Patent Publication Number: US-2013236874-A1

Title: Method and system for producing at least one patient-specific surgical aid

Description:
RELATED APPLICATION 
     This application claims priority from U.S. Provisional Application No. 61/536,756, filed 20 Sep. 2011, and from U.S. patent application Ser. No. 13/622,460, filed 19 Sep. 2012, the subject matter of both of which is incorporated herein by reference in its entirety. The present application is a continuation-in-part of the latter application. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an apparatus and method for producing at least one patient-specific surgical aid and, more particularly, to a method and apparatus for using a physical model of a native patient tissue to help produce at least one patient-specific surgical aid. 
     BACKGROUND OF THE INVENTION 
     In the installation of a prosthetic shoulder joint into a patient&#39;s body, a glenoid component is implanted into the glenoid vault of the patient&#39;s scapula. An obverse surface of the glenoid component is configured for articulating contact with a humeral component carried by the patient&#39;s humerus. A reverse surface of the glenoid component is secured to the bone surface of the glenoid vault. 
     Because the shoulder prosthesis is normally provided to correct a congenital or acquired defect of the native shoulder joint, the glenoid vault or joint surface often exhibits a pathologic, nonstandard anatomic configuration. A surgeon must compensate for such pathologic glenoid vault anatomy when implanting the glenoid component in striving to achieve a solid anchoring of the glenoid component into the glenoid vault. Detailed preoperative planning, using two- or three-dimensional internal images of the shoulder joint, often assists the surgeon in compensating for the patient&#39;s anatomical limitations. During the surgery, an elongated pin may be inserted into the surface of the patient&#39;s bone, at a predetermined trajectory and location, to act as a passive landmark or active guiding structure in carrying out the preoperatively planned implantation. This “guide pin” may remain as a portion of the implanted prosthetic joint or may be removed before the surgery is concluded. This type of pin-guided installation may be useful in any joint replacement procedure—indeed, in any type of surgical procedure in which a surgeon-placed fixed landmark is desirable. 
     In addition, and again in any type of surgical procedure, modern minimally invasive surgical techniques may dictate that only a small portion of the bone or other tissue surface being operated upon is visible to the surgeon. Depending upon the patient&#39;s particular anatomy, the surgeon may not be able to precisely determine the location of the exposed area relative to the remaining, obscured portions of the bone through mere visual observation. Again, a guide pin may be temporarily or permanently placed into the exposed bone surface to help orient the surgeon and thereby enhance the accuracy and efficiency of the surgical procedure. 
     A carefully placed guide pin or other landmark, regardless of the reason provided, will reduce the need for intraoperative imaging in most surgical procedures and should result in decreased operative time and increased positional accuracy, all of which are desirable in striving toward a positive patient outcome. Co-pending U.S. patent application Ser. No. 13/282,509, filed 27 Oct. 2011 and titled “System and Method for Association of a Guiding Aid with a Patient Tissue” (the entire contents of which are incorporated herein by reference) discloses a guide, which may be patient-specific, for helping associate a landmark with a patient tissue. However, the guide of this co-pending application is described, in relevant part, as being planned using a computer and generated (e.g., via three-dimensional printing or rapid prototyping) with the landmark-guiding features in place. In contrast, a user may wish to manufacture or generate a guide without the use of a computer in some situations. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present invention, a method for producing at least one patient-specific surgical aid is described. A physical model of a native patient tissue is provided. The physical model has at least one surface of interest. A constraining wall is placed in contact with at least a portion of the physical model. A moldable substance is placed into contact with at least a portion of the surface of interest. An impression of the surface of interest is maintained upon the moldable substance. The moldable substance is solidified into a patient-specific surgical aid. The patient-specific surgical aid is removed from the physical model. 
     In an embodiment of the present invention, a system of providing at least one patient-specific surgical aid is provided. A physical model of a native patient tissue is provided. The physical model has at least one surface of interest. A constraining wall for contacting at least a portion of the physical model is provided. A moldable substance for contacting at least a portion of the surface of interest and for maintaining an impression of the surface of interest thereupon is provided. The moldable substance is solidified into a patient-specific surgical aid. The patient-specific surgical aid is removed from the physical model for use. 
     In an embodiment of the present invention, a method for producing at least one patient-specific surgical aid is described. A native patient tissue having at least one patient tissue surface of interest is provided. A moldable substance is placed into contact with at least a portion of the patient tissue surface of interest. An impression of the patient tissue surface of interest is maintained upon the moldable substance. The moldable substance is solidified into a patient-specific surgical aid. The patient-specific surgical aid is removed from the native patient tissue. 
