FOR IMPLANT REVISION SURGERY

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] The present application claims the priority of United States Patent Application No. 62/189,941, filed on July 8, 2015, which is incorporated by reference in its entirety.

FIELD OF THE INVENTION

[002] The present disclosure pertains to patient specific instrumentation (PSI) used in orthopedic surgery and, more particularly, to PSI used for implant revision.

BACKGROUND OF THE INVENTION

[003] An implant revision surgery is a process by which an existing implant is removed to be replaced by a new implant. However, due to the bond between the implant to be removed and the bone, the bone is often damaged during implant removal. As a result, the subsequent positioning and installation of a replacement implant may lack precision due to damaged bone surfaces. For instance, in knee revision surgery, machining of the bone surfaces using conventional cutting blocks may lack precision as conventional bone landmarks used for defining the orientation of the cutting block may be altered or removed during the removal of the implant .

[004] Patient specific instrumentation (hereinafter "PSI") pertains to the creation of instruments that are made specifically for the patient. PSI are typically manufactured from data using imaging to model bone geometry. Therefore, PSI have surfaces that may contact the bone in a predictable way as such contact surfaces are specifically manufactured to match the surface of a bone of a given patient. It would therefore be desirable to use PSI technology in an implant revision process.

SUMMARY OF THE DI SCLOSURE

[005] It is an aim of the present disclosure to provide a method for creating a PSI jig for implant revision surgery.

[006] It is a further aim of the present disclosure to provide a system for creating a PSI implant revision jig model .

[007] Therefore, in accordance with a first embodiment of the present disclosure, there is provided a method for creating at least one model of a patient-specific instrumentation jig for implant revision using a processing system, comprising: obtaining at least one image of at least part of a bone requiring implant revision and of an implanted implant on the bone, the at least one image being patient specific; identifying at least one reference anchor surface on the bone from the at least one image of the bone, the reference anchor surface configured to receive at least one guide reference; determining an implant abutment surface on the implanted implant; and generating and outputting a virtual reference jig model using at least the identified reference anchor surface and the determined implant abutment surface, the reference jig model comprising at least one contact surface corresponding to the determined implant abutment surface for complementary connection with the determined implant abutment surface, at least one guide interfacing portion configured to guide a planting of the at least one guide reference in the reference anchor surface, and a patient-specific geometry between the at least one contact surface and the at least one guide interfacing portion, to the patient-specific geometry adapted to position and/or orient the at least one guide interfacing portion relative to the at least one reference anchor surface, during the planting of the at least one guide reference in the at least one reference anchor surface, when the at least one contact surface is complementarily connected with the determined implant abutment surface.

[008] Further in accordance with the first embodiment, a revision jig model is in some instances generated using at least the position and orientation of the at least one guide reference and a virtual model of a replacement implant, the jig model comprising at least one guide interfacing portion configured to engage the at least one guide reference, at least one tool interface portion positioned and/or oriented relative to the guide reference and at least one patient- specific geometry between the at least one guide interfacing portion of the jig model and the at least one tool interface portion, the at least one tool interface portion adapted to be interfaced with a tool altering the bone to perform cuts for subsequently installing the replacement implant. [009] Still further in accordance with the first embodiment, generating the revision jig model comprises in some instances creating a bone contact surface configured to contact the reference anchor surface.

[0010] Still further in accordance with the first embodiment, generating and outputting the reference jig model comprises in some instances using a virtual model of a replacement implant, a planned position of the replacement implant, and a virtual model of a stock revision jig to create the patient-specific geometry of the reference jig model. [0011] Still further in accordance with the first embodiment, obtaining the at least one image comprises in some instances obtaining radiographic images only.

[0012] Still further in accordance with the first embodiment, generating the reference jig model comprises in some instances obtaining a virtual 3D model of the implanted implant for creating the at least one contact surface.

[0013] Still further in accordance with the first embodiment, creating the at least one contact surface comprises in some instances creating a negative surface of a portion of the implant abutment surface.

[0014] Still further in accordance with the first embodiment, the at least one guide reference is in some instances a pair of guide pins, and wherein generating the reference jig model comprises in some instances defining pin guides in the at least one guide interfacing portion.

