Inertial Sensor Based Surgical Navigation System

Abstract

An inertial sensor based surgical navigation system for knee replacement surgery is disclosed. Inertial sensors composed of six-degree-of-freedom inertial chips, whose measurements are processed through a series of integration, quaternion, and kalman filter algorithms, are used to track the position and orientation of bones and surgical instruments. The system registers anatomically significant geometry, calculates joint centers and the mechanical axis of the knee, develops a visualization of the lower extremity that moves in real time, assists in the intra-operative planning of surgical cuts, determines the optimal cutting planes for cut guides and the optimal prosthesis position and orientation, and finally navigates the cut guides and the prosthesis to their optimal positions and orientations using a graphical user interface.

1 . A surgical navigation system, comprising:
 at least one inertial sensor that measures its own motion without an external reference and is configured to be removably coupled to an object, wherein the object is at least one of a portion of a patient's anatomy or a surgical instrument;   a computer system having a processor in communication with the at least one inertial sensor, the computer system being configured to:
 receive from the at least one inertial sensor, data indicative of an orientation of the at least one inertial sensor in a common coordinate system that defines orientation coordinates relative to an initial orientation of the at least one inertial sensor; 
 compute, from the received data, an orientation of the object in the common coordinate system; and 
   a user interface in communication with the computer system and configured to provide feedback to a user that indicates the computed orientation of the object within the common coordinate system.   
     
     
         2 . The surgical navigation system of  claim 1 , wherein the computer system is further configured to:
 receive from the at least one inertial sensor, data indicative of a position of the at least one inertial sensor in the common coordinate system that defines position coordinates relative to an initial position of the at least one inertial sensor; and   compute, from the received data, a position of the object in the common coordinate system;   
       and wherein the feedback provided to the user by the user interface also indicates the computed position of the object within the common coordinate system. 
     
     
         3 . The surgical navigation system of  claim 2 , wherein the at least one inertial sensor is configured to be removably coupled to a bone of a patient, and wherein the computer system is further configured to compute a joint center from the position and the orientation of the object while the bone is moved. 
     
     
         4 . The surgical navigation system of  claim 3 , wherein the bone is a femur and the joint center is a hip joint center. 
     
     
         5 . The surgical navigation system of  claim 1 , wherein the at least one inertial sensor is configured to be removably coupled to a bone of a patient, and wherein the computer system is further configured to compute a joint center from the orientation of the object while the bone is moved. 
     
     
         6 . The surgical navigation system of  claim 5 , wherein the bone is a femur and the joint center is a hip joint center. 
     
     
         7 . The surgical navigation system of  claim 5 , wherein the computer system is configured to control the user interface to provide instructions to a user for moving the bone of the patient in order to determine the joint center. 
     
     
         8 . The surgical navigation system of  claim 1 , wherein the at least one inertial sensor comprises at least a first inertial sensor configured to be removably coupled to the portion of the patient's anatomy and a second inertial sensor configured to be removably coupled to the surgical instrument. 
     
     
         9 . The surgical navigation system of  claim 1 , wherein the at least one inertial sensor is removably coupled to the portion of the patient's anatomy and the computer system is configured to compute a cutting angle relative to the portion of the patient's anatomy based on the computed orientation of the object. 
     
     
         10 . The surgical navigation system of  claim 9 , wherein the portion of the patient's anatomy comprises a bone in a lower extremity and the computer system is configured to compute the cutting angle relative to a mechanical axis of the portion of the patient's anatomy. 
     
     
         11 . The surgical navigation system of  claim 1 , wherein the computer system is configured to compute a cutting plane angle based on the computed orientation of the object, and wherein the feedback provided to the user by the user interface comprises an indication of the cutting plane angle. 
     
     
         12 . The surgical navigation system of  claim 11 , wherein the cutting plane angle is a coronal cutting plane angle. 
     
     
         13 . The surgical navigation system of  claim 12 , wherein the coronal cutting plane angle comprises at least one of a varus angle or a valgus angle. 
     
     
         14 . The surgical navigation system of  claim 11 , wherein the cutting plane angle is a sagittal cutting plane angle. 
     
     
         15 . The surgical navigation system of  claim 1 , wherein the user interface comprises a display in communication with the computer system, and wherein the computer system computes an object display element from the computed orientation of the object and the display comprises a graphical user interface that receives the object display element from the computer system and displays the object display element to provide a graphical depiction of the orientation of the object in the common coordinate system. 
     
     
         16 . The surgical navigation system of  claim 15 , wherein the feedback indicates a planned resection plane, and wherein the graphical user interface displays a planned surgical cut display element and the object display element together to provide a graphical depiction of the orientation of the planned resection plane relative to the orientation of the object in the common coordinate system. 
     
     
         17 . A surgical navigation system, comprising:
 at least one inertial sensor that measures its own motion without an external reference and is configured to be removably coupled to an object, wherein the object is at least one of a portion of a patient's anatomy or a surgical instrument;   a computer system having a processor in communication with the at least one inertial sensor, the computer system being configured to:
 receive from the at least one inertial sensor, data indicative of a position of the at least one inertial sensor in a common coordinate system that defines position coordinates relative to an initial position of the at least one inertial sensor; 
 compute, from the received data, a position of the object in the common coordinate system; and 
   a user interface in communication with the computer system and configured to provide feedback to a user that indicates the computed position of the object within the common coordinate system.   
     
     
         18 . The surgical navigation system of  claim 17 , wherein the at least one inertial sensor is configured to be removably coupled to a bone of a patient, and wherein the computer system is further configured to compute a joint center from the position of the object while the bone is moved. 
     
     
         19 . The surgical navigation system of  claim 18 , wherein the bone is a femur and the joint center is a hip joint center. 
     
     
         20 . The surgical navigation system of  claim 17 , wherein the user interface comprises a display in communication with the computer system, and wherein the computer system computes an object display element from the computed position of the object and the display comprises a graphical user interface that receives the object display element from the computer system and displays the object display element to provide a graphical depiction of the position of the object in the common coordinate system.