Reference device

Abstract

A reference device for application onto a patient, the reference device comprising: a support plate; a first positioning element extending from the support plate; a second positioning element extending from the upper support plate; a third positioning element extending from the upper support plate; an electronic direction monitor housing adapted to receive an electronic direction monitor; and a docking station adapted to receive the housing, thereby defining a reference point external to and relative to the patient's anatomy, wherein the first positioning element, the second positioning element, and the third positioning element are positioned to be pressed down onto the patient to provide a reference direction for the electronic direction monitor with respect to a predetermined anatomical location.

Description

[Technical Field]

[0001] The present invention relates to surgical instruments and methods, and more particularly to a referencing apparatus that can be applied to a patient before or during a surgical procedure, such as hip surgery requiring an artificial joint component. [Background technology]

[0002] The discussion of the prior art within this specification is not, and should not be construed as, an admission of the level of common general knowledge in the field of the invention. Rather, the discussion of the prior art is provided merely to aid the reader in understanding the invention and is included without prejudice.

[0003] Although the following discussion is directed to hip replacement surgery, those skilled in the art will understand that the present invention is not limited to this particular field of use and may be adapted for use with any bony structure or various types of surgery.

[0004] Hip replacement surgery involves restoring function to the hip joint's ball-and-cup joint using an artificial cup (acetabular cup) or ball (femoral stem), or both. A ball-and-cup joint allows the hip joint to rotate to varying degrees in different directions (as opposed to the relatively limited rotation of the knee joint).

[0005] Historically, hip replacement (arthroplasty) surgery required a curved incision of up to 40 cm (7 to 12 inches) to provide sufficient access for the surgeon to manually manipulate the hip joint and femur. An artificial cup was attached to the hip socket, or the head of the femur was removed and replaced with an artificial ball, or both.

[0006] After the incision is made, the ligaments and muscles are separated, allowing the surgeon access to the hip bone. It is this part of the surgery that typically leaves the ligaments and muscles somewhat weakened after surgery. Until they heal, which often takes about one month to six weeks, the patient must follow special hip precautions to prevent dislocation of the new hip.

[0007] A typical procedure for hip replacement surgery includes the following: Removal of the femoral head: Once in the hip joint, the femoral head is dislocated from the acetabulum. The femoral head is then removed by cutting open the femoral neck with a power saw. Acetabular reaming: After removing the femoral head, cartilage is removed from the acetabulum using a power drill and a special reamer. The reamer shapes the bone into a hemispherical shape to precisely fit the metal shell of the acetabular component. Insertion of the Acetabular Component: A trial component, an exact replica of the patient's hip replacement, is used to ensure the receiving joint is the correct size and fit. Once the correct size and shape of the acetabulum is determined, the acetabular component is inserted into place. In uncemented types of hip replacements, the metal shell is held in place simply by the tightness of the fit, or screws hold the metal shell in place. In cemented types, a special epoxy cement is used to "glue" the acetabular component to the bone. Femoral canal preparation: To initiate the femoral head replacement, a special file is used to shape and carve the femur to the exact shape of the metal stein of the femoral component. A trial component is again used to confirm the correct size and shape. The surgeon also tests the movement of the hip joint. Insertion of the femoral stem: Once the size and shape of the canal are precisely fitted to the femoral 15 component, the stem is inserted into the femoral canal. Again, for uncemented versions of the femoral component, the stem is held in place by the tightness of its fit in the bone (similar to the friction that holds a nail hammered into a hole drilled in a wooden board with a diameter slightly smaller than the nail). For cemented versions, the femoral canal is milled to a size slightly larger than the femoral stem. An epoxy 20-based cement is then used to bond the metal stem to the bone. · Femoral head attachment: A metal ball that replaces the femoral head is attached to the femoral stem. · Completion of the hip replacement: Before the incisions are closed, x-rays are taken to ensure the new prosthesis is in the correct position.

[0008] Such surgery has many problems: Hospitalization of more than 3 days, postoperative pain, and several weeks of rehabilitation. Each cm of incision increases the risk of post-operative blood clots and infection by 10 times. Surgeons rely on their experience and eyes to ensure accurate placement of the cup in the three-dimensional hip socket and alignment of the ball / femur with the cup to achieve proper function of the joint. Misalignment can lead to postoperative complications such as foot misalignment, incorrect leg length, and / or incorrect soft tissue tension. The long-term effects of misaligned prosthetic components can also include premature component wear, aseptic loosening of components, and potentially early repeat surgery.

