Abstract:
A resection guide locator includes a bone engagement portion with surfaces that are complementary to the surface topographies of a bone to be resected during surgery. A housing includes a socket defined by a resilient annular wall that is sized and arranged so to accept a resection guide by press-fit to thereby position and hold the resection guide within the socket. The resection guide is maintained in a predetermined, preferred position while the surfaces are releasably locked in position on the bone. A method is disclosed for forming and using the resection guide locator.

Description:
This application is related to, and claims the benefit of U.S. provisional patent application Ser. No. 61/154,845, filed Feb. 24, 2009, and entitled Patient Specific Surgical Guide Mount. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to surgical guides, and the fixtures used to locate such guides in relation to a patient&#39;s body during orthopedic procedures, such as, total knee, hip, or ankle replacement surgery, and methods for designing and using such instrument locators. 
     BACKGROUND OF THE INVENTION 
     Total joint (knee, hip, and ankle) replacement prostheses are known in the art. In many instances, a specially designed jig or fixture enables the surgeon to make accurate and precise bone resections of the femoral surface, the tibial surface, or both in order to accept such prostheses. The ultimate goal with any total joint prosthesis is to approximate the function of the natural, healthy structures that the prosthesis is replacing. Should the prosthesis not be properly attached to the femur, tibia, ankle or foot, any misalignment could result in discomfort to the patient, gate problems, or degradation of the prosthesis. 
     For example, when attaching a knee prosthesis it is desirable to orient the prosthesis such that the pivot axis of the knee joint lies within a transverse plane that is generally oriented perpendicular to the mechanical axis of the femur. The mechanical axis lies along a line which intersects the femoral head and the center of the ankle. In the prior art, the mechanical axis had been determined from an inspection of a radiograph of the femur to be resected prior to, or even during the surgery. During the actual operation, the mechanical axis was determined by computing its valgus angle from the femoral shaft axis. It was then necessary to manually align any cutting guide and its fixtures with respect to the femoral shaft axis in order to achieve an optimum cut. 
     Often such cutting guides included a femoral intramedullary stem which was inserted through a pre-drilled passage way formed in the intercondylar notch and upwardly through the femur along the femoral shaft axis. The stem often included a bracket which supports a distal femur cutting guide. The bracket included a first pin which extended through the cutting guide to act as a pivot axis. A second pin was attached to the bracket so as to extend through an arcuate slot in the cutting guide. The cutting guide included pairs of opposing slots formed along its sides which were oriented to be perpendicular to a central axis of symmetry of the cutting guide. When the cutting guide was pivoted, such that the central axis of symmetry lay along the mechanical axis, so as to form the appropriate angle with the femoral shaft axis, the cutting guide slots were positioned to be perpendicular to the mechanical axis. The cutting guide was then locked into the predetermined angle with the femoral shaft axis. 
     In more recent times, computer-aided design techniques have been coupled with advances in imaging technology to improve joint replacement prostheses and methods. For example, in U.S. Pat. No. 5,735,277, a process of producing an endoprosthesis for use in joint replacement is disclosed in which a reference image for determining contour differences on a femur and a tibia, are obtained by comparing a corrected preoperative image of a damaged knee joint with a postoperative image. This technique is then used as the basis for preparing corresponding femoral and tibial components of an endoprosthesis. 
     In U.S. Pat. No. 6,944,518, a method for making a joint prosthesis is provided in which computed tomography, commonly known as a CAT scan (CT) data from a patient&#39;s joint is used to design a prosthesis. The CT data is downloaded into a computer aided design software in order to design at least an attachment part, and possibly a functional part, of the prosthesis. The attachment part can be used to attach or otherwise associate the functional part to the patient&#39;s bone. 
     In U.S. Pat. No. 5,370,692, a method for producing prosthetic bone implants in which imaging technology is used to define hard tissue characteristics (size, shape, porosity, etc.) before a trauma occurs (“pre-trauma” file) by archival use of available imaging techniques (computed tomography, magnetic resonance imaging, or the like). Loss of hard tissue is determined by imaging in the locale of the affected tissue after the injury (“post-trauma” file). The physical properties of the customized prosthetic device are specified by comparison of the pre-trauma and post-trauma files to produce a solid model “design” file. This specification may also involve secondary manipulation of the files to assist in surgical implantation and to compensate for anticipated healing process. The design file is mathematically processed to produce a “sliced file” that is then used to direct a manufacturing system to construct a precise replica of the design file in a biocompatible material to produce the implant. 
