Patent Publication Number: US-10307174-B2

Title: Apparatus and method for providing a reference indication to a patient tissue

Description:
RELATED APPLICATION 
     This is a continuation non-provisional application Ser. No. 14/628,781 filed on Feb. 23, 2015 which is a continuation non-provisional application Ser. No. 13/472,662 filed on May 16, 2012 which claims priority from U.S. Provisional Application No. 61/487,908, filed 19 May 2011, the subject matter of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an apparatus and method for providing a reference indication to a patient tissue and, more particularly, to a method and apparatus for guiding resection and modification of a patient tissue to receive a prosthetic implant component in a desired implant position. 
     BACKGROUND OF THE INVENTION 
     Minimally invasive surgery (“MIS”) is quickly becoming standard for the implantation of prosthetic components into a patient. For example, the use of an MIS shoulder replacement technique involves a skin incision of approximately 7-9 cm and is performed without the previously required laying-open of the patient&#39;s entire shoulder area. MIS techniques for joint replacement may reduce trauma to the patient, with less pain, less blood loss, shorter convalescence, faster stabilization, and fewer post-operative restrictions on exercising of the joint. The use of MIS may also give the prosthetic joint a better fixation and function than traditional surgery, which in turn can contribute to an increased lifetime for the prosthetic joint. MIS also can be done with considerably shorter hospitalization time than traditional techniques, and may even be available for outpatient procedures, providing an economic benefit linked to positive patient outcome in many cases. 
     In a prosthetic shoulder joint replacement, whether accomplished via MIS or any other suitable surgical technique, the humeral head is removed and replaced with a prosthetic head which is fixed to the bone using a stem within the humeral metaphysis and/or diaphysis shaft. The humeral head articulates with the native glenoid (hemiarthroplasty) or with a prosthetic glenoid component. The humeral osteotomy is made at or near the anatomic neck of the humerus. This osteotomy defines a humeral head neck shaft angle and version of the final implant. In patients with deformity associated with arthritis, the anatomic neck is difficult to define, making it difficult for the surgeon to determine to precise location of this osteotomy. Standard generic stock cutting guides currently used for this procedure still require the surgeon to identify these anatomic landmarks to place the cutting guides. 
     One factor which may lead to success for a total shoulder replacement technique is the provision of a clear overall view of the wound during the operation in order to achieve precise surgery and the desired positioning for the prosthetic components. In the precise surgery associated with the implantation of a shoulder replacement prosthetic component, it is important for the head of the humerus to be removed with great precision. For this purpose an osteotomy template is generally used, whereby the level and orientation of the planned cutting plane is transferred to the patient&#39;s humerus to guide the surgeon. With the preoperative planning procedures that are currently under development, a computer model of the patient&#39;s humerus will often be produced, based on CT, radiographic, or other preoperatively obtained images. Based on this model, a desired cutting plane for the patient&#39;s humerus can be determined. 
     Osteotomy templates exist for use in conventional surgery, but there is currently a need for improved osteotomy templates. A resection guide for use in many hip, shoulder, or other types of prosthetic replacements, whether using MIS or another surgical style, would be useful than currently used guides by being considerably smaller, intended for insertion through different openings, employing different anatomical landmarks, allowing for a more accurate osteotomy, and easier to position in the planned position than the currently used resection guides. 
     Since traditional osteotomy templates are not adapted to the individual patient, they require the surgeon to remove pathologic bone to identify landmarks in order to place the template and make a cut or to use the anatomic landmarks to make an osteotomy without any template or cutting guide. The difficulty lies in the surgeon&#39;s ability to identify anatomic landmarks in the pathologic condition. This means that for patients with anatomical deviations, there is a reduction in precision with traditional multi-use osteotomy templates, thereby giving a final result that is not optimal. For patients with greater anatomical deviations, moreover, the majority of multi-use templates will be difficult to use on account of limitations in the possibilities for adjustment. Even for patients without great deviations, when using multi-use templates it will be necessary to carry out adjustments of the osteotomy template during the operation, resulting in an increased risk of error, increased operating time and thereby an increased risk of complications. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present disclosure, there is provided an apparatus for providing a reference indication to a patient humerus, the apparatus comprising: a primary locating block including a patient-specific primary mating surface contoured and configured for mating contact with at least a portion of a diaphysis of the humerus, the primary mating surface being custom-configured to mate with the humerus in a predetermined primary mating orientation responsive to preoperative imaging of the patient humerus, and at least one mounting feature; and at least one secondary item configured for selective engagement with the primary locating block and including a patient-specific secondary mating surface being contoured and configured for mating contact with at least a portion of the epiphysis of the humerus, the secondary item being custom-configured to mate with the humerus in a predetermined secondary mating orientation responsive to preoperative imaging of the humerus, the secondary mating orientation being non-coincident with the primary mating orientation, and the secondary item providing a first reference indication to the portion of the epiphysis of the humerus; wherein the mounting feature of the primary locating block is configured for engagement with the at least one secondary item in a predetermined secondary mounting relationship, the secondary mounting relationship being custom-configured for the patient humerus responsive to preoperative imaging of the patient humerus such that the primary locating block and the at least one secondary item are in the predetermined secondary mounting relationship when respectively and concurrently in said mating contact with at least the diaphysis and the epiphysis of the patient humerus. 