[0009] Attempts to overcome these problems include the following: WO 2003 / 037192 discloses a jig (impaction tool) for use in bone surgery, thus allowing the use of smaller incisions. In hip replacement surgery, the jig allows the use of incisions of 4 to 7 cm (2 to 3 inches), i.e., keyhole surgery. Other advantages include shorter hospital stays, less bleeding, less pain, fewer post-operative dislocations, and faster recovery. WO2005 / 046475 discloses a gauge that assists in the accurate placement of artificial joints when using jigs in keyhole surgery, since the surgeon can no longer see the fit of the cup into the hip socket or the fit between the ball and cup. WO2010 / 031111 discloses a brace designed to define a reference point relative to the patient during use to define a position for placement of an artificial joint.

[0010] The gauge provided in WO2005 / 046475 enabled efficient use of the impaction tool of WO2003 / 037192. Commercial examples include the NivNav Hip System available from MAC Surgical. However, the gauge only functions in two dimensions, and optimal placement of the cup in the hip joint still relies heavily on the surgeon's eye and experience.

[0011] A further attempt to overcome these problems is provided by WO 2010 / 031111, the contents of which are incorporated herein by cross-reference in their entirety. This prior art document discloses a brace (3) in the form of a clamp that can be attached to a patient to define reference points relative to the patient's anatomy. This prior art clamp has multiple pads (14, 16, 17, 18) that are positioned against various points on the patient's anatomy. However, it has been recognized by the inventors that this clamp can be obstructive to at least some surgical procedures and does not easily accommodate surgical drapes typically used in many surgical settings. Summary of the Invention

[0012] It is an object of the present invention to overcome or ameliorate at least one or more of the disadvantages of the prior art, or to provide a useful alternative.

[0013] According to a first aspect of the present invention, there is provided a datum device for application on a patient. The datum device may include a support plate. The datum device may further include a first positioning element extending from the support plate. The datum device may further include a second positioning element extending from the upper support plate. The datum device may further include a third positioning element extending from the upper support plate. The datum device may further include an electronic orientation monitor housing adapted to receive an electronic orientation monitor. The datum device may further include a docking station adapted to receive the housing, thereby defining a reference point external to and relative to the patient's anatomy. The first positioning element, the second positioning element, and the third positioning element may be positioned to be depressed onto the patient to provide a reference orientation for the electronic orientation monitor with respect to a predetermined anatomical location.

[0014] According to a particular arrangement of the first aspect, there is provided a reference device for application on a patient, the reference device including a support plate, a first positioning element extending from the support plate, a second positioning element extending from an upper support plate, a third positioning element extending from the upper support plate, an electronic direction monitor housing adapted to receive an electronic direction monitor, and a docking station adapted to receive the housing, thereby defining a reference point external to and relative to the patient's anatomy, wherein the first positioning element, the second positioning element, and the third positioning element are arranged to be pressed down onto the patient to provide a reference direction for the electronic direction monitor with respect to a predetermined anatomical location.

[0015] The housing may be a sterile housing. The housing may comprise a body with an opening adapted to receive the directional monitor, a load funnel with an angled leading wall and an insertion wall to allow the sterile directional monitor to be inserted into the sterile housing while preventing contamination of the sterile housing, and a locking means comprising a sealed frame adapted to engage with a docking station, the frame pivotally attached to the body of the housing. The housing may be a clamshell housing.

[0016] The load funnel may be a transfer shield adapted to be placed over the opening of the housing to protect the sterile components of the housing during use while the monitor is inserted into the housing through the shield.

[0017] The locking means may include a central opening shaped to receive the docking station therein, thereby securing the electronic orientation monitor to a reference device for orienting the orientation monitor relative to the patient.

[0018] The first and second locator elements may be first and second anterior superior iliac spine locator elements. The third locator element may be a pubic bone locator element. The first and second locator elements may include a patient connection plate. The patient connection plate may be positioned to be secured to the patient above the anterior superior iliac spine.

[0019] The electronic direction monitor may be dockable with the docking station in either a first docking configuration or a second docking configuration. The electronic direction monitor may be housed in an electronic direction monitor housing. The electronic direction monitor housing may be positioned to engage with the support plate to provide a reference direction for the electronic direction monitor.

[0020] The first docking configuration may define a first orientation of the electronic directional monitor relative to the reference device, and the second docking configuration may define a second orientation of the electronic directional monitor relative to the reference device.

