Abstract:
Paired bones are individually secured in an anatomically relevant manner onto independent, parallel positioned platforms, and configured into motorized models for the purpose of teaching and assessing clinicians&#39; ability to identify and compare the relative positions of bony landmarks within the coronal and sagittal planes. One platform can be powered by two motors to generate precise landmark asymmetries, moving the platforms in the coronal plane and around a horizontal axis. As the platform shears upward or rotates forward, the landmarks on the bone attached to that platform can be moved superiorly compared to the other side. A central computer can instruct the motors of a plurality of models to move predetermined amounts via a two-way wireless communications link. The model can communicate back to the computer once the movement is completed, assuring a high level of precision in obtaining the intended positional asymmetry or informing the user that the move exceeds the limits of the model.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/788,152 filed on Mar. 15, 2013, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates to models (apparatuses) and methods for teaching and determining competency of clinician&#39;s skills in assessing the relative position of bony landmarks of the skeleton. 
       BACKGROUND 
       [0003]    There are several palpatory diagnostic and treatment methods that have been developed to evaluate characteristics of the musculoskeletal system. One method evaluates the relative position of bony protuberances within the cardinal planes, primarily the coronal and sagittal planes. This method can be used, for example, when evaluating lower body and lower limb musculoskeletal disorders, including osteo/rheumatoid arthritis, spinal cord and other central nervous system (CNS) disorders, CNS degenerative diseases, low back pain, pelvic pain, postural and gait abnormalities, and obstetrics-gynecological disorders. Literature indicates that this form of testing has been used for at least a century, but a system to objectively evaluate the accuracy of the performance of this type of testing has only recently been considered. 
         [0004]    The pelvis is one example of a region of the body where these tests are routinely used by clinicians in several manual medicine disciplines, including osteopathic physicians, chiropractors, physical therapists, for example. Pelvic landmarks commonly evaluated are the iliac crests, the anterior superior iliac spine (ASIS), the posterior superior iliac spine (PSIS), the pubic tubercles and the ischial tuberosities. 
         [0005]    Muscle contraction during walking and running has been shown to cause changes in the relative position of the pelvic bones and thus their associated landmarks. For over a century, anecdotal reporting has proposed that when the relative position of the pelvic bones becomes too asymmetric, the pelvic joints (sacroiliac joints and pubic symphysis) lose mobility so when muscles pull on them, compression of joint surfaces, abnormal movement characteristics, and pain often results. Manual interventions have been designed to diminish the asymmetry of these landmarks and improve pelvic bone movement characteristics, which anecdotally have been associated with improved function and pain reduction/resolution. Consequently this method of manual testing, evaluating positional asymmetry of landmarks, has both diagnostic and treatment outcome functions. 
         [0006]    Evaluating the validity of landmark asymmetry testing has been challenged by the lack of a methodology to objectively measure landmark asymmetries. Direct determination of positional asymmetry of pelvic landmarks in living humans (in vivo), for example, does not exist at this time. There remains a need, therefore, for a system that allows accurate control of the relative position of bones that exhibit asymmetry, such as the pelvic bones, using models of the human pelvis. The system should allow for an objective and accurate assessment of asymmetry and provide feedback to students and practitioners performing positional asymmetry tests of the pelvis. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    In one aspect, the present disclosure provides a motorized model for assessing skeletal landmark asymmetries between corresponding opposing paired bones in a vertebrate. The motorized model comprises a bone including a skeletal landmark coupled to a stationary platform, and a corresponding opposing bone coupled to a moveable platform that is connected to a shear motor adapted to drive the moveable platform linearly relative to the stationary platform. A controller is in communication with the shear motor, and is programmed to receive asymmetry data from a user to provide a selected asymmetry between the bone and corresponding bone, and to drive the shear motor to provide the selected asymmetry for analysis of landmarks associated with the bone. The asymmetry between the bone and the corresponding bone can be evaluated for training purposes. 