     In an embodiment of the present invention, a system of providing at least one patient-specific surgical aid is described. A moldable substance for contacting at least a portion of a patient tissue surface of interest of a native patient tissue is provided. The moldable substance is configured to maintain an impression of the patient tissue surface of interest thereupon. The moldable substance is solidified into a patient-specific surgical aid when in contact with at least a portion of the patient tissue surface of interest before removal of the patient-specific surgical aid from the native patient tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the invention, reference may be made to the accompanying drawings, in which: 
         FIGS. 1-3  are perspective views of one structure of the present invention in a first configuration; 
         FIGS. 4-6  are perspective views of the structure of  FIGS. 1-3  in a second configuration; 
       FIGS.  7  and  9 - 10  are perspective views of the structure of  FIGS. 1-3  in a third configuration; 
         FIG. 8A  is a partial cross-sectional view taken along line A-A in  FIG. 7 ; 
         FIG. 8B  is a partial cross-sectional view taken along line B-B in  FIG. 7 ; 
         FIG. 8C  is a partial cross-sectional view taken along line C-C in  FIG. 7 ; 
         FIGS. 11-13  are perspective views of another structure of the present invention;  FIGS. 14A-14F  are perspective views depicting an example sequence of operation of the present invention; 
         FIG. 15  is a perspective view of another structure of the invention in a first configuration; 
         FIGS. 16A-16C  are partial cross-sectional views of the structure of  FIG. 15 ; 
         FIG. 17  is a partial cross-sectional view of another structure of the invention; 
         FIG. 18  is a top view of an example use environment for an embodiment of the present invention; 
         FIG. 19  is a top view of the embodiment of  FIG. 18  in the example use environment of  FIG. 18 ; 
         FIG. 20  is a partial cross-sectional view taken along line  20 - 20  in  FIG. 19 ; 
         FIG. 21A  is a top view of the embodiment of  FIG. 18  in another example use environment; 
         FIG. 21B  is a side view of the embodiment of  FIG. 18  in the example use environment of  FIG. 21A ; 
         FIG. 22A  is a top view of the embodiment of  FIG. 18  in another example use environment; 
         FIG. 22B  is a side view of the embodiment of  FIG. 18  in the example use environment of  FIG. 22A ; 
         FIG. 23  is a top view of the of the embodiment of  FIG. 18  in the example use environment of  FIG. 18 ; and 
         FIG. 24  is a partial cross-sectional view taken along line  24 - 24  in  FIG. 23 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The patient tissue is shown and described herein at least as a scapula and an acetabulum, and the prosthetic implant component is shown and described herein at least as a glenoid prosthetic shoulder component and an acetabular prosthetic hip component, but the patient tissue and corresponding prosthetic implant component could be any desired types such as, but not limited to, hip joints, shoulder joints, knee joints, ankle joints, phalangeal joints, metatarsal joints, spinal structures, long bones (e.g., fracture sites), or any other suitable patient tissue use environment for the present invention. The below description presumes that the system, apparatus, and method described is being used in conjunction with a surgical procedure (namely, an at-least-partial joint replacement or resurfacing), but the system, apparatus, and method described may be used in any desired manner and for any desired purpose without harm to the present invention. 
     In accordance with the present invention,  FIGS. 1-3  depict three different perspective views of a physical model  100  (sometimes called a “surrogate model”) of a native patient tissue—here, the glenoid fossa and surrounding scapular structures. The term “native patient tissue” and variants thereof is used herein to indicate a patient tissue of interest in its condition at the time of surgical preparation, having any included natural or artificial structures of interest, whether congenital or acquired. The term “model” is used herein to indicate a replica or copy of a physical item, at any relative scale and represented in any medium, physical or virtual. (However, herein the model will be presumed to be a physical model  100 , as opposed to a virtual model located only on a computer system.) The patient tissue model may be a total or partial model of a subject patient tissue, and may be created in any suitable manner. For example, and as presumed in the below description, the patient tissue model may be a tangible representation of a virtual model generated using computer tomography (“CT”) data imported into a computer aided drafting (“CAD”) system. Additionally or alternatively, the patient tissue model may be based upon a virtual model created with the aid of digital or analog radiography, magnetic resonance imaging, or any other suitable imaging means. The patient tissue model will generally be displayed for the user to review and manipulate preoperatively, such as through the use of a physical model or (in the case of a virtual model) the use of a computer or other graphical workstation interface. 
     The patient&#39;s name, identification number, surgeon&#39;s name, and/or any other desired identifier may be molded into, printed on, attached to, or otherwise associated with the physical model  100  in a legible manner. Particularly when based upon a virtual model, the physical model  100  may be made by any suitable method such as, but not limited to, selective laser sintering (“SLS”), fused deposition modeling (“FDM”), stereolithography (“SLA”), laminated object manufacturing (“LOM”), electron beam melting (“EBM”), 3-dimensional printing (“3DP”), contour milling, computer numeric control (“CNC”), other rapid prototyping methods, or any other desired manufacturing process. 
     As examples of physical model  100  generation means omitting the step of the preoperative-imaging based virtual model, the physical model may be directly generated from the native patient tissue using a microscribe three-dimensional scanning/replicating device and/or using a molding system to take an impression of the patient&#39;s tissue from which the physical model can be made. 
     Regardless of how the physical model  100  comes into existence, it represents a three-dimensional, physically manipulable representation of a particular native patient tissue. The physical model  100  has at least one surface of interest  102  (substantially the glenoid fossa, in the embodiment shown in the Figures). The term “surface of interest” is used herein to indicate a surface of the physical model  100  which the user wishes to replicate and/or reference with the patient-specific surgical aid. As one of ordinary skill in the art will be aware, a “surface of interest”  102  in most cases will not have clearly defined borders, but that person of ordinary skill in the art will be able to instinctively differentiate between a surface of interest and another patient tissue, which is not a surface of interest, for a particular application of the present invention. 
     As an example, the physical model  100  of the Figures depicts a portion of a scapula which will be undergoing a glenoid resurfacing and/or replacement procedure. Therefore, one surface of interest  102  that will be referenced herein is the glenoid fossa surface. As shown in  FIGS. 1-3 , at least one landmark  104  may be associated with the physical model  100 . Here, two landmarks  104   a  and  104   b  (each of which is a bore or aperture) are present, with the former being located on the glenoid fossa surface and the latter being located to one side of the glenoid fossa surface, shown here on the glenoid rim at/near the base of the coracoid process. The term “landmark”  104  is used herein to indicate any guiding aid which serves as a detectable indicator of a particular position on a “marked” substrate (here, the patient tissue or the physical model  100  representing such). The landmarks  104  discussed with respect to the present invention are presumed to be affixed or otherwise rigidly associated with a particular patient tissue so that a user can confidently maintain a sense of physical and/or visual orientation within the operative field. Suitable landmarks  104  may include, but are not limited to, visual “written” marks (e.g., a thin layer of a substance left behind after contact with a crayon, surgical pen, or the like), other written marks outside the visual spectrum (e.g., a UV-fluorescent paint), guide pins, fasteners (e.g., screws, nails, staples, or the like), radioactive tags, bovie cautery burn marks, metallic or nonmetallic devices attached to the desired landmark site (e.g., a rivet, tack, or the like), or even modifications of the patient tissue itself (e.g., notches, inscribed lines, drill holes, or the like, as with the landmarks  104   a  and  104   b  shown in the Figures). 