     In an embodiment of the present disclosure, there is provided a method of providing a reference indication to a patient humerus, the method comprising: obtaining a primary locating block including a patient-specific primary mating surface contoured and configured for mating contact with at least a portion of a diaphysis of the humerus, and at least one mounting feature; mating the primary mating surface with the patient humerus in a primary mating orientation predetermined at least partially responsive to preoperative imaging of the patient tissue; obtaining at least one secondary item including a patient-specific secondary mating surface being contoured and configured for mating contact with at least a portion of the epiphysis of the humerus; engaging the mounting feature of the primary locating block with the at least one secondary item in a predetermined secondary mounting relationship, the secondary mounting relationship being custom-configured for the patient humerus responsive to preoperative imaging of the patient humerus; and mating the secondary mating surface with the patient humerus in a secondary mating orientation predetermined at least partially responsive to preoperative imaging of the patient humerus, the secondary mating orientation being non-coincident with the first mating orientation; obtaining a first reference indication to at least a portion of the patient humerus with the secondary item when the primary mating surface and the secondary mating surface are respectively and concurrently in said mating with at least the diaphysis and the epiphysis of the patient humerus. 
     In an embodiment of the present invention, a system for facilitating at least one of resection, repositioning, drilling, trimming, and configuration verification of a patient tissue of a long bone is provided. A primary locating block includes a patient-specific primary mating surface contoured for mating contact with a nontarget portion of the long bone. The primary mating surface is custom-configured to mate with the nontarget portion of the patient tissue in a predetermined primary mating orientation responsive to preoperative imaging of the long bone. At least one mounting feature is provided to the primary locating block. At least one secondary item is configured for selective engagement with the primary locating block. The secondary item is at least one of a noncustomized stock secondary item and a patient-specific secondary item. The secondary item provides a reference indication to at least a portion of the long bone to facilitate at least one of resection, repositioning, drilling, trimming, and configuration verification of a target portion of a long bone. The mounting feature of the primary locating block is configured for engagement with at least one secondary item in a predetermined secondary mounting relationship. The secondary mounting relationship is custom-configured for the long bone responsive to preoperative imaging of the long bone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the invention, reference may be made to the accompanying drawings, in which: 
         FIG. 1  is a perspective side view of a configuration of an embodiment of the present invention; 
         FIGS. 2A-2E  are individual perspective views of various components of the embodiment of  FIG. 1 ; 
         FIG. 3  is a side view of an example use environment for the embodiment of  FIG. 1 ; 
         FIGS. 4-9  illustrate a sequence of operation of the embodiment of  FIG. 1  in the use environment of  FIG. 3 ; 
         FIG. 10  schematically depicts a surgical step in the sequence of operation of  FIGS. 4-9 ; and 
         FIG. 11  is a perspective side view of a configuration of an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In accordance with the present invention,  FIG. 1  depicts an example configuration of an apparatus  100  for providing a reference indication to a patient tissue (omitted from the view of  FIG. 1 ) and which may be used for guiding resection and modification of a patient tissue to receive a prosthetic implant component in a desired implant position, or for any other desired purpose. The patient tissue is shown and described herein at least as a humeral long bone and the implant component is shown and described herein at least as a humeral prosthetic shoulder component of a known type having a stem inserted into a bored-out humeral intramedullary canal. However, the patient tissue and corresponding 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. For example, the implant component could be an internal fixation device (e.g., a bone plate), a structure of a replacement/prosthetic joint, or any other suitable artificial device to replace or augment a missing or impaired part of the body. The implant component will be described herein as a prosthetic implant component. 
