Femoral Baseplate Total Hip Replacement

Abstract

The present invention relates to a femoral baseplate total hip replacement. A method for making mass-customized femoral bone baseplates comprises: (i) establishing anatomical landmarks on multiple bone models of a statistical atlas; (ii) establishing instrument landmarks on multiple bone models of a statistical atlas; (iii) establishing limits for reference plane calculation on multiple bone models of a statistical atlas, wherein the reference plane represents the boundary of a prosthetic implant; (iv) establishing attachment sites for the mass-customized femoral bone baseplate using anatomical landmarks, instrument landmarks and reference planes; and (v) manufacturing the mass-customized femoral bone baseplates constructed to be attached to a femur, wherein the attachment sites of the mass-customized femoral bone baseplates are predetermined to avoid collision with the prosthetic implant during implantation.

Description

[0001] This application is a divisional application of invention patent application No. 201680080353.4, which entered the Chinese national phase and whose application date is December 15, 2016 and whose invention name is “Femoral Baseplate Total Hip Replacement”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 267,370, filed December 15, 2015, entitled “FEMORALBASE PLATE THA,” the disclosure of which is incorporated herein by reference.

[0004] Technical Field and Background Art

[0005] The present disclosure relates to optimizing the shape, arrangement and screw attachment location of a femoral baseplate that can be used with a posterior approach for total hip arthroplasty using a surgical navigation system that includes an inertial measurement unit. As will be discussed in more detail below, the shape of the femoral baseplate is taken from the average surface curvature of a statistical map of the femur at a defined baseplate attachment site. The baseplate attachment site can be dependent on screw length and location so that, when properly placed, the attachment screw does not strike the intended rasp and rod components.

[0006] It should be noted that Patent Cooperation Treaty Application No. PCT / US14 / 69411 filed on December 9, 2014 is incorporated herein by reference. Portions of the above application are attached hereto as Appendix A. Summary of the invention

[0007] A first aspect of the present invention is to provide a method for making mass-customized femoral bone baseplates, comprising: (i) establishing anatomical landmarks on multiple bone models of a statistical atlas; (ii) establishing instrument landmarks on multiple bone models of a statistical atlas; (iii) establishing definitions for reference plane calculation on multiple bone models of a statistical atlas, wherein the reference plane represents the boundary of a prosthetic implant; (iv) using the anatomical landmarks, instrument landmarks and reference planes to establish attachment sites for the mass-customized femoral bone baseplates; and (v) manufacturing the mass-customized femoral bone baseplates constructed to be attached to the femur, wherein the attachment sites of the mass-customized femoral bone baseplates are predetermined to avoid collision with the prosthetic implant during implantation.

[0008] In a more detailed embodiment of the first aspect, establishing anatomical landmarks includes: for each of the multiple bone models of the statistical atlas, calculating the tip of the lesser trochanter point of the femur. In yet another more detailed embodiment, establishing anatomical landmarks includes: for each of the multiple bone models of the statistical atlas, calculating a plane tangent to the femoral shaft and marking the edge of the lesser trochanter. In a further embodiment, establishing anatomical landmarks includes: for each of the multiple bone models of the statistical atlas, calculating the overall anatomical axis of the femur. In yet another more detailed embodiment, establishing anatomical landmarks includes: for each of the multiple bone models of the statistical atlas, calculating the projection of the lesser trochanter point on the overall anatomical axis of the femur. In a more detailed embodiment, establishing anatomical landmarks includes: for each of the multiple bone models of the statistical atlas, calculating the projection of the lesser trochanter point on the plane marking the edge of the lesser trochanter. In a more detailed embodiment, establishing anatomical landmarks includes: for each of the multiple bone models of the statistical atlas, calculating the projection of the lesser trochanter point on the plane marking the edge of the lesser trochanter. In a more detailed embodiment, establishing anatomical landmarks includes: for each of the multiple bone models of the statistical atlas, calculating the inside-out direction, the inside-out direction being the vector between the projection of the lesser trochanter point on the overall anatomical axis of the femur and the lesser trochanter point of the femur. In another more detailed embodiment, establishing anatomical landmarks includes: calculating the anterior-posterior direction for each of the multiple skeletal models of the statistical atlas, wherein the anterior-posterior direction is the cross product of the overall anatomical axis of the femur and the medial-lateral direction. In yet another more detailed embodiment, establishing anatomical landmarks includes: calculating the up-down direction for each of the multiple skeletal models of the statistical atlas, wherein the up-down direction is the direction of the overall anatomical axis of the femur. In yet another more detailed embodiment, establishing instrumental landmarks includes: calculating the offset lesser trochanter point for each of the multiple skeletal models of the statistical atlas, wherein the offset lesser trochanter point is the projection of the lesser trochanter point on the plane marking the edge of the lesser trochanter offset by 1 mm in the medial-lateral direction.