     The marking location and marking trajectory/orientation, as appropriate, of each landmark  104  on the physical model  100  may be predetermined by a user before the landmark is associated with the physical model. This predetermination may occur intraoperatively, while the user is able to directly see the condition of the surgical site and associate the landmark(s)  104  with the corresponding physical model  104  accordingly. However, it is also contemplated that a predetermination of the desired marking location and desired marking trajectory for each landmark  104  could be accomplished preoperatively, with reference to preoperative imaging of the patient tissue. For example, a system similar to that of co-pending U.S. patent application Ser. No. 13/282,550, filed 27 Oct. 2011 and titled “System of Preoperative Planning and Provision of Patient-Specific Surgical Aids”, the entire contents of which are incorporated herein by reference, or any suitable preoperative planning system could be used. Using this or any other planning means (including “dead reckoning”, “eyeballing”, or other non-planned or non-assisted placement methods), a user can create a physical model  100  for observation, manipulation, rehearsal, or any other pre-operative tasks, having any number and type of landmarks  104  associated therewith, for any reason(s). 
     Optionally, and particularly when a computer-assisted pre-operative planning method is used, virtual landmarks  104  may be virtually placed on a virtual patient tissue model. In order to transfer those virtual landmarks  104  to the physical world for intra-operative use, the physical model  100  may be at least partially custom-manufactured responsive to preoperative imaging of the patient tissue, the physical model  100  having at least one landmark  104  associated therewith as generated. 
     Turning to  FIGS. 4-6 , three perspective views are shown of a physical model  100  having landmarks  104   a,    104   b  which are guide pins, protruding from the surface of the physical model. The guide pin landmarks  104   a,    104   b  could either be stock or bespoke guide pins inserted into previously provided bores in the physical model  100 , or could be originally formed as protrusions from the physical model. Unlike two-dimensional “marking” landmarks which merely denote a marking location, the guide pin landmarks  104   a,    104   b  shown in  FIGS. 4-6  are three-dimensional and therefore include both a marking location and a marking trajectory. 
     Speaking more generally, the guide pin landmarks  104   a,    104   b  of  FIGS. 4-6  are examples of non-native (i.e., non-native patient tissue) structures which are associated with the surface of interest  102  (For certain use environments of the present invention, the glenoid rim guide pin landmark  104   b  may be considered to be “outside” the surface of interest  102 , depending on the metes and bounds of the surgical procedure being planned.). Optionally, and as is the case with the guide pin landmarks  104   a,    104   b  of  FIGS. 4-6 , the non-native structure may be an information feature providing clinically useful information to a user. 
     “Clinically useful” information is used herein to indicate any information, other than the structure of the native patient tissue itself, that assists one of ordinary skill in the art with some pre- and/or intra-operative task. An “information feature” is any physical feature or characteristic of the physical model  100  which signifies or communicates the clinically useful information to the user, optionally in combination with a preoperative plan. Optionally, the information feature may be substantially separated from the surface of interest. 
       FIGS. 7-10  illustrate various structures which can assist with providing at least one patient-specific surgical aid using a molding fabrication process according to the present invention.  FIGS. 7-10  each include at least a portion of a physical model  100  having two guide pin landmarks  104   a,    104   b  protruding therefrom.  FIGS. 7-10  each also depict at least one constraining wall which may be provided for contacting at least a portion of the physical model  100 , such as at least a portion of the surface of interest  102 . For example, and as shown in  FIG. 7 , four of these optional constraining walls are shown schematically via dotted lines: an outer wall  706  defining at least one perimeter boundary of a patient-specific surgical aid, an inner wall  708  defining at least one inner recess  710  of the patient-specific surgical aid (omitted from  FIGS. 9-10  for clarity), and two guide bushings  712   a  and  712   b  which each are associated with a guide pin landmark  104   a  and  104   b,  respectively, to define a guiding aperture (not shown) through a thickness of the patient-specific surgical aid, as will be discussed below. 
     The constraining wall(s) of the present invention, when provided, may be of any suitable size, shape, configuration, material, construction, or other physical property, and may be integrally formed in a one-piece manner with the physical model  100  or separately provided by any agent, at any time, and with any degree (or none) of attachment or connection, permanent or temporary, to the physical model  100 . The dimensions, construction, material(s), configuration(s), attachment(s), and other properties of a suitable constraining wall(s) may be readily determined by one of ordinary skill in the art for a particular application of the present invention. Because of the wide range of possible arrangements and constructions available for such, the constraining walls are simply shown schematically as dotted lines in FIGS.  7  and  9 - 10 . 
     Regardless of their specific properties, each constraining wall is contemplated for use in helping to form a patient-specific surgical guide  814 , as shown in the cross-sectional views of  FIGS. 8A ,  8 B, and  8 C. The patient-specific surgical guide  814  will, for most applications of the present invention, be molded from the physical model  100 , optionally with the assistance of one or more constraining walls. That is, a moldable substance  816  will be placed into contact with at least a portion of the surface of interest  102 . (In  FIGS. 8A-8C , the moldable substance  816 , which makes up the body of the patient-specific surgical guide  814  as denoted by the shaded portions of those Figures, is shown as being slightly separated from adjacent surfaces for clarity of depiction. In reality, the moldable substance  816  can be placed into a mating relationship with those adjacent surfaces, as desired by a user.) 