         [0008]    In one embodiment, the bone and the corresponding bone comprise a right and left hip bone, respectively, and the motorized model is calibrated to provide an anterior bone zero where corresponding landmarks of the left and right ASIS, the left and right iliac crest, and the left and right pubic tubercle sets on the first and second hips are aligned in the coronal plane. The bones can be coupled to the corresponding platform with the posterior side of the hip bone facing opposite the platform. The model can be calibrated to define a posterior bone zero in which the right and left iliac crest, right and left posterior superior iliac spine and the right and left ischial tuberosities are aligned in the coronal plane. 
         [0009]    In another aspect, a system of motorized models for assessing skeletal landmark asymmetries in the corresponding bones of vertebrates is disclosed. The system includes a plurality of motorized bone models. Each of the motorized bone models comprises a stationary platform. A moveable platform is moveably coupled adjacent the stationary platform and to a shear motor and a rotational motor for linearly moving the moveable platform relative to the stationary platform and rotating the moveable platform relative to the stationary platform. One of a right bone and a left bone is coupled to the stationary platform, and the other of the right and left bones coupled to the moveable platform. A motor control is in communication with the shear motor and the rotational motor for driving the moveable platform to a selected position, and a model communications device in communication with the motor control for receiving commands for driving the shear and rotational motors. A central computer includes a user input device for receiving commands from a user for driving the moveable platform to a user selected asymmetry, and a central communications device in communication with the user input device for receiving commands from the user and the model communications device to provide commands to the motor control for driving the shear motor and the rotational motor. When the moveable platform is moved, an asymmetry is created between the right and left bones as selected by the user. The communications link between the central communications device and the corresponding model communication devices can be a wireless communications link. 
         [0010]    In another aspect, the right and left bones can comprise a right and a left hip bone, respectively, and the model can be calibrated to define a posterior bone zero in which the right and left iliac crest, right and left posterior superior iliac spine and the right and left ischial tuberosities are aligned in the shear direction. Alternatively, the left and right bones can comprise a left and right hip bone, and the motorized model can be calibrated to provide an anterior bone zero where corresponding landmarks of the left and right ASIS, the left and right iliac crest, and the left and right pubic tubercle sets on the left and right hip bones are aligned in the shear direction. 
         [0011]    In still another aspect, a method for emulating skeletal landmark asymmetry in a vertebrate for use in teaching evaluation of asymmetries is disclosed. The method comprises the steps of mounting one of a corresponding right and left bone to a stationary platform, mounting the other of the corresponding right and left bone to a moveable platform adapted to be driven in at least one of a shear and a rotational direction relative to the stationary platform, and moving the moveable platform to a home position, wherein landmarks corresponding to the right and left bone are aligned in the shear direction. The moveable platform can then be driven to a selected position defining an asymmetry, wherein the asymmetry can be evaluated by a medical practitioner for training purposes. The right and left bones can be corresponding pelvic bones. The anterior side of each of the right and left pelvic bones can be mounted opposing the corresponding stationary and moveable platforms, and the landmarks can be defined as an anterior bone zero aligned in the shear direction are the left and right ASIS, the left and right iliac crest, and the left and right pubic tubercle sets. Alternatively, posterior side of each of the right and left pelvic bones opposing the corresponding stationary and moveable platforms, and the landmarks aligned in the shear direction to define a posterior bone zero can be the right and left iliac crest, right and left posterior superior iliac spine and the right and left ischial tuberosities. 
         [0012]    In still another aspect, a method for calibrating a motorized model for assessing skeletal landmark asymmetries in the corresponding bones of vertebrates is disclosed. The motorized model comprises right and left corresponding bone structures mounted to corresponding platforms, wherein at least one of the platforms is linearly or rotationally moveable relative to the other of the platforms through predetermined coordinates. The method includes the steps of marking at least one bony protuberance identifying a landmark, acquiring images of the marker at a plurality of the predetermined coordinates, and calculating the position of the marker in each of the acquired images in three dimensional space. A position of the moveable platform is then adjusted relative to the stationary platform through a plurality of predetermined positions. The calculations can be adjusted to account for a difference between a centroid of the marker and the position of the landmark, wherein the system can consistently reproduce asymmetries in the model. In one embodiment, the marker can be an infrared marker, and the images can be acquired using an infrared camera. 