[0021] According to a second aspect of the present invention, there is provided a method of calibrating an electronic orientation monitor using a reference device as defined in the first aspect. The method may include the step of positioning a patient connection plate on the left anterior superior iliac spine. The method may further include the step of positioning a patient connection plate on the right anterior superior iliac spine. The method may include the further step of connecting first and second positioning elements to the respective patient connection plates. The method may include the further step of positioning a third positioning element relative to the pubic bone. The method may include the further step of placing the electronic orientation monitor in a sterile housing comprising means for receiving a non-sterile monitor while preventing contamination of the sterile housing. The method may include the further step of engaging the housing with the monitor contained therein with a docking station located on the reference device to assume a reference orientation external to and relative to the patient. The method may include the further step of calibrating the electronic orientation monitor.

[0022] According to a particular arrangement of the second aspect, there is provided a method of calibrating an electronic orientation monitor using a reference device as defined in the first aspect, the method comprising the steps of positioning a patient connection plate on the left anterior superior iliac spine, positioning a patient connection plate on the right anterior superior iliac spine, connecting first and second positioning elements to the respective patient connection plates, positioning a third positioning element relative to the pubic bone, placing the electronic orientation monitor within a sterile housing comprising means for receiving a non-sterile monitor while preventing contamination of the sterile housing, engaging the housing with the monitor contained therein with a docking station located on the reference device to assume a reference orientation external to and relative to the patient, and calibrating the electronic orientation monitor.

[0023] The datum may be positioned anterior to the patient during the step of engaging the datum with the surgical drape and during calibration of the electronic orientation monitor. An anterior approach may be used for surgical access to the patient's acetabulum.

[0024] During the above steps, the patient may be positioned to lie in a face up position.

[0025] According to a third aspect of the present invention, there is provided a method of calibrating an electronic orientation monitor using a reference device as defined in the first aspect. The method may include positioning a surgical drape on a patient. The method may further include engaging a plurality of positioning elements with respect to the surgical drape such that the surgical drape is positioned between the plurality of positioning elements and each of a plurality of predefined anatomical locations on the patient, causing a docking station disposed on the reference device to assume a reference orientation relative to the plurality of predefined anatomical locations. The method may further include placing the electronic orientation monitor in a sterile housing comprising means for receiving a non-sterile monitor while preventing contamination of the sterile housing, and docking the housing with the docking station to orient the electronic orientation monitor in the reference orientation. The method may further include calibrating the electronic orientation monitor.

[0026] According to a particular arrangement of the third aspect, there is provided a method of calibrating an electronic orientation monitor using a reference device as defined in the first aspect, the method comprising the steps of: positioning a surgical drape on a patient; engaging a plurality of positioning elements with respect to the surgical drape such that the surgical drape is positioned between the plurality of positioning elements and each of a plurality of predefined anatomical sites on the patient, causing a docking station disposed on the reference device to assume a reference orientation relative to the plurality of predefined anatomical sites; disposing the electronic orientation monitor in a sterile housing comprising means for receiving a non-sterile monitor while preventing contamination of the sterile housing, and docking the housing with the docking station to orient the electronic orientation monitor in the reference orientation; and calibrating the electronic orientation monitor. [Brief explanation of the drawings]

[0027] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a perspective view of a datum device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of the datum of the embodiment of FIG. [Figure 2A] FIG. 2A is a perspective view of a further embodiment of a datum. [Figure 2B] FIG. 2B is a perspective view of a further embodiment of a datum. [Figure 3] 3 is a partial perspective view of a first or second positioning element used with the datum of FIG. 1; [Figure 4] 4 is a cross-sectional view of the first or second positioning element of FIG. 3. FIG. [Figure 5] FIG. 5 is an exploded view of an electronic direction monitor for use with the reference device of FIG. [Figure 5A] 5A and 5B show an alternative embodiment of an electronic direction monitor housing including a clamshell case and a transport shield. [Figure 5B]5A and 5B show an alternative embodiment of an electronic direction monitor housing including a clamshell case and a transport shield. [Figure 5C] FIG. 5C is an exploded view of the alternative electronic direction monitor of FIG. 5A. [Figure 6] 6 is a perspective view of a clamshell case for the electronic direction monitor of FIG. 5. FIG. [Figure 7] FIG. 7 is a side view of the clamshell case of FIG. [Figure 8A] 8A and 8B show the clamshell housing engaged with the datum embodiment of FIG. [Figure 8B] 8A and 8B show the clamshell housing engaged with the datum embodiment of FIG. [Figure 9] FIG. 9 is a perspective view of the electronic directional monitor of FIG. 5 attached to a surgical impactor. DETAILED DESCRIPTION OF THE INVENTION