[0015] Still further in accordance with the first embodiment, identifying the at least one reference anchor surface on the bone comprises in some instances identifying one of the medial epiphyseal bone and the anterior cortex from a femur. [0016] Still further in accordance with the first embodiment, identifying the at least one reference anchor surface on the bone comprises in some instances identifying one of the medial aspect, the lateral aspect and the superior tubercle from a tibia.

[0017] Still further in accordance with the first embodiment, generating and outputting a virtual reference jig model comprises in some instances generating and outputting at least one of an additive printing instructions model and a numerical control machining instructions model .

[0018] Still further in accordance with the first embodiment, the at least one patient-specific instrumentation jig is in some instances fabricated.

[0019] In accordance with a second embodiment of the present disclosure, there is provided a system for generating at least one patient specific instrumentation jig model for implant revision, comprising: a reference anchor surface identifying module configured to identify at least one reference anchor surface from at least one patient specific image of at least one portion of a bone and of an implanted implant, the reference anchor surface configured to receive at least one guide reference; an implant abutment surface determining module configured to determine at least one implant abutment surface from the patient specific bone image; and a PSI reference jig model generator module configured to generate and output a reference jig model using at least the identified reference anchor surface and the determined implant abutment surface, the reference jig model comprising at least one contact surface corresponding to the determined implant abutment surface for complementary connection with the determined implant abutment surface, at least one guide interfacing portion configured to guide a planting of the at least one guide reference in the reference anchor surface, and a patient-specific geometry between the at least one contact surface and the at least one guide interfacing portion, the patient-specific geometry adapted to position and/or orient the at least one guide interfacing portion relative to the at least one reference anchor surface, for during the planting of the at least one guide reference in the at least one reference anchor surface, when the at least one contact surface is complementarily connected with the determined implant abutment surface .

[0020] Further in accordance with the second embodiment, a PSI revision jig model generator module generates in some instances a revision jig model using at least the position and orientation of the at least one guide reference and a virtual model of a replacement implant, the jig model comprising in some instances at least one guide interfacing portion configured to engage the at least one guide reference, at least one tool interface portion positioned and/or oriented relative to the guide reference and at least one patient-specific geometry between the at least one guide interfacing portion of the jig model and the at least one tool interface portion, the at least one tool interface portion adapted to be interfaced with a tool altering the bone to perform cuts for subsequently installing the replacement implant .

[0021] Still further in accordance with the second embodiment, the PSI revision jig model generator module creates in some instances a contact surface for contact with the reference anchor surface . [0022] Still further in accordance with the second embodiment, the PSI reference jig model generator module configured to use in some instances a virtual model of a replacement implant, a planned position of the replacement implant, and a virtual model of a stock revision jig to create the patient-specific geometry of the reference jig model.

[0023] Still further in accordance with the second embodiment, the at least one patient specific image comprises in some instances radiographic images only. [0024] Still further in accordance with the second embodiment, the PSI reference jig model generator module is configured to obtain in some instances a virtual 3D model of the implanted implant to create the at least one contact surface . [0025] Still further in accordance with the second embodiment, the PSI reference jig model generator module is configured to create in some instances the at least one contact surface by creating a negative surface of a portion of the implant abutment surface . [0026] Still further in accordance with the second embodiment, the at least one guide reference in some instances comprises a pair of guide pins, and the PSI reference jig model generator module is configured to define pin guides in the at least one guide interfacing portion. [0027] Still further in accordance with the second embodiment, the reference anchor surface identifying module is configured to identify in some instances the at least one reference anchor surface on the bone by identifying one of the medial epiphyseal bone and the anterior cortex from a femur .

[0028] Still further in accordance with the second embodiment, the reference anchor surface identifying module is configured to identify in some instances the at least one reference anchor surface on the bone by identifying one of the medial aspect, the lateral aspect and the superior tubercle from a tibia.

[0029] Still further in accordance with the second embodiment, the system is configured to generate and output in some instances at least one of an additive printing instructions model and a numerical control machining instructions model .

[0030] The feature or features of one embodiment may be applied to other embodiments, even though not described or illustrated, unless expressly prohibited by this disclosure or the nature of the embodiments.

[0031] Some details associated with the present embodiments are described above and others are described below.

