Patent Publication Number: US-2022226031-A1

Title: Joint osteotomy system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 16/669,809, filed Oct. 31, 2019, which is a continuation of co-pending U.S. patent application Ser. No. 16/668,639, filed Oct. 30, 2019, which is a continuation of International Patent Application No. PCT/US2017/044419, filed on Jul. 28, 2017, the entireties of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     The ankle is a joint that acts much like a hinge. The joint is formed by the union of three bones. The ankle bone is the talus. The top of the talus fits inside a socket that is formed by the lower end of the tibia and the fibula, the small bone of the lower leg. Arthritis, bone degeneration, and/or injury can cause ankle joint deterioration resulting in pain, reduced range of motion, and decreased quality of life. In many cases, physicians are recommending ankle replacement surgery with an implant as an option. 
     A primary ankle replacement surgery can include replacement of portions of one or more of the bones of the ankle with one or more implants. The primary ankle replacement surgery can correct misalignments, deformities, and other issues of the ankle joint. In some cases, a revision surgery is necessary to correct additional deformities, misalignments, or other issues of the ankle joint not corrected during a primary ankle replacement surgery and/or that develop after the primary ankle replacement surgery. 
     SUMMARY 
     In various embodiments, a system includes a first spacer sized and configured to be received within a joint space of a first bone. The first spacer defines a body extending between a first surface and a second surface. The system further includes an adjustable guide includes a guide adapter and a guide body. The guide adapter is configured to couple the adjustable guide to the first spacer. The guide body is adjustable along a first axis with respect to the guide adapter. 
     In various embodiments, a system includes a first spacer sized and configured to be received within a joint space of a first bone. The first spacer defines a body extending between a first surface and a second surface. The system further includes at least one shim comprising a body extending between an upper surface and a lower surface. The upper surface is configured to couple the at least one shim to the second surface of the first spacer. The system also includes an adjustable guide comprising a guide adapter configured to be coupled the first spacer and a guide body. The guide body comprises a first leg and a second leg extending from the guide body and spaced apart to define a slot sized and configured to receive a coupling element extending from the guide adapter. The guide body is adjustable along a first axis with respect to the guide adapter. 
     In various embodiments, a method includes coupling a first spacer to a joint space of a first bone. The first spacer defines a body extending between a first surface and a second surface. The first surface is positioned in contact with the first bone. A second spacer is coupled to a second bone. The second spacer defines a body extending between a first surface and a second surface. The second surface of the first spacer is configured to abut the second surface of the second spacer to position the first bone and the second bone in a predetermined alignment. An adjustable guide is coupled to one of the first spacer or the second spacer. 
     In various embodiments, a system includes a first spacer sized and configured to be received within a joint space of a first bone, a second spacer sized and configured to be coupled to a second bone, and at least one shim comprising a body extending between an upper surface and a lower surface. The first spacer and the second spacer each include a body extending between a first surface and a second surface. the upper surface of the at least one shim is configured to couple the at least one shim to the second surface of the first spacer and the lower surface is configured to couple the at least one shim to the second surface of the second spacer. The first spacer, the second spacer, and the at least one shim are configured to position the first bone and the second bone in a predetermined alignment. 
     In various embodiments, a system includes a first spacer sized and configured to be received within a resected bone space of a first bone, a second spacer sized and configured to be coupled to a second bone, and at least one shim comprising a body extending between an upper surface and a lower surface. The first spacer and the second spacer each include a body extending between a first surface and a second surface. The first surface of the first spacer is configured to couple the first spacer to a lock detail of an implant coupled to the first bone. The upper surface of the at least one shim is configured to couple the at least one shim to the second surface of the first spacer and the lower surface is configured to couple the at least one shim to the second surface of the second spacer. The first spacer, the second spacer, and the at least one shim are configured to position the first bone and the second bone in a predetermined alignment. 
     In various embodiments, a method includes coupling a first spacer to a joint space of a first bone. The first spacer defines a body extending between a first surface and a second surface. The bone contacting surface is positioned in contact with the resected bone space. A second spacer is coupled to a second bone. The second spacer defines a body extending between a first surface and a second surface. An upper surface of a first shim is coupled to the second surface of the first spacer and a lower surface of the first shim is coupled to the second surface of the second spacer. The first spacer and the second spacer position the first bone and the second bone in a predetermined alignment. The first shim has a predetermined thickness configured to correct laxity between the first bone and the second bone. 
     In various embodiments, a system includes a first spacer sized and configured to be received within a joint space of a first bone and a second spacer sized and configured to be coupled to a second bone. The first spacer includes a body extending between a first surface and a second surface. The second surface defines an adjustment channel. The second spacer includes a body extending between a first surface and a second surface and an adjustment body extending from the second surface. The adjustment body is sized and configured to be inserted into the adjustment channel in a telescoping arrangement. The first spacer and the second spacer are configured to position the first bone and the second bone in a predetermined alignment. 
     In various embodiments, a method includes coupling a first spacer to a joint space of a first bone. The first spacer includes a body extending between a first surface and a second surface. The second surface defines an adjustment channel extending into the body. A second spacer is coupled to a second bone. The second spacer includes a body extending between a first surface and a second surface and an adjustment body extending from the second surface. The adjustment body is sized and configured to be inserted into the adjustment channel in a telescoping arrangement. The first spacer and the second spacer are configured to position the first bone and the second bone in a predetermined alignment. A spacing between the first spacer and the second spacer is adjusted by sliding the adjustment body within the adjustment channel. The spacing between the first spacer and the second spacer is configured to correct for laxity between the first bone and the second bone. 
     In various embodiments, a system includes a monolithic spacer having a body extending between a first surface and a second surface and an adjustable guide. The first surface is configured to abut a joint space of a first bone and the second surface includes a patient-specific topography matching a second bone. The adjustable guide includes a guide adapter configured to be coupled the monolithic spacer and a guide body defining a resection slot. The guide body comprises a first leg and a second leg extending from the guide body and spaced apart to define a slot sized and configured to receive a coupling element extending from the guide adapter. 
     In various embodiments, a system includes a body sized and configured to be receiving within a joint space and defining a tool path extending from a first side of the body to a second side of the body. The tool path is sized and configured to receive a surgical tool therethrough. A first bone engaging structure extends from the body in a first direction. The first bone engaging structure includes a first surface that is complementary to a surface topography of the bone. A drill guide is sized and configured to be received within tool path defined by the body. The drill guide defines an aperture sized and configured to receive the surgical tool therethrough. At least one shim is configured to be coupled to a bottom surface of the body. The shim includes a coupling element extending from an upper surface and the body defines a first complementary recess sized and configured to receive the coupling element therein. 
     In various embodiments, a system includes a first spacer sized and configured to be received within a joint space of a first bone and a first shim. The first spacer defines a body extending between a first surface and a second surface. The first shim includes a body extending between an upper surface and a lower surface. The upper surface is configured to couple the first shim to the second surface of the first spacer and the lower surface is configured to abut a second bone to position the first bone and the second bone in a predetermined alignment. 
     In various embodiments, a method includes positioning a first spacer within a joint space of a first bone and coupling a first shim to a surface of the first spacer. The first bone and a second bone are positioned in a predetermined alignment by abutting the first shim with the second bone. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The features and advantages of the present invention will be more fully disclosed in, or rendered obvious by the following detailed description of the preferred embodiments, which are to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein: 
         FIG. 1  illustrates the bones of a human foot and ankle; 
         FIGS. 2A and 2B  are schematic representations of a scanned image of a human foot and ankle joint; 
         FIG. 3  illustrates a bone preparation instrument coupled to a first bone by a conversion instrument, in accordance with some embodiments; 
         FIG. 4  illustrates a front side plan view of the bone preparation instrument of  FIG. 3 , in accordance with some embodiments; 
         FIG. 5  illustrates a side view of the bone preparation instrument of  FIG. 3 , in accordance with some embodiments. 
         FIG. 6  illustrates a spacer assembly positioned between a first bone and a second bone of a joint, in accordance with some embodiments; 
         FIG. 7  illustrates a side view of the spacer assembly of  FIG. 6 , in accordance with some embodiments; 
         FIG. 8  illustrates a front view of the spacer assembly of  FIG. 6 , in accordance with some embodiments; 
         FIG. 9  illustrates an exploded view of the spacer assembly of  FIG. 6 , in accordance with some embodiments; 
         FIG. 10  illustrates an isometric view of a first spacer positioned within a resected bone space of a first bone, in accordance with some embodiments; 
         FIG. 11  illustrates a front view of the first spacer of  FIG. 10 , in accordance with some embodiments; 
         FIG. 12  illustrates a bottom isometric view of the first spacer of  FIG. 10 , in accordance with some embodiments; 
         FIG. 13  illustrates another embodiment of a first spacer configured to be positioned within a resected bone space of a first bone, in accordance with some embodiments; 
         FIG. 14  illustrates an isometric view of a second spacer configured to abut a second bone, in accordance with some embodiments; 
         FIG. 15  illustrates a bottom isometric view of the second spacer of  FIG. 14 , in accordance with some embodiments; 
         FIG. 16  illustrates an isometric view of a shim, in accordance with some embodiments; 
         FIG. 17  illustrates a bottom view of the shim of  FIG. 16 , in accordance with some embodiments; 
         FIG. 18  illustrates an isometric view of an adjustable guide, in accordance with some embodiments; 
         FIG. 19  illustrates an exploded view of the adjustable guide of  FIG. 18 , in accordance with some embodiments; 
         FIG. 20  illustrates a side view of a guide adapter of the resection guide of  FIG. 18 , in accordance with some embodiments; 
         FIG. 21  illustrates a top view of the guide adapter of  FIG. 20 , in accordance with some embodiments; 
         FIG. 22  illustrates an isometric view of a guide body of the adjustable guide of  FIG. 18 , in accordance with some embodiments; 
         FIG. 23  illustrates a front view of the resection guide of  FIG. 22 , in accordance with some embodiments; 
         FIG. 24  illustrates a rear isometric view of the resection guide of  FIG. 22 , in accordance with some embodiments; 
         FIG. 25  illustrates an isometric view of a locking knob of the adjustable guide of  FIG. 18 , in accordance with some embodiments; 
         FIG. 26  illustrates a top view of the locking knob of  FIG. 25 , in accordance with some embodiments; 
         FIG. 27  illustrates the spacer assembly of  FIG. 6  having one or more guide elements inserted through an adjustable guide assembly, in accordance with some embodiments. 