         [0013]    These and other aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a block diagram of a motorized pelvic model system constructed in accordance with any combinations of the present invention. 
           [0015]      FIG. 2  is a top view of a motorized pelvic model with the anterior side of the pelvic bones coupled to a platform so the posterior pelvic landmarks can be assessed. 
           [0016]      FIG. 3  is a perspective view of an alternate motorized pelvic model with the posterior side of the pelvic bones coupled to a platform so the anterior pelvic landmarks can be assessed. 
           [0017]      FIG. 4  is a top view of the platforms of  FIGS. 2 and 3  with the translatable plate removed illustrating the rotational axis for a rotating top plate. 
           [0018]      FIG. 5  is an image of the rotatable top plate with the translatable plate removed demonstrating an end contact switch regulating movement around the rotational axis. 
           [0019]      FIG. 6  is a bottom view of the stationary base plate demonstrating the bracing of a mechanical central box to the base plate and a lower hinge for the rotational axis actuator. 
           [0020]      FIG. 7  is a side view from the inferior or “foot” of the motorized model, looking towards the “head” of the model, illustrating a covered model with the pliable material overlying the model. 
           [0021]      FIG. 8  is an image illustrating the motorized pelvic bone model. 
           [0022]      FIG. 9  is a perspective view of a multi-station system of motorized pelvic bone models with a plurality of models controlled by a central computer. 
           [0023]      FIG. 10  is an illustration of a screen provided on a display of the central computer to wirelessly connect with the satellite models and control their movements. 
           [0024]      FIGS. 11 and 12  illustrate translatable motion of one hip relative to the other. 
           [0025]      FIGS. 13 and 14  illustrate rotational motion of one hip relative to the other. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Referring now to the Figures and more particularly to  FIG. 1 , a block diagram of a motorized bone model  10  for assessing landmark asymmetries is shown. As shown here, models of “paired bones,” here a left hip bone  12  and a right hip bone  14 , are coupled to a stationary (left) and movable (right) platform  16  and  18 , respectively. A rotational motor  22  and a shear motor  24  are coupled to the moveable (right) platform  18  and receive commands from a motor controller  20  to drive the platform  18  linearly and rotationally relative to the left platform  16  to simulate asymmetries between the bones. Commands to the motor controller  20  can be provided from a remote computer  26  which can be, for example, controlled by an instructor teaching a student to evaluate asymmetries in the pelvis as described more fully below. 
         [0027]    Referring still to  FIG. 1 , the remote computer  26  can be an off-the-shelf computing system including a processor  30  and corresponding memory (not shown), a display  34 , and a user interface  36 , which can be a keyboard, a touch screen incorporated as part of display  34 , a mouse, or various other types of devices for receiving information from a user. The remote computer  26  communicates to the motor controller  20  through a communication device  38  which can provide a wired or wireless communication link to a corresponding communications device  40  in the controller  20 . The communications are directed to a control board  42  in the motor controller  20 , which can include a processor driving a transistor or other switching device to selectively apply power to the rotational and shear motors  22  and  24 , as is known in the art. The motors  22  and  24  can be, for example, stepper motors, although servo motors or other types of motors capable of precise movement can also be used. 
         [0028]    Referring now to  FIG. 2 , a top view of one embodiment of the motorized model  10  is shown. The embodiment shown here is a posterior model, with the posterior side of the hip bones  12  and  14  exposed so that the relative positions of three landmarks, the iliac crest  50 , PSIS  52  and the ischial tuberosities  54  can be palpated by a student or other clinician to determine the relative position of the landmarks on the right hip  12  as compared to the left hip  14 . Referring now also to  FIG. 3 , an alternate anterior embodiment is shown. Here, the posterior sides of the hip bones  12  and  14  are coupled to the left and right platforms  16  and  18 , respectively, with the anterior shown. This configuration allows an examiner to evaluate the landmarks on the anterior side of the pelvis, the iliac crest  50 , the ASIS  62  ( FIG. 3 ) and the pubic tubercles  64 . 