     In U.S. Pat. No. 5,798,924, a method for producing endoprosthesis where a data block of a three-dimensional actual model of existing bone structure of a patient is acquired using CT scanning. In a computer, the actual model is subtracted from the data block of an existing or CT scan-generated three-dimensional reference model. Then from the difference, a computer-internal model for the endoprosthesis is formed. The data blocks of the actual model and reference model are converted into the data of a CAD free-form surface geometry. 
     None of the forgoing methods or devices have adequately provided surgeons with a way to generate patient specific prostheses, surgical instruments, guides, and fixtures, nor have they aided in reducing the number or complexity of the fixtures used to locate resection guides in relation to the patient&#39;s body during orthopedic procedures, such as, total knee, hip, or ankle replacement surgery. 
     SUMMARY OF THE INVENTION 
     A method for forming a resection guide locator is provided that includes generating an anatomically accurate image of a bone, including details regarding its surface topographies. A femoral head, a distal femur, a distal tibia and a proximal tibia are each identified, and five millimeter thick slices are obtained, at three millimeter spacings. Sagittal slices may also be used in connection with the invention at 2 millimeter intervals and essentially zero millimeter spacing. A 2D T1 FSE (T1 weighted fast spin echo) imaging sequence is obtained and then anatomically accurate image is converted to a digital model. A digital representation of a resection guide locator is added to the digital model so as to form a composite digital model. Advantageously, one of the surface topographies is mapped complementarily onto a bone engagement portion of the resection guide locator, which is then manufactured based upon the composite digital model so that a manufactured resection guide locator is formed including the complementary surface topography on a bone engagement portion, and with a receptacle pocket sized to receive a resection guide with a press-fit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein: 
         FIG. 1  is a perspective view of femoral and tibial resection guides mounted within resection guide locators that have been formed in accordance with the present invention and located upon portions of a femur and a tibia, respectively; 
         FIG. 2  is a schematic representation of a scanned image of a human knee joint; 
         FIG. 3  is a schematic representation of the scanned image of the human knee joint shown in  FIG. 2 , after conversion to a computer model in accordance with the present invention; 
         FIG. 4  is a schematic representation similar to  FIG. 7 ; 
         FIG. 5  is a schematic representation, similar to  FIG. 3 , showing proposed resection lines and local coordinates superpositioned upon the computer model of  FIG. 3 , in accordance with the present invention; 
         FIG. 6  is a schematic representation similar to  FIGS. 4 and 5 , but showing a femoral and a tibial resection guide locator represented within the computer model of  FIG. 3  in accordance with the present invention; 
         FIG. 7  is a schematic representation similar to  FIGS. 4 ,  5 , and  6 , showing a digital representation of the femoral and tibial prostheses (in cross section) superimposed within the model in accordance with the present invention; 
         FIG. 8  is a perspective view of a femoral resection guide locator formed in accordance with the present invention; 
         FIG. 9  is a rear perspective view of the femoral resection guide locator shown in  FIG. 8 ; 
         FIG. 10  is an elevational view of the front side of the femoral resection guide locator shown in  FIG. 9 ; 
         FIG. 11  is an elevational view of the bottom of the femoral resection guide locator shown in  FIGS. 8 ,  9  and  10 ; 
         FIG. 12  is a perspective view of a tibial resection guide locator formed in accordance with the present invention; 
         FIG. 13  is a perspective bottom view of the tibial resection guide locator shown in  FIG. 12 ; 
         FIG. 14  is a top view of the tibial resection guide locator shown in  FIG. 13 ; 
         FIG. 15  is a rear elevational view of the tibial resection guide locator shown in  FIG. 14 ; 
         FIG. 16  is a perspective view of a typical tibial resection guide; 
         FIG. 17  is a front elevational view of the tibial resection guide shown in  FIG. 16 ; 
         FIG. 18  is a side perspective view of the tibial resection guide shown in  FIG. 17 ; 
         FIG. 19  is a perspective view of a femoral resection guide mounted within a femoral resection guide locator positioned upon the condyles of a femur; and 
         FIG. 20  is a perspective view of a tibial resection guide mounted within a tibial resection guide locator positioned upon the articular surfaces of a tibia. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. When only a single machine is illustrated, the term “machine” shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. In the claims, means-plus-function clauses, if used, are intended to cover the structures described, suggested, or rendered obvious by the written description or drawings for performing the recited function, including not only structural equivalents but also equivalent structures. 