     The apparatus  100  includes a primary locating block  102  and at least one secondary item  104  configured for selective engagement with the primary locating block. The primary locating block  102  includes a patient-specific primary mating surface  106  which is contoured for mating contact with at least a portion of the patient tissue. The term “mating” is used herein to indicate a relationship in which the contours of two structures are at least partially matched or coordinated in at least two dimensions. For example, both the primary mating surface  106  and the patient tissue surface could have profiles that are concavely curved, convexly curved, planar/linear, or any combination of those or other profile shapes. The primary mating surface  106  may be custom-configured to mate with the patient tissue in a predetermined primary mating orientation responsive to preoperative imaging of the patient tissue. The primary locating block also may include at least one mounting feature  108  (two shown). 
       FIGS. 2A-2E  are individual perspective views of various components of the apparatus  100  shown in  FIG. 1 , and include detail on the secondary mounting relationships between each secondary item  104  and the primary locating block  102 .  FIGS. 2A and 2B  depict different aspects of the primary locating block  102 . The primary mating surface  106  of the primary locating block  102  is shown in the view of  FIG. 2A . While it is possible for the primary mating surface  106  to be substantially two-dimensional (e.g., an irregular line) for substantially linear contact with the patient tissue, it is contemplated that, for many applications of the present invention, the primary mating surface  106  will be three-dimensional for mating with a corresponding part or layer of the patient tissue, as shown in  FIGS. 2A and 2B . 
     The secondary item  104 ′ shown in  FIGS. 1 and 2C  includes a positioning indicator  210  which can help to verify the position of at least a portion of the apparatus  100  with respect to the patient tissue. In order to do so, the positioning indicator  210  has a patient-specific secondary mating surface  212  which may be custom-configured to mate with a portion of the patient tissue in a predetermined secondary mating orientation responsive to preoperative imaging of the patient tissue. The secondary mating orientation may be non-coincident with the primary mating orientation. That is, the portion of the patient tissue mated with the secondary mating surface  212  may be different from the portion of the patient tissue mated with the primary mating surface  106 , though the two portions of the patient tissue may be adjacent or even contiguous, depending upon the configuration of the apparatus  100 . The property of “non-coincidence” is independent of the timing of the mating of the surface(s) with the patient tissue, as the primary and secondary mating surfaces  106  and  212  could be non-coincidently mated with the patient tissue at the same time/duration or at different times/durations. 
     Other options for secondary items  104  include a cutting indicator  214 , such as that shown with the secondary item  104 ″ of  FIG. 2D , and a drill guide  216 , such as that shown with the secondary item  104 ′″ of  FIG. 2E . A cutting indicator  214 , when present, is configured for a guiding relationship with a cutting implement performing at least one of a resection and a trimming of the patient tissue. A “guiding relationship” is used herein to indicate that the “guiding” component steadies and/or directs the motion of the “guided” component. For reasons which will later become apparent, a rim  218  of the secondary item  104 ′″ of  FIG. 2E  may also serve as a cutting indicator  214 . A drill guide  216 , when present, guides a penetrating implement into the patient tissue. 
     Each mounting feature  108  of the primary locating block  102  may be configured for engagement with at least one secondary item  104  in the predetermined secondary mounting relationship. For example, the secondary item  104  could include a secondary mounting feature  220  for engagement with the mounting feature  108  of the primary locating block  102  in the predetermined secondary mounting relationship. The secondary mounting relationship may be custom-configured for the patient tissue responsive to preoperative imaging of the patient tissue, and may be made patient-specific by a configuration of the mounting feature  108  and/or the secondary item  104 . It is contemplated that, for most applications of the present invention, there will only be one reasonable secondary mounting relationship for each secondary item  104  with the primary locating block  102 , to provide the user with a high degree of confidence that the preoperatively planned reference indications are being transferred reliably to the actual patient tissue. Keys and/or slots, located on one or both of the primary locating block  102  and the secondary item  104 , may be used to help guide and/or secure the secondary item in a predetermined relationship with the primary locating block. 
     Optionally, at least one anchoring feature could be provided to one or both of the primary locating block  102  and the secondary item(s)  104  for providing at least one of securement, stability, and position indication for that portion of the apparatus  100  relative to the patient tissue. For example, and as shown in  FIGS. 2A and 2B , the anchoring feature includes a plurality of anchoring structures  222  which are each configured to guide an anchoring pin (not shown) into the patient tissue at a predetermined location and trajectory. 