         [0029]    Referring still to  FIGS. 2 and 3 , the stationary left platform  16  can be fixed in position by fasteners such as screws, bolts or other devices  55 . Referring now specifically to  FIG. 3 , the moveable right platform  18  comprises an upper plate  58  moveably secured to a rotatable top plate  60 , which is rotationally mounted to a base plate  61 . A support brace  63  secures the rotatable top plate  60  to the stationary base plate  61  at a predetermined height, which is selected to exceed the known amount of asymmetry of the landmarks in humans, here selected to allow for 3.5 degrees of motion in both directions from the flat, neutral position. The rotatable top plate  60  is coupled to the stationary base plate  61  through rotational bearing  66 , described herein. The left platform  16  is preferably stationary, but can also include a similar construction (not shown) as described for the right platform  18 . 
         [0030]    Referring still to  FIGS. 2 and 3 , slots  57  are provided through the upper plate  58  to receive threaded fasteners  59  to secure the upper plate  58  to the base plate  60  while allowing the shear motor  24  to linearly drive the upper plate  58  to slide (shear) relative to the fixed right platform  18 . The motor controller  20  can be provided in a control box  69 , which can be mounted adjacent platform  16  and can contain the motors necessary for controlling precise movements of the right platform  18 . 
         [0031]    Although a number of different types of components and materials could be used, the upper plate  58  of platform  18  is preferably constructed of aluminum, and the hip bone  14  is coupled to the plate using metal anchoring posts and threaded fasteners such as screws or bolts. The stationary base plate  61  can comprise a solid piece of plasticized material, sized and dimensioned to be received within customized rails ( 132 - FIG. 11 ) on tables, which keep the model immobile during testing. The rotatable top plate  60  can, similarly, be constructed of a plasticized material. The two plates  60  and  61  can be cut from a single piece of material into two suitably sized panels. Construction of the platform  16  (not shown) can be similar or identical to the dimension of the plate  60 . The hip bones  12  and  14  can be made of plastic, fiberglass, or other materials, or actual bones. 
         [0032]    Referring still to  FIG. 3 , the rotatable top plate  60  and base plate  61  can each comprise a recess sized and dimensioned to receive a support brace  63 . Threaded fasteners  67  such as screws or bolts can be used to couple the support brace  63  to the base plate  61 . A rotational bearing  66  couples the support brace  63  to the rotatable top plate  60  allowing rotation about the bearing  66 , as described below. 
         [0033]    Referring now to  FIG. 4 , a bottom view of the rotatable top plate  60  with the translatable top plate removed is shown as coupled to the platform  16 . As described above, rotational bearing  66  couples the rotational top plate  60  to support brace  63  ( FIG. 3 ), while a second rotational bearing  68  couples the rotatable top plate  60  to platform  16 . To improve rigidity and provide precision movement, the rotational bearings  66  and  68  can be fitted with a precision-ground shaft pin running in a sintered bronze sleeve bearing. The sleeve can be press-fitted into the top plate to assure rigidity in the material of the top plate. The outer diameter of the sleeve of 5/16″ adds additional rigidity by better distributing force due to its larger diameter. Clearance between shaft and sleeve is approximately ±0.001″ resulting in minimal, virtually undetectable free play. The free play is sufficiently small that it does not degrade movement. The outer bearing shaft can be bolted to the outer support member. This arrangement provides a strong bond between the shaft and the support member while allowing for easy assembly and disassembly. The bearing sleeve can be press-fit into the top plate and the threaded shaft inserted. The clearance between sleeve and shaft is ±0.001″ making it snug to move with no detectable free play. The rotational motor  22  can include a linkage comprised of two pivot points. 
