Instrument navigation in computer-assisted hip surgery

Abstract

A computer-assisted surgery system comprises a calibrating instrument adapted to be applied to a pelvis in a known manner, and a surgical instrument. A computer-assisted processor unit operating a surgical assistance procedure and comprises at least one portable inertial sensor unit configured to be connected to the at least one calibrating instrument and the at least one surgical instrument, the portable inertial sensor unit outputting readings representative of its orientation. A geometrical relation data module provides a geometrical relation data between the orientation of the portable inertial sensor unit, of the calibrating instrument and of the surgical instrument. A coordinate system module sets a coordinate system of the pelvis in which an anterior-posterior axis of the pelvis is generally in a direction of gravity, and in which a medio-lateral axis of the pelvis is obtained from readings of the at least one portable inertial sensor unit on the calibrating instrument using the geometrical relation data therebetween. A tracking module tracks movements of the at least one surgical instrument relative to the coordinate system using readings from the inertial sensor unit on the surgical instrument using the geometrical relation data therebetween, and calculates navigation data for the movements, the navigation data relating the orientation of the surgical instrument to the orientation of the pelvis. An interface outputs the navigation data.

1 . A computer-assisted surgery system comprising:
 at least one calibrating instrument adapted to be applied to a pelvis in a known manner;   at least one surgical instrument;   a computer-assisted processor unit operating a surgical assistance procedure and comprising:   at least one portable inertial sensor unit configured to be connected to the at least one calibrating instrument and the at least one surgical instrument, the portable inertial sensor unit outputting readings representative of its orientation;   a geometrical relation data module providing a geometrical relation data between the orientation of the portable inertial sensor unit, of the at least one calibrating instrument and of the at least one surgical instrument;   a coordinate system module for setting a coordinate system of the pelvis in which an anterior-posterior axis of the pelvis is generally in a direction of gravity, and in which a medio-lateral axis of the pelvis is obtained from readings of the at least one portable inertial sensor unit on the at least one calibrating instrument using the geometrical relation data therebetween;   a tracking module for tracking movements of the at least one surgical instrument relative to the coordinate system using readings from the inertial sensor unit on the surgical instrument using the geometrical relation data therebetween, and calculating navigation data for the movements, the navigation data relating the orientation of the surgical instrument to the orientation of the pelvis; and   an interface for outputting the navigation data.   
     
     
         2 . The computer-assisted surgery system according to  claim 1 , wherein the at least one calibrating instrument is a medio-lateral digitizer adapted to contact anterior-superior iliac spines of the pelvis, and further wherein the coordinate system module obtains a lateral tilt of the pelvis relative to a cranial-caudal axis of the coordinate system from the medio-lateral digitizer and aligns the medio-lateral axis with said lateral tilt. 
     
     
         3 . The computer-assisted surgery system according to  claim 1 , wherein the at least one calibrating instrument is adapted to contact anterior-superior iliac spines and a pubic tubercle of the pelvis, and further wherein the coordinate system module obtains a tilt of the pelvis relative to a cranial-caudal axis and to the medio-lateral axis of the coordinate system, and aligns the antero-posterior axis and the medio-lateral axis with said lateral tilt. 
     
     
         4 . The computer-assisted surgery system according to  claim 1 , wherein the surgical instrument is one of an impactor and an acetabulum reamer. 
     
     
         5 . The computer-assisted surgery system according to  claim 1 , wherein the geometrical relation data module, the coordinate system module and the tracking module are integrated in the at least one portable inertial sensor unit. 
     
     
         6 . The computer-assisted surgery system according to  claim 5 , further comprising a stand-alone processing device with interface communicating with the at least one portable inertial sensor unit, the stand-alone processing device concurrently operating the surgical assistance procedure to provide guidance to a user. 
     
     
         7 . The computer-assisted surgery system according to  claim 1 , further comprising an updated orientation module having a known orientation of the inertial sensor unit relative to the pelvis, and wherein the coordinate system module updates an orientation of the surgical instrument in the coordinate system using readings of the at least one portable inertial sensor unit when in said known orientation. 
     
     
         8 . The computer-assisted surgery system according to  claim 7 , further comprising a support structure adapted to be secured to the pelvis and having a mount for the portable inertial sensor unit, said known orientation comprising the portable inertial sensor unit in the support structure. 
     
     
         9 . The computer-assisted surgery system according to  claim 7 , wherein the at least one surgical instrument has a light source thereon emitting a planar beam, the known orientation comprising the at least one surgical instrument projecting the planar beam on predetermined landmarks of the pelvis.