     (The location and/or trajectory could be preoperatively chosen, for example, to anchor into solid patient tissue or to avoid disturbing pathologic patient tissue.) In the  FIGS. 2A and 2B  arrangement, the anchoring pin(s) are operative to provide at least one of securement, stability, and position indication for the primary locating block  102  relative to the patient tissue in the primary mating orientation, as will be discussed below. Similarly, as shown in  FIG. 2E , the secondary item  104 ′″ can include one or more anchoring structures  222  which may be used in cooperation with an anchoring pin (not shown) to provide at least one of securement, stability, and position indication for the secondary item relative to the patient tissue at a predetermined location, whether or not the anchoring structure(s) of the secondary item provide trajectory guidance. 
     Using the positioning indicator  210 , cutting indicator  214 , drill guide  216 , and/or any other suitable structure, the secondary item  104 —whatever its specific configuration—may facilitate at least one of resection, repositioning, drilling, trimming, and configuration (e.g., positioning) verification of the patient tissue. These and similar properties are referenced collectively herein as providing “reference indication” to the patient tissue. Reference indication may be useful, for example, in physically transferring preoperatively planned virtual dimensions, angles, resection locations, and other physical properties to the actual patient tissue. To aid this effort, a predetermined secondary mounting relationship may be provided to the apparatus  100 . 
     As shown in  FIGS. 2A and 2B , the primary locating block  102  may include one or more mounting features  108 , with the depicted example embodiment including a keyed female-type mounting feature  108 ′ and a keyed male-type mounting feature  108 ″, both of which are configured to removably accept a correspondingly shaped secondary mounting feature  220  in a male-to-female (or female-to-male) mounting relationship. By way of example, the secondary item  104 ′ of  FIG. 2C  is depicted as including a male-type secondary mounting feature  220  configured for mating with the keyed female-type mounting feature  108 ′, and the secondary items  104 ″ and  104 ′″ of  FIGS. 2D and 2E  both are depicted as including a ring-type female-type secondary mounting feature (including a cylindrical feature extending circumferentially around all or part of the mounting feature  108 ″) for mating with the keyed male-type mounting feature  108 ″, though any suitably-structured mounting features  108  may be provided by one of ordinary skill in the art. The “keyed” features, when present, may include cavities  224  and/or protrusions  226  on either or both of the primary locating block  102  and the secondary item  104 , or any other structures which may help to positively locate, and optionally help maintain, the structures of the apparatus  100  in the predetermined secondary mounting relationship. Optionally, a securement aperture  228  could be provided in either or both of the primary locating block  102  and the secondary item  104  to accept a pin, bolt, screw, nail, wire, or other fastener to help maintain the structures of the apparatus  100  in the predetermined secondary mounting relationship. 
     Because at least the primary mating surface  106  portion of the primary locating block  102  is contemplated to be custom-manufactured for each patient, it also may be possible to custom-configure the mounting feature(s)  108  of the primary locating block, as well, to accept a secondary item  104  in a particular patient-specific orientation. For example, the keyed female-type mounting feature  108 ′ and/or the keyed male-type mounting feature  108 ″ could have appropriate configurations, optionally including cavities  224  and/or protrusions  226  having predetermined relationships with the primary mating surface  106  so that any secondary item  104  mated to the mounting feature will extend therefrom at a predetermined angle. Stated differently, though the keyed male-type mounting feature  108 ″ has a cavity  224  at a particular angular relationship with respect thereto, that cavity  224  could be rotated around the circumference of the mounting feature  108 ″ so that the cavity  224  is located in another angular relationship with respect to the mounting feature (e.g., further clockwise or counterclockwise, in the orientation of  FIG. 2B ), which will result in a mated secondary item  104  achieving a desired and potentially patient-specific orientation with the primary mating surface  106  and, by extension, with the patient tissue. 