     The present invention provides custom manufactured surgical instruments, guides, and fixtures that are based upon a patient&#39;s anatomy as determined by a computer tomography scanner (CT), magnetic resonance imaging machine (MRI), or the like medical imaging technology. For example, a CT or MRI scanned image  1  or series of images may be taken of a patient&#39;s knee  1 , including portions of the limb from the pelvis or the foot ( FIGS. 2 and 3 ). In the case of a total knee replacement, the CT or MRI scanned image data is then converted from, e.g., a DICOM image format, to a solid computer model  3  of the lower limb often including the pelvis, femur, patella, tibia, or foot to determine implant alignment, type and sizing using specialized modeling methods that are often embodied in computer software. Computer generated solid models  3  that are derived from CT or MRI scan image data  1  will often include precise and accurate information regarding the surface contours surrounding the structures that have been imaged, e.g., the surface topography of the bones or contour of fascia that have been imaged. 
     The methods disclosed in U.S. Pat. No. 5,768,134, issued to Swaelens et al., and incorporated herein by reference, have been found to yield adequate conversions of CT or MRI scanned image data  1  to solid computer model  3  usable with the present invention. In some embodiments, images are made of a lower limb, i.e., the pelvis, femur, patella, tibia, and/or foot of a patient using a CT or MRI machine, or other digital image capturing and processing unit ( FIGS. 2 and 3 ). This scanning generates a scanned image of the diseased knee or ankle joint, including adjoining portions of the femur  5  and tibia  6 . The image data  1  is first processed in a processing unit, after which a model is generated using the processed digitized image data. 
     With one embodiment of the invention scanned images of a diseased knee or ankle joint, including adjoining portions of the femur  5  and tibia  6 , were generated using a Hitachi 0.3T Airis Elite open MRI. The Hitachi device comprises an asymmetric two-post open architecture, and provides a 0.3T magnetic field strength in a vertical orientation with high homogeneity. For example, scanned images of a diseased knee joint suitable for use in connection with the present invention incorporated sagittal slices of the knee using the patient&#39;s patella and tibial tubercle as anatomic landmarks. Two millimeter thickness slices, at zero millimeter slice spacing were gathered with the scan boundaries defining an approximate field of view of twelve centimeters proximal and nine centimeters distal of the joint line or the extent of the knee coil. A standard multiple array extremity coil was utilized with imaging set for bright cartilage and dark bone with crisp boundaries. The patient was placed with the leg to be scanned in the middle of the coil. It will be understood that in bilateral cases each leg would be scanned separately. 
     In addition to the forgoing parameters, when generating scanned images of a patient&#39;s knee for use in connection with the present invention, it is often preferable to acquire a FATSEP 3D RSSG imaging sequence with the parameters listed in the Table 1 below. For preferred results, very clear boundaries should be determined between the cartilage and surrounding soft tissues, and the cartilage and bone. The cartilage will often present a bright signal and the bone a dark signal, allowing clear contrast between the two materials. 
     Scanned images (axial slices) of femur  5  and tibia  6  associated with a diseased knee may also be generated utilizing the rapid body coil of the Hitachi 0.3T Airis Elite open MRI. Anatomic landmarks found to be useful for these scans included the femoral head and distal femur as well as the distal tibia and proximal tibia. Five millimeter thick slices, at three millimeter spacing provided preferred results with the present invention. Preferred scan boundaries included the proximal femoral head through distal femur and the most proximal tibial point through most distal tibial point, e.g., the ankle joint. The patient may be placed with leg to be scanned in the middle of the coil, it again being understood that in bilateral cases each leg would be scanned separately. 
     The field of view available from the rapid body coil may not always cover the entire femur or tibia within one scan. In such instances, the femur or tibia may be scanned in two separate regions. Between the two scans the patient will have to move in order to reposition the coil to cover the most proximal or distal regions of interest. It is important in such instances to provide as much overlap as possible between the two scans. The patient&#39;s leg should be placed in the middle of the coil to ensure the largest field of view possible without distortion. The corners of the images at the field of view limits of the coil are susceptible distortion. The patient&#39;s legs should be scanned separately, as bilateral scans place the proximal and distal ends of the knee joint region within the field of view limitation and within areas of possible distortion. Additionally, a 2D T1 FSE (T1 weighted fast spin echo) imaging sequence may be acquired with the parameters listed in the Table 1. It should be noted that the boundaries of the bone, from the ball of the femoral head down to the distal condyles, should be clear for processing. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Hitachi 0.3T Airis Elite Sequence Overview 
               