BRIEF DESCRIPTION OF THE FIGURES

[0032] Fig. 1 is a flow chart showing a method for creating a PSI jig for implant revision in accordance with an embodiment of the present disclosure;

[0033] Fig. 2 is a block diagram showing a system for creating a PSI implant revision jig model in accordance with another embodiment of the present disclosure;

[0034] Fig. 3 is a perspective view of a tibia with a PSI reference jig thereon, to plant guide landmarks; [0035] Fig. 4 is a perspective view of the tibia of Fig. 3, with a PSI revision jig on the guide landmarks;

[0036] Fig. 5 is a perspective view of the tibia of Fig. 4, with an implant after revision; [0037] Fig. 6 is a perspective view of a femur with a PSI reference jig thereon, to plant guide landmarks;

[0038] Fig. 7 is a perspective view of the femur of Fig. 6, with a PSI revision jig on the guide landmarks; and

[0039] Fig. 8 is a perspective view of the femur of Fig. 7, with an implant after revision.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Referring to the drawings, and more particularly to Fig. 1, there is illustrated a method 10 for creating patient specific instrumentation (hereinafter PSI) jig for implant revision. For clarity, reference to patient specific in the present application pertains to the creation of negative corresponding surfaces, i.e., a surface that is the negative opposite of a patient bone/cartilage surface or implant, such that the patient specific surface conforms to the patient bone/cartilage surface, by complementary confirming contact. An instrument may also be patient specific in that it is used to plant guide references in a patient's bone, at a specific pre-planned location based on the patient's specific anatomy - the geometry of the instrument is specific and unique to the patient. The method is particularly suited to be used in knee revision in which the tibial knee implant, the femoral knee implant or both implants need to be replaced. The method may also be used in other orthopedic implant revision surgery, for instance in shoulder revision surgery.

[0041] According to 12, the bone and its implant are modeled. The models may be obtained and/or generated using imaging. The imaging may be done by any appropriate technology such as CT scanning (computerized tomography) , fluoroscopy, or like radiography methods, providing suitable resolution of images. The model of the bone comprises a surface geometry of parts of the bone that are exposed despite the presence of the implant and/or the limitations of the imaging. The model of the bone may include a surface geometry of the implant relative to adjacent bone surfaces, and a 3D geometry of the implant, for instance using a 3D model of implant (e.g., from the manufacturer, etc) . In particular, a combination of radiography and magnetic resonance imagery (MRI) may provide a suitable resolution between implant, bone and cartilage, useful to recognize the boundaries of the implant relative to the bone. The images of the implant may be confirmed, or the model improved using the manufacturer's model of the existing implant. In an embodiment, the method is performed using exclusively radiographic images of the bone and implant. As described hereinafter, PSI jigs will abut directly against the implants being replaced, to position reference landmarks in the bone, whereby radiographic images may provide, on their own, suitable resolution to create the PSI jigs. The radiographic images may also assist in performing a surface matching operation to merge the manufacturer's 3D virtual model of the implant with the bone imaging, if desired. [0042] The bone modeling may comprise generating a 3D surface of the bone if the bone modeling is not directly performed by the imaging equipment, or if not complete. In the instance in which multiple implants must be replaced (e.g., total knee revision) , all bones supporting implants are modeled. Additional structures may be modeled as well, such as cartilage, etc.

[0043] The model of the bone and implanted implant provides data that may be used by an operator, such as a surgeon, to plan revision surgery. In terms of planning, the operator may select the position and orientation of a 3D model of a replacement implant (i.e., a new implant) that will be used in revision surgery by looking at the model and/or may determine locations for cut planes to support the replacement implant. Factors that may come into consideration include orientation in frontal, sagittal and axial plane, native joint line, implanted implant joint line, bone damage, among other factors. Moreover, additional data such as a pre-operative kinematic analysis of the joint, and soft tissue tension, may be part of the data that may be available for the planning of the revision surgery, and may assist in determining a revised implant position and orientation.

[0044] According to 13, reference anchor surfaces are identified on the bone from the model (s) of 12. The reference anchor surfaces are selected as being sufficiently solid to support references such as pins or screws, and as not being altered by the removal of the used implant from the bone. For example, in the case of femoral knee revision, the reference anchor surfaces may be the medial epiphyseal bone and the anterior cortex. The epicondyles may be used to restore the joint line to set the axial position of the replacement implant. Other parts of the femur may also be used as reference anchor surfaces.