         [0034]    Referring still to  FIG. 4 , the shear motor  24  is coupled to linear actuation mechanism  70  which can be, as shown, a lead screw  72  and corresponding end tab  74  recessed or milled into the rotatable top plate  60 . End contact switches  71 ,  78  are secured to the translatable top plate  58  ( FIG. 3 ) and designed to enable movement of + 12  mm from a pre-defined symmetric (“zero”) point. At ±13 mm, the end tab  74  at the end of lead screw  72  will contact an end contact switch  71 ,  78  which provides a signal to the processor on controller  42  ( FIG. 1 ) indicating the end of motion. The end of motion signal in turn triggers the controller  42  and communications device  40  to send a message to the communication device  38  in central computer  26  to notify the user that the end range of motion has been exceeded. The activation of the end contact switches  71 ,  78  can further be used by the motor controller  42  ( FIG. 1 ) in motor controller  20  as a parameter for an automatic homing procedure to the pre-defined symmetric (“zero”) point. Although a number of possible constructions exist, the depth of the recessed part of the top surface of the rotatable top plate  60  can be chosen to accommodate the lead screw  72 , end tab  74  and end contact switches  71  and  78  and is preferably sufficiently shallow to limit weakness in the top plate  60  due to removal of excess material. The end switches  71  and  78  can deactivate the motor shortly before the physical limits of the axis are reached. The shear motor  24  can also include thrust bearings to eliminate axial play and prevent binding of the rotating armature at run time under load. 
         [0035]    Because of the geometry of the stationary base plate  61  with respect to the rotating top plate  60 , the linear actuator element (not shown) of stepper motor  24  driving the rotational axis with a lead screw (not shown) can be mounted with flexible linkages at the top and the bottom connection. The top linkage can be comprised of two ball joints that act as upper bearing and allow for a compact design keeping the vertical profile to a minimum by positioning the ball joint right and left of the lead screw  72 . At the bottom a hinge joint serves as lower bearing permitting angular movement but preventing twisting of the linear actuator. Both bearings are precision devices with no detectable free play for a tight but flexible linkage between the linear actuator  70 , the base plate  61  and the top plate  60 . 
         [0036]    The upper joint can comprise a ball joint in the form of rod ends which provide convenient and rigid attachment to an angle member rigidly attached to the rotatable top plate  60 . A threaded precision-ground shaft can be used to facilitate a rigid attachment to the vertical lead screw in the form of a cross member. The threaded precision-ground shaft can be drilled out in the middle to accommodate the vertical lead screw. The same screws bolting the ball of the ball joint to the threaded shaft can be used to clamp the vertical lead screw firmly between them. 
         [0037]    The lower bearing can comprise a conventional strap hinge modified with a sleeve bearing. To minimize free play and produce a precision joint a sleeve-and-shaft bearing can be used. The bearing can be comprised of two sleeves and one common shaft. The two loops of one half of the strap hinge have a diameter slightly less than the outer diameter of the bearing sleeves. The sleeves are press-fitted firmly into the loops for a tight and rigid attachment. The loops of the other half of the hinge are crimped to yield an inner diameter slightly less than the diameter of the precision-ground bearing shaft to again provide a tight and rigid press-fit. The thus modified hinge is a precision linkage without detectable free play. No axial movement of the sleeves or the shaft is possible since they are firmly press-fitted into the hinge loops. 
         [0038]    Referring now to  FIG. 5 , a contact switch  80  is coupled to the top end of the base plate  61  and a corresponding contact switch (not shown) is coupled to the opposite end. These contact switches are activated when the rotatable top plate  60  rotates more than  3 . 5  degrees from a platform neutral position and provides an end of travel signal to controller  42 . In summary, the end contact switches  71 ,  78 , and  80  for linear and rotational motion serve as safety features as well as fix points for a homing procedure. Once a homing procedure is performed, the controller  42  can accurately assess and communicate the current position of the platform  18 . 