             
          
           
               
                   
                 Hip-Knee 
                 Knee 
                 Ankle-Tibia 
               
               
                   
                   
               
             
          
           
               
                 Coil 
                 Rapid Body 
                 Multiple Array 
                 Rapid Body 
               
               
                   
                 Coil 
                 Extremity Coil 
                 Coil 
               
               
                 Study (Pulse 
                 2D T1 FSE 
                 FATSEP 3D RSSG 
                 2D T1 FSE 
               
               
                 Sequence) 
               
               
                 TR (ms) 
                 2700   
                 61  
                 2700   
               
               
                 TE (ms) 
                 10  
                  28.5 
                 10  
               
               
                 Plane 
                 Axial 
                 Sagittal 
                 Axial 
               
               
                 Slice Thickness (mm) 
                 5 
                 2 
                 5 
               
               
                 Slice Spacing (mm) 
                 3 
                 0 
                 3 
               
               
                 NEX 
                 2 
                 1 
                 2 
               
               
                 Flip Angle 
                 90  
                 90  
                 90  
               
               
                 Matrix 
                 256*256 
                 512*512 
                 256*256 
               
               
                 Acquisition Time 
                 5:46 
                 15:37 
                 5:46 
               
               
                 (min:sec) 
               
               
                   
               
             
          
         
       
     