     The moldable substance  816  may be any suitable material, or combination of materials, which is capable of maintaining an impression of the surface of interest  102  thereupon. Examples of suitable reusable or single-use moldable substances include, but are not limited to, modeling clay, gelatins, urethane and silicone rubber, urethane and epoxy casting resins, other epoxies, latexes, adhesives, cements (e.g., bone cement or any other type), glues, foams (e.g., florists&#39; foam, aerosol foams, or any other type), other plastic materials, candy, closely packed wadding/gauze/batting, powders, putty, pinscreen-based devices (e.g., structures using similar principles to those disclosed in U.S. Pat. No. 4,654,989, issued Apr. 7, 1987 to Ward Fleming), and the like. Particularly if the moldable substance  816  has relatively high viscosity and/or is a solid, one or more of the constraining walls discussed herein may be omitted if not needed to constrain a moldable substance that itself has sufficient physical properties to maintain position as desired by the user. 
     The moldable substance  816  should be able to be solidified into a patient-specific surgical aid  814 , which can then be removed from the physical model  100  for use. The term “solidify” is used herein to indicate that the moldable substance  816  dries, sets, cures, or otherwise takes on a definite physical form (optionally with the use of an oven, fan, light of a certain wavelength [e.g., ultraviolet], or other “curing” aid) sufficient to substantially maintain the impression of the surface of interest  102  upon removal of the patient-specific surgical aid  814  from the physical model  100 . “Solidify” is also used herein to reference the process, if any, of “finalizing” a configuration of a moldable substance  816  that is substantially solid in raw material form (e.g., florists&#39; foam) sufficiently for the moldable substance to maintain the format of the patient-specific surgical aid  814 , whether or not any phase change from raw to “solidified” form of the moldable substance occurs. A “solidified” patient-specific surgical aid  814  may still be somewhat pliant or supple, or even include portions (e.g., “pockets”) of fluid material, and be considered sufficiently “solidified” for a particular application. Conversely, the “solidified” patient-specific surgical aid  814  may be substantially rigid. 
     Optionally, a release agent or other intermediate substance (e.g., a lubricant, mold release spray or powder, wax, thin film [e.g., plastic wrap], or the like) may be placed on at least a portion of the surface of interest  102  before the moldable substance  816  is placed into contact with at least a portion of the surface of interest, for any desired reason including protecting the surface of interest from the moldable substance or vice versa, facilitating removal of the patient-specific surgical aid  814  from the physical model  100 , or for any other reason. In this case, the contact between the moldable substance  816  and the affected portion(s) of the surface of interest  102  may be indirect. 
     Each constraining wall (e.g., the outer wall  706 , inner wall  708 , guide bushing  712 , or any other constraining wall as desired) may be provided and used to help contain or block flow of the moldable substance  816  before it is solidified, to help define the area of the physical model  100  which is a surface of interest  102 , to help insulate or separate portions of the patient-specific surgical aid  814  from each other, and/or for any other desired reason. The moldable substance  816  may come into contact with at least a portion of the constraining wall—this is evident in  FIGS. 8A-8C , in which a relatively fluid moldable substance has been poured into a mold cavity comprised of the surface of interest  102  and the constraining walls. To facilitate the molding process, the physical model  100  may be arranged with a substantial part of the surface of interest  102  being located at a topmost position (if it is not already), and optionally oriented to be substantially level to a local ground plane, before the moldable substance  816  is brought into contact with the surface of interest—in this manner, a suitable amount of the moldable substance may be assisted by gravity in reaching all desired portions of the surface of interest. However, it is contemplated that the constraining wall(s) need not solely provide containment of the moldable substance  816 , and other structures (not shown) might also be used to facilitate the molding process. Additionally or alternatively, it is contemplated that a portion of the moldable substance  816  may be molded without need for containment, due to the viscosity of the moldable substance  816 , the orientation of the physical model  100  with respect to the local gravitational field, or for any other reason. 
     Optionally, at least one constraining wall may be incorporated into, and become a part of, the patient-specific surgical aid  814  during and/or via the molding process (for example, to help give rigidity and structure to the patient-specific surgical aid). In such case, the affected constraining wall(s) may be detached or otherwise removed from contact with the physical model  100  as the patient-specific surgical aid  814  is removed from the physical model. 
       FIG. 8A  depicts a simple cross-section through the thickness of the patient-specific surgical aid  814 , wherein the moldable substance  816  has been poured into the outer wall  706 . The outer wall  706  may be placed somewhat arbitrarily to provide an outer border for the patient-specific surgical aid  814 . Alternately, at least a portion of the outer wall  706  itself may be an information feature and contain clinically useful information, such as a “cookie cutter” type border indicator showing where the underlying patient tissue should be resected. 
       FIG. 8B  depicts a slightly more complex cross-section than in  FIG. 8A , with at least one non-native structure (here, the guide pin landmark  104   a ) bring associated with the physical model  100  in this cross-section. Here, a molded feature incorporated in the patient-specific surgical aid  814  is based upon the guide pin landmark  104   a.  That is, a bore or aperture  818  protrudes through the patient-specific surgical aid  814  as a negative space where the guide pin landmark  104   a  has prevented the presence of the moldable substance  816 . Optionally, and as shown here, the guide bushing  712  or at least a portion of another constraining wall may be interposed between at least a portion of the non-native structure and the moldable substance  816 . When the patient-specific surgical aid  814  is solidified and removed from the physical model  100 , the guide pin landmarks  104  may either go with, and be considered a part of, the patient-specific surgical aid or may be removed therefrom. 