     One of ordinary skill in the art will understand that the secondary mounting relationship, in which a secondary item  104  is held (usually removably held) by the primary locating block  102  in a predetermined relative position, may be made patient-specific by the arrangement and configuration of the mounting feature  108  which interacts with the secondary item. The secondary mounting relationship also or instead can be made patient-specific by the arrangement and configuration of the secondary mounting feature  220  (of the secondary item  104 ) which interacts with the primary locating block  102  (e.g., the arrangement and configuration of the cavities  224 , protrusions  226 , or any other portion of the secondary mounting feature  220  or any mounting feature  108  of the primary locating block). In this manner, one of ordinary skill in the art will be able to design a patient-specific component of the apparatus  100  (e.g., the primary locating block  102 ) which interacts with one or more stock or non-patient-specific components of the apparatus (e.g., the secondary item(s)  104 ) to provide some degree of patient-specificity in the apparatus as a whole. This patient-specificity of an apparatus  100  for providing a reference indication may be desirable for facilitating a surgical operation and might otherwise be unavailable, prohibitively expensive, and/or undesirably time-consuming to achieve. 
     An example patient tissue use environment for an apparatus  100  according to an embodiment of the present invention is shown in  FIG. 3 . The patient tissue depicted in  FIG. 3  is a long bone, more specifically a humerus  324 , though the apparatus  100  may be used with any suitable patient tissue. The central portion of the humerus  324  is a diaphysis (shown approximately at  326 ), with an epiphysis (shown approximately at  328 ) at either end of the humerus. The below description presumes that the humeral head  330  (the epiphysis  328  on the right side of the page, in the orientation of  FIG. 3 ) is being resected and the intramedullary canal (i.e., the interior of the diaphysis  326 ) is being broached, reamed, and/or drilled out to accept a stem of a humeral prosthetic shoulder joint component, with at least a portion of the surgical procedure being performed with the assistance of the apparatus  100 . The apparatus  100 , shown in various optional configurations in  FIGS. 1 and 4-9 , may be at least partially custom-manufactured for a particular patient responsive to preoperative imaging of the patient tissue. For example, the apparatus  100 , or portions thereof, may be wholly custom-made (e.g., using rapid prototyping techniques) or may be modified from a stock guide or guide blank (not shown). It is contemplated that at least a part of the apparatus  100  is a patient-specific, single-use, bespoke feature suited only for use at the indicated surgical site, though one of ordinary skill in the art could create an apparatus—or components thereof—which uses a patient-specific “disposable” structure connected to a stock, generic “reusable” carrier (e.g., a reusable secondary item  104 ′ could carry a disposable/replaceable positioning indicator  210 ). However, for cost and complexity reasons, users of the apparatus  100  in particular applications of the present invention may prefer to have a patient-specific and disposable primary locating block  102  and an assortment of both reusable and patient-specific/disposable secondary items  104 , and this is the situation that will be presumed in the below description. 
     Regardless of the whole/partial custom manufacture status, the apparatus  100  may be configured responsive to at least one of preoperative imaging of the patient tissue and preoperative selection of the stock prosthetic implant. For example, a system similar to that of co-pending U.S. Provisional Patent Application No. 61/408,392, filed Oct. 29, 2010 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. In this manner, a user can create a patient tissue model for observation, manipulation, rehearsal, or any other preoperative tasks. 
     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. 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 based upon computer tomography (“CT”) data imported into a computer aided drafting (“CAD”) system. Additionally or alternatively, the patient tissue model may be based upon 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 computer or other graphical workstation interface. 
     During preoperative planning, the user can view the patient tissue model and, based upon knowledge of other patient characteristics (such as, but not limited to, height, weight, age, and activity level), choose a desired stock prosthetic implant. Because three-dimensional image models are available of many stock prosthetic implants, the user may be able to “install” the stock prosthetic implant virtually in the patient tissue model via a preoperative computer simulation. During such a simulation, the user can adjust the position of the stock prosthetic implant with respect to the patient tissue, even to the extent of simulating the dynamic interaction between the two, to refine the selection, placement, and orientation of the stock prosthetic implant for a desired patient outcome. 
     Once a chosen stock prosthetic implant has been virtually placed in a desired position and orientation with respect to the patient tissue, it will be understood that some mechanical modification—including, but not limited to, resection, repositioning, drilling, trimming—might need to be made to the native patient tissue to accomplish the desired prosthetic implant placement. The modification information for the particular patient tissue achieved via preoperative imaging and/or computer simulation/modeling may be transferred to a physical aid for the user through the custom manufacture of an apparatus  100 . When the preoperative planning has been finalized, a virtual apparatus  100  may be generated, having particular characteristics chosen with respect to the virtual implant and the virtual patient tissue. The user may then have the opportunity to adjust the virtual implant, if desired, before a physical implant is produced. 
