106  is coupled via the hook shaped projection  232 . The flexion-extension angle can be monitored using the tracker  278  coupled with the navigation system in a similar manner as monitoring the varus-valgus angle adjustment. Each rotation of the sleeve  206  will result in a predetermined linear advancement of the cross-member  214  in controlled increments. This advancement is controlled by the pitch of the threads on the threaded rod  216  and the threads on the internally threaded sleeve  206 . As a result of the threaded engagement between the rod  216  and sleeve  206 , the cross-member  214  will maintain its position upon termination of rotation of the sleeve. For those reasons as previously described, this avoids the necessity of a clamping or locking assembly to maintain the resection guide  104  in proper flexion-extension angular adjustment.  
         [0050]     The resection level, i.e., proximal-distal, for the resection guide  104  is adjusted using the resection level adjustment assembly  110 . The resection level is accordingly adjusted by rotation of the threaded adjustment rod  168  by attaching a suitable implement to the engagement member  134  providing continuous variable adjustment. As the threaded rod  168  is rotated, the housing  114  of the adjustment assembly  102  is displaced in controlled increments away from the yoke  152  while being guided by the pair of spaced apart shafts  164 . Due to the threaded engagement of the threaded rod  168  with the housing  114 , the resection level of the resection cutting guide  104  can be controlled, as well as avoiding the need for a secondary locking or clamping assembly.  
         [0051]     After the resection cutting guide  104  has been properly adjusted in varus-valgus angle, flexion-extension angle and resection level, a pin (not shown) is inserted into the bore  194  of the cannulated wheels  192 . The pins are aligned perpendicular to the femur  282  by rotating the cannulated wheels  192 . The pins are then attached to the femur  282  to fixate the resection cutting guide  104 . If required, additional cross-pins may be used in openings extending through the resection cutting guide  104 .  
         [0052]     The pins securing the femoral fixation plate  106  are removed to free the adjustment assembly  102  from the femur  282 . The adjustment assembly  102  is detached from the resection cutting guide  104  by depressing knob  268  in order to release the locking assembly  264 . Subsequently, a suitable surgical instrument such as cutting blade may be inserted into the slot  188  to effect resection of the femur  282 .  
         [0053]     Referring to  FIGS. 2 and 9 , there is shown the construction of a tibial alignment guide generally designated by reference numeral  284 . The tibial alignment guide  284  includes a common adjustment assembly  102 , a tibial fixation plate  286  and a resection cutting guide  288 . Due to the anatomical nature of the proximal tibia, it is generally preferred to provide a separate resection cutting guide  288  for the left and right tibia. In this regard, the resection cutting guide  288  is illustrated as a right tibia resection guide, the left tibia resection guide being a mirror image thereof.  
         [0054]     The tibial fixation plate  286  as also shown in  FIG. 10  is constructed in a similar manner as the femoral fixation plate  106 . In this regard, the tibial fixation plate  286  includes a C-shaped plate  220  formed by a pair of spaced apart legs  222 ,  224 , supporting pin reinforcement guides  226 . The shape of the plate  220  is altered to accommodate mounting of the plate to the tibia  290  as shown in  FIG. 9 . By way of example, one or more projecting pins  292  of varying length can be attached to the plate  220  for supporting the fixation plate onto the proximal compartments of the tibia  290 . The tibia fixation plate  286  is rotationally coupled to the yoke  152  as previously described with respect to the femoral fixation plate  106 . In an alternative embodiment as shown in  FIG. 11 , the tibial fixation plate  286  is provided with a plurality of adjustable pins  294  which are threadingly received within the pin reinforcement guided  226 . The pins  294  include a threaded shaft  296 , which upon rotation by knob  298 , advances the pointed end  300  to adjust the length of a respective pin  294 .  
         [0055]     The tibial resection cutting guide  288  is generally similar in construction to the femoral resection cutting guide  104 , but for the inclusion of only a single cannulated wheel  192 . By way of further description, the tibial resection cutting guide  288  is provided with a housing  302  supporting the elongated slot  188  adjacent rear wall  178 . A single cannulated wheel  192  is rotationally supported within cutout  190 . The flexion-extension adjustment assembly  112  is coupled to the forward end of the housing  302  in the manner as previously described with respect to the femoral resection cutting guide  104 . As shown, the flexion-extension adjustment assembly  112  is arranged off center, e.g., on the left side of the housing  302  while the cannulated wheel  192  is positioned within the right side of the housing. The construction of the left tibial resection cutting guide would reverse the positions of the flexion-extension adjustment assembly  112  and cannulated wheel  192 .  
         [0056]     The tibial resection cutting guide  288  is mounted to the adjustment assembly  202  in the manner as previously described with respect to the femoral resection cutting guide  104 . The assembled tibial alignment guide  284  is shown in  FIG. 9 . The tibial resection cutting guide  288  is similarly positioned using a tracker  178  in operative association with a navigation system. After fixing the tibial fixation plate  286  to the proximal compartments of the tibia, the resection cutting guide  288  is adjusted in varus-valgus angle, flexion-extension angle and resection level. This is accomplished using the varus-valgus adjustment assembly  108 , resection level adjustment assembly  110 , and flexion-extension adjustment assembly  112  as previously described.  
         [0057]     Although the invention herein has been described with reference to particular embodiments, it is to be understood that the embodiments are merely illustrative of the principles and application of the present invention. It is therefore to be understood that numerous modifications may be made to the embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the claims.