     Particularly when the diameter of the guide pin is chosen to correspond to a desired drill bit size, the guide pin landmarks  104  may assist with creating a drill guide aperture  818  in the patient-specific surgical aid  814 , the drill guide aperture having the desired marking location and marking trajectory embodied in the corresponding guide pin landmark. Because contact between a rotating tool (such as a drill bit) and the moldable substance  816  forming the body of the patient-specific surgical aid  814  may degrade or break down the walls of the drill guide aperture  818 , a guide bushing  712  type constraining wall (particularly if made of an abrasion-resistant material, such as stainless steel) may become an integral part of the patient-specific surgical aid  814  to limit the size of the aperture, resist abrasion (by preventing contact between the drill bit and the moldable substance  816 ), and/or serve as a guide for the drill bit. 
       FIG. 8C  depicts a cross-section in which the inner recess  710  has been left free of moldable substance  816  for some reason. For example, the user may want to maintain a direct line of sight with the surface of interest  102  in that area, the inner recess  710  may provide material cost and/or weight savings for the patient-specific surgical aid  814 , the inner recess  710  may mark a desired cutting plane for a step in the surgical procedure, the inner recess may be configured to accept a handle or other auxiliary tool structure, a portion of the patient tissue within the inner recess may be pressure-sensitive, or the inner recess may have been provided for any other reason. When the patient-specific surgical aid  814  is removed from the physical model  100 , the inner recess  710  will remain “open”, and the inner wall  708  may be incorporated into the patient-specific surgical aid to maintain integrity (e.g., size and/or shape) of the inner recess. However, the inner recess  710  is omitted from successive Figures for clarity of depiction. 
       FIGS. 9-10  illustrate the manner in which the constraining walls (i.e., the outer wall  706  and guide bushings  712   a  and  712   b ) relate to the physical model  100  before and during the molding process for the patient-specific surgical aid  814 . 
       FIGS. 11-13  depict various perspective views of the completed patient-specific surgical aid  814  after having been solidified and removed from a physical model  100 , such as the physical model  100  shown in  FIGS. 9-10 . As can be seen from the substantially bottom view of  FIG. 11 , the bottom surface  1120  substantially reproduces the contours of the surface of interest  102 . Accordingly, the patient-specific surgical aid  814  produced using the above-described process should substantially mate with a native patient tissue (corresponding to the physical model  100 ) when placed upon the appropriate native patient tissue and aid the user in positively transferring landmark  104  marking locations and/or marking trajectories, or any other clinically useful information embodied in the patient-specific surgical aid to the native patient tissue. For example, the patient-specific surgical aid  814  may be used similarly to the devices disclosed in co-pending U.S. patent application Ser. No. 13/282,509, filed 27 Oct. 2011 and titled “System and Method for Association of a Guiding Aid with a Patient Tissue”, the entire contents of which are incorporated herein by reference. 
     With reference to  FIGS. 12-13 , the guide bushings  712   a,    712   b  have been incorporated into the patient-specific surgical aid  814 , such as to guide a drill bit or guide pin into the underlying native patient tissue at a specified location and trajectory. Because the patient-specific surgical aid  814  is contemplated to only mate securely with the native patient tissue in a single relative orientation, the user has a reasonably high degree of confidence that the drill bit or guide pin is being guided into the underlying native patient tissue in the desired location and/or trajectory. 
     Accordingly, at least a part of the patient-specific surgical aid  814  is a patient-specific, single-use, bespoke component suited only for use at a surgical site corresponding to the surface of interest  102 , though one of ordinary skill in the art could create a guide (not shown) which uses a patient-specific “disposable” structure (which may be substantially limited to the surface of interest) connected to a stock, generic “reusable” carrier (which may help the user in manipulating, stabilizing, securing, or otherwise interacting with the “disposable” structure as desired. 
       FIGS. 14A-14F  depict an example sequence of operation of the present invention. FIG. 
       14 A includes two physical models  100   a  (on the left, in the orientation of  FIG. 14A) and 100   b  (on the right, in the orientation of  FIG. 14A ). Physical model  100   a  is bare, with no landmarks included. Physical model  100   b  includes landmarks  104   a  and  104   b,  which are each guide pins as previously described. In  FIG. 14B , guide bushings  712 , serving as constraining walls, have been placed around each of the landmarks  104   a  and  104   b.    FIG. 14C  depicts the physical model  100   b  with the inserted landmarks  104   a  and  104   b  and the surrounding guide bushings  712 . In  FIG. 14C , a moldable substance  816  has been placed into contact with at least a portion of the surface of interest  102 . Once the moldable substance  816  has solidified sufficiently to maintain an impression of the surface of interest  102  thereupon, it is removed and serves as a patient-specific surgical aid  814 , seen alone in  FIG. 14D . Here, the guide bushings  712  are incorporated into the patient-specific surgical aid  814 .  FIGS. 14E-14F  depict different views of the patient-specific surgical aid  814  placed in a use position atop the bare physical model  100   a,  which includes no landmarks  104 . (This bare physical model  100   a  is used in  FIGS. 14E-14F  as an easily viewed proxy for the patient tissue upon which that physical model was based, for the sake of the present discussion.) As can be seen in  FIGS. 14E-14F , the guide bushings  712  are each held by the patient-specific surgical aid  814  at a location and trajectory that will direct a guide pin inserted therethrough into an insertion location and trajectory that substantially replicates the landmarks  104   a  and  104   b  present on the physical model  100   b  which was used to create the patient-specific surgical aid. 
       FIGS. 15-16C  illustrate a second embodiment of the present invention for use with a second physical model  100 ′. The embodiment of  FIGS. 15-16C  is similar to the embodiment of  FIGS. 1-14F  and therefore, structures of  FIGS. 15-16C  that are the same as or similar to those described with reference to  FIGS. 1-14F  have the same reference numbers with the addition of a “prime” mark. Description of common elements and operation similar to those in the previously described embodiments will not be repeated with respect to the second embodiment. 
     As shown in  FIG. 15 , the physical model  100 ′ of the patient tissue embodies a hip and an acetabulum, as opposed to the scapula and glenoid of  FIGS. 1-14F . In  FIG. 15 , two landmark  104 ′ guide pins have been placed, with one landmark  104 ′a being located inside the acetabulum and a second landmark  104 ′b being located outside the rim of the acetabulum. 
     Because the acetabulum is a relatively large void in a patient tissue, the user will probably want to avoid creating a single patient-specific surgical aid  814 ′ which includes both of the landmarks  104 ′ a  and  104 ′ b  in the positions depicted in  FIG. 15 , at least because it would take a relatively large quantity of moldable substance  816 ′ to fill the acetabulum and also come into molding contact with the area of the pelvis near the second landmark  104 ′ b.  That large quantity of moldable substance  816 ′ may be expensive, difficult to obtain, difficult to work with (e.g., does not solidify well), or may otherwise be undesirable to use. 
     Accordingly, while a single patient-specific surgical aid  814 ′ could be created in this situation,  FIGS. 16A-16C  depict, schematically and sequentially, the creation of two spaced-apart surgical aids  814 ′ a  and  814 ′ b,  which is contemplated as being a more likely scenario for most users of the present invention.  FIG. 16A  is a cross-sectional view of the physical model  100 ′ including both landmarks  104 ′ a  and  104 ′ b.  In  FIG. 16B , guide bushings  712 ′ a  and  712 ′ b  have been placed around the landmarks  104 ′ a  and  104 ′ b,  respectively. 
       FIG. 16C  shows the landmarks  104 ′ a  and  104 ′ b,  the guide bushings  712 ′ a  and  712 ′ b,  and two outer walls  706 ′ a  and  706 ′ b,  with each outer wall substantially surrounding one landmark-guide bushing pair.  FIG. 16C  also shows moldable substance  816 ′ a  and  816 ′ b,  which has been provided within the outer walls  706 ′ a  and  706 ′ b,  respectively. The moldable substance  816 ′ a  and  816 ′ b  may be the same at each location, or may differ, as desired by the user. For example, the moldable substance  816 ′ b  at/near the acetabular rim may be more viscous than the moldable substance  816 ′ a  within the acetabulat cavity, particularly if the orientation of landmark  104 ′ b  and/or outer wall  706 ′ b  would make the moldable substance  816 ′ b  prone to slide off the acetabular rim without achieving sufficient thickness to provide the desired bottom surface  1120  for the completed patient-specific surgical aid  814 ′ a.    
       FIG. 17  illustrates an alternate patient-specific surgical aid  814 ′ in an example use environment corresponding to the second physical model  100 ′. As shown in  FIG. 17 , a landmark  104 ′ can be located at a position, such as the depicted acetabular rim, with a constraining wall having a guide bushing  712 ′ which is supported by a remote locator  1722 . An anchor end  1724  of the remote locator  1722  is located adjacent, and optionally contacting, the physical model  100 ′ at a location which is provided with a moldable substance  816 ′. Here, the moldable substance  816 ′ is constrained by an outer wall  706 ′, to reduce the volume of moldable substance needed to replicate the surface of interest  102 ′ (here, the acetabular fovea) while securing the anchor end  1724  of the remote locator  1722  sufficiently to memorialize the location and/or trajectory of the landmark  104 ′ in the patient-specific surgical aid  814 ′ for transference to the native patient tissue. 
     The remote locator  1722 , as well as any constraining wall feature supported thereby, may be at least partially patient-specific (e.g., designed and/or produced with the aid of pre-operative images of the native patient tissue), or may be a generic/stock component. The body of the remote locator  1722  could be configured to mate with, or follow closely along a contour of, a native patient tissue, or could instead have no particular relationship with the native patient tissue save that needed to span the distance between the landmark  104 ′ or other desired remote endpoint and the location at which the moldable substance  816 ′ is applied to create the patient-specific surgical aid  814 ′. 
       FIGS. 18-24  illustrate a third embodiment of the present invention for use with a native patient tissue  1822 . The embodiment of  FIGS. 18-24  is similar to the embodiments of  FIGS. 1-16C  and therefore, structures of  FIGS. 18-24  that are the same as or similar to those described with reference to  FIGS. 1-16C  have the same reference numbers with the addition of a double “prime” mark. Description of common elements and operation similar to those in the previously described embodiments will not be repeated with respect to the third embodiment. 
     In  FIG. 18 , a native patient tissue  1822  (here, a glenoid of a scapula) is shown in situ, exposed via a surgical wound  1824 . The native patient tissue  1822  has at least one patient tissue surface of interest  1826 . The patient tissue surface of interest  1826  may be in a congenital or acquired “natural” state (i.e., a state as encountered at the time the surgical wound  1824  is made) and/or may have been at least partially altered during the instant surgical procedure, optionally according to a preoperative surgical plan. 