     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 apparatus  100 , or portions thereof, in a legible manner. The apparatus  100  may be made of any suitable material or combination of materials, and may be created using 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 from a suitable material, computer numeric control (“CNC”), other rapid prototyping methods, or any other desired manufacturing process. 
     Regardless of how the components thereof were provided,  FIG. 4  depicts a patient-specific secondary item  104 ′ which has been brought into selective engagement with the primary locating block  102  in a predetermined secondary mounting relationship to form an apparatus  100 , which has been positioned in contact with the humerus  324 . The primary mating surface  106  of the primary locating block  102  has been placed into a predetermined primary mating orientation with a nontarget portion of the humerus  324 —i.e., a portion of the humerus which is relatively constant and unchanging during the use of the apparatus  100 , and the secondary mating surface  212  of the secondary item  104 ′ has been placed into a predetermined secondary mating orientation with a target portion of the humerus. In the example of  FIGS. 4-9 , the nontarget portion of the humerus  324  includes at least a portion of the diaphysis of the humerus, and a target portion of the humerus includes at least a portion of the epiphysis  328  of the humerus. 
     As shown in  FIG. 4 , the secondary item  104 ′ is of the type which includes a positioning indicator  210 , and a secondary mating surface  212  of the positioning indicator mates with a predetermined portion of the humeral head  330  to help confirm the position of the apparatus  100  with respect to the humerus  324 , and optionally to help steady the primary locating block  102  during the initial stages of use of the apparatus in the surgical procedure. (Both of these functions of the secondary item  104 ′ may be considered the provision of a reference indication.) Here, the primary mating surface  106  of the primary locating block  102  has been mated with at least a portion of the bicipital groove (not shown). Once the user is reasonably confident that the primary locating block  102  is in the desired primary mating orientation with respect to the humerus  324 , one or more anchoring pins  432  may interact with respective anchoring structures  222  to substantially secure the primary locating block  102  to the humerus in the aforementioned manner. 
     Turning to  FIG. 5 , the patient-specific secondary item  104 ′ has been left in the secondary mounting relationship with the keyed female-type mounting feature  108 ′ (optionally to steady the apparatus  100  during this phase of surgery), and a stock (non-patient-specific) secondary item  104 ″ has been placed into a secondary mounting relationship with the keyed male-type mounting feature  108 ″ of the primary locating block  102 . A cutting indicator  214  (here, a slot in the secondary item  104 ″) has been placed at a desired cutting plane location for resection of the humeral head  330 . Although the secondary item  104 ″ is a stock component, one of ordinary skill in the art can readily understand, with reference to  FIG. 5 , how arrangement and orientation of the keyed male-type mounting feature  108 ″ of a patient-specific primary locating block  102 —e.g., setting a desired rotation position of the cavity  224  with respect to the rest of the mounting feature  108 ″—will dictate a desired patient-specific secondary mounting relationship sufficient to place even a stock secondary item  104 ″ in a desired relative position to the humeral head  330 . For example, the secondary mounting relationship could be adjusted during preoperative planning to configure a patient-specific primary locating block  102  and thereby place the cutting indicator  214  at a desired angle with respect to the humeral head  330 . 
     As shown, the secondary item  104 ″ includes a cutting indicator  214  which is a slot configured to accept and guide a surgical saw to resect the humeral head  330  as desired. The secondary item  104 ″ also or instead could guide a surgical saw or other cutting instrument along a top guiding surface  534  thereof to perform the desired resection. Because the surgical saw or other cutting instrument is sharp and may move unpredictably due to irregularities in the patient tissue, or due to imprecise use of the tool, it may be desirable for the secondary item  104 ″ containing the cutting indicator  214  to be at least partially made of metal or other material(s) that are durable and generally resistant to being fragmented. The material choice should be selected to avoid shedding of debris from the secondary item  104 ″ into the patient&#39;s tissue due to contact between the tool and the secondary item. A metal (or other durable-material) patient-specific construct may be difficult and/or expensive to fabricate, however. The present invention provides for the use of a stock, non-patient-specific secondary item  104 ″ to be reused for multiple patients because the configuration of the primary locating block  102  and the specifics of the secondary mounting relationship allow patient-customization of the guiding function of the cutting indicator  214  without requiring patient-customization of the secondary item  104 ″ containing that cutting indicator. 
     In  FIG. 6 , the humeral head  324  has been removed along a prescribed cutting plane to leave an osteotomy surface  636 . The secondary items  104 ′ and  104 ″ have been removed from the mounting features  108 ′ and  108 ″, respectively, leaving the primary locating block  102  anchored to the nontarget tissue of the humerus  324  by the anchoring pins  432  interacting with the anchoring structures  222 . 
     Continuing to  FIG. 7 , a patient-specific secondary item  104 ′″ has been placed into a secondary mounting relationship with the mounting feature  108 ″ of the primary locating block  102 , while mounting feature  108 ′ has been left empty. Secondary item  104 ′″ includes an osteotomy plate  738  which extends at a predetermined angle from the locating block  102  when the secondary item  104 ′″ is in the secondary mounting relationship. It is contemplated that this angle will bring the osteotomy plate  738  into substantially full contact with the osteotomy surface  636  of the humerus  324  and therefore serve as a positioning indicator by providing a reference indication that either verifies that the humeral head  330  was resected according to the preoperative plan or guides additional machining operations to correct a resection that did not occur as planned. 
       FIGS. 8 and 9  depict various additional views of the arrangement of  FIG. 7 , though the apparatus  100  remains substantially unchanged from the view of  FIG. 7  to the view of  FIG. 8 . In  FIG. 8 , a top view of the osteotomy surface  636  and overlying osteotomy plate  738  is shown. Optionally, and as depicted here, the osteotomy plate  738  may bear a relationship to the prosthetic shoulder joint component being installed such that the osteotomy plate represents a “footprint” of the prosthetic shoulder joint component. Additionally or alternately, the osteotomy plate  636  can have a perimeter/profile shape chosen by the user (not necessarily based upon a prosthetic component) to act as a template or guide to help impart/transfer any desired shape or borders to the humerus  324  or another remaining patient tissue structure. Whether or not this implant “footprint” relationship is present, portions of the osteotomy surface  636  visible from above and located lateral to the rim  218  of the secondary item  104 ′″ may be undesirable osteophytes  838  and may be removed by the user to smooth the eventual interface between the humerus  324  and the prosthetic shoulder joint component. In this way, the rim  218  acts as a template or cutting indicator  216  to guide the user in resecting or otherwise removing undesirable patient tissue during the surgical procedure. 
     In  FIG. 9 , the osteophytes  838  have been removed, and the orientation of this Figure instead emphasizes the drill guide  216  of the secondary item  104 ′″. The secondary item  104 ′″ includes a drill guide  216  for providing a reference indication to guide drilling, broaching, rasping, or other machining of the diaphysis  326  to accommodate a penetrating portion of the prosthetic shoulder joint component. One or more removable drill guide spacers  940  could be associated, as a group or singly, with the drill guide  216 . (As shown here, the drill guide spacer(s)  940  are nested within the drill guide  216  and may serve as “bushings” to shield contact between the drill guide and the drill or other tool being guided.) Through sequential use of the drill guide spacer(s)  940 , a succession of drilling, broaching, rasping, or other machining operations can be guided to gradually enlarge an aperture in the patient tissue through use of successively larger tools. The drill guide  216  may be patient-specific to guide a drill  1042  or other penetrating implement (shown schematically in  FIG. 10 ) to carry out a preoperatively planned drilling or other penetrating procedure at a predetermined location having a desired relationship to the body of the humerus  324 . Optionally, the drill guide  216  may also include a drill stop (e.g., an upper rim of the drill guide structure) which provides a reference indication or even restricts excessive penetration of the penetrating implement into the intramedullary canal of the diaphysis  326 . 
     When the desired reference indications have all been performed, the apparatus  100  may be removed from the patient tissue and the surgical procedure can then proceed apace. The patient-specific portions of the apparatus  100  are discarded and the stock or non-patient-specific portions of the apparatus  100  are sterilized and returned to inventory for later use with other patients. 
     The secondary mounting relationship shown in the Figures includes a male-to-female frictional fitting interaction between the mounting feature(s)  108  of the primary locating block  102  and the secondary mounting feature(s)  220  of the secondary item(s)  104 . It is contemplated that the frictional fit between these two components be firm enough to retain the secondary item(s)  104  in engagement with the primary locating block  102  until the user exerts a reasonable force to remove the secondary item(s) from the primary locating block. Generally, the user will wish to perform this removal without dislodging the primary mounting surface  106  from the patient tissue. However, one of ordinary skill in the art can readily provide mounting feature(s)  108  of the primary locating block  102  and secondary mounting feature(s)  220  of the secondary item(s)  104  which interact and engage together in any desired manner, and using any desired intermediary fastening means/techniques, such as, but not limited to, adhesives, frictional engagement of any type (e.g., male/female roles reversed from those shown), additional fasteners (e.g., cotter pins), threadable engagement, captured-ball mechanisms, external-collar mechanisms, magnets, securement aperture(s)  228 , any other suitable mounting feature types, or any combination thereof. 