[0028] Broadly, the present invention relates to a datum 100 for application to a patient for hip surgery, such as, but not limited to, hip replacement surgery. Referring to the drawings, the datum 100 of the present invention is used to assist a surgeon in orienting a prosthetic component relative to the patient's anatomy during surgery. The datum 100 can be placed on the patient by the surgeon, allowing for easy and reliable orientation of the electronic orientation monitor 46 within the housing 12. Once oriented, the electronic orientation monitor can be detached from the datum 100 and attached to the prosthetic component, providing details of the prosthetic component's location for reliable and accurate insertion into the patient. The prosthetic component may be, for example, a surgical impactor used to place the prosthetic component within the patient. The orientation monitor provides position details of the impactor corresponding to the location of the prosthetic component to ensure accurate placement of the prosthetic component within the patient. The orientation monitor 46 includes an inertial measurement unit (IMU) including a three-axis digital gyroscope and a three-axis digital accelerometer. In certain embodiments, the IMU is an integrated digital gyroscope and accelerometer sensor specifically designed for inertial measurements and offers increased dynamic range, improved sensitivity, higher accuracy, lower bias, and lower drift compared to traditional gyroscope / accelerometer implementations. In certain embodiments, the selected IMU enables accurate position recognition and determination without the need for additional navigational components, such as magnetometer or compass components, which may experience interference from local magnetic fields (e.g., from medical imaging equipment) that adversely affect the accuracy of critical orientation parameters that must be determined by the orientation monitor 46. In certain embodiments, the surgeon may be provided with the ability to select or input specific artifact angles and related data into the orientation monitor 46 to assist and fine-tune the orientation calibration with respect to the patient's unique anatomy.

[0029] The preferred embodiment is particularly suited to assisting a surgeon in properly positioning an acetabular cup within a reamed acetabulum during hip surgery, such as a total or partial hip replacement or revision. When used in this context, the datum 100 is pressed down from above onto the patient's pelvis to assume a reference position for orienting the electronic direction monitor 46 to assist in positioning the surgical impactor and prosthetic components.

[0030] This detailed description describes the use of datum 100 and electronic directional monitor 46 to aid in the insertion of a prosthetic joint component in the form of an acetabular cup into a reamed acetabulum of a patient's pelvis where an anterior approach is used for surgical access to the patient's acetabulum. An important part of this process is the use of datum 100 to calibrate electronic directional monitor 46, which may be similar to the monitor disclosed in applicant's earlier application no. WO 2010 / 031111, the contents of which are incorporated herein by cross-reference in their entirety. However, those skilled in the art will understand that the present invention may be used in other surgical contexts.

[0031] Referring to the drawings, the datum device 100 comprises the following components: a frame 10 for positioning the electronic orientation monitor in a reference position relative to the patient; First and second anterior superior iliac spine (ASIS) positioning elements 14; a third, pubic positioning element 16; Electronic direction monitor 46, and ·Electronic direction monitor housing 12.

[0032] Frame 10 includes an upper support plate in the form of a channel portion 11 and a T-channel portion 15 extending perpendicularly from channel portion 11. A first ASIS locating element 14 extends outward from the base of one longitudinal end of channel portion 11, and a second ASIS locating element 14 extends from the opposite longitudinal end of channel portion 11. A third pubic locating element 16 extends outward from the base of T-channel portion 15.

[0033] The force application plate 13 forms part of the channel portion 11 and provides an interface for a downward force applied to the reference device 100 on the patient via the positioning elements 14, 16 and orients the electronic orientation monitor 46.

[0034] The first and second ASIS positioning elements 14 connect to the channel portion 11 and extend generally perpendicularly outward relative to the channel portion 11. In one embodiment, to provide the ability to use a single size datum 100 for patients of different sizes and hip profiles, the first and second ASIS positioning elements 14 are attached to the channel portion 11 such that they can be fixed in different positions. In one embodiment, the connecting surface of the channel portion 11 has multiple fixation points from which the first and second ASIS positioning elements 14 can be selected for attachment. In an alternative embodiment, the underside of the channel portion 11 includes rails with attachment points for the first and second ASIS positioning elements 14. The attachment points can be locked in place as desired.