     As shown in  FIG. 19 , a moldable substance  816 ″ is placed into contact with at least a portion of the patient tissue surface of interest  1826 . An impression of the patient tissue surface of interest  1826  is maintained, in any suitable manner and at any desired resolution, upon the moldable substance  816 ″. For example, bone cement may be placed upon the patient tissue surface of interest  1826  (optionally constrained by a constraining wall, not shown) and then at least partially solidified to “hold” a negative, molded contour replicating the patient tissue surface of interest on a bottom surface of the resulting pile of bone cement. Optionally, a release agent or other intermediate substance (e.g., a lubricant, mold release spray or powder, wax, thin film [e.g., plastic wrap], or the like) may be placed on at least a portion of the patient tissue surface of interest  1826  before the moldable substance  816 ″ is placed into contact with at least a portion of the patient tissue surface of interest. 
     Once the moldable substance  816 ″ has been solidified into a patient-specific surgical aid  814 ″, the patient-specific surgical aid can be removed from the native patient tissue  1822  as desired by the user. A cross-sectional view of the completed patient-specific surgical aid  814 ″ is shown in  FIG. 20 . It is contemplated that the patient-specific surgical aid  814 ″ of the third embodiment could be intentionally less-solidified when removed from the native patient tissue  1822  than a corresponding patient-specific surgical aid of the first and/or second embodiments is when removed from the corresponding physical model for any desired reason, including, but not limited to, avoiding damage to the native patient tissue, facilitating structural changes to the patient-specific surgical aid  814 ″, limiting contact time between the moldable substance  816 ″ and the native patient tissue, or the like. 
     Once removed from the native patient tissue  1822 , the patient-specific surgical aid  814 ″ of the third embodiment can be manually and/or automatically physically altered as desired by the user. For example, the patient-specific surgical aid  814 ″ could be drilled, cut, reformed, or otherwise re-structured or re-shaped according to a preoperative plan and/or spontaneously as desired by a user (e.g., “eyeballed” or “dead reckoned”), though it is contemplated that at least the portion of the patient-specific surgical aid upon which the impression of the patient tissue surface of interest  1826  is maintained will remain in its as-molded condition, for reasons which will become apparent below. 
     It is contemplated that additional moldable substance  816 ″ (the same type as used for at least a portion of the patient-specific surgical aid  814 ″ or any other type) may be provided to the patient-specific surgical aid after removal from the native patient tissue  1822 . For example, at least one non-native structure (e.g., a landmark  104 ″ or a remote locator, not shown) could be placed beside the patient-specific surgical aid  814 ″ and additional moldable substance  816 ″ could be “potted” on or otherwise added to the arrangement to physically link the non-native structure and the patient-specific surgical aid. The non-native structure could be an information feature providing clinically useful information to a user. Optionally, one or more constraining walls (not shown), such as, but not limited to, an outer wall, an inner wall, and a guide bushing could be added to, or otherwise associated with, the patient-specific surgical aid  814 ″ before or after the patient-specific surgical aid is removed from the native patient tissue  1822 . 
     When both a constraining wall and a non-native structure are provided to the patient-specific surgical aid  814 ″, at least a portion of the constraining wall could be interposed between at least a portion of the non-native structure and the moldable substance  816 ″. For example, the moldable substance  816 ″ could be formed upon the patient tissue surface of interest  1826 , optionally with the assistance of an inner wall-type constraining wall, into a toroidally shaped patient-specific surgical aid  814 ″ having a central aperture allowing access to the underlying patient tissue surface of interest therethrough. Once that toroidally shaped patient-specific surgical aid  814 ″ has been at least partially solidified and removed from the native patient tissue  1822 , the user can place a guide bushing  712  into the central aperture at a desired location and trajectory, and then “fill” the central aperture around the guide bushing with the same, or a different, moldable substance  816 ″ to hold the guide bushing at the desired location and trajectory. Particularly when a moldable substance  816 ″ is added to the patient-specific surgical aid  814 ″ after the patient-specific surgical aid has been removed from the native patient tissue  1822 , it is contemplated that the added moldable substance might be prevented from extending below the bottom (surface of interest impression-holding) side of the patient-specific surgical aid, so as not to protrude therefrom and prevent the patient-specific surgical aid from being re-mated with the patient tissue surface of interest  1826 . As other options for a location/trajectory “memorialization” (or “capture” of any other physical construct/property) via the patient-specific surgical aid  814 ″, a moldable substance  816 ″ and/or a non-moldable substance (not shown, e.g. a non-native structure) could be provided to any surface of the patient-specific surgical aid  814 ″ to assist with holding a guide bushing, guiding a surgical tool, or otherwise indicating clinically useful information to a user. 
     Regardless of the manner in which the patient-specific surgical aid  814 ″ is handled after removal from the native patient tissue  1822 , any physical alteration(s) to the patient-specific surgical aid will result in the production of an altered patient-specific surgical aid. 
       FIGS. 21A-22B  depict the use of a physical model  100 ″ to help physically alter a patient-specific surgical aid  814 ″.  FIGS. 21A-21B  depict top and side views, respectively, of a physical model  100 ″ at least partially corresponding to the native patient tissue  1822 . Optionally, though not shown, at least one physical alteration of the native patient tissue  1822  could be also embodied in the physical model  100 ″. This physical alteration, when present, could be at least the result of a preoperative surgical planning process. In other words, the physical model  100 ″, when not reflective of a pre-surgical condition of the native patient tissue  1822 , could be a predictive model (preoperatively created with anticipation of the effect that at least one surgical task [e.g., reaming, drilling] would have on the native patient tissue during the surgery if performed as planned) and/or could be a reactive model (created during the surgical procedure, such as via intraoperative scanning and manufacture, with actual knowledge of the effect that the performed surgical task(s) had on the native patient tissue). 