     In accordance with the present invention, interactive processing and preparation of the digitized image data is performed which includes the manipulation and introduction of additional extrinsic digital information  8 , such as, predefined reference locations  9  for component positioning and alignment  10  so that adjustments to the surgical site, that will require resection during surgery, may be planned and mapped onto computer model  3  ( FIGS. 4 and 5 ). After the interactive processing of the digitized image data, it is possible to go back to original CAD data to obtain a higher resolution digital representation of the patient specific surgical instrument, prostheses  7   a ,  7   b  ( FIG. 7 ) guide, or fixture so as to add that digital representation to the patient&#39;s image data model. 
     For example, when the system of the present invention is used for knee replacement surgery, a digital representation of a femoral resection guide mount  20  may be added to the patient&#39;s image data model ( FIGS. 1 and 6 ). In the context of a total knee replacement, femoral resection guide mount  20  may be formed for placement on the exposed condyles of a patient&#39;s femur to assure precise and accurate positioning of a femoral resection guide  26  which is used to direct and control bone resection of femur  5  during surgery. Although the femoral resection guide  26  can take various forms and configurations, the present invention will be described with reference to a distal resection guide currently offered by applicant Wright Medical Technology, Inc. (Wright Medical Part No. K001-2659). Significantly, femoral resection guide mount  20  provides this precise and accurate positioning function without the need for other external fixtures or the use of an intramedullary stem inserted through the intercondylar notch and upwardly through femur  5  along the femoral shaft axis. A digital representation of a tibial resection guide mount  22  may also be added to the patient&#39;s image data model ( FIG. 6 ). Tibial resection guide mount  22  is similarly formed for placement on the exposed superior articular surface of a patient&#39;s tibia  6  to assure precise and accurate positioning of a tibial resection guide  28  used to direct and control bone resection of the superior articular surface of the exposed tibia during surgery. 
     Referring to  FIGS. 8-11 , a femoral resection guide mount  20  according to one embodiment of the invention is formed from a resilient polymer material of the type that is suitable for use in connection with stereo lithography or the like manufacturing equipment. Resection guide mount  20  comprises a unitary block including a bifurcated condylar yolk  25  and a guide receptacle  29 . Bifurcated yolk  25  includes a pair of spaced apart arms  30 ,  31  that project outwardly from a base  33 . Arm  30  has a lower or bone engaging surface  36  and a through-bore  42 , and arm  31  has a lower or bone engaging surface  40  and a through-bore  38 . Through the previously discussed imaging operations, the bone engaging surfaces  36 ,  40  are configured for complimentary matching with anatomical surface features of a selected region of the patient&#39;s natural bone. For the fermoral resection guide mount  20  embodiment of  FIGS. 8-11 , the selected bone region comprises the condyles of the patient&#39;s femur. 
     Guide receptacle  29  includes a pair of wings  44 , 46  that project outwardly, in opposite directions from base  33  and in spaced relation to arms  30 , 31 . Each wing  44 ,  46  includes a pylon  48  projecting upwardly to support guide housing  49  such that an elongate slot  52  is defined between base  33  and guide housing  49 . Slot  52  is sized and shaped to allow a typical surgical saw, of the type often used for bone resection, to pass through from a correspondingly positioned and sized slot in resection guide  26  without contact, or with only incidental contact with resection guide locator  20 . An annular wall  55 , having a shape that is complementary to the outer profile of femoral resection guide  26 , projects outwardly in substantially perpendicular relation to a back wall  61  and thereby defines a recess  58 . In some preferred embodiments, recess  58  is sized so as to accept femoral resection guide  26  with a “press-fit”. By press-fit it should be understood that annular wall  55  is sufficiently resilient to deflect or compress elastically so as to store elastic energy when femoral resection guide  26  is pushed into recess  58 . Of course, it will also be understood that femoral resection guide  26  will have an outer circumferential shape that is complementary to the circumferential shape of recess  58 , but slightly larger in size, for press-fit embodiments. Also, femoral resection guide  26  may be retained within recess  58  by only frictional engagement with annular wall  55  or, in less preferred embodiments, resection guide  26  can simply slide into recess  58  without operative contact or only incidental engagement with annular wall  55 . First through-bores  62 ,  64  are defined in back wall  61  in spaced relation to one another, with a second through-bore  67 , 69  being associated with each first through-bore  62 , 64 . In the embodiment shown in  FIGS. 8-11 , the first through-bores  62 ,  64  are large square or rectangular openings, a configuration that eases manufacture, reduces material use, and provides sufficient space for driving pins, wires, screws or other appropriate fasteners through a plurality of adjacent bores provided on the femoral resection guide  26 . A groove  70  is defined in the outer surface of base  33  and centrally located with respect to recess  58 . 