[0009] In yet another more detailed embodiment of the first aspect, establishing an instrument landmark includes: for each of the multiple bone models of the statistical atlas, calculating the position of the fasteners for the mass-customized femoral bone baseplate, the position being the intersection of the lines pointing to and passing through the offset lesser trochanter point in the anterior-posterior direction. In yet another more detailed embodiment, establishing an instrument marker includes: for each of the multiple bone models of the statistical atlas, calculating the midpoint between two fasteners for the mass-customized femoral bone baseplate to establish a position where the third fastener is offset between zero millimeters and ten millimeters in the lateral and lateral directions. In a further detailed embodiment, establishing an instrument landmark includes: for each of the multiple bone models of the statistical atlas, calculating the position of the fasteners for the mass-customized femoral bone baseplate, the position being the closest point on the femoral bone model to the offset lesser trochanter point. In yet another more detailed embodiment, establishing an instrument landmark includes: for each of the multiple bone models of the statistical atlas, calculating the position of the fasteners for the mass-customized femoral bone baseplate, the position being offset distally in the direction of the anatomical axis. In a more detailed embodiment, establishing an instrument landmark includes: calculating a femoral plate plane for each of the multiple bone models of the statistical atlas, the femoral plate plane being a plane containing the position of at least one fastener of the mass-customized femoral bone baseplate. In a more detailed embodiment, establishing an instrument landmark includes: calculating the direction of the fastener of the mass-customized femoral bone baseplate for each of the multiple bone models of the statistical atlas. In another more detailed embodiment, the direction is perpendicular to the femoral plate plane. In yet another more detailed embodiment, the femoral plate plane is rotated inwardly between ten and thirty degrees around an axis connecting the positions of the multiple fasteners of the mass-customized femoral bone baseplate. In yet another more detailed embodiment, establishing a definition includes: defining a reference plane for each of the multiple bone models of the statistical atlas, the reference plane being perpendicular to the proximal anatomical axis and the neck axis and passing through the anatomical axis point.

[0010] In a more detailed embodiment of the first aspect, establishing a definition includes: calculating a reference plane for each of the multiple bone models of the statistical atlas, the reference plane being a plane rotated between zero and ten degrees and translated between zero millimeters and 15 millimeters. In yet another more detailed embodiment, establishing a definition includes: calculating the distance between the ends of each of the multiple fasteners for the mass-customized femoral bone baseplate. In a further detailed embodiment, the method also includes: for each of the multiple bone models of the statistical atlas, indicating that any fastener of the multiple fasteners that passes through the reference plane is identified as having a collision. In yet another more detailed embodiment, the bone contact surface of the mass-customized femoral bone baseplate is constructed to approximate the shape of the femur at the expected attachment site on the femur. In a more detailed embodiment, the mass-customized femoral bone baseplate includes a plurality of orifices, the size of the orifices being determined to receive corresponding fasteners. In a more detailed embodiment, the mass-customized femoral bone baseplate includes a plurality of orifices, the size of the orifices being determined to receive corresponding pins. In another more detailed embodiment, the mass-customized femoral bone baseplate includes a plurality of pins.

[0011] In a more detailed embodiment of the first aspect, at least one of the plurality of apertures is threaded. In yet another more detailed embodiment, at least one of the plurality of apertures is angled to establish a predetermined angled path for at least one of the corresponding fasteners.

[0012] A second aspect of the present invention is to provide a femoral bone baseplate assembly comprising: a plate having a bone contact surface, the bone contact surface being configured to approximate the external morphology of a femur, the plate comprising a first plurality of holes, the first plurality of holes being angled relative to the bone contact surface and being configured to orient corresponding fasteners in a predetermined angled orientation, the plate comprising a second plurality of holes, at least one hole in the second plurality of holes being threaded, wherein each of the holes extends through the bone contact surface and through a top surface opposite the bone contact surface.

[0013] In a more detailed embodiment of the second aspect, at least one of the first plurality of orifices comprises a collar that is recessed relative to the top surface and the bone contact surface. In yet another more detailed embodiment, each of the first plurality of orifices comprises a collar that is recessed relative to the top surface and the bone contact surface. In a further detailed embodiment, the first plurality of orifices are oriented into a triangular configuration. In yet another detailed embodiment, the first plurality of orifices are arranged along a straight line. In a more detailed embodiment, the longitudinal axes of each of the plurality of first orifices are not parallel to each other. In a more detailed embodiment, at least one of the second plurality of orifices comprises a substantially uniform longitudinal cross-section. In another more detailed embodiment, at least one of the second plurality of orifices comprises an uneven longitudinal cross-section. In yet another more detailed embodiment, each of the second plurality of orifices comprises a substantially uniform longitudinal cross-section. In yet another more detailed embodiment, the second plurality of orifices are arranged along a straight line.

