Patent Publication Number: US-2022226044-A1

Title: Orthopaedic planning systems and methods of repair

Description:
BACKGROUND 
     This disclosure relates to orthopaedic procedures and, more particularly, to systems and methods for planning the repair of bone defects and restoration of functionality to a joint. 
     Many bones of the human musculoskeletal system include articular surfaces. The articular surfaces articulate relative to other bones to facilitate different types and degrees of joint movement. The articular surfaces can erode or experience bone loss over time due to repeated use or wear or can fracture as a result of a traumatic impact. These types of bone defects can cause joint instability and pain. 
     Bone deficiencies may occur along the articular surfaces. Some techniques utilize a bone graft and/or implant to repair a defect adjacent the articular surfaces. 
     The surgeon may establish a surgical plan relating to preparation of a surgical site, selection of an implant, and placement of the implant along the surgical site. Surgical planning may include capturing an image of the surgical site and determining a position of an implant based on the image. 
     SUMMARY 
     This disclosure relates to planning systems and methods. The planning systems may be utilized for planning orthopaedic procedures to restore functionality to a joint, including determining a contact area between an implant and a cortical area of an associated bone. 
     A system for planning an orthopaedic procedure of the present disclosure may include a computing device including a processor coupled to a memory. The processor may be configured to execute a planning environment including a display module, a spatial module and a comparison module. The memory may be configured to store one or more implant models and one or more bone models. The spatial module may be configured to establish an outer perimeter and an inner perimeter along a first reference plane, and the inner and outer perimeters may be associated with respective inner and outer profiles of a cortical wall of the selected bone model. The display module may be configured to display in a first display window of a graphical user interface a selected one of the implant models and a selected one of the bone models relative to a first image plane. The comparison module may be configured to determine a cortical area and a contact area. The cortical area may correspond to an area between the inner perimeter and the outer perimeter along the first reference plane. The contact area may correspond to a first region of overlap between the selected implant model and the cortical area in which the selected implant model contacts the selected bone model along the first reference plane. The comparison module may be configured to cause the display model to display at least one indicator relating to the contact area in the graphical user interface. 
     A method of planning an orthopaedic procedure of the present disclosure may include selecting a bone model from a plurality of bone models by interacting with a graphical user interface, selecting an implant model from a plurality of implant models by interacting with the graphical user interface, displaying in a first display window of a graphical user interface a selected one of the implant models and a selected one of the bone models relative to a first image plane, determining an outer perimeter and an inner perimeter along a first reference plane, wherein the inner and outer perimeters may be respectively associated with inner and outer profiles of a cortical wall of the selected bone model, determining a cortical area and a contact area, wherein the cortical area may correspond to an area between the inner perimeter and the outer perimeter along the first reference plane, and the contact area may correspond to a first region of overlap between the selected implant model and the cortical area in which the selected implant model contacts the selected bone model along the first reference plane, and displaying in the first display window at least one indicator relating to the contact area. 
     A system for planning an orthopaedic procedure of the present disclosure may include a computing device including a processor coupled to a memory. The processor may be configured to execute a planning environment including a display module, a spatial module and a comparison module. The memory may be configured to store an implant model and a bone model. The spatial module may be configured to establish a perimeter along a reference plane, and the perimeter may be associated with a profile of a cortical wall of the bone model. The display module may be configured to display in a display window of a graphical user interface the implant model and the bone model relative to an image plane. The comparison module may be configured to determine a cortical area and a contact area, the cortical area bounded by the perimeter, and the contact area may correspond to a region of overlap between the implant model and a cortical area in which the implant model contacts the bone model along the reference plane. 
     The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary planning system. 
         FIG. 2  illustrates another exemplary planning system including a user interface. 
         FIG. 3  illustrates the user interface of  FIG. 2 . 
         FIG. 4  illustrates an exemplary resection angle of a bone. 
         FIGS. 5A-5C  illustrate exemplary resections of the bone of  FIG. 4  relative to different resection angles. 
         FIGS. 6A-6B  illustrate a bone model and an associated bone resected along a resection plane. 
         FIGS. 7A-7B  illustrate perimeters of exemplary bone models. 
         FIGS. 8-10  illustrate exemplary cortical areas and contact areas. 
         FIGS. 11-13  illustrate exemplary user interfaces displaying cortical areas and contact areas. 
         FIG. 14  illustrates an exemplary method of planning an orthopaedic procedure. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     This disclosure relates to surgical planning. The planning systems described herein may be utilized for orthopaedic procedures and may be utilized to create, edit, execute and/or review surgical plans. The surgeon may utilize the planning systems pre-operatively, intra-operatively and/or post-operatively. The planning systems and method disclosed herein may include determining a manner in which to resect a bone, and may also include determining placement of a selected implant relative the resection surface. The planning systems may determine a contact area between the implant and a cortical area of the bone along the resection surface. The planning systems may display or otherwise present the contact area in a manner that improves positioning of the implant, which may improve healing of the patient. 
     A system for planning an orthopaedic procedure according to an exemplary aspect of the present disclosure may include a computing device including a processor coupled to a memory. The processor may be configured to execute a planning environment including a display module, a spatial module and a comparison module. The memory may be configured to store one or more implant models and one or more bone models. The spatial module may be configured to establish an outer perimeter and an inner perimeter along a first reference plane, and the inner and outer perimeters may be associated with respective inner and outer profiles of a cortical wall of the selected bone model. The display module may be configured to display in a first display window of a graphical user interface a selected one of the implant models and a selected one of the bone models relative to a first image plane. The comparison module may be configured to determine a cortical area and a contact area. The cortical area may correspond to an area between the inner perimeter and the outer perimeter along the first reference plane. The contact area may correspond to a first region of overlap between the selected implant model and the cortical area in which the selected implant model contacts the selected bone model along the first reference plane. The comparison module may be configured to cause the display model to display at least one indicator relating to the contact area in the graphical user interface. 
     In some implementations, the comparison module may be configured to update the contact area in response to relative movement between the selected implant model and the selected bone model along the first reference plane. 
     In some implementations, the display module may be configured to set the first image plane to be parallel to the first reference plane. 
     In some implementations, the at least one indicator may include a visual contrast between the contact area and a remainder of the cortical area that excludes the contact area. 
     In some implementations, the spatial module may be configured to determine a bone area defined as an area surrounded by the outer perimeter along the first reference plane. The comparison module may be configured to determine a percentage of the contact area with respect to the bone area. The at least one indicator may be generated in response to the percentage of the contact area exceeding at least one predefined contact threshold. 
     In some implementations, the spatial module may be configured to establish a resection plane along the selected bone model. The resection plane may be defined by a resection angle. The display module may be configured to set the first reference plane to be coincident with the resection plane. The display module may be configured to set the first image plane to be parallel to the resection plane. 
     In some implementations, a volume of the selected implant model may be partially received in a volume of the selected bone model along the resection plane. 
     In some implementations, the comparison module may be configured to update the cortical area and the contact area in response to a change in the resection angle. 
     In some implementations, the graphical user interface may include a second display window. The display module may be configured to display in the second display window the selected implant model and the selected bone model relative to a second image plane. The second image plane may be transverse to the first image plane. 
     In some implementations, the spatial module may be configured to define a calcar region of the cortical area. The calcar region may extend through a calcar of a bone associated with the selected bone model. The comparison module may be configured to determine a second region of overlap between the calcar region and the first region of overlap. The at least one indicator may include a first indicator that identifies a portion of the first region of overlap that excludes the second region of overlap. The at least one indicator may include a second indicator that identifies the second region of overlap. 
     In some implementations, the first indicator and the second indicator may establish visual contrasts between each other and a remainder of the cortical area that excludes the contact area. 