     Referring to  FIGS. 12-18 , a tibial resection guide mount  22  according to one embodiment of the invention is formed from a resilient polymer material of the type that is suitable for use in connection with stereo lithography, selective laser sintering, or the like manufacturing equipment, e.g., a polyamide powder repaid prototype material is suitable for use in connection with selective laser sintering. Resection guide mount  22  comprises a unitary block including a bifurcated yolk  75  and a guide receptacle  79 . Bifurcated yolk  75  includes a pair of spaced apart arms  80 ,  81  that project outwardly from a base  83 . Arm  80  has a lower surface  86  and arm  81  has a lower surface  90 . 
     Guide receptacle  79  includes a pair of wings  84 ,  86  that project outwardly, in opposite directions from base  83  and in spaced relation to arms  80 , 81 . Each wing  84 , 86  includes a pylon  88  projecting upwardly to support guide housing  89  such that an elongate slot  94  is defined between base  83  and guide housing  89 . Slot  94  is sized and shaped to allow a typical surgical saw, of the type often used for bone resection, to pass through from a correspondingly positioned and sized slot in resection guide  28  without contact, or with only incidental contact with resection guide locator  22 . An annular wall  95 , having a shape that is complementary to the outer profile of tibial resection guide  28 , projects outwardly in substantially perpendicular relation to a back wall  101  and thereby defines a recess  108 . Recess  108  is sized so as to accept tibial resection guide  28  with a press-fit. First through-bores  112 ,  114  are defined in back wall  101  in spaced relation to one another, with a second through-bore  117 ,  119  being associated with each first through-bore  112 ,  114 . 
     Returning to the digital image models  3  previously disclosed, and considering a generalized digital model of resection guide mount  20  added to the patient&#39;s femur image data, the anatomic surface features of the patient&#39;s femur, e.g., the condylar surface topography, may be complementarily mapped onto each of lower surface  36  and lower surface  40  of arms  30 ,  31 . It will be understood that complementary mapping of the digital images results in localized prominences on the surface of a bone, e.g., a condyle or articular surface, becoming localized concavities on lower surface  36  or lower surface  40 , while localized concavities on the surface of a bone become localized prominences on lower surface  36  or lower surface  40 . In this way, each of lower surface  36  and lower surface  40  is redefined with a complementary, substantially mirror image of the anatomic surface features of a selected region of the patient&#39;s femur. As a consequence of this complementary bone surface mapping, resection guide mount  20  releasably “locks” on to the complementary topography of the corresponding portion of the patient&#39;s natural femur, e.g., the condylar surfaces, without the need for other external or internal guidance fixtures. A substantially identical mapping is carried out in connection with the design of a patient specific tibial resection guide mount  22 . 
     A visual presentation of the virtual alignment results between the patient&#39;s femur and resection guide mount  20  is created and forwarded to the surgeon to obtain approval of the results prior to manufacturing ( FIGS. 1 ,  19 ,  20 ). Upon receipt of the surgeon&#39;s approval, resection guide mount  20 , and in appropriate instances resection guide mount  22 , is manufactured and returned to the surgeon for use in the surgery. 
     During a total knee replacement the present invention is used in the following manner. The surgeon first orients resection guide mount  20  on femur  5  until lower surfaces  36 ,  40  of resection guide mount  20  “lock” to the topography of the exposed surface  4  of femur  5 . With resection guide mount  20  locked onto the patient&#39;s femur, a surgeon press-fits an appropriately configured Distal Resection Guide  26  (e.g. Wright Medical Technology, Inc. Part No. K001-2659) in recess  58  of resection guide mount  20 . As indicated in  FIGS. 19-20 , this results in the resection guide mount  20 , and particularly the guide receptacle portion  29  of the resection guide mount  20 , being sandwiched between the resection guide  26  and the patient&#39;s bone. Pins are driven into through-bores of the resection guide  26 , but advantageously the pins do not come into contact with the portions of resection guide mount  20  that define through-bores  62 ,  64  or  67 ,  69 . These through-bores are often the most proximal on resection guide mount  20 . With resection guide mount  20  held securely in place, a drill bit is advanced into through-bores  38  and  42 , through-bores  62 ,  64  defined in back wall  61 , and/or into second through-bores  67 , 69 . It is often preferable for the drill to protrude about 15 mm into through-bores  38  and  42  into the femoral bone so the drill holes will be present after the distal resection. Increased hole depth may be necessary in the event of a larger distal resection to correct a flexion contracture. For additional stability, fixation pins (not shown) may be left in through-bores  38  and  42 , but must be removed prior to resection. With the resection guide mount  20  thus accurately positioned with respect to the selected bone region and the resection guide  26 -guide mount  20  construct appropriately secured to the patient&#39;s bone, the surgeon uses a conventional surgical blade and the resection slot of the resection guide  26  to resect the patient&#39;s bone. 
     It is to be understood that the present invention is by no means limited only to the particular constructions herein disclosed and shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.