         [0039]    Referring again to  FIGS. 3 and 4 , the contents of the control box  69  includes motors  22  and  24  which can be stepper motors. As described above, the motors  22  and  24  are connected to lead screws  72  which can be precision-machined have near-zero backlash. The rotational motor  22  and corresponding lead screw are mounted with flexible linkages at the top and the bottom connection. The flexible linkages can be, for example, ball joints that act as upper bearing and a hinge joint that acts as lower bearing. These motor/lead screw complexes are perfectly accurate up to 0.25 mm. The stepper motors  22  and  24  were chosen due to their small size, low power consumption and low vibration. The controller can include a motor driver for driving each of the shear motor  22  and the rotational motor  24  and a microcontroller, which controls the stepper motor drivers. Power to the motors and digital circuits can be provided by an AC adapter supplying, for example, 2A of DC current at 12V. The housing enclosure of the control box  69  can be fabricated from a non-conducting material (ABS plastic) to allow free travel of radio waves without shielding effects. 
         [0040]    Referring now to  FIG. 6 , the control box  69  containing the motor controller  20 , shear motor  24  and rotational motor  22  is shown coupled to the base plate  61 . Cutouts in the base plate  61  receive bracing elements  82  and  84  which can be coupled to the base plate  61  and box  69  with mechanical fasteners such as screws, bolts or other coupling devices, and allow the control box  69  to be inlaid into the stationary base plate without affecting the slope of the bottom surface of the model  10 . A hinge  86  couples the platform  18  to the box, and is positioned between braces  82  and  84  to provide a flexible support for the rotational motor  24  actuating the rotational axis. 
         [0041]    Referring now to  FIGS. 7 and 8  the hip bones  12  and  14  of the motorized pelvic bone model  10  can be covered with a foam pad and fabric  90  or other material selected to simulate soft tissue and skin. The model  10  can be secured on an exam table  92  by coupling the model between rails  94  to keep the model from sliding in any direction. The rails provide a guide that prevents lateral movement of the base while the student exerts pressure, and no hardware extends beyond the left or right sides. Because the model  10  is placed flat on the table between the rails  94  no hardware extends below the bottom of the base plate. 
         [0042]    Referring again to  FIG. 1 , and now also to  FIG. 9  in operation, a plurality of motorized models  10  are in communication with remote computer  26 . The communication between communication device  38  in remote computer  26  and communication device  40  in motor controller  20  are preferably wireless, and allow for telemetry communication between the central computer  26  and the motor controller  20  in a corresponding motorized model  10  over a distance of at least 100 ft. The communication device  40  in each motorized model  10  can be configured as a network end point. Alternatively, wired communication, such as a direct cable connection between the central computer  26  and a model  10  can be provided. 
         [0043]    The remote computer  26  communicates to each of the motorized models  10  through communications device  38  and corresponding communication device  40 . In one embodiment, for example, the remote computer  26  comprises a node in a star-configured network that conforms to the international IEEE 802.15.4 standard. In this configuration the communications device  38  can comprise a coordinator radio that can establish a two-way communication with the communications device  40  in each motorized model  10 . Communications can be provided through a universal serial bus (USB) port on the computer  26 . The communications device  40  on each of the motorized pelvic models  10  can include a “router” radio. Each such “router” radio may communicate with the “coordinator” radio connected to the computer  26  in a network. The motorized models  10  typically do not communicate directly with each other. Although a number of different ranges is possible, in one embodiment, a range of wireless communication of 100 feet indoor/urban range and a minimum of 200 feet outdoor/RF line-of-sight between the central computer and any motorized model was found suitable for the application. 
         [0044]    Referring again to  FIG. 1 , the display  34  and user interface  36  of the computer  26  allow an operator, such as an instructor, to enter end range parameters of the moveable aluminum plate and rotatable top plate, and to input the desired asymmetry setting for the specific landmark. The remote computer  26  informs the operator when the movements have completed or exceeded the designated range of movement. A separate set of criteria can be established for each motorized model  10  and these can be provided on separate tabs in the instruction. 