     In some implementations, the spatial module may be configured to determine the outer perimeter in response to user interaction that defines a first set of points adjacent to the outer profile of the cortical wall. The spatial module may be configured to determine the inner perimeter in response to user interaction that defines a second set of points adjacent to the inner profile of the cortical wall. 
     In some implementations, the selected bone model may correspond to a bone associated with a joint. 
     A method of planning an orthopaedic procedure according to an exemplary aspect of the present disclosure may include selecting a bone model from a plurality of bone models by interacting with a graphical user interface, selecting an implant model from a plurality of implant models by interacting with the graphical user interface, displaying in a first display window of a graphical user interface a selected one of the implant models and a selected one of the bone models relative to a first image plane, determining an outer perimeter and an inner perimeter along a first reference plane, wherein the inner and outer perimeters may be respectively associated with inner and outer profiles of a cortical wall of the selected bone model, determining a cortical area and a contact area, wherein the cortical area may correspond to an area between the inner perimeter and the outer perimeter along the first reference plane, and the contact area may correspond to a first region of overlap between the selected implant model and the cortical area in which the selected implant model contacts the selected bone model along the first reference plane, and displaying in the first display window at least one indicator relating to the contact area. 
     In some implementations, the method may include updating the contact area in response to moving the selected implant model relative to the selected bone model. 
     In some implementations, the method may include selecting a resection angle to define a resection plane along the selected bone model. The method may include setting the first reference plane to be coincident with the resection plane. The method may include setting the first image plane to be parallel to the resection plane. 
     In some implementations, the method may include displaying in a second display window of the graphical user interface the selected implant model and the selected bone model relative to a second image plane. The second image plane may be transverse to the first image plane. 
     In some implementations, the method may include setting the second image plane to be perpendicular to the first image plane. The method may include positioning the selected implant model along the resection plane such that a volume of the selected implant model may be partially received in a volume of the selected bone model. 
     In some implementations, the method may include updating the determined cortical area and the determined contact area in response to changing the selected resection angle. 
     In some implementations, the method may include determining a bone area, wherein the bone area is defined as an area surrounded by the outer perimeter along the first reference plane. The method may include determining a percentage of the contact area with respect to the bone area. The method may include displaying the percentage of the contact area in the graphical user interface. The at least one indicator may include a first indicator and a second indicator. The method may include displaying the first indicator in response to the percentage of the contact area meeting at least one predefined contact threshold, but displaying the second indicator in response to the percentage of the contact area being below the at least one predefined contact threshold. 
     In some implementations, the method may include determining a second region of overlap between the contact area and a calcar region of the cortical area. The calcar region may extend through a calcar of a bone associated with the selected bone model. The method may include displaying a perimeter of the second region of overlap in the first display window. The method may include displaying a perimeter of a remainder of the contact area in the first display window that excludes the second region of overlap. The method may include displaying a perimeter of a remainder of the cortical area in the first display window that excludes the contact area. 
     In some implementations, the at least one indicator may include a first indicator and a second indicator. The method may include determining a cancellous area of the selected bone model. The cancellous area may correspond to an area along the first reference plane that is surrounded by the inner perimeter. The first region of overlap may be associated with a first weight, the second region of overlap may be associated with a second weight, the cancellous area may be associated with a third weight, and the first weight may be greater than the third weight but may be less than the second weight. The method may include determining a weighted value of the contact area according to the first, second and third weights. The method may include displaying the first indicator in the graphical user interface in response to the weighted contact area exceeding at least one predefined weighted contact threshold, but displaying the second indicator in the graphical user interface in response to the weighted contact area being below the at least one predefined weighted contact threshold. 
     In some implementations, the at least one indicator may include a third indicator and a fourth indicator. The method may include determining a bone density of the selected bone model along the contact area based on the weighted value of the contact area. The method may include displaying the third indicator in the graphical user interface in response to the bone density exceeding at least one predefined density threshold, but displaying the fourth indicator in the graphical user interface in response to the bone density being below the at least one predefined density threshold. 
     In some implementations, the method may include selecting a resection angle to define a resection plane along the selected bone model. The method may include setting the first reference plane to be coincident with the resection plane. The method may include setting the first image plane to be parallel to the resection plane. The method may include performing at least one of the following steps in response to the weighted contact area being below the at least one predefined weighted contact threshold: selecting another implant model from the plurality of implant models; changing the selected resection angle; moving the selected implant model along the resection plane; and/or rotating the selected implant model about an implant axis that extends through the resection plane. 
     In some implementations, the selected bone model may correspond to a bone associated with a joint. 
     In some implementations, the bone may be a humeral head of a humerus. 
     A system for planning an orthopaedic procedure according to an exemplary aspect of the present disclosure may include a computing device including a processor coupled to a memory. The processor may be configured to execute a planning environment including a display module, a spatial module and a comparison module. The memory may be configured to store an implant model and a bone model. The spatial module may be configured to establish a perimeter along a reference plane, and the perimeter may be associated with a profile of a cortical wall of the bone model. The display module may be configured to display in a display window of a graphical user interface the implant model and the bone model relative to an image plane. The comparison module may be configured to determine a cortical area and a contact area, the cortical area bounded by the perimeter, and the contact area may correspond to a region of overlap between the implant model and a cortical area in which the implant model contacts the bone model along the reference plane. 
     In some implementations, the comparison module may be configured to cause the display model to display an indicator relating to the contact area in the graphical user interface. 
       FIG. 1  illustrates an exemplary planning system  20  that may be utilized for planning surgical procedures. The system  20  may be used for planning orthopaedic procedures, including pre-operatively, intra-operatively and/or post-operatively to create, edit, execute and/or review surgical plans. 
     The system  20  may include a host computer  22  and one or more client computers  24 . The host computer  22  may be configured to execute one or more software programs. In some implementations, the host computer  22  is more than one computer jointly configured to process software instructions serially or in parallel. 
     The host computer  22  may be in communication with one or more networks such as a network  26  comprised of one or more computing devices. The network  26  may be a private local area network (LAN), a private wide area network (WAN), the Internet, or a mesh network, for example. 
     The host computer  22  and each client computer  24  may include one or more of a computer processor, memory, storage means, network device and input and/or output devices and/or interfaces. The input devices may include a keyboard, mouse, etc. The output device may include a monitor, speakers, printers, etc. The memory may, for example, include UVPROM, EEPROM, FLASH, RAM, ROM, DVD, CD, a hard drive, or other computer readable medium which may store data and/or other information relating to the planning techniques disclosed herein. The host computer  22  and each client computer  24  may be a desktop computer, laptop computer, smart phone, tablet, or any other computing device. The interface may facilitate communication with the other systems and/or components of the network  26 . 
     Each client computer  24  may be configured to communicate with the host computer  22  directly via a direct client interface  28  or over the network  26 . The client computers  24  may be configured to execute one or more software programs, such as a various surgical tools. The planning package may be configured to communicate with the host computer  22  either over the network  26  or directly through the direct client interface  28 . In another implementation, the client computers  24  are configured to communicate with each other directly via a peer-to-peer interface  30 . 
     Each client computer  24  may be operable to access and locally and/or remotely execute a planning environment  32 . The planning environment  32  may be a standalone software package or may be incorporated into another surgical tool. The planning environment  32  may provide a display or visualization of one or more bone models and related images and one or more implant models via one or more graphical user interfaces (GUI). Each bone model, implant model, and related images and other information may be stored in one or more files or records according to a specified data structure. 
     The system  20  may include at least one storage system  34 , which may be operable to store or otherwise provide data to other computing devices. The storage system  34  may be a storage area network device (SAN) configured to communicate with the host computer  22  and/or the client computers  24  over the network  26 , for example. In implementations, the storage system  34  may be incorporated within or directly coupled to the host computer  22  and/or client computers  24 . The storage system  34  may be configured to store one or more of computer software instructions, data, database files, configuration information, etc. 