[0014] In yet another more detailed embodiment of the second aspect, the second plurality of orifices are arranged in a triangular configuration. In yet another more detailed embodiment, the longitudinal axis of each of the plurality of second orifices is parallel to each other. In another detailed embodiment, the longitudinal axis of each of the plurality of second orifices is not parallel to each other. In yet another more detailed embodiment, the assembly further comprises a rod mounted to the plate, the rod having an inertial measurement unit, the inertial measurement unit being mounted to the rod in a spaced relationship relative to the plate, wherein the specific relationship between the inertial measurement unit and the plate remains constant. In a more detailed embodiment, the assembly further comprises a rod mounted to the plate, the rod having an inertial measurement unit, the inertial measurement unit being mounted to the rod in a spaced relationship relative to the plate, wherein the specific relationship between the inertial measurement unit and the rod remains constant. In a more detailed embodiment, the assembly further comprises a rod mounted to the plate, the rod having an inertial measurement unit, the inertial measurement unit being mounted to the rod in a spaced relationship relative to the plate, wherein because the rod is removably coupled to the plate, the specific relationship between the inertial measurement unit and the plate can be changed. In another more detailed embodiment, the assembly further comprises a rod removably mounted to the plate, the rod having an inertial measurement unit, the inertial measurement unit mounted to the rod in a spaced relationship relative to the plate, wherein the rod comprises at least one protrusion, the at least one protrusion being configured to be received within at least one of the second plurality of apertures. In yet another more detailed embodiment, the assembly further comprises a rod removably mounted to the plate, the rod having an inertial measurement unit, the inertial measurement unit mounted to the rod in a spaced relationship relative to the plate, wherein the rod comprises a plurality of protrusions configured to be received within the second plurality of apertures. In yet another more detailed embodiment, the assembly further comprises a rod removably mounted to the plate, the rod having an inertial measurement unit, the inertial measurement unit mounted to the rod in a spaced relationship relative to the plate, wherein the rod comprises a protrusion, the protrusion being configured to be received within at least one of the second plurality of apertures, and wherein the rod comprises an aperture configured to receive the protrusion of the plate.

[0015] Accurate surgical navigation has been a goal that has been pursued (but not achieved) for quite some time (HolyGrail). The applicant has pioneered the use of an inertial measurement unit (IMU) as part of a surgical navigation system, where the IMU provides detailed information about changes in the anatomical position and orientation of surgical equipment and implants that takes into account magnetic anomalies. As part of using the IMU, one of the problems faced by the applicant is the installation of a reference IMU in the context of a total hip replacement procedure, where the installation meets two conditions. First, the reference IMU must be mounted to the femur in a manner that does not cause considerable movement between the femur and the IMU due to loose fasteners or other clearance, because the clearance means that the movement of the reference IMU does not necessarily indicate the movement of the bone to which the IMU is mounted. Secondly, the reference IMU should be mounted on the femur in a position that can be accessed by the surgeon, but this position does not hinder the surgeon's surgical area (including areas where bones are removed or the surface of the bones is trimmed and areas where the intramedullary canal is expanded) to avoid repositioning the reference IMU during surgery. This can be quite challenging given that minimally invasive surgical procedures are drastic procedures and necessarily result in a significantly confined space in which to set up the reference IMU, while still avoiding the surgeon's operating field.

[0016] In order to solve these problems, the present applicant has innovatively proposed a method for identifying the attachment area of ​​a femoral baseplate (and a novel femoral baseplate), which can be installed to at least one of the front and rear sides of the femur during total knee replacement. The accompanying method uses a statistical atlas and identifies one or more locations on the femur where the femoral baseplate can be installed, which will provide good fixation, but will not excessively interfere with the surgeon's surgical area or require intraoperative repositioning with reference to an IMU. For example, the attached method performs similar calculations on a population of bone models in a statistical atlas to identify whether a specific location or area for the attachment of a femoral baseplate will be preferred by establishing a fixed position, depth, and orientation and comparing it with a bone model to find an installation scheme. In a preferred sense, this installation scheme is a scheme that allows the use of a longer fixture (e.g., a surgical screw), but is performed in a manner that avoids contact or collision with the surgeon's surgical area (which includes the intramedullary canal, and the location where the femur will be bone cut). By performing these calculations on a statistical atlas, the applicant has identified preferred anterior and posterior regions where fixation is suitable for a large portion of the population without requiring a patient-specific solution. At the same time, the applicant has developed a mass-customized substrate mounted on the femur, the substrate comprising a bone contact surface that approximates the topography of the femur at the mounting location. The approximation of this surface topography increases the stiffness of the connection between the femur and the substrate. Before or after the resulting femoral substrate is mounted to the femur, the substrate can be mounted to the rod and IMU, allowing the movement of the IMU to indicate the movement of the femur (and providing the functionality of the reference IMU), while allowing the rod to extend through the incision in a manner that avoids the surgeon's operating area, so that total joint replacement can be performed without the need to reposition the reference IMU. This solution can obviously save time, reduce anatomical trauma, and reduce the pressure on the surgeon by providing the surgeon with the information they need as part of surgical navigation without excessive interference during surgery and without the need for repositioning and recalibration of the reference IMU, which would be required if the reference IMU was repositioned intraoperatively. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a diagram depicting a proximal portion of a femur including the ball of the femur and a proposed attachment site for a bone baseplate according to the present disclosure.

[0018] Figure 2 is a partially resected femoral bone model illustrating the placement of three surgical screws and the trajectory and position relative to the femoral intramedullary canal and the boundaries of the femoral stem of the orthopaedic implant positioned within the intramedullary canal.

[0019] Figure 3is a partially resected femoral bone model showing the boundaries of the femoral intramedullary canal and the femoral stem of the orthopedic implant located within the intramedullary canal.

[0020] Figure 4 Shown with reference plane in place Figure 3 Partially resected femoral bone model.

[0021] Figure 5 is a table showing the mean, standard deviation, minimum distance, and maximum distance of the corresponding screw distal ends relative to a reference plane using modeling and calculation according to the present disclosure.

[0022] Figure 6 is a graph depicting 13 strikes in which a first screw passed through a reference plane, and how far the first screw extended beyond the reference plane once it passed.

[0023] Figure 7 is a graph depicting 10 strikes in which the second screw passed through a reference plane, and how far the second screw extended beyond the reference plane once it passed.

[0024] Figure 8 is a diagram depicting 2 strikes where the third screw passes through the reference plane, and how far the third screw extends beyond the reference plane once it passes.

[0025] Fig. 9 is a diagram showing a first exemplary skeletal reference assembly (without an IMU) placed on the anterior portion of the femur.

[0026] Fig.10 is a diagram showing a first exemplary bone reference assembly placed on the anterior portion of a femur.

[0027] Fig.11 is a top elevation perspective view of an exemplary femoral baseplate according to the present disclosure.

[0028] Fig.12 yes Fig.11 A bottom upside-down perspective view of an exemplary femoral baseplate.

[0029] Fig.13 yes Fig.11 Top view of an exemplary femoral baseplate.

[0030] Fig.14 is a right side view of an exemplary rod according to the present disclosure.

[0031] Fig.15 yes Fig.14 Elevation perspective view of the pole.

[0032] Fig.16 is a profile diagram of an alternative exemplary rod.

[0033] Fig.17 yes Fig.14 An outline diagram of an exemplary rod.

[0034] Fig.18 is an elevational perspective view of a fastener according to the present disclosure.

[0035] Fig.19 yes Fig.14 Bottom view of a portion of the rod.

[0036] Fig. 20 is a partially exploded view showing a fastener, a femoral baseplate, and a portion of a stem prior to being assembled into individual components of a first exemplary bone reference assembly.

[0037] Fig.21 After assembly Fig. 20 Left and right elevation perspective views of the component.

[0038] Fig. 22 is a diagram showing a second exemplary skeletal reference assembly (without an IMU) placed on the posterior portion of the femur.

[0039] Fig.23 is a diagram showing a second exemplary bone reference assembly placed on the posterior portion of the femur.

[0040] Fig.24 is a top elevation perspective view of a second exemplary femoral bone baseplate according to the present disclosure.

[0041] Fig.25 yes Fig.24 A bottom upside-down perspective view of an exemplary femoral baseplate.

[0042] Fig.26 yes Fig.24 Top view of an exemplary femoral baseplate.

[0043] Fig. 27 is a right side view of a second exemplary lever according to the present disclosure.

[0044] Fig.28 yes Fig. 27 Elevation perspective view of the pole.

[0045] Fig.29 is an elevational perspective view of a fastener according to the present disclosure.

[0046] Fig.30 is a left elevation perspective view of components of a second exemplary skeletal reference assembly.

[0047] Fig.31 is a right elevation perspective view of components of a second exemplary skeletal reference assembly.

[0048] Fig.32 yes Fig. 27 A bottom view of a portion of a second exemplary rod.

[0049] Fig.33 is a partially exploded view showing a fastener, a femoral baseplate, and a portion of a stem prior to being assembled into individual components of a second exemplary bone reference assembly. DETAILED DESCRIPTION

[0050] Exemplary embodiments of the present disclosure are described and illustrated below to cover various aspects of plastic surgery, including surgical navigation aids, surgical navigators, and mass-customized instruments for use with surgical navigators. Of course, it will be apparent to those of ordinary skill in the art that the embodiments discussed below are exemplary in nature and may be reconstructed without departing from the scope and spirit of the invention. However, for clarity and precision, the exemplary embodiments discussed below may include optional steps, methods, and features that those skilled in the art should recognize as not being necessary conditions to fall within the scope of the invention.

[0051] like Figure 1 As shown, multiple femoral skeletal models 100 (which can exceed 150 models, but of course can be less) as part of a statistical atlas (wherein the skeletal model includes an intramedullary canal 110 model) are used to identify the approximate attachment site 102 (i.e., landmark) of the femoral skeletal baseplate using the skeletal model geometry. In other words, in the roughly same skeletal model region of two or more skeletal models of the atlas, the attachment site 102 for the femoral skeletal baseplate is depicted on each femoral skeletal model 100 of the atlas. Based on the location propagation, the atlas includes local geometric data about the size (including surface contour) of the surface of each skeletal model, wherein the femoral skeletal baseplate attachment site 102 overlaps with the surface or is otherwise defined by the surface. In this way, the bone contact surface of the femoral skeletal baseplate can be established by averaging or otherwise using the size of the skeletal model at the location of the attachment site 102 after propagating the attachment site on the statistical atlas.

[0052] The following series of steps are exemplary in nature and detail an exemplary femoral bone baseplate attachment site 102 (landmark) method in the context of establishing anatomical landmarks and references on a bone model 100 of a statistical atlas used. Although not required, the following steps can be performed for each bone model 100 used as part of a statistical atlas. By way of example, each bone model 100 used as part of a statistical atlas is evaluated to: (1) calculate the tip of the lesser trochanter point (LT); (2) calculate a plane (LTEP) tangent to the femoral shaft that marks the edge of the lesser trochanter; (3) calculate the femoral global anatomical axis (AA); (4) calculate the projection of the lesser trochanter point on the femoral global anatomical axis (PLTPAA); (5) calculate the projection of the lesser trochanter point on the plane that marks the edge of the lesser trochanter (PLTPLTEP); (6) calculate the medial-lateral direction as the vector between PLTPAA and LT; (7) calculate the anterior-posterior direction as the cross product of the femoral global anatomical axis and the medial-lateral direction; (8) calculate the superior-inferior direction as the direction of the femoral global anatomical axis.

[0053] about Figure 2, the following series of steps are exemplary in nature, and an exemplary femoral bone baseplate attachment site 102 (landmark) method is described in detail in the context of establishing instrument landmarks and directions on the skeletal model 100 of the statistical atlas used. For example, the screw positions for fixing the femoral bone baseplate to the femur and the directions that the screws 104-108 will take relative to the bone are derived from a series of placement steps relative to appropriate anatomical landmarks. In this way, the screw positions and directions are repeatable for each skeletal model 100 of the statistical atlas, and therefore allow for general analysis in the statistical atlas used as a whole. Although not required, the following steps can be performed for each skeletal model used as a part of the statistical atlas. In an exemplary manner, each bone model 100 used as part of the statistical atlas is evaluated to: (1) calculate the offset lesser trochanter point, which is 1 mm offset in the medial-lateral direction from PLTPLTEP (Shifted_PLTPLTEP); (2) calculate the position screw #1 (S1) 106, which is the intersection of a line pointing in the anterior-posterior direction and passing through Shifted_PLTPLTEP with the femoral bone model; (3) calculate the position screw #2 104 and screw #3 108, which is the midpoint between the positions of screw #1 (S1) 106 and is offset by 5 mm in the medial-lateral direction (MP_S2_S3); (4) Calculate the position of screw #2 (S2) 108, which is the point on the femoral bone model closest to the MP_S2_S3 point and is offset by 1 mm proximally in the direction of the anatomical axis; (5) Calculate the point of screw #3 (S3) 104, which is the point on the femoral bone model closest to the MP_S2_S3 point and is offset by 1 mm distally in the direction of the anatomical axis; (6) Calculate the femoral plate plane, the femoral plate plane is a plane containing the screw positions of all three screws (screw #1 (S1) 106, screw #2 (S2) 108, screw #3 (S3) 104); (7) calculating the direction of screw #1 (S1) 106, which is the normal direction of the femoral plate plane; and (8) calculating the directions of screw #2 (S2) 108 and screw #3 (S3) 104, which are the normal directions of the femoral plate plane after the femoral plate plane is rotated inward 20 degrees around the axis connecting the position of screw #2 (S2) 108 and the position of screw #3 (S3) 104.