         [0045]    Once the wireless connection has been established between the remote computer  26  and the motorized models  10 , each model  10  can be provided instructions individually. Initially, and prior to use, the remote computer identifies and logs a home position or neutral position for the motorized pelvic model  10 , within the coronal plane, and the end limits of the shear range. To calibrate the home position, the user directs the translatable top plate  58  to move to the extreme negative shear limit, identified by the activation of the end contact switch. This position is logged by the firmware, and the translatable top plate  58  is reversed toward the positive shear limit for a pre-determined distance, approximately half-way between the shear limits. This position is designated as shear home position to which all subsequent shear movements are referenced such that the firmware can infer at all times the actual shear position. This process is repeated for the rotational motion. The platform motor is instructed to rotate the rotatable top plate to the extreme negative position, identified by the activation of the end contact switch. This position is logged by the firmware and the rotatable top plate is reversed toward the positive rotational limit for a pre-determined angle, approximately half-way between the rotational limits. This position is designated as rotational home position to which all subsequent rotational movements are referenced such that the firmware can infer at all times the actual rotational position. 
         [0046]    For proper comparison and alignment of motorized models  10 , a “bone zero” is logged for each landmark. “Bone zero” defines the platform position where the asymmetry for a particular landmark has zero rotation and shear space. The definition of bone zero is the measurement of shear that is recorded when the rotation is zero, and the shear is adjusted such that the pair of landmarks are exactly even in the coronal plane, as determined by an overhead laser beam that is projected vertically from directly above the model onto the model itself. 
         [0047]    On the anterior pelvic model, there is a bone zero for the left and right ASIS, the left and right iliac crest, and the left and right pubic tubercle sets. For example, when the shear is set to 3 mm, the ASIS landmarks are symmetrical within the coronal plane, while the Pubic tubercles may be symmetrical at a shear of −2 mm, and the iliac crests may be symmetrical at a shear setting of 6 mm. For the posterior pelvic models bone zero is evaluated for the Iliac Crest, Posterior Superior Iliac Spine (PSIS), and Ischial Tuberosity landmarks. 
         [0048]    To establish “bone zero,” infrared markers are then placed on each of the landmarks for a calibration process. An infrared camera system is used to identify the location of each infrared marker in three dimensions as the remote computer  26  commands the motor controller  20  for each model  10  to move to a number of predetermined positions along both the coronal plane and around the rotational axes. After the images are acquired, the location in three dimensional space of each of the infrared markers and corresponding landmarks is calculated at each of the predetermined settings along the axes. Due to the fact that the camera system measures 3D landmark locations using the centroid of the infrared marker (which can be, for example, about 3 mm away from the mark on the bones used to locate the bone zero settings), the remote controller adjusts the actual location of the landmarks based upon the bone zero vs. the centroid calculations. 
         [0049]    Once bone zero has been identified for all relevant markers on the models, the platforms are returned to home position (0) and the movable plate is sheared +/−1, 2, and 3 mm in the coronal plane, and +/−1, 2, and 3 degrees around both directions of the rotational axis, to begin calibration and setting standardization process for testing purposes. Three different calibration trials with 40 different combinations of shear and rotational settings can be performed to assure accurate and reproducible identification of asymmetries for each landmark. The +/−1, 2, and 3 mm can be located at positions equidistant along the coronal plane, with + causing shearing movement in the cephalad direction in relation to the model&#39;s anatomy and − causing shearing movement in the pedal direction related to the model&#39;s anatomy. Similarly, the rotation adjustments are designated as 0 (a home position) and +/−1, 2, and 3 degree increments. Here, the increments are positioned around the rotational axis from the home position to the end of motion, with the positive rotation adjustments resulting in positive z displacements of the landmarks, and the negative rotation adjustments resulting in negative z displacements of the landmarks. In this embodiment, each round of calibration consists of the following 40 settings: S0, R0; S0, R1; S0, R2; S0, R3; S0, R−1; S0, R−2; S0, R−3; S1, R0; S1, R1; S1, R2; S1, R3; S1, R−1; S1, R−2; S1, R−3; S2, R0; S2, R1; S2, R2; S2, R3; S2, R−1; S2, R−2; S2, R−3; S3, R0; S−1, R0; S−1, R1; S−1, R2; S−1, R3; S−1, R−1; S−1, R−2; S−1, R−3; S−2, R0; S−2, R1; S−2, R2; S−2, R3; S−2, R−1; S−2, R−2; S−2, R−3; and S−3, R0. 