[0035] The third, pubic locator element 16 connects to the T-channel portion 15 and extends outwardly, generally perpendicular to the T-channel portion 15. In one embodiment, to provide the ability to use a single size datum 100 for patients of different sizes and hip profiles, the third, pubic locator element 16 is attached to the T-channel portion 15 so that it can be fixed in different positions. In one embodiment, the connecting surface of the T-channel portion 15 has multiple fixation points from which the third, pubic locator element 16 can be selected for attachment.

[0036] In an alternative embodiment, the underside of the T-channel portion 15 includes a rail with a third attachment point for a pubic bone locating element 16. The attachment point can be locked into place if desired.

[0037] Extending from the channel portion 11 are docking stations 19 configured to receive an electronic orientation monitor 46 contained within the housing 12. The docking stations 19 are designed to be highly toleranced and to precisely position the monitor 46 in a defined location so as not to compromise the accuracy of the measurement system. Engaging any one of the docking stations 19 with the electronic orientation monitor 46 contained within the housing 12 defines a reference point relative to the patient's anatomy. This reference point is external to the patient and is used to orient the electronic orientation monitor 46 to a reference orientation. While in this orientation, the electronic orientation monitor 46 acquires reference orientation information that is used to calibrate the electronic orientation monitor 46 to the reference orientation. In one embodiment, as shown in FIG. 1, the docking station 19 of the frame 10 includes a central opening 17, and the docking station 19 is contoured to receive and secure the electronic orientation monitor 46 in place. In a further embodiment of a frame, such as frame 70 of FIG. 2B, the docking station 19 does not include an opening therein.

[0038] The first and second ASIS positioning elements 14 include a rod extension 20 extending from the base of the channel portion 11, a base 21, and a patient connection plate 18. The patient connection plate 18 is positioned to be secured to the patient's body over the patient's ASIS. The position of the patient connection plate 18 determines where the first and second ASIS positioning elements 14 are positioned on the patient.

[0039] The pubic locator element 16 extends as a bar from the channel portion 11 and terminates in a pubic probe 23 that is configured to lie within the patient's pubic eminence during use. With the pubic probe 23 positioned between the patient's pubic eminences and the first and second ASIS locator elements 14 in place on the connecting plate 18, a known reference position of the channel portion 11 and the datum device 100 as a whole relative to the patient is then known.

[0040] In this known position, the electronic orientation monitor 46 can be placed on the docking station 19 in the electronic orientation monitor housing 12 appropriate for the side of the hip they are operating on, according to the surgeon's personal preference. That is, regardless of which hip the surgeon is operating on, the surgeon can place the orientation monitor 46 in the housing 12 and attach the housing to either of the two docking stations 19 (on the left or right side of the frame 10, 70). In practice, the range of desired positions selectable by the surgeon for the orientation monitor 46 is limited by the patient's anatomy and clinical effectiveness. The position selected by the surgeon is determined by a combination of the type of implant and the patient's anatomy, modulated by the surgeon's clinical judgment. The datum 100 can be thought of as establishing a commonly used / accepted predefined orientation with respect to the patient's anatomy. The addition of the orientation monitor 46 to the device 100 provides the surgeon with live position feedback, which allows the surgeon to place the implant in a desired position that may differ from the predefined position, if the surgeon deems it appropriate.

[0041] 2A illustrates an alternative embodiment 50 of frame 10 in which channel portion 11 and T-channel portion 15 of the previous embodiment are replaced with rigid non-channel arms 51 and 52, respectively, and replaced with non-channel frame 50. Adjustment slots 52 and 53 are provided in at least one of arms 51 and also in T-section 54 for adjustment of the spacing between first and second ASIS locator elements 14 with foot 22, and for adjustment of pubic locator element 16 with respect to the patient's unique anatomy. The particular embodiment illustrated in FIG. 2A is described in further detail in Australian Patent No. AU2013204941, the contents of which are incorporated herein in their entirety by cross-reference.

[0042] FIG. 2B shows an alternative embodiment 70 of frames 10 and 50, in which a channel frame is again not used, and slots 71 and 72 on arms 74 of frame 70 and slot 75 on T-section 76 (similar in nature to slots 52 and 53 in FIG. 2A ) are provided. In this embodiment, ASIS locator element 14 terminates in a lever lock system that engages with slots 71 and 72, respectively, of frame 70. Similarly, pubic locator element 16 terminates in a lever lock system that engages with slot 75 so that ASIS locator element 14 and pubic locator element 16 can be adjusted to position a patient's anatomical features and then locked into place. As shown in FIG. 2A , slots 71 and 72 on arms 74 and slot 75 on T-section 76 may optionally be provided with a series of regularly spaced detents to assist in properly positioning locator elements 14 and 16 and to assist with locking clamps to secure locator elements 14 and 16 in place.