[0054] about Figure 3 and Figure 4, the following series of steps are exemplary in nature, and an exemplary femoral bone baseplate attachment site (landmark) method is detailed in the context of establishing a definition for reference plane 112 calculation on the bone model of the statistical atlas used. Reference plane 112 is a plane representing the significant boundary of the implant component relative to the bone (e.g., femur) in question. In an exemplary form, reference plane 112 is defined so that it represents the expected component placement (femoral implant rod) plus a significant placement error margin to provide a conservative estimate of the external volume boundary of the orthopedic implant component relative to the bone. For explanation and evaluation, any fixing screw 104-108 is identified as having potential impact if its placement will cause any part of the screw to pass through the boundary described by reference plane 112. Although not required, the following steps can be performed on each bone model 100 that is part of the statistical atlas. In an exemplary manner, each bone model 100 used as part of the statistical atlas is evaluated to: (1) define a reference plane 112 (ref_temp_plane) that is perpendicular to the proximal anatomical axis and the cervical axis and passes through the anatomical axis points; (2) calculate the reference plane 112 as a plane rotated 5 degrees (the error boundary of the system) and translated 7 mm (determined by using an average file width measured at 5 mm and a built-in 2 mm buffer or safety zone); (3) calculate the distance between the end of each of the three screws (S1, S2, S3) 104-108 and the reference plane 112, and indicate that any screw that passes through the reference plane is identified as having an impact. For the foregoing purposes, the screw length is set to 13 mm and is assumed to be flush with the outer surface of the bone model after installation / fixation. Furthermore, Figure 3 and Figure 4 A femoral stem prosthesis 116 is depicted positioned partially within the intramedullary canal 110 .

[0055] Reference Figure 5-8 , an evaluation is calculated and determined for all skeletal models 100 used as part of the statistical atlas. Figure 5 As shown, the diagram provides the mean, standard deviation, minimum size and maximum size in millimeters for the distance from the end of the corresponding screw 104-108 to the reference plane. The above analysis was performed on 150 atlas bone models. As part of the calculation and determination, 116 of the 150 bone models had no collision between any of the three screws and the reference plane. Of the remaining 34 bone models, 15 bone models had collisions of the screws 104-108 relative to the reference plane 112. It is worth noting that the reference plane 112 is defined based on femoral geometry landmarks, which may not be associated with the boundaries of the segmented intramedullary canal model in some cases.

[0056] The results calculated and determined on all bone models 100 used as part of the statistical map produce the attachment site 102, and the shape of the femoral bone baseplate surface is constructed to approximate a bone surface that is mass-customized to accommodate varying implant sizes over a range of patient femur sizes.

[0057] Utilizing the established shapes of the exemplary femoral bone baseplate surface and attachment sites, the femoral bone baseplate 200 can be manufactured and used as part of a total hip replacement procedure to align one or more inertial measurement units 202 relative to a patient's femur 204 as part of a surgical navigation effort. As will be discussed in more detail below, the exemplary femoral bone baseplate 200 works with one or more inertial measurement units 202 and rods 206 to form a bone reference assembly 210. In this way, the inertial measurement unit (IMU) 202 is secured to a bone 204 (in exemplary form, a femur) in a fixed position and used as a reference IMU, where the fixed position is maintained throughout the surgical procedure (which may include final implant placement within the intramedullary canal of the femur). Reference is made to Appendix A included herein, which describes in more detail the interaction between a reference IMU and a second IMU mounted to a surgical tool or surgical implant as part of surgical navigation to provide information about the relative positions of these objects when there may not be a direct line of sight to one or more of the bone, implant, and surgical tool.

[0058] like Fig.10 Depicted, exemplary bone reference assembly 210 for femur 204 includes inertial measurement unit 202, rod 206, and bone baseplate 200 (in exemplary form, femoral bone baseplate). Although not necessarily limited to application at an attachment site on the anterior region of the femur, the foregoing exemplary embodiment may be referred to as exemplary anterior bone reference assembly 210.

[0059] like Figure 11-13Described in more detail, the shape and fixed position of the exemplary femoral bone base plate 200 are mathematically established and confirmed using the bone model 100 from the statistical atlas. The exemplary femoral bone base plate 200 includes a distal bone contact surface 214, which has a topography that roughly matches and cooperates with the topography of the front of the femur exposed as a part of the total hip replacement process. Opposite to the bone contact surface 214 is a rod engagement surface 216, which is planar in the exemplary form. A series of holes 220-224 extend from the bone contact surface 214 through the femoral bone base plate 200 to the rod engagement surface 216. In this exemplary embodiment, the femoral bone base plate 200 includes three holes 220, and the holes 220 are constructed to receive screw fasteners (not shown) to mount the base plate 200 to the femur 204. In an exemplary manner, each hole 220 includes a recessed collar 226, and the collar 226 is operable to change the barrel diameter of each hole so that the hole at the rod interface surface 216 has a larger diameter than the hole at the bone contact surface 214. Two additional holes 222 are provided that receive alignment bolts associated with the rod 206. Also provided are fastener holes 224 that may include helical threads configured to receive fasteners to retain the femoral baseplate in engagement with the rod 206.

[0060] Reference Figure 14-19 , the exemplary rod 206 includes a distal adapter 230 having a pair of alignment bolts 232 extending therefrom, the alignment bolts 232 being configured to be received within corresponding holes 222 of the femoral skeletal baseplate 200. In the exemplary form, each alignment bolt 232 includes a linear cylindrical shape that is received within a cylindrical bore of a corresponding hole 222. Here, the distal adapter 230 includes its own through hole 234, which is configured to receive a fastener 250 (e.g., Fig.18 252) to mount the distal adapter to the femoral bone baseplate 200. In this embodiment, the distal adapter 230 includes a series of interconnected arcuate cutouts 236 that do not obstruct the hole 220 of the femoral bone baseplate 200. An elongated neck 240 extends proximally from the distal adapter 230, terminating at a proximal connector 242 configured to engage the IMU 202. The rod 206 is angled in three dimensions so that it can extend through a typical anterior THA cutout before and after external rotation of the femur. The rod 206 has two configurations for receiving the IMU 202. The first configuration of the rod 206 features a connector 242 to receive a locking feature of the IMU 202. The second configuration of the rod 206 features a slide on which the IMU 202 is mounted.

[0061] Reference Fig. 20 and Fig.21Attaching the rod 206 to the femoral skeletal baseplate 200 includes aligning the rod's bolt 232 with the corresponding hole 222 of the baseplate. For example, the bolt 232 is designed to fit snugly relative to the boundary of the hole 222 to avoid significant play between the rod 206 and the baseplate 200. After the bolt 232 is received within the hole 222, the through hole 234 of the adapter 230 should be aligned with the hole 224 of the baseplate 200 so that the fastener 250 can extend through the smooth bore 234 and its threads 252 can engage with the protruding threads of the hole 224. In this way, when the fastener 250 is rotated clockwise, the head of the fastener can operate to clamp the adapter 230 between the baseplate 200. Once the fastener 250 is properly torqued, the rod 206 and the baseplate 200 are fixedly mounted to each other. After being mounted to one another, the holes 222 of the base plate can be accessed by a drill and then by screws to mount the assembly 210 to the femur 204 , assuming that the IMU 202 is mounted to the rod 206 .

[0062] When the assembly 210 is mounted to the femur, during anterior total hip replacement, the assembly is placed on the anterior portion of the proximal femur along the intertrochanteric line and perpendicular to the femoral neck axis. It can be fixed to the anterior femur with three 3.5 mm x 20 mm cancellous screws (not shown). In this way, the reference IMU 202 is securely fixed to the patient's femur.

[0063] Reference Fig. 22 and Fig.23 , an alternative exemplary embodiment of a bone reference assembly 310 for a femur 304 includes an inertial measurement unit 302, a rod 306, and a bone baseplate 300 (in the exemplary form, a femoral bone baseplate). Although not necessarily limited to application to an attachment site on the posterior region of the femur, the aforementioned exemplary embodiment may be referred to as an exemplary posterior bone reference assembly 310.

[0064] like Figure 24-26Described in more detail, the shape and fixed position of exemplary femoral bone base plate 300 are established mathematically and confirmed using the bone model 100 from the statistical atlas. Exemplary femoral bone base plate 300 includes a distal bone contact surface 314, and the topography of the distal bone contact surface 314 matches and cooperates with the topography of the femur posterior exposed as a part of the total hip replacement process. Opposite to the bone contact surface 314 is a rod engagement surface 316, which is planar in the exemplary form. A series of holes 320-324 extend from the bone contact surface 314 through the femoral bone base plate 300 to the rod engagement surface 316. In this exemplary embodiment, the femoral bone base plate 300 includes three holes 320, and the holes 320 are constructed to receive screw fasteners (not shown) to mount the base plate 300 to the femur 304. In an exemplary manner, each hole 320 includes a recessed collar 326 operable to change the barrel diameter of each hole such that the hole at the rod engaging surface 316 has a larger diameter than the hole at the bone contacting surface 314. Two additional holes 322 are provided that receive alignment bolts associated with the rod 306. Fastener holes 324 are also provided that may include helical threads configured to receive fasteners to retain the femoral bone baseplate in engagement with the rod 306.

[0065] Reference Fig. 27 and Fig.28 , the exemplary rod 306 includes a distal adapter 330 having a pair of alignment bolts 332 extending therefrom, the alignment bolts 332 being configured to be received within corresponding holes 322 of the femoral skeletal baseplate 300. In the exemplary form, each alignment bolt 332 includes a linear cylindrical shape that is received within the cylindrical bore of the corresponding hole 322. At the same time, the distal adapter 330 includes its own through hole 334, which is configured to receive a fastener 350 (e.g., Fig.29 352) to mount the distal adapter to the femoral bone baseplate 300. In this exemplary embodiment, the distal adapter 330 includes a pair of arcuate cutouts 336 that do not obstruct the hole 320 of the femoral bone baseplate 300. An elongated neck 340 extends proximally from the distal adapter 330, terminating in a proximal coupling 342 configured to engage the IMU 302. The rod 306 is angled in three dimensions so that it can extend through a typical posterior THA incision before and after external rotation of the femur. The rod 306 has two configurations to receive the IMU 302. The first configuration of the rod 306 features a coupling 342 to receive a locking feature of the IMU 302. The second configuration of the rod 306 features a slide on which the IMU 302 is mounted.