         [0050]    During the calibration process, three trials are run for each setting. The remote computer  26  calculates the bone zero settings by using the data from the infrared position capturing camera system to determine the actual asymmetries between the left and right landmarks at the full array of settings that are tested during the calibration process. Specifically, as the model is moved through these 40 different settings, the remote computer  26  uses adjustment between the actual landmarks and the centroids of the markers to calculate the actual asymmetries at these 40 different settings. Although a number of infrared, position capturing cameras are available, in one embodiment of the invention, the 3D camera system was a T10 series camera manufactured by VICON, Hauppauge, N.Y. 
         [0051]    Referring now to  FIG. 10 , an exemplary display screen  100  that can be provided on display  34  at remote computer  26  is shown. The display screen  100  provides tabs  102  allowing a user to access controls for each of a number of motorized models  10 . Here, tabs  102  are shown providing access to ten separate motorized models  10 , although this number can be varied. For each model  10 , the display can include a window  104  for the user to enter commands to position the motorized model  10  relative to the “bone zero” position and a window  106  to position the motorized model  10  relative to the home position, allowing the user to enter landmark asymmetry settings for both the shear or coronal plane as well as degree of rotation. If the positioning exceeds the limits of model  10 , the firmware will stop the motors immediately and raise a warning flag. The warning flag can indicate to the user that a limit has been exceeded, that only a fraction of the instructed movement could be completed and what the current actual position is. 
         [0052]    Referring now to  FIGS. 11 through 14 , in operation, when the shear motor  24  is actuated the hip bone  14  coupled to moveable platform  18  is driven linearly resulting in a linear offset, and therefore a shear asymmetry between the hip bones  12  and  14 . The translational axis is actuated by sliding the upper plate  58  of the moveable platform back and forth on the rotatable top plate  60 . After any movement, the new position is communicated to the computer  26 . The sliding upper plate  58  is restricted to linear motion only by guides. 
         [0053]    Similarly when the rotational motor  24  is rotated the moveable platform  18  and hip bone  14  are rotated relative to the position of the stationary platform  16  and hip bone  12 , resulting in a rotational asymmetry. The platform  18  can be preferably moved precisely at 0.01 mm increments up to ±12 mm of asymmetry in the coronal plane and at least ±3 degrees of rotation from neutral position with precision about 0.01 degrees. As the platform moves a predetermined amount, the associated hip landmarks also move. In one embodiment, the accuracy of the translational movement with the infrared camera system was shown to be better than 0.25 mm and the accuracy of repeating rotational movement was shown to be less than 0.1 degrees. The range of motion that can be generated is beyond the range of normal and abnormal positional asymmetries of the landmarks found in the human pelvis, and the bones can be positioned with a level of precision beyond what human examiners are typically able to differentiate. Consequently this system can fully evaluate the accuracy of students or clinicians performing this form of testing. 
         [0054]    The operator of computer  26  can be, as discussed above, an instructor selecting a level of asymmetry for student medical practitioners. The instructor selects an asymmetry and drives the motorized model  10  to provide the selected asymmetry. The students are asked to provide an assessment of the asymmetry, which can be used to evaluate the students&#39; skills and to train the students to properly evaluate asymmetry. 
         [0055]    It should be understood that the methods and apparatuses described above are only exemplary and do not limit the scope of the invention, and that various modifications could be made by those skilled in the art that would fall within the scope of the invention. For example, although a specific platform configuration including one stationary and one moveable platform is described, either the right or left platform can be moveable, or both platforms can be linearly or rotationally moveable, or both. In addition, the bones used in the models can be actual bones, or bones constructed from plastic, plaster, or other types of materials. Although specific sets of paired bones are shown and described, corresponding paired bones from the body of a human or other vertebrate that include skeletal landmarks can be similarly mounted and evaluated as described above. To apprise the public of the scope of this invention, the following claims are made: