Determining anatomical orientations

Abstract

Methods, systems, and apparatus for determining anatomical orientations are described. Data is received that indicates a position of a reference device configured to move with a pelvis of a subject. Data is received that indicates locations corresponding to a reference surface. Data is received that indicates locations on the pelvis. One or more anatomical orientations are determined based on the locations corresponding to the reference surface and the locations on the pelvis. The anatomical orientations are registered to the reference device.

What is claimed is: 
     
         1 . An apparatus comprising:
 one or more processing devices; and   one or more data storage devices storing instructions that are operable, when executed by the one or more processing devices, to cause the one or more processing devices to perform operations comprising:
 receiving data indicating a position of a reference device configured to move with a pelvis of a subject, 
 receiving data indicating locations on a reference surface, receiving data indicating locations on the pelvis, 
 determining a first anatomical orientation of the subject based on the data indicating the locations on the reference surface, 
 determining a second anatomical orientation that extends along a substantially medial-lateral direction based on the data indicating the locations on the pelvis, and 
 registering the first anatomical orientation and the second anatomical orientation to the reference device. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the operations further comprise:
 determining a surgical trajectory based on the first anatomical orientation and the second anatomical orientation;   determining a position of a tool relative to the surgical trajectory based on a position of the reference device; and   outputting data indicating the position of the tool relative to the surgical trajectory.   
     
     
         3 . The apparatus of  claim 2 , wherein determining the surgical trajectory based on the first anatomical orientation and the second anatomical orientation comprises determining an orientation at a predetermined inclination angle and a predetermined anteversion angle relative to the first anatomical orientation and the second anatomical orientation. 
     
     
         4 . The apparatus of  claim 1 , wherein the operations further comprise:
 determining a third anatomical orientation of the subject that is orthogonal to the first anatomical orientation and the second anatomical orientation; and   registering the third anatomical orientation to the reference device that is configured to move with the pelvis.   
     
     
         5 . The apparatus of  claim 1 , wherein:
 receiving data indicating locations on the reference surface comprises receiving data indicating at least three locations on a substantially planar surface; and   determining the first anatomical orientation comprises determining an orientation of a coronal plane of the subject based on the at least three locations.   
     
     
         6 . The apparatus of  claim 5 , wherein the operations further comprise receiving information indicating a pelvic tilt angle;
 wherein determining the orientation of the coronal plane of the subject comprises determining the orientation of the coronal plane using information indicating the pelvic tilt angle.   
     
     
         7 . The apparatus of  claim 5 , wherein receiving data indicating locations on the pelvis comprises receiving data indicating at least two locations on the pelvis that are located substantially along a medial-lateral axis; and
 wherein determining the second anatomical orientation comprises determining an orientation of a transverse plane of the subject based on the data indicating at least two locations on the pelvis, the orientation of the transverse plane being orthogonal to the orientation of the coronal plane of the subject.   
     
     
         8 . The apparatus of  claim 7 , wherein the at least two locations include locations corresponding to a left anterior superior spine of an ilium of the pelvis and a right anterior superior spine of the ilium. 
     
     
         9 . The apparatus of  claim 1 , wherein the data indicating the position of the reference device configured to move with the pelvis of the subject indicates a position of the reference device corresponding to a first position of the subject lying on the reference surface. 
     
     
         10 . The apparatus of  claim 9 , wherein the data indicating the position of the reference device configured to move with the pelvis of the subject indicates a position of the reference device corresponding to a second position of the subject that is different from the first position; and wherein the operations further comprise:
 adjusting the anatomical orientations based on the position of the reference device corresponding to the second position;   determining a position of a surgical axis relative to the adjusted anatomical orientations; and   determining a position of a tool relative to the surgical axis based on the position of the reference device corresponding to the second position of the subject.   
     
     
         11 . The apparatus of  claim 1 , wherein receiving the data indicating the position of the reference device comprises receiving data indicating a position of an electromagnetic field sensor or a fiducial of the reference device. 
     
     
         12 . The apparatus of  claim 1 , wherein receiving the data indicating locations on a reference surface comprises receiving data indicating locations of at least three different points on a planar reference surface while the subject is lying in a supine position on the planar reference surface;
 wherein receiving the data indicating locations on the pelvis comprises receiving data indicating locations corresponding to a left anterior superior spine of an ilium of the pelvis and a right anterior superior spine of the ilium; and   wherein determining the first anatomical orientation comprises:
 receiving data indicating a pelvic tilt angle, and 
 determining an orientation of a coronal plane of the subject based on the at least three different points on the planar reference surface and the data indicating the pelvic tilt angle, 
   wherein determining the second anatomical orientation comprises determining an orientation of a medial-lateral axis or transverse plane of the subject based on the locations corresponding to the left anterior superior spine of the ilium and the right anterior superior spine of the ilium.   
     
     
         13 . The apparatus of  claim 12 , wherein the operations further comprise:
 determining a surgical trajectory for the subject using the first anatomical orientation and the second anatomical orientation;   after the subject has been moved from the supine position to a lateral position, receiving data indicating the position of a surgical tool relative to the position of the reference device while the subject is in the lateral position;   determining an orientation of the surgical tool relative to the surgical trajectory based on the data indicating the position of the surgical tool relative to the position of the reference device while the subject is in the lateral position; and   outputting data indicating the orientation of the surgical tool relative to the surgical trajectory.   
     
     
         14 . A system comprising:
 a first reference device;   one or more second reference devices;   a communication module in communication with the first reference device and the one or more second reference devices;   a control unit operably coupled to the communication module, the control unit being configured to perform operations comprising:
 receiving data indicating an orientation of the first reference device while the first reference device is coupled to a pelvis of a subject, 
 receiving data indicating different locations of the one or more second reference devices when the one or more second reference devices are coupled to a substantially planar reference surface, 
 receiving data indicating different locations of the one or more second reference devices when the one or more second reference devices are coupled to different locations on the pelvis, 
 determining a first anatomical orientation of the subject based on the data indicating the different locations of the one or more second reference devices when the one or more second reference devices are coupled to a substantially planar reference surface, 
 determining a second anatomical orientation that extends along a substantially medial-lateral direction of the subject based on the data indicating the different locations of the one or more second reference devices when the one or more second reference devices are coupled to the different locations on the pelvis, and 
 registering the orientations of the one or more anatomical reference planes to the first reference device. 
   
     
     
         15 . A method comprising:
 determining a first orientation relative to a subject based on an orientation of a reference surface;   determining a second orientation that extends along a substantially medial-lateral direction of the subject based on features of a pelvis of the subject; and   registering the first orientation and the second orientation to a reference device that is configured to move with the pelvis.