[0043] 2B also includes a magnet positioning feature 77 that is sensed by the orientation monitor 46 when engaged with either of the docking stations 19. The positioning feature 77 senses the placement of the orientation monitor housing 12, including the orientation monitor 46, and helps ensure that the datum 100 is used as intended and to avoid errors that may occur if, for example, the monitor 46 or frame 10, 50, 70 is used before being properly calibrated.

[0044] As best shown in FIGS. 3 and 4 , the patient connection plate 18 includes a central ring protrusion 29 defined by the perimeters 22 of the first and second ASIS locating elements 14, a central opening 30 defined by the central ring protrusion 29, a base 27, and a base protrusion 28. The central ring protrusion 29 acts to be received in a recess 32 defined by the perimeters 22 of the first and second ASIS locating elements 14. With the patient connection plate 18 secured in place on both the left and right second ASIS locating elements, the recesses 32 on the first and second ASIS locating elements 14 can be placed over the central ring protrusion to orient the datum 100 in a reference orientation when the pubic locating element 16 is also in place. The ring structure of the patient connection plate 18 also allows the surgeon to easily position the patient connection plate 18 directly over the patient's ASIS when the patient is covered by surgical drapes.

[0045] 4 illustrates the fixation of the patient connection plate 18 to the patient. An adhesive sterile film 35 is applied to the patient's skin 36. The connection plate adhesive 34 is applied to the adhesive film 35 over the anterior-superior iliac spine and is used to fixate the patient's lateral side and orient the electronic direction monitor 46 to a reference direction. During this orientation, the electronic direction monitor 46 acquires reference direction information that is used to calibrate the electronic direction monitor 46 to the reference direction. A patient cover sheet 33 can be accommodated between the patient connection plate 18 and the first and second anterior-superior iliac spine positioning elements 14.

[0046] 5-8 show the electronic direction monitor 46 and the electronic direction monitor housing 12. The electronic direction monitor housing 12 is a sterile housing so that the electronic direction monitor 46 does not need to be sterile for patient use. In one embodiment, the electronic monitor housing 12 is a clamshell housing. The electronic monitor housing 12 includes a body 24 for receiving the electronic direction monitor 46, a lid 41, a load funnel 37, and a locking means 80.

[0047] The clamshell housing 12 serves three primary functions. 1. It provides a physical barrier to biological contamination of the directional monitor. 2. It provides physical vibration isolation from the high levels of shock experienced when the directional monitor is used. 3. It maintains proper alignment of the directional monitor. Because the accuracy of the directional monitor is very sensitive to any misalignment, the clamshell has a built-in alignment feature to maintain proper alignment during use.

[0048] Clamshell housing 12 is preferably designed to be supplied as a sterile, single-use part. Reuse of clamshell housing 12 may pose safety risks to the patient through one or more of the following: · Misalignment due to wear and tear from reuse. Misalignment due to deformation caused by washing or handling. Contamination leading to infection due to incorrect or inadequate resterilization.

[0049] Load funnel 37 includes an angled leading wall 38 and an insertion wall 39. The load funnel is sterile and prevents non-sterile components from contacting the sterile components of electronic direction monitor housing 12. The load funnel is inserted into electronic direction monitor housing 12 to allow the non-sterile electronic direction monitor 46 to be inserted into electronic direction monitor housing 12. When within electronic direction monitor housing 12, the non-sterile electronic direction monitor 46 can be used in a sterile environment and can withstand forces applied to electronic direction monitor housing 12, as described further below. Housing 12 also preferably includes one or more internal positioning features adapted to ensure proper alignment of monitor 46 within housing 12, and therefore, ensure reproducible and accurate direction measurements.

[0050] In an alternative embodiment shown in Figure 5A, the load funnel 37 is replaced with a transfer shield 60. The shield 60 is placed over the opening in the housing 12 to protect the sterile components of the housing 12 while the monitor 46 is inserted into the housing 12 through the shield 60. The shield 60 provides improved protection for the sterile components of the housing 12 during insertion of the monitor 46 over the load funnel 37 of Figure 5. The housing 12 protects the navigation unit during use, providing shock insulation and a physical barrier against biological contamination.

[0051] Electronic direction monitor housing 12 includes body 24, cap 41, clip 42, and clip lock 47 that is positioned to receive and lock clip 42 and cap 41 into place to seal body 24. Cap 41, clip 42, and clip lock 47 are part of lid 43 of electronic direction monitor housing 12. Cap 41 pivots about its connection with lid 43 to seal body 24.

[0052] A locking means 80 extends from the base of the electronic direction monitor housing 12 to engage the docking station 19 and secure the electronic direction monitor 46 to the reference device 100 for obtaining a reference direction.

[0053] The locking means 80 includes vertical extension members 25 extending vertically from the main body 24. There are front and rear pairs of vertical extension members 25 that form a square profile. Support frame members 26 extend between the front and rear vertical extension members 25 to form an enclosed frame. The vertical extension members 25 are attached to the main body at upper pivot points 45, allowing the vertical extension members 25 to rotate about the upper pivot points 45. The support frame members 26 are attached to the vertical extension members 25 using lower pivot points 44, allowing the ends of the vertical extension members 25 to pivot about the support frame members 26. It will be described below that the mounting means is further adapted to engage a mounting frame 90 that includes vibration isolation features for absorbing forces applied longitudinally to the electronic direction monitor housing 12. The isolation features in certain embodiments include spring features 91, as described below and shown, for example, in FIG. 5B.

[0054] The enclosed frame of the locking means 80 includes a central opening 48 shaped to receive the docking station 19 therein, securing the electronic directional monitor 46 to the reference device 100 and orienting the electronic directional monitor 46 relative to the patient for further surgical use.

[0055] A further embodiment of the electronic monitor housing 12 is shown in Figures 5A-5C. In this further embodiment, the angle of the housing 24 is set at a tilted angle by a mounting frame 90 to provide better viewing by the surgeon and surgical staff. The mounting frame 90 is configured to precisely engage the docking station 19 of the datum device 100. The spring features 91 of the mounting frame 90 act to isolate the orientation monitor housing 12 and the installed orientation monitor 46 from environmental vibrations during operation, improving the positional accuracy that can be provided by the orientation monitor 46.

[0056] 6 and 7 show additional views of the above-disclosed clamshell housing 12. Figures 8A and 8B depict the clamshell housing 12 engaged with the frame 70 of the datum device 100.

[0057] Referring to FIG. 9 , the electronic directional monitor housing 12 with the electronic directional monitor 46 inserted is attached to an insertion instrument 52 having an acetabular cup 54, with the orientation assumed by the electronic directional monitor 46. The surgeon manipulates the insertion instrument 52 into a position where the cup is adjacent to the patient's hipbone, and a display (not shown) on the electronic directional monitor 46 guides the surgeon to orient the insertion instrument so that the current orientation of the electronic directional monitor 46 is equal to the reference orientation (or so that the current orientation has some other desired relationship to the reference orientation). The display provides the surgeon with position and orientation information, including yaw / tilt axis and anteversion / pitch axis directions, allowing the surgeon to precisely orient the prosthetic tool with the patient's unique anatomy. The orientation monitor 46 can provide orientation information to the surgeon in many different ways, depending on the particular surgeon's preferences. For example, the orientation of the insertion instrument 52 relative to the patient's hipbone may be communicated to the surgeon through a simple target display, or the extent to which the instrument 56 is off-target may be visually communicated. Further examples of directional indicators may include a "bubble level" visual indicator, or a numerical indicator, depending on the surgeon's personal preference.

[0058] Once the desired orientation is achieved, the electronic orientation monitor 46 provides instructions to the surgeon, such as visual and / or audible indications on a display, prompting the surgeon to evaluate the trial cup or strike the impactor plate 55 to transmit force through the shaft 53 to impact the acetabular cup 54 into the patient's reamed acetabulum.

[0059] When placed on the insertion tool 52, the electronic directional monitor housing 12 is positioned to isolate shock from the electronic directional monitor 46. The vertical extension member 25 pivots about pivot points 44 and 45 to move the support frame member 26 forward or rearward to isolate the force applied to the impactor plate 55 from the electronic directional monitor 46. The spring formation 91 of the embodiment of the housing 12 as seen in FIG. 5B is particularly adapted for shock isolation from the insertion tool during use.

[0060] From the foregoing, it will be appreciated that datum 100 is configured for exclusively anterior engagement with the patient and the patient connection plate 18 thereon during the step of forcing the datum into engagement with the surgical drape and during calibration of the electronic direction monitor. This compares favorably with the clamp disclosed in WO 2010 / 031111, which requires both anterior and posterior engagement with the patient, as it has been realized by the inventors that the clamp of WO 2010 / 031111 may, in practice, cause undesirable injury to the surgeon.