         FIG. 28  illustrates the guide body of  FIG. 22  coupled to a first guide element and a second guide element, in accordance with some embodiments. 
         FIG. 29  illustrates a spacer assembly including a first spacer configured to be coupled to an implant installed in a first bone, in accordance with some embodiments 
         FIG. 30  illustrates the spacer assembly of  FIG. 29  having an adjustable guide coupled thereto, in accordance with some embodiments. 
         FIG. 31  illustrates a spacer assembly including a monolithic spacer, in accordance with some embodiments; 
         FIG. 32  illustrates an isometric view of the monolithic spacer of  FIG. 31 , in accordance with some embodiments; 
         FIG. 33  illustrates a rear view of the monolithic spacer of  FIG. 32 , in accordance with some embodiments; 
         FIG. 34  illustrates a spacer assembly including a monolithic spacer and a cutting guide coupled thereto, in accordance with some embodiments; 
         FIG. 35  illustrates a spacer assembly including a first spacer and a second spacer coupled in a telescoping arrangement, in accordance with some embodiments; 
         FIG. 36  illustrates an isometric view of a first spacer and a second spacer coupled in a telescoping arrangement, in accordance with some embodiments; 
         FIG. 37  illustrates a first spacer of the spacer assembly of  FIG. 36 , in accordance with some embodiments; 
         FIG. 38  illustrates a second spacer of the spacer assembly of  FIG. 36 , in accordance with some embodiments; 
         FIG. 39  illustrates an isometric view of a spacer assembly including a first spacer and one or more shims configured to abut a second bone of a joint, in accordance with some embodiments; 
         FIG. 40  illustrates an isometric view of a spacer assembly including a first spacer and a fixed angle shim configured to abut a second bone of a joint, in accordance with some embodiments; 
         FIG. 41  illustrates the fixed angle shim of  FIG. 40 , in accordance with some embodiments; 
         FIG. 42  illustrates a drill guide mount configured to be coupled to at least one shim, in accordance with some embodiments; and 
         FIG. 43  illustrates the drill guide mount of  FIG. 42  coupled to a first bone and a first shim configured to be coupled to the drill guide mount, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top,” “bottom,” “proximal,” “distal,” “superior,” “inferior,” “medial,” and “lateral” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected,” 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. Like elements have been given like numerical designations to facilitate an understanding of the present subject matter. 
     As used herein, the term “substantially” denotes elements having a recited relationship (e.g., parallel, perpendicular, aligned, etc.) within acceptable manufacturing tolerances. For example, as used herein, the term “substantially parallel” is used to denote elements that are parallel or that vary from a parallel arrangement within an acceptable margin of error, such as +/−5°, although it will be recognized that greater and/or lesser deviations can exist based on manufacturing processes and/or other manufacturing requirements. 
     The disclosed systems and methods may advantageously utilize custom manufactured surgical instruments, guides, and/or fixtures that are based upon a patient&#39;s anatomy to maximize the accuracy of the guides and/or surgical instruments during a surgical procedure. These custom instruments, guides, and/or fixtures may be created by imaging a patient&#39;s anatomy with a computer tomography (“CT”) scanner, a magnetic resonance imaging (“MRI”) machine, or like medical imaging technology prior to surgery and utilizing these images to create patient-specific instruments, guides, and/or fixtures. This is generally termed as a preoperative assessment or plan and may be used in conjunction with intra-operative tools to accurately implement such a plan. Exemplary preoperative assessments or plans may allow a surgeon to specify the size, position, and/or orientation of a patient&#39;s anatomical components and/or subsequent implant components within the joint or bone at issue based upon preoperative CT or MRI images. Of course, final component size and position may be determined intra-operatively through direct visualization of the implants or various sizing instrumentation by the surgeon with or without the aid of fluoroscopy. 
     The disclosed systems and methods can be applied to a revision surgery for primary replacement of ankle joint  12 . Examples of primary ankle techniques using patient-specific surgical jigs and fixtures are described in U.S. Patent Appl. Pub. No. 2015/0257899, published Sep. 17, 2015, entitled “Ankle Replacement System and Method” and U.S. Pat. No. 8,808,303, issued on Aug. 19, 2014 and entitled “Orthopedic Surgical Guide,” each of which is incorporated by reference herein in its entirety. Although the following description of the custom patient-specific instruments are described with respect to a foot  10  and ankle  12  ( FIG. 1 ), one of ordinary skill in the art will understand that the systems and methods may be utilized in connection with other joints including, but not limited to, knees, hips, shoulders, and the like. As shown in  FIG. 1 , a typical human foot  10  includes an ankle joint  12  formed between a talus  14 , which is disposed on a calcaneus  20 , a tibia  16 , a fibula  18 , and a navicular  22 . 
     Upon completion of a primary replacement surgery, one or more articulation surfaces of ankle joint  12  are replaced with one or more implants. For example, in some embodiments, tibial implant and/or a talar implant replace articulation surfaces of a talus  12  and/or a tibia  14 , respectively. A revision procedure is applied to a joint that has previously been subject to a replacement procedure. The revision procedure modifies the joint replacement through making additional resections, replacing existing implants with alternative implants, and/or adding additional or removing implants at the joint. For example, in some embodiments, the systems and methods disclosed herein can be used for an ankle revision procedure in which the ankle joint has previously been subject to a replacement procedure. 
     During a primary and/or a revision surgery, a CT or MRI scanned image or series of images may be taken of a patient&#39;s ankle  12  (or other joint) and then converted from, e.g., a DICOM image format, to a solid computer model of the ankle including the calcaneus, talus, tibia, navicular, and fibula to determine implant alignment, type, and sizing using specialized modeling methods that are often embodied in computer software. Computer generated models (e.g., CAD models) that are derived from the data of the CT or MRI scan image 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 connected tissue (e.g., fascia, cartilage, etc.) that have been imaged. Imaging and generation of patient-specific implants is further described in U.S. Pat. No. 5,768,134, issued on Jun. 16, 1998, entitled “Method for Making a Perfected Medical Model on the Basis of Digital Image Information of a Part of the Body,” which is incorporated herein by reference in its entirety. In some embodiments, the CT and/or MRI scan image includes foreign bodies, such as one or more implants previously installed in the joint  12  during a primary replacement surgery, as described in greater detail in International Patent Application No. PCT/US15/20414, which published as WO 2016/148675, which is incorporated herein in its entirety. It will be understood that by surface topography it is meant the location, shape, size and distribution of surface features such as concavities and prominences or the like. 
     In some embodiments, after establishing a primary ankle replacement, a revision procedure can be performed re-using instrumentation from the primary replacement procedure and/or using additional instrumentation. For example, in some embodiments, a revision procedure can include the use of a conversion instrument  200 . The conversion instrument  200  is configured to couple a cutting guide to one of the first bone  14  and/or the second bone  16  to allow one or more revision resections to be formed. The revision resections are configured to further modify the first bone  14  and/or the second bone  16  to receive alternative and/or additional revision implants. 
     As illustrated in  FIGS. 3-5 , in some embodiments, a guide  250  and a conversion instrument  200  can be coupled to a first bone  14  by sliding the guide  250  and/or the conversion instrument  200  over one or more pins inserted into the first bone  14 . As best seen in  FIG. 4 , conversion instrument  200  includes an elongate body  202  extending from a region for fixation (shown at the proximal end  204  in the illustrated embodiment) to a region for attaching other bone preparation instruments (shown at the distal end  206  in the illustrated embodiment). Conversion instrument  200  includes a first and second oblong sections  208 ,  210  that extend transversely with respect to the longitudinal direction of instrument  200 . Each oblong section  208 ,  210  defines a respective plurality of interconnected holes  212 ,  214 . 
     The distal end  206  of instrument  200  includes a dovetail joint  216  defining a cavity  218  between rails  220  at the distal end  206  of instrument  200 . Cavity  218  is sized and configured to receive a locking wedge  222  as best seen in  FIG. 5 . A through-hole  224  extends from a first side  226  to a second side  228  of the distal end  206  of instrument  200  and is sized and configured to receive a locking bolt  230  therein. Locking bolt  230  is configured to a press locking wedge against a dovetail member  252  of a guide  250 , such as a cut guide, a drill guide, and/or coronal sizing and drill guide. Holes  258  are defined by the distal end  206  of instrument  200  on either side of dovetail joint  216 . Holes  258  are sized and configured to receive pins  210  therein. 