     In some implementations, the system  20  is a client-server architecture configured to execute computer software on the host computer  22 , which is accessible by the client computers  24  using either a thin client application or a web browser executing on the client computers  24 . The host computer  22  may load the computer software instructions from local storage, or from the storage system  34 , into memory and may execute the computer software using the one or more computer processors. 
     The system  20  may include one or more databases  36 . The databases  36  may be stored at a central location, such as the storage system  34 . In another implementation, one or more databases  36  may be stored at the host computer  22  and/or may be a distributed database provided by one or more of the client computers  24 . Each database  36  may be a relational database configured to associate one or more bone models  38  and one or more implant models  40  to each other and/or a surgical plan  42 . Each surgical plan  42  may be associated with a respective patient. Each bone model  38 , implant model  40  and surgical plan  42  may be assigned a unique identifier or database entry. The database  36  may be configured to store data corresponding to the bone models  38 , implant models  40  and surgical plans  42  in one or more database records or entries, and/or may be configured to link or otherwise associate one or more files corresponding to each respective bone model  38 , implant model  40  and surgical plan  42 . Bone models  38  stored in the database(s)  36  may correspond to respective patient anatomies from prior surgical cases, and may be arranged into one or more predefined categories such as sex, age, ethnicity, defect category, procedure type, etc. 
     Each bone model  38  may include information obtained from one or more medical devices or tools, such as a computerized tomography (CT), magnetic resonance imaging (MRI) machine and/or X-ray machine, that obtains one or more images of a patient. The bone model  38  may include one or more digital images and/or coordinate information relating to an anatomy of the patient obtained or derived from the medical device(s). Each implant model  40  may include coordinate information associated with a predefined design. The planning environment  32  may incorporate and/or interface with one or more modeling packages, such as a computer aided design (CAD) package, to render the models  38 ,  40  as two-dimensional (2D) and/or three-dimensional (3D) volumes or constructs. 
     The predefined design may correspond to one or more components. The implant models  40  may correspond to implants and components of various shapes and sizes. Each implant may include one or more components that may be situated at a surgical site including screws, anchors and/or grafts. Each implant model  40  may correspond to a single component or may include two or more components that may be configured to establish an assembly. Each bone model  38  and implant model  40  may correspond to 2D and/or 3D geometry, and may be utilized to utilized to generate a wireframe, mesh and/or solid construct in a display. 
     Each surgical plan  42  may be associated with one or more of the bone models  38  and implant models  40 . The surgical plan  42  may include one or more revisions to bone model  38  and information relating to a position of an implant model  40  relative to the original and/or revised bone model  38 . The surgical plan  42  may include coordinate information relating to the revised bone model and a relative position of the implant model  40  in predefined data structure(s). Revisions to each bone model  38  and surgical plan  42  may be stored in the database  36  automatically and/or in response to user interaction with the system  20 . 
     One or more surgeons and other users may be provided with a planning environment  32  via the client computers  24  and may simultaneously access each bone model  38 , implant model  40  and surgical plan  42  stored in the database(s)  36 . Each user may interact with the planning environment  32  to create, view and/or modify various aspects of the surgical plan  42 . Each client computer  24  may be configured to store local instances of the bone models  38 , implant models  40  and/or surgical plans  42 , which may be synchronized in real-time or periodically with the database(s)  36 . The planning environment  32  may be a standalone software package executed on a client computer  24  or may be provided as one or more services executed on the host computer  22 , for example. 
       FIG. 2  illustrates an exemplary planning system  120  for planning a surgical procedure. The system  120  may be utilized for various orthopaedic and other surgical procedures, such as an arthroplasty to repair a joint. The system  120  may be utilized in the placement of an implant, such as an implant incorporated into a shoulder prosthesis, for example. Although the planning systems and methods disclosed herein primarily refer to repair of a humerus during an anatomic or reverse shoulder reconstruction, it should be understood that the planning system  120  may be utilized in the repair of other locations of the patient and other surgical procedures including repair of a glenoid and other joints such as a wrist, hand, hip, knee or ankle, and including repair of fractures. 
     The system  120  may include a computing device  144  including at least one processor  146  coupled to memory  148 . The computing device  144  can include any of the computing devices disclosed herein, including the host computer  22  and/or client computer  24  of  FIG. 1 . The processor  146  may be configured to execute a planning environment  132  for creating, editing, executing and/or reviewing one or more surgical plans  142  during pre-operative, intra-operative and/or post-operative phases of a surgery. 
     The planning environment  132  may include at least a data module  150 , a display module  152 , a spatial module  154  and a comparison module  156 . Although four modules are shown, it should be understood that fewer or more than four modules may be utilized and/or one or more of the modules may be combined to provide the disclosed functionality. 
     The data module  150  may be configured to access, retrieve and/or store data and other information in the database(s)  136  corresponding to one or more bone model(s)  138 , implant model(s)  140  and/or surgical plan(s)  142 . The data and other information may be stored in one or more databases  136  as one or more records or entries  158 . In some implementations, the data and other information may be stored in one or more files that are accessible by referencing one or more objects or memory locations references by the records or entries  158 . 
     The memory  148  may be configured to access, load, edit and/or store instances of one or more bone models  138 , implant models  140  and/or surgical plans  142  in response to one or more commands from the data module  150 . The data module  150  may be configured to cause the memory  148  to store a local instance of the bone model(s)  138 , implant model(s)  140  and/or surgical plan(s)  142  which may be synchronized with records  158  in the database(s)  136 . 
     The display module  152  may be configured to display data and other information relating to one or more surgical plans  142  in at least one graphical user interface (GUI)  162 . The computing device  144  may be coupled to a display device  160 . The display module  152  may be configured to cause the display device  160  to display information in the user interface  162 . A surgeon or other user may interact with the user interface  162  via the planning environment  132  to create, edit, execute and/or review one or more surgical plans  142 . 
     Referring to  FIG. 3 , with continuing reference to  FIG. 2 , the user interface  162  may include one or more display windows  164  and one or more objects  166 . The objects  166  may include graphics such as menus, tabs and buttons accessible by user interaction, such as tabs  166 T, buttons  166 B,  166 R,  166 S,  166 V, drop-down lists  166 L, and directional indicator  166 D. Geometric objects including selected bone model(s)  138  and implant model(s)  140  and other information relating to the surgical plan  142  may be displayed in one or more of the display windows  164 . 
     The implant model  140  may include one or more components. For example, the implant model  140  may include at least a first component  140 A and a second component  140 B coupled to the first component  140 A to establish an assembly. The first component  140 A may be configured to be at least partially received in a volume of a selected one of the bone models  138 . The second component  140 B may have an articulation surface dimensioned to mate with an articular surface of an opposed bone or implant. 
     The display windows  164  may include first, second and third display windows  164 - 1 ,  164 - 2 ,  164 - 3 . Although three display windows  164  are illustrated in  FIG. 3 , it should be understood that fewer or more than three display windows  164  can be utilized in accordance with the teachings disclosed herein. 
     The first, second and third display windows  164 - 1 ,  164 - 2 ,  164 - 3  may be associated with respective first, second and third image planes IP 1 , IP 2 , IP 3  (shown in dashed lines for illustrative purposes). The first, second and/or third image planes IP 1 , IP 2 , IP 3  may be substantially perpendicular or otherwise transverse to each other. 