[0061] Although the present invention has been described with reference to specific embodiments, those skilled in the art will appreciate that it can be embodied in many other forms.

Claims

1. 1. A datum device for application onto a patient, comprising: A support plate; a first positioning element extending from the support plate; a second positioning element extending from the support plate; a third positioning element extending from the support plate; and an electronic directional monitor housing having an opening through which a surgical electronic directional monitor is inserted that is removably engageable with the support plate and the surgical instrument, the support plate being usable to take measurements to calibrate the surgical electronic directional monitor for use with the surgical instrument; a docking station to which the electronic surgical direction monitor is attached, the docking station adapted to receive the housing, thereby defining a reference point external to and relative to the patient's anatomy; the first positioning element, the second positioning element, and the third positioning element are positioned to be depressed onto a patient to provide a reference orientation for the electronic orientation monitor with respect to a predetermined anatomical location; Reference device.

2. The datum of claim 1 , wherein the housing is a sterile housing.

3. The housing includes: a body including the opening adapted to receive the orientation monitor; a load funnel having angled leading and insertion walls to allow a sterile directional monitor to be inserted into the sterile housing while preventing contamination of the sterile housing; a locking means comprising an enclosed frame adapted to engage the docking station, the frame pivotally mounted to the body of the housing; The reference device of claim 2 , comprising:

4. 4. The datum of claim 3, wherein the load funnel is a transfer shield adapted to be placed over the opening in the housing to protect sterile components of the housing during use while a monitor is inserted into the housing through the shield.

5. 5. The datum of claim 3, wherein the locking means comprises a central opening shaped to receive the docking station therein, thereby securing the electronic orientation monitor to the datum for orienting the orientation monitor relative to the patient.

6. The datum of any one of claims 1 to 5, wherein the housing is a clamshell housing.

7. The datum of claim 1 , wherein the first and second locator elements are first and second anterior superior iliac spine locator elements.

8. The datum of claim 1 , wherein the third locator element is a pubic locator element.

9. The datum of claim 1 , wherein the first and second positioning elements include a patient connection plate.

10. 10. The datum of claim 1, wherein the patient connection plate is positioned for fixation to the patient above the anterior superior iliac spine.

11. 11. A datum as claimed in any preceding claim, wherein the electronic heading monitor is housed in an electronic heading monitor housing.

12. 12. A datum according to claim 10 or claim 11, wherein the electronic direction monitor housing is arranged to engage the support plate to provide a reference direction for the electronic direction monitor.

13. 13. The datum of claim 1, wherein an electronic direction monitor is dockable with the docking station in either a first docking configuration or a second docking configuration.

14. the first docking configuration defines a first orientation of the electronic orientation monitor relative to the reference device; the second docking configuration defining a second orientation of the electronic orientation monitor relative to the reference device; 14. The reference device of claim 13.

15. 10. A method for calibrating an electronic direction monitor using the reference device of claim 1, comprising: positioning a patient connection plate on the left anterior superior iliac spine; positioning a patient connection plate on the right anterior superior iliac spine; connecting first and second positioning elements to respective patient connection plates; positioning a third positioning element relative to the pubic bone; placing the electronic orientation monitor within a sterile housing that includes means for receiving a non-sterile monitor while preventing contamination of the sterile housing; engaging a housing with a monitor contained therein with a docking station disposed on the reference device to assume a reference orientation external to and relative to the patient; calibrating the electronic direction monitor; A method comprising:

16. 16. The method of claim 15, wherein the datum is positioned in front of the patient during the step of engaging the datum with a surgical drape and during calibration of the electronic orientation monitor.

17. 17. The method of claim 15 or claim 16, wherein an anterior approach is used to surgically access the patient's acetabulum.

18. 18. The method of any of claims 15 to 17, wherein the patient lies in a supine position during the steps.

19. 10. A method of calibrating an electronic direction monitor using the reference device of claim 1, comprising: positioning a surgical drape over the patient; engaging the plurality of positioning elements with respect to the surgical drape such that the surgical drape is positioned between the plurality of positioning elements and each of a plurality of predefined anatomical sites on the patient, causing a docking station disposed on the reference device to assume a reference orientation with respect to the plurality of predefined anatomical sites; placing an electronic orientation monitor in a sterile housing having means for receiving a non-sterile monitor while preventing contamination of the sterile housing, and docking the housing with the docking station to orient the electronic orientation monitor in a reference direction; calibrating the electronic direction monitor; A method comprising:

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