[0045] As another example, in the case of tibial knee implant replacement, the reference anchor surfaces may be that of the medial and lateral aspects as well as the superior tubercle portion of the tibia. In this case, the medial and lateral aspects may be used to restore the joint line by setting the axial position of the replacement implant. Other parts of the tibia may also be used as anchor surfaces. Similar considerations are taken into account in the case of shoulder surgery. In both cases, the anchor surfaces are in close proximity to the implanted implant (the implant already present, but to be removed in the revision process, also referred to as used implant or removed implant) as it is in the vicinity of the removed implant that bone alterations will be performed. Although the reference anchor surface (s) is in close proximity to the removed implant, the anchor surface will not substantially be damaged by the removal of the used implant . [0046] In another embodiment, other factors influencing the selection of the reference anchor surface (s) are the planned location of the replacement implant, of the cut planes, and the geometry of stock/generic cutting blocks.

[0047] According to 14, an abutment surface on the implanted implant is determined, for subsequent support of a PSI reference jig that is used to plant the guide references. As the implanted implant has a known geometry - via the manufacturer's model and the modeling of 12 -, the implanted implant is an available support for a PSI instrument before it is removed. The implanted implant not only has a known geometry, but also forms the joint surface of the articulation, whereby it may be a strategic PSI instrument support to ensure accuracy in reference placement .

[0048] The determination of the implant abutment surface takes into account the location of the guide reference (s) , the implant abutment surface being for instance in relatively close proximity to the reference anchor surfaces. Other factors taken into consideration in the determination include any wear on the surface of implant, which worn implant surface may be avoided to use instead unaltered parts of the implant, which unaltered parts would match the manufacturer's model of the implant. A negative-contour matching surface could hence be based directly on the manufacturer's model, for being applied against the implanted implant .

[0049] According to 15, using the reference anchor surface (s) identified in 13, and the implant abutment surface (s) determined in 14, a PSI reference jig model is generated. The jig model will have a contact surface (s) defined to abut against the implant abutment surface (s) obtained in 14, in a predictable and precise manner. Moreover, the PSI reference jig model may have guiding features (e.g., guide holes) to guide an operator in anchoring the guide references in the bone, such that the guide references are at the planned position and orientation.

[0050] In an embodiment, the PSI reference jig model is generated to enable the subsequent use of stock cutting jigs. In such a case, the PSI reference jig model is devised taking into consideration the geometry of the planned location of the replacement implant, of the cut planes, and the geometry of stock/generic cutting blocks. The PSI reference jig model may be in any appropriate format, such as an additive printing execution file or model, a numerical control machining file, etc. [0051] According to 16, using the position and orientation of the guide references, the geometry of the replacement implant that is known (i.e., obtained from a database, from the manufacturer, generated as a PSI implant, etc), and possibly the reference anchor surfaces as obtained from the bone model (s), a PSI revision jig model may be generated, as an alternative to using a stock/generic cutting jig. The jig model will have a guide interfacing portion adapted to be connected to the guide landmarks. The jig model may also have a contact surface (s) defined to abut against the reference anchor surface (s) obtained in 13, in a predictable and precise manner, with this contact surface not necessarily but possibly being a negative contour surface. Typically, the PSI revision jig is a cutting block or cutting guide that will allow planes to be cut upon which will be anchored the implant. The PSI revision jig model of 16 therefore comprises cutting planes, guides, slots, or any other tooling interface or tool, oriented and/or positioned to allow bone alterations to be formed in a desired location of the bone, relative to the contact surface (s) . Thus, PSI revision jig model may also take into consideration any revision planning done by the operator (e.g., surgeon), to therefore allow the removal of sufficient bone material to reproduce desired gaps between cut planes on adjacent bones, etc. The PSI revision jig model may be in any appropriate format, such as an additive printing execution file or model, a numerical control machining file, etc. [0052] According to 17, once the PSI reference jig model has been generated, the PSI reference jig may be created, with numerical control machining, additive printing, a combination thereof and/or any other suitable method. When installing the PSI reference jig on the implanted implant bone, the contact surface (s) on the PSI jig is (are) applied against the corresponding implant abutment surface (s) of 14, with a unique complementary match that will ensure that the planned positioning is reached. The operator can then use the PSI reference jig to position the guide reference (s) in the reference anchor surface (s) as planned.

[0053] According to 18, once the PSI revision jig model has been generated, the PSI revision jig may be created, if such a PSI jig is used instead of a stock cutting jig. If the PSI revision jig is created, it may be done by numerical control machining, additive printing, a combination thereof and/or any other suitable method. When installing the PSI revision jig on the bone, the jig will be mounted onto the guide references (e.g., pins, screws) , and therefore has another guide interfacing portion. It may also be desired that a contact surface (s) on the PSI revision jig is (are) applied against the anchor surface (s) of 13. The PSI jig created in 18 may then be used intra-operatively after the implant is removed to allow alterations to be made on the bone. For instance, in the case of total knee revision, jigs are used to perform femoral distal and tibial cuts.

[0054] While a specific order has been provided above, other orders are considered as well. For instance, it is contemplated to determine the abutment surface before identifying the reference anchor surfaces. Other step inversions are contemplated as well, for instance if a stock (i.e., non PSI) cutting jig is used.

[0055] Now that a method for creating a PSI reference jig and a PSI revision jig for implant replacement has been defined, a system is set forth.

[0056] A system for the creation of PSI jig models is generally shown at 20 in Fig. 2. The system 20 may comprise an imaging unit 30, such as a CT scan or an X-ray machine, so as to obtain images of the bone and implant . As an alternative, images may be obtained from an image source 31. As an example, a CT scan may be operated remotely from the system 20, whereby the system 20 may simply obtain images and/or processed bone and implant models from the image source 31. [0057] The system 20 comprises a processor unit 40 (e.g., computer, laptop, etc.) that comprises different modules so as to ultimately produce a jig model (s) . The processing unit 40 of the system 20 may therefore comprise a bone/implant model generator 41 receiving images from sources 30 or 31 to generate a 3D model of the bone with the implant, prior to implant revision. In accordance with the method 10 of Fig. 1, the 3D model of the bone with implant may comprise data pertaining to the surface geometry of a relevant portion of a bone and of the implant, including surfaces of the bone that are exposed despite the presence of the implant .

[0058] The bone/implant model generator 41 will create the 3D model of the bone and implant that is then used by a reference anchor surface identifying module 42A and an implant abutment surface determining module 42B of the processing unit 40. Alternatively, the modules 42A and 42B may use a 3D model provided by the image source 31, provided the model obtained from the image source 31 comprises sufficient data. The virtual 3D model of the bone and implant may be generated using the manufacturer's model of the implant, whether it be via the image source 31 or via the bone/ implant model generator 41.

[0059] The reference anchor surface identifier 42A identifies surfaces on the bone that may substantially not be altered by the removal of the damaged implant . The reference anchor surface (s) is (are) selected as being sufficiently solid to serve as support for guide landmarks such as pins of screws, and as not obstructing the removal of the implant. For example, reference is made to step 13, in which examples are provided for appropriate reference anchor surfaces on the femur and the tibia in the case of total knee replacement. The reference anchor surface identifier 42A may identify the reference anchor surface using planned cut planes and/or planned replacement implant geometry and position and orientation, as well as stock cutting jig geometry.

[0060] The implant abutment surface determining module 42B identifies abutment surfaces on the implant that will serve as support for a PSI reference jig, to plant the guide landmarks in the bone surfaces identified by the reference anchor surface identifier 42A. For example, reference is made to step 14, in which examples are provided for appropriate implant abutment surfaces . The implant abutment surface determining module 42B may provide target implant abutment surface (s) for the operator to participate in the selection. [0061] Once the reference anchor surface (s) is (are) identified and the implant abutment surface are determined, a PSI revision jig model generator module 43A may generate a revision jig model (unless a stock cutting jig is used), whereas a PSI reference jig model generator module 43B will generate a reference jig model. As in 16 and 17 of the method 10, the reference jig model will have a contact surface (s) defined to abut against the implant determined by the module 42B, in a predictable and precise manner, for the planting of guide references. The revision jig model will have a guide interfacing portion to be mounted to the guide references, and may also be devised to contact the reference anchor surface. As the PSI revision jig will support a tool to perform alterations on the bone, the jig model comprises cutting planes, guides, slots, or any other tooling interface or tool, trackers, oriented and/or positioned to allow bone alterations to be formed in a desired location of the bone, relative to the contact surface (s) .

[0062] Thus, jig model generator modules 43A and 43B may also take into consideration any revision planning done by the operator (e.g., surgeon) . The jig model generator modules 43A and 43B may also take into consideration a geometry of the existing damaged implant, the replacement implant (e.g., obtained from an implant database 44), in addition to the anchor surface (s) .

[0063] Accordingly, the system 20 outputs PSI jig model (s) 50 that will be used to create the PSI reference jig and optionally the PSI revision jig. The PSI reference jig serves to place the guide references while the PSI revision jig, or alternatively a stock cutting jig, is then used intra-operatively to resurface bone for subsequent implant installation, based on the positioning and path of the guide references, as described for method 10 in Fig. 1.

[0064] Exemplary embodiments are now provided, with a tibial application and a femoral application, among numerous other possibilities.

[0065] Referring concurrently to Figs. 3-5, a knee portion of a tibia is generally shown at 60, with an implanted implant 61, to be revised. A PSI reference jig 62 has a body 63 having a geometry specific to the patient, to space in a given position and orientation a PSI contact surface 64 from a guide interfacing portion 65 as planned. Hence, the guide references, shown as pins 66, are planted in the reference anchor surface, shown in the embodiment as the posterior face of the tibia 60. The PSI contact surface 64 of the jig 62 abuts against a tibial plateau portion of the implant 61 in a unique complementary manner, and may also have PSI contact surfaces for abutment with the tibia 60, as observed .

[0066] Once the guide reference pins 66 are planted at Fig. 3, the PSI reference jig 62 may be removed, leaving the pins 66 positioned and oriented as planned. As shown in Fig. 4, the implanted implant 61 may be removed, and the PSI revision jig or stock cutting jig 67 may be slid onto the pins 66. The jig 67 is shown as a cutting block, defining cut slots or planes to remove parts of the tibia 60. The jig 67 may be patient specific by having a geometry to its body defined as a function of the patient's anatomy, for the cut slots or planes to be located based on the position of guide interfacing portion 68 (e.g., pin slots) . Alternatively, the jig 67 may be a stock jig, the PSI reference jig 62 being configured to place the pins 66 in a given position for the jig 67 to be available from stock.

[0067] Referring to Fig. 5, once the cuts have been made using the jig 67, the pins 66 and the jig 67 may be removed, and a revised implant 69 may be installed.

[0068] Referring concurrently to Figs. 6-8, a femur is generally shown at 70, at the knee joint, with an implanted implant 71, to be revised. A PSI reference jig 72 has a body 73 having a geometry specific to the patient, to position and orient a PSI contact surface 74 relative to a guide interfacing portion 75 based on pre-operative planning. Hence, the guide references, shown as pins 76, are planted in the reference anchor surface, shown in the embodiment as the anterior face of the femur 70. The PSI contact surface 74 of the jig 72 abuts against a distal end of the implant 71, and may also have PSI contact surfaces for abutment with the femur 70, as observed.

[0069] Once the guide reference pins 76 are planted at Fig. 6, the PSI reference jig 72 may be removed, leaving the pins 76 positioned and oriented as planned. As shown in Fig. 7, the implanted implant 71 may be removed, and the PSI revision jig or stock cutting jig 77 may be slid onto the pins 76. The jig 77 is shown as a cutting block, defining cut slots or planes to remove parts of the femur 70. The jig 77 may be patient specific by having the geometry of its body defined as a function of the patient's anatomy, for the cut slots or planes to be located based on the position of guide interfacing portion 78, with abutment against the femur 70 if desired. [0070] Referring to Fig. 8, once the cuts have been made using the jig 77, the pins 76 and the jig 77 may be removed, and a revised implant 79 may be installed.

[0071] It is considered to use the reference guides as guides for a robotic arm to cut the planes on the bone. In such a case, no revision jig model would be required. Instead, a navigation file could be provided for a robotic system to perform surgery based on the placement on the reference guides .

[0072] While the methods and systems described above have been described and shown with reference to particular steps performed in a particular order, these steps may be combined, subdivided or reordered to form an equivalent method without departing from the teachings of the present disclosure. Accordingly, the order and grouping of the steps is not a limitation of the present disclosure.