[0066] refer to Figure 30-Figure 33 Attaching the attachment rod 306 to the femoral skeletal baseplate 300 includes aligning the rod's bolt 332 relative to the corresponding hole 322 of the baseplate. For example, the bolt 332 is designed to fit snugly relative to the boundary of the hole 322 to avoid significant play between the rod 306 and the baseplate 300. After the bolt 332 is received within the hole 322, the through hole 334 of the adapter 330 should be aligned with the hole 324 of the baseplate 300 so that the fastener 350 can extend through the smooth bore 334 and its threads 352 can engage the protruding threads of the hole 324. In this way, when the fastener 350 is rotated clockwise, the head of the fastener can operate to clamp the adapter 330 between the baseplate 300. Once the fastener 350 is properly torqued, the rod 306 and the baseplate 300 are fixedly mounted to each other. After being mounted to one another, the base plate's hole 322 can then be accessed by a drill and subsequently a screw to mount the assembly 310 to the femur 304 , assuming the IMU 302 is mounted to the rod 306 .

[0067] When mounting the assembly 310 to the femur, during a posterior total hip replacement, the assembly is placed on the posterior portion of the proximal femur along the intertrochanteric line and perpendicular to the femoral neck axis. It can be secured to the posterior femur with three 3.5 mm x 20 mm cancellous screws (not shown). In this way, the reference IMU 202 is securely secured to the patient's femur.

[0068] Based on the above description, it should be apparent to those of ordinary skill in the art that, although the methods and apparatus described herein constitute exemplary embodiments of the present disclosure, the present invention is not limited to these specific embodiments, and such embodiments may be changed without departing from the scope of the present invention as defined by the claims. In addition, it should be understood that the present invention is defined by the claims, and it is not intended that any limitation or element describing the exemplary embodiments set forth herein be incorporated into the interpretation of any claim element unless such limitation or element is expressly stated. Similarly, it should be understood that it is not necessary to satisfy any or all of the identified advantages or purposes of the present invention disclosed herein in order to fall within the scope of any claim, because the present invention is defined by the claims, and even though they may not be explicitly discussed herein, there may be inherent and / or unforeseen advantages of the present invention.

Claims

1. A femoral baseplate assembly, comprising: a plate having a bone contacting surface configured to approximate the topography of an exterior of a femur, the plate including a first plurality of apertures angled relative to the bone contacting surface and configured to orient corresponding fasteners in a predetermined angled orientation, the plate including a second plurality of apertures, at least one aperture of the second plurality of apertures being threaded, wherein each of the apertures extends through the bone contacting surface and through a top surface opposite the bone contacting surface, and A rod mounted to the plate via a distal adapter, the rod also including a proximal connector configured to engage an inertial measurement unit, wherein the distal adapter includes: an alignment bolt configured to be received within a corresponding aperture of the plate; and a through hole configured to receive a fastener configured to engage at least one of the second plurality of apertures to mount the distal adapter to the plate.

2. The femoral baseplate assembly of claim 1, wherein at least one of the first plurality of apertures comprises a collar that is recessed relative to the top surface and the bone contacting surface.

3. The femoral baseplate assembly of claim 1, wherein each of the first plurality of apertures comprises a collar that is recessed relative to the top surface and the bone contacting surface.

4. The femoral baseplate assembly of claim 1, wherein the first plurality of apertures are oriented in a triangular configuration.

5. The femoral baseplate assembly of claim 1, wherein the first plurality of apertures are arranged along a straight line.

6. The femoral baseplate assembly of claim 1, wherein the longitudinal axis of each of the first plurality of apertures are not parallel to one another.

7. The femoral baseplate assembly of claim 1, wherein at least one of the second plurality of apertures comprises a substantially uniform longitudinal cross-section.

8. The femoral baseplate assembly of claim 1, wherein at least one of the second plurality of apertures comprises a non-uniform longitudinal cross-section.

9. The femoral baseplate assembly of claim 1, wherein each of the second plurality of apertures comprises a substantially uniform longitudinal cross-section.

10. The femoral baseplate assembly of claim 1, wherein the second plurality of apertures are arranged along a straight line.

11. The femoral baseplate assembly of claim 1 , wherein the second plurality of apertures are arranged in a triangular configuration.

12. The femoral baseplate assembly of claim 1, wherein the longitudinal axis of each of the second plurality of apertures are parallel to one another.

13. The femoral baseplate assembly of claim 1, wherein the longitudinal axis of each of the second plurality of apertures are not parallel to one another.

14. The femoral baseplate assembly of claim 1, wherein a specific relationship between the inertial measurement unit and the plate remains constant.

15. The femoral baseplate assembly of claim 1, wherein a specific relationship between the inertial measurement unit and the rod remains constant.

16. The femoral baseplate assembly of claim 1, wherein because the rod is removably coupled to the plate, the particular relationship between the inertial measurement unit and the plate can be varied.

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