     The conversion instrument  200  can be secured to a guide  250  by having dovetail extension  252  of guide  250  be received within dovetail joint  216 . A hex driver is used to tighten locking bolt  230  within hole  224 . The rotation of locking bolt  230  causes the engagement end of locking bolt, which can be threaded or have another engagement feature disposed thereon, engage a corresponding structure disposed within distal end of instrument  200  and axially move such that shoulders of bolt  230  contact angled surfaces of a locking wedge. The axial movement of bolt  230  forces the bottom surface of the locking wedge against dovetail extension, which is frictionally locked by rails  220 . Additional examples of positioning and use of the conversion instrument  200  are disclosed in U.S. Pat. Appl. Pub. 2015/0257899, published on Sep. 17, 2015, and entitled “Ankle Replacement System and Method,” which was previously incorporated herein in its entirety. 
     As discussed above, during a revision surgery, one or more additional and/or alternative revision cuts can be formed in a bone, such as first bone  14  and/or second bone  16 . In some embodiments, a revision cutting guide can be positioned with reference to a preoperatively planned deformity correction based on anatomic references and/or surgeon preferences. The joint  12  can be positioned to match the pre-operatively planned deformity correction using a spacer assembly. The spacer assembly positions the first bone  14  and/or the second bone  16  in the preoperatively planned deformity correction and further guides the placement of a revision cutting guide, as discussed in greater detail below. 
       FIG. 6  illustrates a spacer assembly  300  positioned between a first bone  14  and a second bone  16  of a joint  12  and an adjustable guide  600  coupled thereto, in accordance with some embodiments. Spacer assembly  300  includes a first spacer  400  and a second spacer  500 . First spacer  400  and second spacer  500  are configured to position the first bone  14  and the second bone  16  in a corrected alignment. In some embodiments, the corrected alignment of joint  12  corresponds to a preoperatively planned deformity correction that is planned based on anatomic references and/or surgeon preferences. Spacers  400 ,  500  set one or more degrees of freedom of joint  12 . For example, in various embodiments, the spacers  400 ,  500  can correct one or more of a varus/valgus orientation, a flexion/extension orientation, an inversion/eversion orientation, an anterior/posterior position, a medial/lateral position, and/or a proximal/distal position between the first bone  14  and the second bone  16  intraoperatively. The first spacer  400 , the second spacer  500 , and/or the adjustable guide  600  may be manufactured from a resilient polymer material of the type that is suitable for use in connection with stereo lithography, selected laser sintering, 3D printing, or the like manufacturing equipment, e.g., a polyamide powder repaid prototype material is suitable for use in connection with the selective laser sintering. 
     As illustrated in  FIG. 9 , first spacer  400  includes a first (or bone contacting) surface  404  configured to abut first bone  16  and second spacer  500  includes a first (or bone contacting) surface  504  configured to abut second bone  16 . Each of first spacer  400  and second spacer  500  further include respective second (or coupling) surfaces  406 ,  506  configured to be positioned in an abutting relationship. When spacers  400 ,  500  are positioned against respective first and second bones  14 ,  16 , respective coupling surfaces  406 ,  506  are abutting and position first and second bones  14 ,  16  to surface-match the anatomy of the joint  12  in a corrected alignment. For example, in various embodiments, the spacers  400 ,  500  position the first bone and a second bone in one or more of a pre-operatively determined varus/valgus orientation, flexion/extension orientation, inversion/eversion orientation, anterior/posterior position, medial/lateral position, and/or proximal/distal position. Although embodiments are discussed having a first spacer  400  and/or a second spacer  500  coupled to a bone, it will be appreciated that the first spacer  400  and/or the second spacer  500  can be coupled to an implant installed in a bone, such as an implant installed during a prior replacement surgery and/or installed concurrently during a current replacement and/or revision surgery. 
     As best shown in  FIG. 7 , in some embodiments, an adjustable guide  600  is configured to couple to one or both of first spacer  400  and/or second spacer  500 . Adjustable guide  600  is adjustable in one or more directions with respect to spacers  400 ,  500  and/or the joint  12  to set a resection depth and/or position for first bone  14  and/or second bone  16 . For example, in some embodiments, adjustable guide  600  is adjustable in a proximal/distal direction, a superior/inferior direction, and/or any other suitable direction with respect to spacers  400 ,  500 . The adjustable guide is configured to locate a revision cut in second bone  16 . Although embodiments are discussed herein including an adjustable guide  600  configured to locate a revision cut in second bone  16 , it will be appreciated that adjustable guide  600  can include guide elements corresponding to additional and/or alternative cuts and/or revisions in first bone  14  and/or second bone  16 . 
       FIGS. 10-12  illustrate a first spacer  400   a  configured to abut first bone  14 , in accordance with some embodiments. In some embodiments, first spacer  400   a  is configured to interface with existing bone, cartilage, and/or other soft tissue of first bone  14 . For example, in some embodiments, first spacer  400   a  is a tibial spacer configured to abut a tibia. In other embodiments, first spacer  400   a  is configured to abut a pre-existing implant coupled to the first bone  14 . The pre-existing implant can include an implant inserted during a previous ankle replacement surgery and/or inserted during a current ankle replacement surgery. 
     Spacer  400   a  includes a body  402  having a thickness extending between a bone contacting surface  404  and an opposing coupling surface  406 . Body  402  further extends longitudinally between a proximal surface  408   a  and a distal surface  408   b , as best seen in  FIG. 10 , and has a width extending between a first side surface  410   a  and a second side surface  410   b  as best seen in  FIG. 11 . Body  402  is sized and configured for insertion into a resected portion of first bone  14 . Bone contacting surface  404  defines a patient-specific profile complimentary to a surface of the first bone  14 . For example, bone contacting surface  404  can be configured to interface with existing bony anatomy of first bone  14  and/or cartilage or other soft tissue coupled to first bone  14 . 
     As best seen in  FIGS. 10 and 12 , body  402  defines one or more first fixation holes  416   a ,  416   b  extending therethrough. First fixation holes  416   a ,  416   b  extend from one of first or second side surfaces  410   a ,  410   b  to the other of first and second side surfaces  410   a ,  410   b . The fixation holes  416   a ,  416   b  are angled with respect to first and second side surfaces  410   a ,  410   b  such a first side of each of the fixation holes  416   a ,  416   b  is positioned proximally of a second side. In some embodiments, fixation holes  416   a ,  416   b  extend through body  402  along intersecting hole axis, although it will be appreciated that the fixation holes  416   a ,  416   b  can extend through the body  402  along non-intersecting hole axis in some embodiments. 
     In some embodiments, a bone engaging structure  412  extends from a proximal surface  408   a  of body  402  in a superior direction above bone contacting surface  404 . Bone engaging structure  412  has a length extending between a bone contacting surface  414   a  and an opposing surface  414   b , a thickness extending between an upper surface  420   a  and a lower surface  420   b , and a width extending between a first side surface  426   a  and a second side surface  426   b . In some embodiments, bone contacting surface  414   a  includes a patient-specific profile configured to surface-match a portion of first bone  14  and/or soft-tissue coupled to first bone  14 . Bone engaging structure  412  is configured to abut a surface of first bone  14  and maintain the first spacer  400   a  in a fixed anterior/posterior position with respect to first bone  14 . In some embodiments, the portion of the first bone  14  that is surface-matched by bone engaging structure  412  is the anterior surface of a tibia, although one of ordinary skill in the art will understand that bone engaging structure can be configured to surface match other bones and surfaces. 
     Referring now to  FIG. 11 , bone engaging structure  412  defines a slot  430  extending from opposing surface  414   b  at least partially into block  412 . In some embodiments, slot  430  extends from opposing surface  414   b  to bone contacting surface  414   a . Slot  430  is sized and configured to receive a portion of a resection guide  600  therein, such as a flat coupling element  612  described in greater detail with respect to  FIGS. 18-21 . In some embodiments, bone engaging structure  412  defines one or more second fixation holes  428   a - 428   b  extending from opposing surface  414   b  to bone contacting surface  414   a . Second fixation holes  428   a - 428   b  are each sized and configured to receive a fixation element therethrough. The fixation elements can include any suitable fixation element, such as a k-wire, screw, pin, and/or any other suitable fixation element. In some embodiments, the fixation elements are configured to maintain first spacer  400  in a fixed position with respect to first bone  14 . In some embodiments, first fixation holes  416   a - 416   b  and/or second fixation holes  428   a - 428   b  include a position corresponding to one or more fixation elements previously coupled to the first bone  14  by one or more additional surgical elements. 
     In some embodiments, coupling surface  406  of spacer  400   a  is configured to abut and/or couple to spacer  500  as best seen in  FIG. 6 . Coupling surface  406  includes a recess  422  extending from a proximal edge of coupling surface  406  proximally into the body  402 . Recess  422  is sized and configured to receive a complementary coupling feature of second spacer  500 , such as a mating protrusion  510 , discussed in greater detail with respect to  FIGS. 14-15 . Recess  422  couples first spacer  400   a  to second spacer  500  in a predetermined arrangement. In some embodiments, recess  422  is a U-shaped recess, although it will be appreciated that recess  422  can have any shape complementary to the shape of mating protrusion  510  of second spacer  500 . 
     In some embodiments, coupling surface  406  defines a dovetail joint  440 . Dovetail joint  440  has a similar construction to the dovetail joint  216  described above with respect to the conversion instrument  200 . A cavity  442  is defined in a coupling surface  406  between rails  444  as best seen in  FIG. 11 . Cavity  442  is sized and configured to receive a corresponding dovetail extension  712  extending from a shim  700 , as discussed in greater detail with respect to  FIGS. 16-17 . Although embodiments are discussed herein including a dovetail joint  440 , it will be appreciated that the coupling surface  406  can define any suitable structure or cavity sized and configured to couple to an extension  712  defined by the shim  700 . In some embodiments, the dovetail joint  440  is omitted. 
     With reference to  FIG. 13 , in some embodiments, a first spacer  400  includes a bone engaging extension  418  extending from an upper surface  420   a  of bone engaging structure  412 . Bone engaging extension  418  extends above upper surface  420   a  of the bone engaging structure  412 . Bone engaging extension  418  includes a body  450  extending between a bone contacting surface  452   a  and an opposing surface  452   b . In some embodiments, bone contacting surface  452   b  is surface-matched to a portion of first bone  14 . Bone engaging extension  418  defines at least alignment hole  424  extending therethrough. Alignment hole  424  is configured to provide a visual indication during fluoroscopy and/or other imaging procedures to ensure proper alignment of the first spacer  400  prior to insertion of one or more fixation elements. 
       FIGS. 14-15  illustrates another example of a second spacer  500   a  configured to abut second bone  16 , in accordance with some embodiments. The second spacer  500   a  is similar to the second spacer  500  discussed above in conjunction with  FIGS. 6-9 , and similar description is not repeated herein. Second spacer  500   a  is configured to interface with existing bone, cartilage, and/or other soft tissue of second bone  16 . For example, in some embodiments, second spacer  500   a  is a talar spacer configured to abut a talus. In other embodiments, second spacer  500   a  is configured to abut a pre-existing implant coupled to second bone  16 . The pre-existing implant can include an implant inserted during a previous ankle replacement surgery and/or inserted during a current ankle replacement surgery. 
     In some embodiments, second spacer  500   a  includes a body  502  having a thickness extending between a bone contacting surface  504  and a coupling surface  506 . The body  502  further extends longitudinally between a proximal surface  508   a  and a distal surface  508   b  and has a width extending between a first side surface  510   a  and a second side surface  510   b . Body  502  is sized and configured to abut a portion of second bone  16  and/or soft tissue coupled to second bone  16 , such as a resected and/or non-resected superior surface of second bone  16 . In some embodiments, bone contacting surface  504  defines a patient-specific profile surface-matched to second bone  14 . 
     Coupling surface  506  is positioned in an opposing relationship with coupling surface  406  of first spacer  400   a  when first and second spacers  400   a ,  500   a  are positioned within joint  12 . In some embodiments, each of the coupling surfaces  406 ,  506  define a planar surface. Coupling surface  506  can have a greater, lesser, and/or equal surface area as coupling surface  406 . Although embodiments are discussed herein including planar coupling surfaces  406 ,  506 , it will be appreciated that coupling surfaces  406 ,  506  can have any suitable matching surface topography configured to position first bone  14  and second bone  16  in one or more of a pre-operatively determined varus/valgus orientation, flexion/extension orientation, inversion/eversion orientation, anterior/posterior position, medial/lateral position, and/or proximal/distal position. 
     In some embodiments, a mating element  512  extends from coupling surface  506 . Mating element  512  is sized and configured to couple second spacer  500   a  to one or more superiorly positioned elements, such as first spacer  400   a . In some embodiments, mating element  512  includes a cylindrical protrusion sized and configured to be received within channel  420  formed in coupling surface  406 . The coupling between mating element  512  and channel  420  provides constraint of one or more degrees of freedom (such as medial/lateral, proximal/distal etc.) of joint  12  while allowing for adjustment of one or more other degrees of freedom (such as internal/external rotational flexibility, anterior/posterior translation, etc.) of joint  12 . Although embodiments are discussed herein including a cylindrical protrusion, it will be appreciated that mating element  512  can include any suitable cross-section configured for insertion into channel  420  and can extend any suitable distance above coupling surface  506 . 
     In some embodiments, second spacer  500   a  defines one or more fixation holes  514   a - 514   b  each being respectively sized and configured to receive a fixation element therein. Fixation holes  514   a - 514   b  extend from a first surface, such as coupling surface  506  and/or proximal surface  508   a , to a second surface, such as bone contact surface  504  and/or distal surface  508   b . Each of the fixation elements can include any suitable fixation element, such as a k-wire, a screw, and a pin, to list only a few possibilities. Second spacer  500   a  is maintained in a fixed position with respect to second bone  16  by inserting one or more fixation elements through one or more of fixation holes  514   a - 514   b . In some embodiments, one or more of fixation holes  514   a - 514   b  include a position corresponding to a fixation element previously coupled to second bone  16  by one or more additional surgical instruments and/or guides. 
     In some embodiments, a bone engaging structure  520  extends in an inferior direction from the body  502 . The bone engaging structure has a length extending between a bone contacting surface  522   a  and an opposing surface  522   b , a thickness extending between an upper surface  524   a  and a lower surface  524   b , and a width extending between a first side surface  526   a  and a second side surface  526   b . In some embodiments, bone contacting surface  522   a  and/or lower surface  524   b  include a patient-specific profile configured to surface-match a portion of first bone  16  and/or soft-tissue coupled to first bone  16 . Bone engaging structure  520  is configured to abut a surface of first bone  16  and maintain second spacer  500   a  in a fixed anterior/posterior position with respect to second bone  16 . 
     In some embodiments, laxity can exist between first bone  14  and second bone  16  after installation of the first spacer  400  and/or the second spacer  500 . Laxity in joint  12  may not be fully known pre-operatively and/or may change intra-operatively, for example, due to ligament release, tendon release, tendon transfer, osteotomy, etc. In some embodiments, one or more shims  700  can be inserted between respective spacers  400 ,  500  to distract first bone  14  from second bone  16 .  FIGS. 16-17  illustrate a shim  700  configured to be positioned between first spacer  400  and second spacer  500  to correct laxity in joint  12 , in accordance with some embodiments. Shim  700  may be manufactured from a resilient polymer material of the type that is suitable for use in connection with stereo lithography, selected laser sintering, or the like manufacturing equipment, e.g., a polyamide powder repaid prototype material is suitable for use in connection with the selective laser sintering. 
     Shim  700  includes a body  702  extending between an upper surface  704  and a lower surface  706 . Body  702  has a predetermined thickness extending from the upper surface  704  to the lower surface  706 , such as, for example, a thickness in the range of 1 mm-6 mm, such as 1 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 5 mm, and/or any other suitable thickness. Body  702  extends longitudinally between a proximal side  708   a  and a distal side  708   b  and has a width extending between a first side  710   a  and a second side  110   b . In some embodiments, body  702  can have a generally rectangular shape, although it will be appreciated that body  702  can have any suitable regular and/or irregular shape configured to be received within a joint space between a first bone and a second bone. In some embodiments, body  702  is sized and configured to correspond to one or more of the coupling surfaces  406 ,  506  of respective first and second spacers  400 ,  500 . 
     In some embodiments, upper surface  704  includes a dovetail extension  712  configured to couple shim  700  to first spacer  400  and/or a shim positioned in contact with the upper surface  704 . The dovetail extension  712  includes a projection  714  sized and configured to be inserted within cavity  442  formed in first spacer  400 . The dovetail extension  712  is positioned at a proximal edge of the upper surface  704 , although it will be appreciated that dovetail extension  712  can extend from any suitable location of upper surface  704  such that dovetail extension  712  is aligned with cavity  442  when shim  700  is aligned with first spacer  400 . In some embodiments, the dovetail extension  712  is omitted. Although embodiments are discussed herein including a dovetail extension  712 , it will be appreciated that the shim  700  can be coupled to the first spacer using any suitable coupling elements, such as a non-dovetail projection, a fixation device, a magnetic coupling, one or more rails, a ball-detent coupling, a spring-clip coupling, and/or any other suitable connection. 
     In some embodiments, a recess  716  is defined in lower surface  706  of shim  700 . Recess  716  is sized and configured to receive protrusion  510  of second spacer  500 . Recess  716  couples shim  700  to second spacer  500 . In some embodiments, protrusion  510  and recess  716  constrain one or more degrees of freedom of joint  12  (such as medial/lateral position, proximal/distal position, flexion/extension orientation, etc.) while allowing adjustment of one or more other degrees of freedom (such as inversion/eversion orientation, anterior/posterior position, etc.). In some embodiments, recess  716  is similar and/or identical to recess  422  formed in first spacer  400 . Although embodiments are illustrated having a shim  700  positioned between first spacer  400  and second spacer  500 , it will be appreciated that one or more shims  700  can be positioned between first spacer  400  and first bone  14  and/or second spacer  500  and second bone  16 , and are within in the scope of this disclosure. In some embodiments, the bone contact surfaces  406 ,  506  of first spacer  400  and/or second spacer  500  include one or more features similar to those discussed above configured to couple the respective bone contact surface  406 ,  506  to shim  700 . 
     In some embodiments, recess  716  is a dovetail joint A cavity  718  is defined in a lower surface  706  between rails  720 . Cavity  718  is sized and configured to receive a corresponding dovetail extension  712  extending from a second shim  700 . Although embodiments are discussed herein including a dovetail joint, it will be appreciated that the lower surface  706  can define any suitable recess  716  sized and configured to couple to an extension  712  defined by a second shim  700 . In some embodiments, the recess  716  is omitted. 