     Regardless of the origins of the physical model  100 ″, it is presumed that at least a portion of the surface of interest  102 ″ of the physical model reflects or replicates the actual condition of the patient tissue surface of interest  1826  with sufficient resolution/fidelity for the patient-specific surgical aid  814 ″ (having been removed from the native patient tissue  1822 ) to be placed into contact with the surface of interest of the physical model (optionally mated therewith) in a position that approximates the position in which the patient-specific surface of interest was created upon the patient tissue surface of interest, as shown in the top and side views of  FIGS. 21A-21B . 
     Once the patient-specific surgical aid  814 ″ is located in the desired orientation with respect to the physical model  100 ″, at least one physical alteration may be made to the patient-specific surgical aid to create an altered patient-specific surgical aid  2228 . For example, and as shown in  FIGS. 22A-22B , a landmark  104 ″ could be inserted into the (unaltered) patient-specific surgical aid  814 ″ at a desired location and trajectory that the altered patient-specific surgical aid  2228  could then embody/incorporate physically for transfer to the native patient tissue  1822 . As another example, one edge of the patient-specific surgical aid  814 ″ could be trimmed off (not shown) to indicate a cutting plane location to a user. Optionally, the moldable substance  816 ″ forming the patient-specific surgical aid  814 ″ could be chosen and/or manipulated in any suitable manner to facilitate the physical alteration—e.g., the moldable substance  816 ″could be associated with the physical model  100 ″ when only partially solidified so that a landmark  104 ″ can be inserted and/or manipulated/oriented therethrough more easily. It is contemplated, though, that the patient-specific surgical aid  814 ″ will be sufficiently “set” in most use environments of the present invention to maintain the impression of the patient tissue surface of interest  1826  without substantial alteration of that impression by the surface of interest  102 ″ of the physical model  100 ″ 
     The location, orientation, and other physical properties of the landmark  104 ″, non-native structure, constraining wall, and/or other physical alteration of the patient-specific surgical aid  814 ″ could be preplanned (e.g., using preoperative planning software and/or preoperative physical rehearsals/tests) and/or spontaneous (e.g., “eyeballed” or “dead reckoned”) and may be provided in any suitable manner, including by being at least partially embodied in the physical model  100 ″ before alteration of the patient-specific surgical aid. 
     Once the altered patient-specific surgical aid  2228  has been created as desired, it may be removed from the physical model  100 ″, tested and/or subjected to additional treatments (e.g., curing, sterilization) as desired, and then placed back into contact with at least a portion of the patient tissue surface of interest  1826  in a location and orientation at least approximating those in which the patient-specific surgical aid  814 ″ was created, as shown in  FIG. 23 . The altered patient-specific surgical aid  2228  can then be used to facilitate at least one surgical task. As shown in this Figure, for example, an aperture  818 ″ embodying the location and trajectory of the landmark  104 ″ with respect to the physical model  100 ″ has been incorporated into the altered patient-specific surgical aid  2228 . Therefore, a surgical task of drilling into the patient tissue surface of interest  1826  at the desired location and/or trajectory of the landmark can be facilitated by the altered patient-specific surgical aid  2228 . Any other information feature, providing clinically useful information to a user, may similarly be provided by the altered patient-specific surgical aid  2228 , and one of ordinary skill in the art can readily provide an appropriate altered patient-specific surgical aid  2228  for a particular use environment of the present invention. Once the altered patient-specific surgical aid  2228  is no longer desired at the native patient tissue  1822 , it can be removed and the surgical procedure continued apace. 
     While aspects of the present invention have been particularly shown and described with reference to the preferred embodiment above, it will be understood by those of ordinary skill in the art that various additional embodiments may be contemplated without departing from the spirit and scope of the present invention. For example, the specific methods described above for using the described system are merely illustrative; one of ordinary skill in the art could readily determine any number of tools, sequences of steps, or other means/options for virtually or actually placing the above-described apparatus, or components thereof, into positions substantially similar to those shown and described herein. Any of the described structures and components could be integrally formed as a single piece or made up of separate sub-components, with either of these formations involving any suitable stock or bespoke components and/or any suitable material or combinations of materials; however, the chosen material(s) should be biocompatible for most applications of the present invention. The mating relationships formed between the described structures need not keep the entirety of each of the “mating” surfaces in direct contact with each other but could include spacers or holdaways for partial direct contact, a liner or other intermediate member for indirect contact, or could even be approximated with intervening space remaining therebetween and no contact. Though certain components described herein are shown as having specific geometric shapes, all structures of the present invention may have any suitable shapes, sizes, configurations, relative relationships, cross-sectional areas, or any other physical characteristics as desirable for a particular application of the present invention. Any structures or features described with reference to one embodiment or configuration of the present invention could be provided, singly or in combination with other structures or features, to any other embodiment or configuration, as it would be impractical to describe each of the embodiments and configurations discussed herein as having all of the options discussed with respect to all of the other embodiments and configurations. Clinically useful information could include written or other legible information, as well as spatial or other physically discernible information. An air knife, water stream, or other fluid/dynamic barrier could be used as a constraining wall. The system is described herein as being used to plan and/or simulate a surgical procedure of implanting one or more prosthetic structures into a patient&#39;s body, but also or instead could be used to plan and/or simulate any surgical procedure, regardless of whether a non-native component is left in the patient&#39;s body after the procedure. One or more moldable substance(s)  816  could be applied and/or solidified in a laminated/layered manner to provide desired material properties to the patient-specific surgical aid  814  during and/or after initial fabrication. At least a portion of the patient-specific surgical aid  814  could be pre-fabricated, optionally with the aid of preoperative planning software, for combination with the moldable substance  816 . A device or method incorporating any of these features should be understood to fall under the scope of the present invention as determined based upon the claims below and any equivalents thereof. 
     Other aspects, objects, and advantages of the present invention can be obtained from a study of the drawings, the disclosure, and the appended claims.