     The display module  152  may be configured to display in the first, second and third display windows  164 - 1 ,  164 - 2 ,  164 - 3  a selected one of the one or more bone models  138  and a selected one of the one or more implant models  140  relative to the respective image planes IP 1 , IP 2 , IP 3 . The display module  152  may be configured such that the selected bone model  138  and/or selected implant model  140  may be selectively displayed and hidden (e.g., toggled) in one or more of the display windows  164  in response to user interaction with the user interface  162 , which may provide the surgeon with enhanced flexibility in reviewing aspects of the surgical plan  142 . 
     The display module  152  may be configured to display 2D representation(s) of the selected bone model  138  and/or selected implant model  140  in the first and/or second display windows  164 - 1 ,  164 - 2 . The surgeon may interact with the respective display windows  164 - 1 ,  164 - 2  or another portion of the user interface  162  to move the selected bone model  138  and/or selected implant model  140  in 2D space (e.g., up, down, left, right). The image planes P 1  and/or P 2  may be locked to a single respective 2D perspective, as illustrated in  FIG. 3 . In other implementations, the display module  152  may be configured to display 3D representation(s) of the selected bone model  138  and/or selected implant model  140  in the first and/or second display windows  164 - 1 ,  164 - 2 . 
     The selected bone model  138  may correspond to a bone associated with a joint, such as a humerus as illustrated in  FIG. 3 . The display module  152  may be configured to display a sectional view of the selected bone model  138  and/or selected implant model  140  in the first viewing window  164 - 1 . The sectional view may be presented as an image of the bone associated with the selected bone model  138 . The display module  152  may be configured to set the first image plane IP 1  to be parallel to the sectional view. An orientation of the sectional view may be predefined or may be specified in response to user interaction with the user interface  162 . 
     The spatial module  154  may be configured to establish a resection plane R 1  along the selected bone model  138  (R 1  shown in dashed lines in window  164 - 1  for illustrative purposes). A volume of the selected implant model  140  may be at least partially received in a volume of the selected bone model  138  along the resection plane RE The resection plane R 1  may be defined by a resection angle α, as illustrated in  FIG. 4 . The resection angle α may be defined with respect to an angle between the resection plane R 1  and a longitudinal axis A of a bone B associated with the selected bone model  138 . The spatial module  154  may be configured to cause the display module  152  to display an excised portion of the selected bone model  138  to be displayed in the first display window  164 - 1  in a different manner than a remainder of the bone model  138  on an opposed side of the resection plane R 1 , such as a relatively darker shade as illustrated by the humeral head in  FIG. 3 . In other implementations, the excised portion may be hidden from display in the first display window  164 - 1 . The spatial module  154  may determine the excised portion by comparing coordinates of the bone model  138  with respect to a position of the resection plane R 1 , for example. 
     The display module  152  may be configured to set the second image plane IP 2  of the second display window  164 - 2  to be parallel to a first reference plane REF 1 . The display module  152  may be configured to set the first reference plane REF 1  to be coincident with the resection plane RE Arranging the second display window  164 - 2  such that a viewpoint of the surgeon is substantially normal to the resection plane R 1  may provide improved visualization and positioning of the selected implant model  140  relative to a resected surface of the selected bone model  138 . 
     The user interface  162  may arranged in one or more tabs  166 T. The surgeon may interact with each of the tabs  166 T to specify various aspects of a surgical plan  142 . For example, the surgeon may select a first tab  166 T- 1  to view or specify aspects of the surgical plan  142  for one portion of a joint, such as a glenoid, and may select a second tab  166 T- 2  to view or specify aspects of the surgical plan  142  for another portion of the joint, such as a humerus, as illustrated in  FIG. 3 . 
     The user may interact with a first set of menu items  166 M- 1  associated with the first display window  164 - 1  to select and specific various aspects of an implant model  140  from the database  136  ( FIG. 2 ). For example, the user may interact with the drop-down lists  166 L in the first set of menu items  166 M- 1  to specify implant type, resection angle and implant size. The resection angle menu item may be associated with the resection plane R 1 , which may be displayed as being substantially perpendicular to the first image plane IP 1 . 
     The user may interact with a set of buttons  166 R to change (e.g., increase or decrease) the resection angle. The user may interact with a set of buttons  166 S adjacent the selected implant model  140  to change (e.g., increase or decrease) a size of a component of the selected implant model  140 . The sets of buttons  166 R,  166 S may be overlaid onto the first display window  164 - 1 . 
     The surgeon may interact with a second set of menu items  166 M- 2  associated with the second display window  164 - 2  to specific various aspects of the selected implant model  140 . For example, the user may interact with the directional indicator  166 D to move a portion of the selected implant model  140  in different directions (e.g., up, down, left, right) relative to the second image plane IP 2 . In some implementations, the surgeon may drag the selected implant model  140  to a desired position in the second display window  164 - 2  utilizing a mouse, and may utilize the directional indicator  166 D to more finely tune the position of the selected implant model  140 . The surgeon may interact with one or more drop-down lists  166 L in the second list of menu items  166 M- 2  to specify a type and/or size of a component of the selected implant model  140 . 
     The display module  152  may be configured to display a 3D representation of the selected bone model  138  and/or selected implant model  140  in the third display window  164 - 3 . The surgeon may interact with the third display window  164 - 3  or another portion of the user interface  162  to move the selected bone model  138  and/or selected implant model  140  in 3D space. In other implementations, the display module  152  may be configured to display a 2D representation of the selected bone model  138  and/or selected implant model  140  in the third display window  164 - 3 . 
     The surgeon may interact with a third set of menu items  166 M- 3  associated with the third display window  164 - 3  to specific various aspects of the selected bone model  138  and/or selected implant model  140 . For example, the surgeon may interact with one or more drop-down lists  166 L in the third set of menu items  166 M- 3  to selectively display and hide components of the selected implant model  140 . The user may interact with one or more buttons  166 V in the third list of menu items  166 M- 3  to toggle between a volume of previous and revised (e.g., resected) states of the selected bone model  138 . 
     The planning environment  132  may be configured such that changes in one of the display windows  164  are synchronized with each of the other windows  164 . The changes may be synchronized between the display windows  164  automatically and/or manually in response to user interaction. 
     The surgeon may interact with the user interface  162  to evaluate implant placement relative to different resection angles for a selected bone model  138 .  FIGS. 5A-5C  illustrate exemplary resections of the bone B of  FIG. 4  relative to different resection angles. Each resection angle is illustrated by a respective bone model  138 - 1  to  138 - 5 , which may correspond to the same bone B. Bone models  138 - 1  to  138 - 5  may be associated with respective resection angles of 145, 140, 135, 130 and 125 degrees and a corresponding resection plane R 1 , for example.  FIG. 5A  may correspond to a side view of the respective bone models  138 - 1  to  138 - 5 .  FIG. 5B  may correspond to a view of the respective bone models  138 - 1  to  138 - 5  parallel to the respective resection planes R 1  (see  FIGS. 5A and 5C ).  FIG. 5C  may correspond to a view of the respective bone models  138 - 1  to  138 - 5  parallel to the respective resection planes R 1 , with outer perimeters  138 P 0 - 1  to  138 P 0 - 5  of the respective bone models  138 - 1  to  138 - 5  and perimeters  140 P- 1  to  140 P- 5  of the respective implant models  140  shown. It should be understood that the arrangements of  FIGS. 5A-5C  are exemplary and other arrangements may be utilized in accordance with the teachings disclosed herein. As illustrated by  FIGS. 4 and 5C , a contour of the bone B associated with the bone model  138  may vary along a length and circumference of the bone B and may therefore have different surface areas and perimeter geometries along the respective resection plane R 1 . 
       FIG. 6A  illustrates an exemplary bone B resected along a resection plane R 1  and aspects of the bone model  138 . Resection of the bone B along the resection plane R 1  exposes cortical bone B 1  and cancellous bone B 2 . The cortical bone B 1  may comprise substantially hard and dense bone tissue, whereas the cancellous bone B 2  may comprise relatively porous, spongy bone tissue, as illustrated in  FIG. 6B . The cortical bone B 1  may establish a cortical wall WC that surrounds the cancellous bone B 2 . 