     In some embodiments, recess  716  is positioned at a proximal edge of lower surface  706 , although it will be appreciated that recess  716  can extend through any portion of lower surface  706  such that recess  716  is aligned with an extension  712  on a second shim  700  when multiple shims are aligned. In some embodiments, recess  716  in lower surface  706  is vertically aligned with extension  712  extending from upper surface  704 . 
       FIG. 13  illustrates a first spacer  400  having a first shim  700   a  and a second shim  700   b  coupled thereto. First shim  700   a  and second shim  700   b  are similar to shim  700  described above in conjunction with  FIGS. 16-17 , and similar description is not repeated herein. First shim  700   a  is coupled to first spacer  400 . Dovetail extension  712   a  extending from upper surface  704   a  of shim  700   a  is inserted into cavity  442  formed in first spacer  400   a . Dovetail extension  712   a  and channel  442  maintain first shim  700   a  in a fixed position with respect to first spacer  400   a . Second shim  700   b  is coupled to first shim  700   a . Dovetail extension  712   b  extending from upper surface  704   b  of second shim  700   b  is inserted into channel  716   a  defined by first shim  700   a . Dovetail extension  712   b  and cavity  716   a  maintain the second shim  700   b  in a fixed position with respect to first shim  700   a  and first spacer  400 . Although embodiments are illustrated with two shims  700   a ,  700   b , it will be appreciated that any number of shims can be inserted between a first spacer  400  and a second spacer  500 . 
     In some embodiments, each of shims  700   a ,  700   b  has a predetermined thickness. For example, in various embodiments, each of shims  700   a ,  700   b  can have a predetermined thickness of about 1 mm to about 5 mm, such as, for example, 1 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 5 mm, and/or any other suitable thickness. It will be appreciated that shims  700   a ,  700   b  can have a greater and/or less thickness in some embodiments. In some embodiments, each of shims  700   a ,  700   b  has a different thickness. For example, in some embodiments, first shim  700   a  has a first thickness and second shim  700   b  has a second thickness that is less than, equal to, or greater than the first thickness. A surgeon can select any suitable combination of shims  700   a ,  700   b  having similar and/or different thicknesses to correct laxity in joint  12 . 
       FIGS. 18-26  illustrate resection guide  600 , in accordance with some embodiments. Resection guide  600  is configured to be coupled to the first spacer  400  and/or the second spacer  500 . Resection guide  600  includes a guide adapter  602 , an adjustable guide body  604 , and an adjustment knob  606 . As best shown in  FIG. 20 , guide adapter  602  includes a body  610  having a flat coupling element  612  and a coupling extension  620  extending from body  610 . Flat coupling element  612  includes a substantially flat body  614  sized and configured for insertion into slot  430  formed in first spacer  400 . Flat body  614  includes one or more coupling elements  616  configured to maintain guide adapter  602  in a fixed position within slot  430 . For example, in some embodiments, coupling elements  616  include leaf-spring elements  618  configured to apply a force to an inner surface of slot  430  to maintain guide adapter  602  in a fixed position with respect to first spacer  400 , although it will be appreciated that any suitable coupling element can be used to maintain flat body  614  in the slot  430 . 
     As best shown in  FIGS. 22-24 , adjustable guide  604  includes a guide body  626  having a first leg  624   a  and a second leg  624   b  extending from a superior edge of the guide body  626 . First leg  624   a  and second leg  624   b  are spaced apart to define an adjustment slot  622 . Adjustment slot  622  is sized and configured to receive a coupling element  620  extending from guide adapter  602 . Coupling element  620  is slideable within slot  622  to adjust the vertical position of adjustable guide  604  with respect to first spacer  400 . As best shown in  FIG. 23 , in some embodiments, first leg  624   a  and/or second leg  624   b  includes one or more indicators  630  corresponding to a resection depth of a cut to be formed in second bone  16 . The resection depth can correspond to a thickness of an implant to be coupled to second bone  16  after forming a resection cut in second bone  16 . In some embodiments, coupling element  620  includes one or more threads configured to threadably couple to a locking element  606 . Although embodiments are illustrated including a first leg  624   a  and a second leg  624   b , it will be appreciated that one of the legs  624   a ,  624   b  can be omitted. 
     In some embodiments, guide body  626  defines a resection slot  660  extending through body  626  from a proximal surface  636   a  to a distal surface  636   b . Resection slot  660  extends longitudinally from a first end  662   a  to a second end  662   b . The longitudinal profile of resection slot  660  corresponds to a cut profile of a resection to be formed in one or more bones of joint  12 , such as second bone  16 . Resection slot  660  is sized and configured to receive a cutting tool (e.g., a reciprocating saw or blade) therein. The cutting tool inserted into the resection slot  660  and manipulated to form a resection and/or revision in first bone  14  and/or second bone  16  after positioning adjustable guide  604  in a selected position. 
     In some embodiments, guide body  626  defines a plurality of first guide holes  632   a - 632   d  and a plurality of second guide holes  634   a - 634   b  extending therethrough. The guide holes  632   a - 632   d ,  634   a - 634   b  are each sized and configured to receive a fixation device therethrough. Each fixation device can include any suitable fixation device, such as a k-wire, a screw, and/or a pin, to list only a few possibilities. In some embodiments, the plurality of first fastener holes  632   a - 632   d  and the plurality of second fastener holes  634   a - 634   b  are sized and configured to receive similar temporary fixation devices, although it will be appreciated that the plurality of first fastener holes  632   a - 632   d  and/or the plurality of second fastener holes  634   a - 634   b  can be sized and configured to receive different temporary fixation devices. 
     In some embodiments, each of the plurality of first fastener holes  632   a - 632   d  extend from a proximal surface  636   a  of guide body  626  to a distal surface  636   b . First guide holes  632   a - 632   d  each extend through guide body  626  along substantially parallel axes. In some embodiments, each of the first guide holes  632   a - 632   d  extend through guide body  626  at a first angle with respect to a horizontal axis of guide body  626 . In the illustrated embodiment, each of the first guide holes  632   a - 632   d  have a hole axis parallel with the horizontal axis of guide body  626 , although it will be appreciated that the first guide holes  632   a - 632   d  can extend through guide body  626  along a hole axis positioned at an angle with respect to the horizontal axis of guide body  626 . 
     In some embodiments, each of the plurality of second guide holes  634   a - 634   b  extend from proximal surface  636   a  of guide body  626  to distal surface  636   b . In some embodiments, each of the second guide holes  634   a - 634   b  extend through the guide body  626  at a second angle with respect to the horizontal axis of the guide body  626 , different than the first angle. In the illustrated embodiment, each of the second guide holes  634   a - 634   b  extend through the guide body  626  along an axis at a second angle between 0 and 90° with respect to the horizontal axis, although it will be appreciated that the second guide holes  634   a - 634   b  can extend through the guide body  626  at any suitable angle. 
     As best shown in  FIGS. 25-26 , in some embodiments, locking element  606  is a locking knob  640  including a body  642  defining a channel  644  extending therethrough. Channel  644  includes one or more mating features  646  configured to couple locking knob  640  to coupling element  620 . For example, in embodiments including a thread  626  formed on coupling element  620 , mating feature  646  includes a complementary internal thread  658 . The locking knob  640  can be threadably engaged with threads  626  of coupling element  620  to advance locking knob  640  onto coupling element  620 . 
     In some embodiments, locking knob  640  includes a tool engagement feature  648 . Tool engagement feature  648  is sized and configured to engage with a tool, such as a wrench, to apply a tightening and/or loosening force to locking knob  640 . In some embodiments, tool engagement feature  648  includes a coupling surface  650  having a hexagonal cross-sectional surface/plane with each side of the coupling surface  650  defining a flat or planar face  670  configured to provide an interference fit between locking knob  640  and the corresponding hexagonal wrench. Although embodiments are discussed herein including a hexagonal coupling surface, it will be appreciated that any suitable tool engagement feature  648  can be used to couple locking knob  640  to a tool. 
     In some embodiments, locking knob  640  includes one or more scalloped gripping surfaces  652   a - 652   b . Scalloped gripping surface  652   a - 652   b  include a plurality of raised surfaces  654  separated by a plurality of channels  656 . The plurality of raised surfaces  654  and/or the plurality of channels  656  provide a textured gripping surface for a user to grip and manipulate locking knob  640 . For example, in some embodiments, scalloped gripping surfaces  652 - 652   b  allow a user to hand tighten and/or loosen locking knob  640  onto coupling element  620  prior to and/or after engagement of a tool with tool engagement feature  648 . Although embodiments are illustrated with two gripping surfaces  652   a - 652   b , it will be appreciated that locking knob  640  can include a lesser and/or greater number of gripping surfaces. 
     In some embodiments, locking knob  640  is configured to be rotatably coupled to coupling element  620 . Locking knob  640  can engaged with threads  626  of coupling element  620  to apply a locking force to adjustable guide  604  to maintain adjustable guide  604  in a fixed position. Locking knob  640  can be loosened and/or partially disengaged from threads  626  to allow vertical adjustment of adjustable guide  604  with respect to guide adapter  602 . For example, in some embodiments, coupling element  620  is sized and configured to slide within slot  622  defined by adjustable guide  604 . Locking knob  640  can include one or more spiral channels  668  extending about body  642 . The spiral channels  668  enable body  642  to be compressed when locking knob  606  is tightened against adjustable guide  604  to increase the force applied to adjustable guide  604 . In the illustrated embodiment, spiral channels  668  allow a distal portion  670  of the locking knob  640  to act as a leaf-spring to increase the force applied to the adjustable guide  604 . 
     Although embodiments are discussed herein including a locking knob  640 , it will be appreciated that locking element  606  can include any suitable coupling mechanism. For example, in various embodiments, locking element  606  can include one or more of a knob, a lever, a toggle, a ball-detent, and/or any other suitable coupling mechanism. 
     The spacer assembly  300  and the adjustable guide assembly  600  can be configured for use in a revision surgery. Prior to a revision surgery, a CT or MRI scanned image or series of images is taken of a patient&#39;s ankle  12  and then converted from, e.g., a DICOM image format, to a solid computer model of the ankle including the calcaneus, talus, tibia, navicular, and fibula to determine implant alignment, type, and sizing using specialized modeling methods that are often embodied in computer software. The computer model illustrates deformities and/or laxity in the joint  12  that was not corrected by and/or occurred subsequent to a previous primary replacement surgery. The computer model can further illustrate foreign objects coupled to the joint  12 , such as implants installed during the primary replacement surgery. 
     After generating the computer model, a first spacer  400 ,  400   a  and a second spacer  500 ,  500   a  are generated to match the solid computer model. The spacers  400 ,  500  can be generated using any suitable method, such as, for example, using a rapid prototyping technique including a processing unit and a rapid prototyping machine, as discussed in greater detail in U.S. Pat. No. 5,768,134, issued on Jun. 16, 1998, entitled “Method for Making a Perfected Medical Model on the Basis of Digital Image Information of a Part of the Body,” which is incorporated herein by reference in its entirety. After generating the spacers  400 ,  500 , the joint  12  of the patient can be surgically accessed and one or more of the preexisting primary implants can be removed from the joint  12 . In some embodiments, a conversion instrument  200  can be used to form one or more additional revision cuts in one of first bone  14  or second bone  16 . 
     After resection of first bone  14  and/or second bone  16  and/or removal of one or more implants from joint  12 , the first spacer  400 ,  400   a  and the second spacer  500 ,  500   a  are positioned within the joint space to position the first and second bones  14 ,  16  in a pre-operatively planned corrected position. The first spacer  400 ,  400   a  is positioned within the resection formed in the first bone  14 . The first spacer  400 ,  400   a  can be manipulated until one or more of the bone contact surfaces  404 ,  414   a  securely engage with the topography of the first bone  14 . As shown in  FIG. 27 , with the first spacer  400   a  engaged with the first bone, one or more temporary fixation devices  350   a , such as k-wires, are inserted through one or more of the fixation holes  416   a - 416   b ,  428   a - 428   b  to temporarily anchor the first spacer  400   a  to the first bone  14 . The second spacer  500 ,  500   a  is positioned in contact with the second bone  16 . For example, the second spacer  500 ,  500   a  can be manipulated until a bone contact surface  504  securely engages with the topography of the second bone  16 . With the second spacer  500 ,  500   a  securely engaged with the second bone  16 , one or more temporary fixation devices  350   b , such as k-wires, are inserted through one or more of the fixation holes  514   a - 514   b  to temporarily anchor the second spacer  500 ,  500   a  to the second bone  16 . 
     With further reference to  FIG. 27 , a coupling surface  406  of first spacer  400   a  is positioned in an abutting relationship with a coupling surface  506  of second spacer  500   a . Mating element  512  extending from coupling surface  506  of second spacer  500   a  is inserted into recess  422  formed in coupling surface  406 . First spacer  400   a  and second spacer  500   a  position first bone  14  and second bone  16  in a predetermined position with respect to one or more of a varus/valgus orientation, a flexion/extension orientation, an inversion/eversion orientation, an anterior/posterior position, a medial/lateral position, and/or a proximal/distal position. In some embodiments, mating element  512  and recess  422  constrain one or more degrees of freedom of joint  12  (such as medial/lateral position, proximal/distal position, flexion/extension orientation, etc.) while allowing adjustment of one or more other degrees of freedom (such as inversion/eversion orientation, anterior/posterior position, etc.). In some embodiments, the first guide  400   a  and/or the second guide  500   a  include one or more features configured to verify an alignment and/or position of the respective guide  400   a ,  500   a , such as through fluoroscopy. 
     After positioning the first spacer  400   a  and/or the second spacer  500   a  in the joint space  12 , one or more shims  700   a ,  700   b  can be coupled to the first spacer  400   a  and/or the second spacer  500   a  to correct laxity in the joint  12 . For example, in the illustrated embodiment, a first shim  700   a  is coupled to a coupling surface  406  of the first spacer  400   a  and a second shim  700   b  is coupled to the first shim  700   a . The second shim  700   b  abuts and couples to the coupling surface  506  of second spacer  500   a . The number and/or thickness of shims  700   a ,  700   b  can be selected intraoperatively to correct pre-existing laxity and/or intraoperatively generated laxity in joint  12 . 
     The surgeon then couples adjustable guide  600  to one of the first spacer  400  and/or second spacer  500 . In the illustrated embodiments, the adjustable guide  600  is coupled to first spacer  400 . The coupling extension  620  of the guide adapter  602  is slideably engaged with the slot  430  formed in the first spacer  400 . Leaf-spring elements  618  apply a force to an inner surface of slot  430  to maintain the guide adapter  602  in a fixed position with respect to first spacer  400 . The adjustable guide  604  is coupled to the guide adapter  602  by inserting the coupling element  620  of the guide adapter  602  into slot  622  defined by the adjustable guide  604 . The locking knob  606  is threadably engaged with the coupling element  620  to lock the adjustable guide  604  to the guide adapter  602 . 
     The surgeon adjusts the vertical position of adjustable guide  604  by loosening locking knob  606  and sliding adjustable guide  604  up/down to adjust a corresponding resection depth of a cut to be formed in the second bone  16 . The position of adjustable guide  604  can be viewed using fluoroscopy. A k-wire, saw blade, and/or other element can be inserted at the desired resection location to visualize the resection and to determine the appropriate resection depth intraoperatively. 
     In some embodiments, markings on adjustable guide  604  indicate the distance of the resection cut in second bone  16  from a resection cut in first bone  14 . The first leg  624   a  and/or the second leg  624   b  of adjustable guide  604  include one or more depth markings to provide a visual indication to the surgeon regarding the depth of the resection cut. The depth of the resection can be further influenced by the thickness of an implant to be coupled to second bone  16 . After selecting a desired resection cut depth, locking element  606  is tightened to fix the position of adjustable guide  604 . As shown in  FIGS. 27-28 , one or more guide elements  352   a - 352   b , such as guide pins, are inserted through one or more of the first guide holes  632   a - 632   d  and/or second guide holes  634   a - 634   b  formed through guide body  626 . 
     After inserting the guide pins, the spacer assembly  300  and all fixation elements, except the guide element  352   a - 352   b , are removed from the joint  12 . The guide body  626  is re-positioned with respect to the second bone  16  by sliding the guide elements  352   a - 352   b  through first guide holes  632   a - 632   d  and/or second guide holes  634   a - 634   b , as shown in  FIG. 28 . A resection cut is formed in second bone  16  by inserting a cutting instrument through resection slot  660  defined by the guide body. In some embodiments, a separate resection cut guide can be coupled to second bone  16  by engaging the resection cut guide with the temporary guide elements in second bone  16 . Removal of spacer assembly  300  prevents a resecting cut from intersecting the spacers and further allows the resection guide body  626  to be positioned closer to the second bone  16 . Additional fixation elements, such as k-wires or guide pins, may be inserted through one or more of fixation holes  634   a - 634   b  to further fix the position of guide body  626  with respect to the second bone  16 . 
     If adjustment of the resection depth is necessary, the guide body  626  can be adjusted by repositioning the guide pins into an alternative set of guide holes  632   a - 632   d . For example, in some embodiments, a first set of guide holes  632   a ,  632   b  is positioned above a second set of guide holes  632   c ,  632   d . The first and second sets of guide holes  632   a - 632   d  allow adjustment of the resection depth by a predetermined amount, for example, a predetermined amount in the range of +/−0-5 mm, such as 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, and/or 5 mm. It will be appreciated that guide holes  632   a - 632   d  can have a greater and/or lesser spacing allowing any predetermined amount of adjustment. 
     After fixing the position of guide body  626 , second bone  16  is resected. Guide body  626 , guide elements  352   a - 352   b , and/or other elements are removed from second bone  16 . The resected space between first bone  14  and second bone  16  is cleared of all resected bone down to the level of the resection cut, such as a flat cut in second bone  16 . 
       FIGS. 29-30  illustrate an alternative embodiment of a spacer assembly  300   b  including a first spacer  400   b  configured to be coupled to an implant  480  installed in first bone  14 , in accordance with some embodiments. The spacer assembly  300   b  is similar to the spacer assembly  300  discussed above in conjunction with  FIGS. 6-9 , and similar description is not repeated herein. The spacer assembly  300   a  includes a first spacer  400   b  and a second spacer  500   b  configured to position the first bone  14  and the second bone  16  in a corrected alignment. In some embodiments, the corrected alignment of joint  12  corresponds to a preoperatively planned deformity correction that is planned based on anatomic references and/or surgeon preferences. First spacer  400   b  and/or second spacer  500   b  set one or more degrees of freedom of joint  12 . For example, in various embodiments, the spacer assembly  300   b  can correct one or more of a varus/valgus orientation, a flexion/extension orientation, an inversion/eversion orientation, an anterior/posterior position, a medial/lateral position, and/or a proximal/distal position between the first bone  14  and the second bone  16  intraoperatively. 
     First spacer  400   b  includes a body  402   a  extending between upper surface  404   a  and a lower surface  406   a . The upper surface  404   a  defines a planar surface. An implant coupling element  482  extends from the upper surface  404   a . The implant coupling element  482  is sized and configured to be received within a lock detail  484  defined by an implant  480  coupled to the first bone  14 . The implant  480  can include any suitable implant, such an articulation implant coupled to the first bone  14  during a previous joint replacement surgery and/or implanted concurrently with a current ankle replacement/revision surgery. 
       FIGS. 31-33  illustrate an alternative embodiment of a spacer assembly  300   c  including a monolithic spacer  800 , in accordance with some embodiments. The spacer assembly  300   c  is similar to the spacer assembly  300  discussed above, and similar description is not repeated herein. The spacer assembly  300   c  includes a monolithic spacer  800  configured to position the first bone  14  and the second bone  16  in a corrected alignment. In some embodiments, the corrected alignment of joint  12  corresponds to a preoperatively planned deformity correction that is planned based on anatomic references and/or surgeon preferences. Monolithic spacer  800  sets one or more degrees of freedom of joint  12 . For example, in various embodiments, the monolithic spacer  800  can correct one or more of a varus/valgus orientation, a flexion/extension orientation, an inversion/eversion orientation, an anterior/posterior position, a medial/lateral position, and/or a proximal/distal position between the first bone  14  and the second bone  16  intraoperatively. 
     As best shown in  FIGS. 32-33 , monolithic spacer  800  includes a body  802  having a thickness extending between a first bone contacting surface  804  and a second bone contacting surface  806 . Body  802  further extends longitudinally between a proximal surface  808   a  and a distal surface  808   b  and has a width extending between a first side surface  810   a  and a second side surface  810   b . First bone contacting surface  804  is configured to abut a surface of first bone  14  and second bone contacting surface  806  is configured to abut a surface of the second bone  16 , such as a superior portion of a talus. In some embodiments, bone contact surfaces  804 ,  806  are configured to engage a previously resected bone surface of respective first bone  14  or second bone  16  and/or define patient-specific profiles configured to surface match respective first bone  14  and/or second bone  16 . For example, first bone contacting surface  804  can be configured to engage a previously resected surface of first bone  14  and second bone contacting surface  806  can be configured to interface with existing bony anatomy and/or cartilage or other soft tissue of second bone  16 . 
     In some embodiments, monolithic spacer  800  includes a bone engaging structure  812  coupled to a proximal surface  808   a  of body  802 . Bone engaging structure  812  extends superiorly from the proximal surface  808   a  terminating above first bone contacting surface  804 . Bone engaging structure  812  extends between a bone contacting surface  814   a  and an opposing surface  814   b , an upper surface  816   a  and a lower surface  816   b , and first and second side surfaces  818   a ,  818   b . In some embodiments, the bone contacting surface  814   a  includes a patient-specific profile configured to surface-match a portion of first bone  14 , such as an anterior surface of a tibia, for example. Bone engaging structure  812  is configured to maintain monolithic spacer  800  in a fixed anterior/posterior position with respect to first bone  14 . Bone engaging structure  812  defines a slot  830  extending from opposing surface  814   b  at least partially into bone engaging structure  812 . In some embodiments, slot  830  extends from opposing surface  814   b  to bone contacting surface  814   a . Slot  830  is sized and configured to receive a flat body  614  of resection guide  600  therein. 
     In some embodiments, monolithic spacer  800  includes a plurality of first fixation holes  820   a - 820   d  extending from opposing surface  814   b  to bone contacting surface  814   a . The one or more fixation holes  820   a - 820   d  are sized and configured to receive a fixation element therethrough. The fixation elements can include any suitable fixation element, such as a k-wire, screw, pin, and/or any other suitable fixation element. The fixation elements are configured to maintain monolithic spacer  800  in a fixed position with respect to first bone  14  and/or second bone  16 . In some embodiments, the fixation holes  820   a - 820   d  are parallel, although it will be appreciated that two or more of fixation holes  820   a - 820   d  can have non-parallel axes. 
     In some embodiments, monolithic spacer  800  includes a plurality of second fixation holes  822   a - 822   b  extending from one of a first side wall  810   a  or a second side wall  810   b  of body  802  to the other of the first side wall  810   a  or the second side wall  810   b . The fixation holes  822   a - 822   b  are angled with respect to first and second side surfaces  810   a ,  810   b  such a first side of each of the fixation holes  822   a - 822   b  is positioned proximally of a second side. In some embodiments, fixation holes  822   a - 822   b  extend through body  802  along intersecting hole axis, although it will be appreciated that the fixation holes  822   a - 822   b  can extend through the body  802  along non-intersecting hole axis in some embodiments. 
     In some embodiments, a kit can include multiple monolithic spacers each having a different thickness. For example, in some embodiments, a kit can include a first monolithic spacer having a first thickness between a first bone contact surface  804  and a second bone contact surface  806  and a second monolithic spacer having a second thickness between a first bone contact surface  804  and a second bone contact surface  806 . The second thickness can be greater than the first thickness. A surgeon can select one of the first monolithic spacer or the second monolithic spacer based on laxity between first bone  14  and second bone  16 . Although embodiments are discussed using two monolithic spacers, it will be appreciated that any number of monolithic spacers having any number of thicknesses can be included, and are within the scope of this disclosure. 
       FIG. 34  illustrates a patient-specific spacer assembly  300   d  including a monolithic spacer  800   a  having a cutting guide  850  coupled thereto, in accordance with some embodiments. The cutting guide  850  is similar to the guide  250  discussed above in conjunction with  FIG. 3 , and similar description is not repeated herein. In some embodiments, the cutting guide  850  is configured to guide a cutting instrument for forming one or more cuts in first bone  14  and/or second bone  16 . Cutting guide  850  can define a slot  860  sized and configured to receive a coupling extension  620  of an adjustable guide  600  therein. 
       FIGS. 35-38  illustrates a spacer assembly  300   e  including a first spacer  400   c  and a second spacer  500   c  having a telescoping connection therebetween, in accordance with some embodiments. The spacer assembly  300   e  is similar to the spacer assembly  300  discussed above, and similar description is not repeated herein. 
     In some embodiments, first spacer  400   c  and second spacer  500   c  are configured to engage one another via a telescoping connection. For example, first spacer  400   c  includes a body  402   c  defining a channel  470  extending from lower surface  406   c  into body  402   c  as best seen in  FIG. 37 . Channel  470  can be a closed and/or open channel having any suitable shape, such as a closed geometric shape (e.g., cylindrical, square, etc.), an open shape, and/or any other suitable shape. For example, in the illustrated embodiment, channel  470  defines a closed square shape extending about the periphery of lower surface  406   a , although it will be appreciated that channel  470  can have any suitable shape. 
     In some embodiments, a plurality of height adjustment holes  472   a - 472   d  extend through body  402   a  from a proximal surface  408   a  into channel  470 . The height adjustment holes  472   a - 472   d  are sized and configured to receive a fixation device therein, such as, for example, a k-wire, a pin, a screw, and/or any other suitable fixation device. Although embodiments are illustrated having four sets of height adjustment holes  472   a - 472   d , it will be appreciated that body  402   a  can define any number of height adjustment holes  472   a - 472   d  extending from any of the surfaces of body  402   a  into channel  470 . 
     In some embodiments, second spacer  500   c  includes an adjustment body  570  extending from upper surface  506   c . Adjustment body  570  extends a predetermined height above upper surface  506   c . Adjustment body  570  includes a perimeter wall  572  defining a hollow interior  574 . Adjustment body  570  is sized and configured for insertion into channel  470  formed in first spacer  400   a . For example, in some embodiments, perimeter wall  572  defines a closed shape corresponding to the closed shape of channel  470 . In other embodiments, perimeter wall  572  defines an open shape corresponding to a portion of channel  470 . Perimeter wall  572  can extend a predetermined height above the upper surface  506   a  that is less than, equal to, or greater than a depth of channel  470 . 
     In some embodiments, perimeter wall  572  defines a plurality of height adjustment holes  574   a - 574   c  extending from a proximal surface  578  to hollow interior  574 . The height adjustment holes  574   a - 574   c  are configured to receive a fixation device therein, such as a k-wire, a pin, a screw, and/or any other suitable fixation device. In some embodiments, height adjustment holes  574   a - 574   c  have a spacing similar and/or identical to the spacing of height adjustment holes  472   a - 472   d  formed in first spacer  400   c , although it will be appreciated that height adjustment holes  574   a - 574   c  can have a greater and/or lesser spacing than height adjustment holes  472   a - 472   d.    
     In use, adjustment body  570  is configured to be inserted into channel  470  to couple first spacer  400   c  to second spacer  500   c . First spacer  400   c  and second spacer  500   c  define a minimum spacing when adjustment body  570  is fully inserted into channel  470 . For example, in some embodiments, adjustment body  570  is inserted into channel  470  until an upper surface of the perimeter wall  572  contacts an inner surface  476  of channel  470 , although it will be appreciated that the adjustment body  570  and/or the channel  470  can be tapered such that the upper surface of the perimeter wall  572  does not contact the inner surface  476  of the channel  470  when fully inserted. If laxity is observed in joint  12 , the distance between first spacer  400   c  and second spacer  500   c  can be increased. 
     In some embodiments, a distance between first spacer  400   c  and second spacer  500   c  can be adjusted by sliding a portion of adjustment body  570  out of channel  470  to increase the distance between first spacer  400   c  and second spacer  500   c . Adjustment body  570  can be adjusted from a minimum spacing (in which the adjustment body  570  has a maximum portion located within the cavity  470 ) to a maximum spacing (in which the adjustment body  570  has a minimum portion located within the cavity  470 ). In various embodiments, the spacing can be adjusted continuously and/or discretely from the minimum spacing to the maximum spacing. 
     In some embodiments, a selected spacing of first spacer  400   c  and second spacer  500   c  is maintained by one or more fixation devices. First spacer  400   c  defines a first plurality of height adjustment holes  472   a - 472   d  and second spacer  500   c  defines a second plurality of height adjustment holes  574   a - 574   c . The position of each of height adjustment holes  472   a - 472   d ,  574   a - 574   c  is selected such that at least one set of the first plurality of adjustment holes  472   a - 472   d  is aligned with at least one set of the second plurality of adjustment holes  574   a - 574   c  when first spacer  400   c  and second spacer  500   c  are positioned at one or more predetermined distances. A fixation element (not shown), such as a pin, can be inserted through one of the first plurality of adjustment holes  472   a - 472   d  and at least partially into a corresponding (i.e., aligned) one of the second plurality of adjustment holes  574   a - 574   c  to maintain first spacer  400   c  and second spacer  500   c  in a selected spacing. In some embodiments, a fixation element is inserted through each adjustment hole in a pair of aligned adjustment holes  472   a - 472   d ,  574   a - 574   c.    
       FIG. 39  illustrates a spacer assembly  300   f  including a first spacer  400   d  and one or more shims  700   c ,  700   d , in accordance with some embodiments. First spacer  400   d  is similar to first spacer  400  discussed above and shims  700   c ,  700   d  are similar to shim  700  described above, and similar description is not repeated herein. In some embodiments, coupling surface  406   d  of the first spacer  400   d  and/or a lower surface  706  of the shims  700   c ,  700   d  are configured to directly contact a surface of second bone  16 . In some embodiments, coupling surface  406   d  and/or the lower surface  706  of each of the shims  700   c ,  700   d  defines a planar surface configured to interact with a partially and/or fully resected surface of the second bone  16 . In other embodiments, the coupling surface  406   d  and/or the lower surface  706  of the shims  700   c ,  700   d  includes a patient-specific surface configured to match a surface topography of at least a portion of the second bone  16 . 
     In some embodiments, the first spacer  400   d  and one or more shims  700   c ,  700   d  are configured to fill a joint space between the first bone  14  and the second bone  16  and position the bones  14 ,  16  in a corrected alignment. In some embodiments, the corrected alignment of the joint  12  corresponds to a preoperatively planned deformity correction that is planned based on anatomic references and/or surgeon preferences. The spacer  400   d  and the one or more shims  700   c ,  700   d  set a varus/valgus and/or flexion/extension relationship between the first bone  14  and the second bone  16  intraoperatively. 
       FIGS. 40-41  illustrates a spacer assembly  300   g  including a first spacer  400   e  and an angled shim  700   e , in accordance with some embodiments. The spacer assembly  300   g  is similar to the spacer assembly  300   f  discussed above in conjunction with  FIG. 39 , and similar description is not repeated herein. The spacer assembly  300   g  includes an angled shim  700   e  having a body  702   e  including one or more angled facets  758   a ,  758   b . The body  702   e  includes a planar upper surface  704   e  and a lower surface  706   e  including a plurality of facets  758   a ,  758   b  each extending at an angle with respect to the upper surface  704   e . For example, in some embodiments, the lower surface  706   e  includes a first facet  758   a  extending at a first angle with respect to the upper surface  704  and a second facet  758   b  extending at a second angle with respect to the upper surface  704 . The first facet  758   a  and the second facet  758   b  are perpendicular, although it will be appreciated that the first facet  758   a  can be positioned at any angle with respect to the second facet  758   b . In some embodiments, the lower surface  706   e  includes a patient-specific profile configured to match a surface profile of the second bone  16 . 
     In some embodiments, the body  702   e  of the shim  700   e  is configured to abut a second bone  16 . The shim  700   e  and the first spacer  400   e  are configured to fill a joint space between first bone  14  and second bone  16  and position bones  14 ,  16  in a corrected alignment. In some embodiments, the corrected alignment of joint  12  corresponds to a preoperatively planned deformity correction that is planned based on anatomic references and/or surgeon preferences. First spacer  400   e  and shim  700   e  set one or more degrees of freedom of joint  12 . For example, in various embodiments, the spacer assembly  300   e  can correct one or more of a varus/valgus orientation, a flexion/extension orientation, an inversion/eversion orientation, an anterior/posterior position, a medial/lateral position, and/or a proximal/distal position between the first bone  14  and the second bone  16  intraoperatively. 
       FIGS. 42-43  illustrate a drill guide mount  900  configured to be inserted into a resected joint  12 , in accordance with some embodiments. The drill guide mount  900  is sized and configured to receive a drill guide cartridge  902 . The drill guide mount  900  may be manufactured from a resilient polymer material of the type that is suitable for use in connection with stereo lithography, selected laser sintering, or the like manufacturing equipment, e.g., a polyamide powder repaid prototype material is suitable for use in connection with the selective laser sintering. 
     Drill guide mount  900  has a somewhat rectangular body  904  having a front side  906 , a rear side  908 , top side  910 , bottom side  912 , and a pair of opposed sides  914  and  916 . Front side  906  defines a recess  918  sized and configured to slideably receive tibial drill guide  902  therein. Recess  918  communicates with a recess  920  defined by bottom side  912  and a recess  922  defined by top side  910  such that body  904  is substantially hollow. Tibial drill guide cartridge  902  has a substantially rectangular elongate body  954  that may be formed from a more substantial material than tibial drill guide mount  900  such as, for example, metals, ceramics, or the like. The geometry of the sides of tibial drill guide cartridge  902  are respectively complementary to the sides  914 ,  916  of tibial drill guide mount  700 . 
     A mounting plate  950 , as best seen in  FIG. 43 , has a substantially rectangular body  952  that is fabricated from a material including, but not limited to, metals, ceramics, or other suitably rigid and durable material. Body  952  defines an aperture  954  the extends from a front side to a back side and has a similar geometry of recess  918  of drill guide mount  900  such that drill guide cartridge  902  may be received therein. Body  952  also defines a pair of through holes  960  that are arranged on body  952  such that they correspond to holes  938  of tibial drill guide mount  700  and are sized and configured to receive a k-wire or pin therein. Additional description of a tibial drill guide mount can be found in U.S. Pat. No. 8,808,303, which is incorporated by reference herein in its entirety. 
     Referring again to  FIG. 42 , bottom side  912  of drill guide mount  900  includes a dovetail joint  970 . Dovetail joint  970  has a similar construction to the dovetail joint  440  described above with respect to the first spacer  400 . A cavity  972  is defined in bottom side  912  between rails  974 . Cavity  972  is sized and configured to receive a corresponding dovetail extension  712  extending from a shim  700 . Although embodiments are discussed herein including a dovetail joint  970 , it will be appreciated that bottom side  912  can define any suitable cavity sized and configured to couple to extension  712  defined by the shim  700 . 
     Shim  700  is configured to provide stability for the tibia drill guide mount  900  and the second bone  16 . For example, one or more shims  700  can be coupled to bottom side  912  fill a space between bottom side  912  and a top surface of resected second bone  16 . In some embodiments, shims  700  are identical to shims used to correct laxity between a first spacer  400  and a second spacer  500 . In other embodiments, one or more shims  700  configured to couple to tibial drill guide mount  900  can have a different profile, different thickness, etc. from the shims positioned between first spacer  400  and second spacer  500 . 
     In some embodiments, once one or more revision cuts are formed in joint  12 , for example using the spacer assembly  300  and adjustable guide  600  discussed above, first bone  14  is prepared for a subsequent drilling operation by inserting the drill guide mount  900  into the resected bone space in first bone  14 . The drill guide mount  900  and method of drill of first bone  14  are similar to the use of a drill guide as described in U.S. Pat. Appl. Pub. 2015/0257899, which is incorporated by reference herein in its entirety. The drill guide  900  is similar to the drill guide described in U.S. Pat. Appl. Pub. 2015/0257899, but includes a dovetail joint  970  for receiving a portion of a shim  700  therein. 
     The disclosed system and method advantageously utilize custom manufactured surgical instruments, guides, and/or fixtures that are based upon a patient&#39;s anatomy to reduce the use of fluoroscopy during a surgical procedure. In some instances, the use of fluoroscopy during a surgical procedure is eliminated altogether. The custom instruments, guides, and/or fixtures are created by imaging a patient&#39;s anatomy with a computer tomography scanner (“CT”), a magnetic resonance imaging machine (“MRI”), or like medical imaging technology prior to surgery and utilizing these images to create patient-specific instruments, guides, and/or fixtures. 
     Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.