     Additionally, one of ordinary skill in the art could also provide symmetrical or otherwise non-directional/non-patient-specific mounting feature(s)  108  of the primary locating block  102  and/or secondary mounting feature(s)  220  of the secondary item(s)  104  which can fit together in many different secondary mounting relationships. In order to make such an arrangement patient-specific, the mounting feature(s)  108  of the primary locating block  102  and/or secondary mounting feature(s)  220  of the secondary item(s)  104  could include visual indicators (e.g., a radial/degree scale on one or both of the mating mounting features  108  and  220 ) to assist the user with achieving a desired predetermined relative position between the primary locating block and the secondary item when in the secondary mounting relationship. 
       FIG. 11  depicts an apparatus  100  according to a second embodiment of the present invention. The apparatus  100  of  FIG. 11  is similar to the apparatus  100  of  FIGS. 1-9  and therefore, structures of  FIG. 11  that are the same as or similar to those described with reference to  FIGS. 1-9  have the same reference numbers with the addition of a lower-case “a”. Description of common elements and operation similar to those in the previously described embodiment will not be repeated with respect to the second embodiment. 
     As shown in  FIG. 11 , the primary locating block  102   a  may include one or more mounting features  108   a , with the depicted example embodiment including a quarter-round mounting feature  108 ′ a  and an ell-shaped mounting feature  108 ″ a , both of which are configured to removably accept a correspondingly shaped secondary mounting feature  220   a  in a male-to-female mounting relationship. The secondary items  104   a  of  FIG. 11  includes a quarter-round secondary mounting feature  220   a  for mating with the quarter-round mounting feature  108 ′ a , and another secondary item (not shown) for use with the second embodiment of  FIG. 11  might include an ell-shaped secondary mounting feature for mating with the ell-shaped mounting feature  108 ″ a . Because at least the primary mating surface  106   a  portion of the primary locating block  102   a  is contemplated to be custom-manufactured for each patient, it also may be possible to custom-configure the mounting feature(s)  108   a  of the primary locating block, as well, to accept a secondary item  104   a  in a particular patient-specific orientation. For example, the quarter-round mounting feature  108 ′ a  and/or the ell-shaped mounting feature  108 ″ a  could be placed into a particular angular relationship with the primary mating surface  106   a  so that any secondary item  104   a  mated to the mounting feature will extend therefrom at a predetermined angle. Stated differently, though the ell-shaped mounting feature  108 ″ a  has a vertex pointing toward the right in the orientation of  FIG. 11 , that ell shape could be rotated so that the vertex points in any other desired direction (e.g., up, down, to the left, etc.) which will result in a mated secondary item  104   a  achieving a desired orientation with the primary mating surface  106   a  and, by extension, with the patient tissue. 
     One of ordinary skill in the art can readily understand, with reference to  FIG. 11 , how arrangement and orientation of the quarter-round mounting feature  108 ′ a  and/or the ell-shaped mounting feature  108 ″ a —e.g., setting a desired rotation position of the quarter-round or ell-shape with respect to the rest of the primary locating block  102   a —will dictate a desired patient-specific secondary mounting relationship sufficient to place the secondary item  104   a  in a desired relative position to the humeral head  330   a . For example, the secondary mounting relationship could be adjusted during preoperative planning to place a cutting indicator (not shown) at a desired angle with respect to the humeral head. 
     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, 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. It is contemplated that at least one of the primary locating block  102  and secondary item(s)  104  may be reusable (optionally sterilizable), and at least one of the primary locating block and secondary item(s) may be disposable. 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. A variety of schemes are described herein for placing the apparatus  100  into the predetermined position with respect to the patient tissue, and these schemes can be used singly or in any suitable combination for a particular application 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. The apparatus  100 , or portions thereof, could be anchored to the patient tissue in any suitable manner, such as, but not limited to, adhesives, integral pegs, other fasteners, frictional engagement, magnets, securement aperture(s)  228 , any other suitable mounting feature types, or any combination thereof. 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.