     The spatial module  154  may be configured to establish or determine at least one perimeter of a bone B associated with the respective bone model  138 , such as an inner perimeter  138 PI and/or outer perimeter  138 PO. The spatial module  154  may be configured to establish or determine the inner perimeter  138 PI and/or outer perimeter  138 PO along a first reference plane REF 1  (shown in dashed lines for illustrative purposes). The first reference plane REF 1  may correspond to the resection plane R 1  ( FIG. 3 ). The inner perimeter  138 PI and outer perimeter  138 PO may be associated with respective inner and outer profiles of the cortical wall WC a bone associated with the selected bone model  138 . The cortical wall WC may correspond to or substantially approximate a cortical wall established by cortical bone tissue C 1  of the bone B. The cortical wall WC may surround a cancellous region CR. The cancellous region CR may correspond to or substantially approximate a region established by cancellous bone tissue C 2  of the bone B. 
     Various techniques may be utilized to determine at least one perimeter associated with a profile of the cortical wall WC of a bone B and the respective bone model  138 , such as the inner perimeter  138 PI and/or outer perimeter  138 PO. The spatial module  154  may be configured to establish at least one perimeter along the reference plane REF 1 , including the inner perimeter  138 PI and/or outer perimeter  138 PO, to establish a cortical area CAL The cortical area CA 1  may correspond to an area between the inner perimeter  138 PI and outer perimeter  138 PO along the first reference plane REF 1 . 
     In some implementations, the spatial module  154  may be configured to execute one or more edge detection algorithms to determine the inner perimeter  138 PI and/or outer perimeter  138 PO that respectively approximate inner and outer boundaries of the cortical wall WC. Edge detection algorithms are known, and generally determine one or more edges in a digital image based gradients established between adjacent pixels in the image. However, utilizing edge detection techniques in accordance with the teachings disclosed herein is not known. The spatial module  154  may be configured to determine the inner and outer boundaries of the cortical wall WC based on gradients established by the cortical bone B 1  and cancellous bone B 2  in the respective image, as illustrated by  FIG. 6A . One would understand how to program the spatial module  154  to execute various edge detection algorithms. 
     In some implementations, the inner perimeter  138 PI and/or outer perimeter  138 PO of the respective bone model  138  is based on one or more predetermined values. Referring to  FIG. 7A , with continuing reference to  FIG. 2 , a predefined thickness T may be assigned to a bone model  238  during configuration of the system  20  or manually by the surgeon by interaction with the user interface  162 . The predefined thickness T may be set based on a statistical analysis of data corresponding to a sample population of one or more prior surgical cases stored in the database  136 . For example, an outer perimeter  238 PO of a cortical wall WC may be determined utilizing one or more edge detection techniques. 
     The spatial module  154  may be configured to apply the predefined thickness T to the outer perimeter  238 PO to establish an inner perimeter  238 PI. The inner perimeter  238 PI may follow a contour of the outer perimeter  238 PO according to the predefined thickness T and approximates a boundary between the cortical wall WC and the cancellous bone B 2  ( FIGS. 6A-6B ). The predefined thickness T may be stored in the respective surgical plan  142  and may be changed in response to user interaction with the user interface  162  to adjust the inner perimeter  238 PI and/or outer perimeter  238 PO. The various parameters disclosed herein may be updated in response to a change in predefined thickness T. The surgeon may change a value of the predefined thickness T based on various factors, such as one or more images and other information presented via the user interface  162  and an evaluation of the surgical case. 
     In some implementations, the surgeon may interact with the user interface  162  to approximate the inner and/or outer boundaries of the cortical wall WC. Referring to  FIG. 7B , with continuing reference to  FIG. 2 , the spatial module  154  may be configured to determine an outer perimeter  338 PO of a bone model  338  in response to user interaction that defines a first set of points PO adjacent to an outer profile of the cortical wall WC. The spatial module  154  may be configured to determine an inner perimeter  338 PI of the bone model  338  in response to user interaction that defines a second set of points PI adjacent to an inner profile of the cortical wall WC. 
     The surgeon may interact with the one of the display windows  164  of the user interface  162 , such as the second display window  164 - 4  ( FIG. 3 ), to position the sets of points PI and/or PO relative to an image of the bone B. The spatial module  154  may be configured to interconnect the set of points PI and/or PO to establish the inner perimeter  338 PI and/or outer perimeter  338 PO of the bone model  338 . The inner perimeter  338 PI and/or outer perimeter  338 PO may approximate the inner and/or outer boundaries of the cortical wall WC. Various techniques may be utilized to interconnect the sets of points PI and/or PO, including linear line segments and best-fit techniques utilizing one or more polynomial relationships, for example. The exemplary techniques disclosed herein may be combined to determine the boundaries of the cortical wall WC of a respective bone B. 
     Referring to  FIG. 8 , with continuing reference to  FIG. 2 , the comparison module  156  may be configured to determine one or more relationships between a selected bone model  438  and a selected implant model  440 , including a cortical area CA 1  and contact area CA 2 . The cortical area CA 1  may be bounded by at least one perimeter. For example, the cortical area CA 1  may correspond to an area between an inner perimeter  438 PI and outer perimeter  438 PO along a first reference plane REF 1 . The cortical area CA 1  may be bounded by the inner perimeter  438 PI and outer perimeter  438 PO. The first reference plane REF 1  may be extend along the resection plane R 1 . The contact area C 2  may correspond to a first region of overlap OR 1  between the selected implant model  440  and the cortical area CA 1  in which the selected implant model  440  contacts the selected bone model  438  along the first reference plane REF 1 . 
     In some implementations, the spatial module  154  may be configured to determine a bone area BA defined as an area surrounded by the outer perimeter  438 PO along the first reference plane REF 1 . The comparison module  156  may be configured to determine a percentage of the contact area CA 2  with respect to the bone area BA. The comparison module  156  may be configured to cause the display module  152  to generate at least one indicator in response to the percentage of the contact area CA 2  exceeding at least one predefined contact threshold, as illustrated by indicator PI in  FIG. 12 . The indicator PI may include various states, such as an UP arrow indicating that the predefined contact threshold(s) are met and a DOWN arrow indicating that the predefined contact threshold(s) are not met. Other example indicators may include a color coding status and a value of the percentage of the contact area CA 2 , as illustrated by indicator PV in  FIG. 12 . 
     The comparison module  156  may be configured to update the determined cortical area CA 1  and/or contact area CA 2  in response to changes in the surgical plan  142 , such as selection of a different implant model  440  and changes in a geometry of the selected bone model  438 . For example, the comparison module  156  may be configured to update the contact area CA 2  in response to relative movement between the selected implant model  440  and the selected bone model  438  along the first reference plane REF 1 . The surgeon may interact with the user interface  162  to cause the selected implant module  440  to move in a direction DIR 1 , as illustrated by implant model  440 ′ in  FIG. 9 . The comparison module  156  may be configured to determine a cortical area CA 1 ′ and contact area CA 2 ′ associated with the change in position of the implant model  440 ′. The cortical area CA 1 ′ associated with the bone model  438 ′ may be equal to the cortical area CA 1  associated with the bone model  438  of  FIG. 8 , but the contact area CA 2 ′ associated with the implant model  440 ′ may differ from the contact area CA 2  associated with the implant module  440  due to the change in position. 
     The comparison module  156  may be configured to determine the contact area CA 2  for different resection angles (a). For example, the surgeon may interact with the user interface  162  ( FIG. 2 ) to change (e.g., increase or decrease) the resection angle (a) to cause a change in orientation of the resection plane R 1  associated with the bone model  438  of  FIG. 8 , as illustrated by modified bone model  538  in  FIG. 10 . The first reference plane REF 1  may be updated in response to the change in the resection angle (a). 
     The spatial module  154  may be configured to adjust a position of the selected implant model  540  relative to the modified bone model  538  in response to the change in resection angle (a), as illustrated in  FIG. 10 . The comparison module  156  may be configured to determine the cortical area CA 1  and contact area CA 2  associated with the change in the resection angle (a). The cortical area CA 1  associated with the bone model  438  of  FIG. 8  may differ from the cortical area CA 1  associated with the modified bone model  538  of  FIG. 10  due to a profile of the respective bone. Accordingly, the contact area CA 2  associated with the bone model  438  may differ from the contact area CA 2  associated with the bone model  538  due to the change in the resection angle (a). One would understand how to program the comparison module  156  with logic to determine areas including the cortical area CA 1  and contact area CA 2 . 
     Referring to  FIG. 11 , with continuing reference to  FIG. 2 , the comparison module  156  may be configured to cause the display module  152  to display at least one or more indicators relating to a contact area CA 2  in a graphical user interface (GUI)  662 . The contact area CA 2  may be associated with a selected bone model  638  and a selected implant model  640 . 
     Referring to  FIG. 12 , with continuing reference to  FIG. 11 , the indicators may include a visual contrast between the contact area CA 2  and a remainder of the cortical area CA 1  that excludes the contact area CA 2 . The contact area CA 2  may be shown in a different shade and/or color than the remainder of the cortical area CAE The visual contrast is shown as hatching in  FIGS. 11-12  for illustrative purposes. The contact area C 2  may establish a first region of overlap OR 1  between the selected implant model  640  and the cortical area CA 1  in which the selected implant model  640  contacts the selected bone model  638  along a first reference plane REF 1 . 
     The display module  152  may be configured to cause the user interface  662  to identify different portions of the contact area CA 2  using various techniques. The spatial module  154  may be configured to define a calcar region RCAL of the cortical area CAE The calcar region RCAL may extend through a calcar of a bone associated with the selected bone model  638 , such as a humerus. The calcar region RCAL may be defined by a calcar arc. The calcar arc may correspond to an arc passing through a point PC. The point PC may be established along a calcar of a humerus, as illustrated in  FIG. 11 . The calcar arc may be defined by a calcar angle (β). The calcar angle (β) may be a predefined value or may be set by the user through interaction with the user interface  662 . The calcar angle (β) may extend less than or equal to approximately 180 degrees along the cortical area CA 1  between boundaries BR 1 , BR 2 . Each boundary BR 1 , BR 2  may be established with respect to the longitudinal axis A of the bone model  638 . In some implementations, the user may set the calcar angle (β) by moving boundary indicators BI 1 , BI 2  in the second display window  664 - 2  about the longitudinal axis A to set a position of the respective boundaries BR 1 , BR 2 . The disclosed techniques may allow the surgeon to vary the calcar region RCAL based on evaluating the bone quality and other conditions of the surgical site, which provides an improvement over prior systems by presenting detailed refinements in the determined contact area CA 2  and isolated subregions of interest based on feedback from the surgeon. 
     Various techniques may be utilized to establish a position of the point PC. The surgeon may interact with the user interface  662  to set a position of one or more points such as points PA, PB, PC to establish an elliptical object YC relative to the bone model  638 , as illustrated in  FIG. 11 . The elliptical object YC may be a “Youderian” circle that characterizes an anatomy of a bone relative to a specified resection plane RE The user may interact with the user interface  662  to establish one or more points along the resection plane R 1  include the points PA, PC. The user may interact with the user interface  662  to establish one or more points adjacent the cortical wall WC, such as point PB. The spatial module  154  may be configured to establish and dimension a respective Youderian circle YC along the points PA, PB and/or PC. 
     The comparison module  156  may be configured to divide the first region of overlap OR 1  between two or more sub-regions and cause the display module  152  to display the sub-regions distinctly from each other in the user interface  662 . The comparison module  156  may be configured to determine a second region of overlap OR 2  between the calcar region RCAL and the first region of overlap OR 1 . A portion of the first region of overlap OR 1  that excludes the second region of overlap OR 2  may define a first subregion SR 1  of the first region of overlap OR 1 . The second region of overlap OR 2  may define as a second subregion SR 2  of the first region of overlap OR 1 . Various techniques can be utilized to determine the subregions SR 1 , SR 2 , including comparing the coordinate spaces of the first region of overlap OR 1 , second region of overlap OR 2  and calcar region RCAL relative to each other to determine overlapping and non-overlapping regions. 
     The comparison module  156  may be configured to cause the display module  152  to display a first indicator I 1  that identifies the first subregion SR 1  and a second indicator I 2  that identifies the second subregion SR 2 . In some implementations, the first indicator I 1  and second indicator I 2  may be textual objects. In other implementations, the first indicator I 1  and second indicator I 2  may establish visual contrasts between the respective first and second subregions SR 1 , SR 2  and a remainder of the cortical area CA 1  that excludes the contact area CA 2 , as illustrated in  FIG. 12 . The comparison module  156  may be configured to cause the display module  152  to display a third indicator I 3  that identifies the remainder of the cortical area CA 1  that excludes the contact area CA 2 . 
     The first indicator I 1  and second indicator I 2  may be displayed in a different shade and/or color than each other and/or the third indicator I 3 . The visual contrast between indicators IL I 2  is shown as different hatching in  FIG. 12  for illustrative purposes. The indicator I 3  omits any hatching in  FIG. 12  for illustrative purposes. The comparison module  156  may be configured to cause the display module  152  to update the indicators I 1 , I 2 , I 3  in response to change(s) relating to the selected bone model  638  and/or selected implant model  640 , such as movement of implant model  640 ′ as illustrated by indicators I 1 ′, I 2 ′, I 3 ′ in  FIG. 13 . The disclosed techniques, including separately identifying the subregions SR 1 , SR 2  of the contact area CA 2 , provides an improvement over prior systems by conveying an enhanced representation of a relationship of the contact area CA 2  with respect to the cortical area CA 1  of the respective bone B and selected resection parameters. The surgeon may interact with the user interface  162  to tailor the surgeon plan  142  in an iterative manner based on this enhanced representation, which may improve efficiency in pre-operative planning, reduce inter-operative time that may otherwise be caused by changes to the surgical plan, and improve the surgical outcome for the patient based on a selection of parameters that more closely aligns with a relationship between the selected implant and an anatomy of the patient including bone quality and geometry along a resected surface. 
     The comparison module  156  may be configured to cause the display module  152  to display one or more parameters associated with the contact area CA 2  in a graphic  668 . The graphic  668  may overlay or be arranged adjacent to the second display window  664 - 2  of the user interface  662 , for example. Example parameters include a cortical coverage parameter  668 A, cancellous coverage parameter  668 B, calcar arc coverage parameter  668 C, bone density parameter  668 D and/or weighted contact area parameter  668 E. 
     The cortical coverage parameter  668 A may be defined as a value of the contact area CA 2  between the inner perimeter  638 PI and outer perimeter  638 P 0  along the resection plane R 1  and may be indicative of a portion of an implant associated with the selected implant model  640  that may be supported by cortical bone along the cortical wall WC. 
     The cancellous coverage parameter  668 B may be defined as a value of the contact area CA 2  surrounded by the inner perimeter  638 PI and may be indicative of a portion of an implant associated with the selected implant model  640  that may be supported by the cancellous bone. The cortical coverage parameter  668 A and cancellous coverage parameter  668 B may be expressed in units of cm{circumflex over ( )}2, for example. 
     The calcar arc coverage parameter  668 C may be defined as a portion of the calcar angle (β) of the calcar arc in which the contact area CA 2  is established along the calcar region RCAL. The value may be less than or equal to the calcar angle (β) of the calcar arc. 
     The bone density parameter  668 D may be defined as an average density of the respective bone along the contact area CA 2 , which may be expressed in units of gram/cm{circumflex over ( )}3, for example. Various techniques may be utilized to determine or approximate the bone density parameter  668 D. For example, a first predefined density value may be defined for cortical bone, and a second, different predefined density value may be defined for cancellous bone. The calcar region CR may comprise relatively more dense/strong bone tissue than other portions of the cortical wall. In some implementations, the second region of overlap OR 2  associated with the calcar region CR may be assigned a different (e.g. greater) predefined density value than a predefined density value associated with a remainder of the contact area CA 2  along the cortical wall WC. Each bone model  138  may include one or more predefined bone density values associated with or assigned to respective portions of a volume of the bone model  138 . For example, each coordinate of the bone model  138  may be assigned a respective bone density value. The bone density values may be the same or may differ for the volume of the bone model  138 . The comparison module  156  may be configured to calculate the bone density parameter  668 D based on a product of an area of the second region of overlap OR 2  and the respective predefined density value. 
     Various techniques can be utilized to determine the weighted contact area parameter  668 E. In some implementations, the spatial module  154  is configured to determine a cancellous area of the selected bone model  638 . The cancellous area may correspond to an area of cancellous bone B 2  ( FIG. 6A ) along the first reference plane REF 1  that is surrounded by the inner perimeter  638 PI, as illustrated by the cancellous region CR. The first region of overlap OR 1  corresponding to the contact area CA 2  may be assigned or otherwise associated with a first weight. The second region of overlap OR 2  between the contact area CA 2  and calcar region RCAL may be assigned or otherwise associated with a second weight. The cancellous area corresponding to the cancellous region CR may be assigned or otherwise associated with a third weight. The first weight may be greater than the third weight but may be less than the second weight. For example, the second weight may be assigned a multiple of 1.5, the first weight may be assigned a multiple of 1, and the third weight may be assigned a multiple of 0.5. The comparison module  156  may be configured to determine a value of the weighted contact area parameter  668 E associated with the contact area CA 2  according to the first, second and third weights. The comparison module  156  may be configure to determine a value of the bone density parameter  668 D based on the value of the weighted contact area parameter  668 E. 
     The comparison module  156  may be configured to update the parameters  668 A- 668 E in response to changes relating to the selected bone model  638  and/or selected implant model  640 . For example, the comparison module  156  may be configured to update the parameters  668 A- 668 E in response movement of the selected implant model  640 , as illustrated by parameters  668 A′- 668 E′ in  FIG. 13 . 
     The comparison module  156  may be configured to cause the display module  152  to display one or more indicators I 3 -I 7  associated with the parameters in the graphic  668 . For example, each indicator I 3 -I 7  may include a color-coded box based a predefined threshold associated with the respective parameter  668 A- 668 E. Each color-coded box may include one or more states. For example, a first color (e.g., green) may indicate that a value of the respective parameter  668 A- 668 E meets the predefined threshold, and a second color (e.g., red) may indicate that the value of the respective parameter  668 A- 668 E does not meet the predefined threshold. The comparison module  156  may be configured to cause the display module  152  to change the state of one or more of the indicators I 3 -I 7  in response to the changes relating to the selected bone model  638  and/or selected implant model  640 . 
     The surgeon may evaluate the indicators I 3 -I 7  and values of the various parameters  668 A- 668 E to revise the respective surgical plan  142  ( FIG. 2 ). For example, the surgeon may evaluate a quality of the bone including the value of the bone density parameter  668 D to values of the cortical coverage parameter  668 A, cancellous coverage parameter  668 B, calcar arc coverage parameter  668 C and/or weighted contact area parameter  668 E. The surgeon may determine that a desired value of the bone density parameter  668 D may or may not be suitable for a particular patient, even though a value of the surface area of the bone along the reference plane REF 1  and/or a value of the contact area CA 2  may be sufficient. The surgeon may interact with the user interface  662  to approach or meet the desired value of the bone density parameter  668 D, such as changing the specified resection angle (a) and/or resection plane R 1 , moving the selected implant model  640  relative to the resection plane R 1 , and/or selected another implant model  140  from the database  136  ( FIG. 2 ). For example, the surgeon may decrease the resection angle (a) to provide relatively more support to the selected implant model  140 . The surgeon may approve a surgical plan  142  having a value of the cortical coverage parameter  668 A that exceeds a predefined threshold, even though a value of the cancellous coverage parameter  668 B is below another predefined threshold, for example. The techniques disclosed herein may therefore provide the surgeon with an additional number of options in implant and surgical technique selection to improve the surgical outcome. 
     The user interface  662  may include at least one button  666 BR ( FIG. 12 ) that may be selected to present literature to the surgeon in assisting the surgeon in making the various selections and modifications to the surgical plan  142 . The literature may include a relative portion of a user manual explaining aspects of the indicators I 1 - 7  and respective parameters  668 A- 668 E and techniques for causing changes in the respective values to achieve a desired outcome. The literature presented to the user in response to selection of the button  666 BR may be based on values of the parameters  668 A- 668 E meeting various criteria, such as being below (or above) predetermined thresholds. 
       FIG. 14  illustrates an exemplary method of planning an orthopaedic procedure in a flowchart  780 . The method may be utilized pre-operatively, intra-operatively and/or post-operatively to create, edit, execute and/or review a respective surgical plan. The method may be utilized to perform an arthroplasty for restoring functionality to shoulders and other joints. Although the method  780  primarily refers to implants for repair of a defect in a humerus during a shoulder reconstruction, it should be understood that the method and disclosed implants may be utilized in other locations of the patient and other surgical procedures, such as the glenoid or any other location disclosed herein. The method  780  can be utilized with any of the planning systems disclosed herein. Fewer or additional steps than are recited below could be performed within the scope of this disclosure, and the recited order of steps is not intended to limit this disclosure. Reference is made to the planning systems  120 ,  620  for illustrative purposes. 
     Referring to  FIGS. 2-3 , with continuing reference to  FIG. 14 , a bone model(s)  138  may be selected from one or more bone models  138  by interacting with a graphical user interface  162  at step  780 A. An implant model  140  may be selected from one or more implant models  140  by interacting with the user interface  162  at step  780 B. Available bone models  138  and implant models  140  in the database(s)  136  may be presented in one or more lists in the user interface  162  that may be selected in response to user interaction, for example. The selected bone model  138  may correspond to a bone associated with a joint, such as a humeral head of a humerus as illustrated in  FIG. 3 . 
     Referring to  FIGS. 11 and 12 , with continuing reference to  FIG. 14 , a selected one of the one or more implant models  640  and a selected one of the one or more bone models  638  may be initially positioned and displayed in one or more windows  664  of the user interface  662  at step  780 C. Each selected bone model  638  and selected implant model  640  may be displayed in the display windows  664 - 1 ,  664 - 2  and  664 - 3  according to any of the techniques disclosed herein, including different orientations and 2D/3D views. Each selected bone model  638  and selected implant model  640  may be displayed in the display window  664 - 2  relative to the viewing plane IP 2 . 
     The selected implant model  640  may be positioned relative to the selected bone model  638  at step  780 D. For example, the selected implant model  640  may be moved from the position illustrated in  FIG. 12  to a position of the selected implant model  640 ′ in  FIG. 13 . A position of the selected implant model  640  may be adjusted in one or more iterations and prior to, during and/or subsequent to any of the steps of method  780 . 
     One or more resection parameters may be set at step  780 E. The resection parameters may include a resection angle (α) and/or resection plane R 1  associated with the resection angle (α) (see  FIG. 4 ). The resection parameters may be stored in the respective surgical plan  142  ( FIG. 2 ). Step  780 E may include selecting a resection angle (α) to define a resection plane R 1  along the selected bone model  638 . Step  780 E may include setting the first reference plane REF 1  to be coincident with the resection plane R 1 . Step  780 E may include setting the image IP 2  plane of the respective window  664 - 2  to be parallel to the resection plane R 1 , as illustrated in  FIG. 12 . 
     Step  780 E may include setting the first image plane IP 1  of the first display window  664 - 1  to be perpendicular to the second image plane IP 2  of the second display window  664 - 2 , as illustrated by  FIG. 11 . Step  780 C and/or step  780 D may include positioning the selected implant model  640  along the resection plane R 1  such that a volume of the selected implant model  640  is partially received in a volume of the selected bone model  638 , as illustrated in  FIG. 11 . 
     At step  780 F a cortical area CA 1  associated with the selected bone model  638  may be determined. The cortical area CA 1  may be determined utilizing any of the techniques disclosed herein. For example, step  780 F may include determining one or more perimeters at step  780 G. Step  780 G may include determining the inner perimeter  638 PI and/or outer perimeter  638 PO along the first reference plane REF 1 , which may correspond to the resection plane R 1 . Step  780 F may include updating the determined cortical area CA 1  in response to changing the selected resection angle (α) and/or changing a shape of the bone model  638  along the resection plane R 1  such as by defining one or more recesses in the resection face. 
     At step  780 H a contact area CA 2  is determined between the selected bone model  638  and the selected implant model  640  along a specified portion of the selected bone model  638 , such as along the reference plane REF 1 . The contact area CA 2  may be determined utilizing any of the techniques disclosed herein. Step  780 H may include determining one or more regions of overlap associated with the contact area CA 2  at step  780 I. Step  780 I may include determining the first region of overlap OR 1  corresponding to the contact area CA 2  and/or determining a second region of overlap OR 2  between the contact area CA 2  and a calcar region RCAL of the cortical area CAL as illustrated in  FIG. 12 . 
     Step  780 H may include updating the contact area CA 2  in response to moving the selected implant model  640  relative to the selected bone model  638 , as illustrated by the implant model  640 ′ of  FIG. 13 . Step  780 H may include updating the determined contact area CA 2  in response to changing the selected resection angle (α). 
     A percentage contact area may be determined at step  780 J. Referring to  FIG. 8 , with continuing reference to  FIG. 14 , step  780 J may include determining the bone area BA and determining a percentage of the contact area CA 2  with respect to the bone area BA. 
     Step  780 H may include determining a weighted value of the contact area CA 2  at step  780 K. The weighted value of the contact area CA 2  can be determined utilizing any of the techniques disclosed herein. Step  780 K may include determining a bone density of the selected bone model  638  along the contact area CA 2  based on the weighted value of the contact area CA 2 . 
     At step  780 L, at least one or more indicators relating to the contact area CA 2  may be displayed in the display window(s)  664  and/or another portion of the user interface  662 , such as the display window  664 - 2  relative to the image plane IP 2 . Step  780 L may include displaying any of the indicators and parameters disclosed herein, including the indicators I 1 -I 7 , PI, PV and parameters  668 A- 668 E of  FIG. 12 . 
     Step  780 L may include displaying a perimeter of the second region of overlap OR 2  along the calcar region RCAL in the display window  664 - 2  as illustrated by indicator IL displaying a perimeter of a remainder of the contact area CA in the display window  664 - 2  that excludes the second region of overlap OR 2  as illustrated by indicator I 2 , and/or displaying a perimeter of a remainder of the cortical area CA 1  in the display window  664 - 2  that excludes the contact area CA 2 , as illustrated by indicator I 3  in  FIG. 12 . The remainder of the cortical area CA 1  that excludes the contact area CA 2  may be a single contiguous region or two or more separate regions based on a placement of the selected implant model  640 . 
     Step  780 L may include displaying the percentage of the contact area CA 2  determined at step  780 J in the user interface  662 . Step  780 L may include displaying a first indicator in response to the percentage of the contact area CA 2  meeting at least one predefined contact threshold, but displaying the second indicator in response to the percentage of the contact area CA 2  being below the at least one predefined contact threshold. The first and second indicators may correspond to different stages of the percentage indicator PI of  FIGS. 12-13 , for example. Step  780 L may include displaying a numerical value of the percentage of the contact area CA 2 , as illustrated by indicator PV of  FIG. 12 . 
     Step  780 L may include displaying a value of the weighted contact area parameter  668 E in the user interface  662  that is determined in step  780 K, as illustrated in  FIG. 12 . Step  780 L may include displaying an indicator in the user interface  662  in response to the weighted contact area exceeding at least one predefined weighted contact threshold, but displaying another indicator in the user interface  662  in response to the weighted contact area being below the at least one predefined weighted contact threshold. The indicator may be different states of the indicator  17  associated with the weighted contact area parameter  668 E, and may include any of the status techniques disclosed herein. 
     The surgeon may perform one or more steps in response to a status or value of any of the parameters disclosed herein, including the parameters  668 A- 668 E and indicators I 1 -I 7 , PI, PV, such as a value of the weighted contact area being below the predefined weighted contact threshold(s). For example, the surgeon may select another one of the implant models  140  stored in the database(s)  136  ( FIG. 2 ). The surgeon may change the selected resection angle (α) at step  780 E. The surgeon may interact with the user interface  662  to move the selected implant model  640  along the resection plane RE In some implementations, the selected implant model  640  may have a non-circular outer perimeter  640 P 0 . The surgeon may interact with the user interface  662 , such as a button  666 R in the second window  664 - 2 , to rotate the selected implant model  640  in a direction RD about an implant axis IA that extends through the resection plane R 1 , as illustrated in  FIG. 11 . 
     Step  780 L may include displaying one or more indicators in the user interface  662  in response to a value of the bone density parameter  668 D exceeding at least one predefined density threshold, but displaying another indicator in the user interface  662  in response to the value of the bone density being below the at least one predefined density threshold. The indicator may be different states of the indicator  16  associated with the bone density parameter  668 D, and may include any of the status techniques disclosed herein. The value of the bone density parameter  668 D may be based on the weighted value of the contact area determined at step  780 K. 
     Referring to  FIG. 2 , with continuing reference to  FIG. 14 , the surgical plan  142  may be updated at step  780 M. Step  780 M may include updating a local instance of the surgical plan  142  and/or updating the surgical plan  142  in the database  136 . One or more iterations of the step(s) of the method  780  may be performed to update the surgical plan  142 . 
     The novel planning systems and methods of this disclosure can be incorporated to a practical application by providing improved positioning of implants relative to a bone surface, such as a resected face of a bone, based on conveying an enhanced representation of implant contact area relative to the cortical wall and other portions of the respective bone. The planning systems and methods may be utilized to more quickly and efficiently establish a surgical plan that reduces intra-operative time and increases precision and reproducibility of an implant position through pre-operative planning consideration of specific information relating to the relationship between the implant and an anatomy of the patient. The selected implant may be viewed substantially normal to a resection surface, which may provide the surgeon a better understanding of a shape of the osteotomy, surface area contact and amount of support and fixation for the selected implant. The planning systems may include various indicators to provide feedback to the surgeon regarding a selected implant and surgical site preparation based on surface area coverage, bone quality and bone density, for example, which can improve implant stability and healing of the patient by more closely tailoring the surgical plan to the specific patient. 
     Although the different non-limiting embodiments are illustrated as having specific components or steps, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
     The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.