Device, method and system for digitizing position and orientation information of hip joint implant components

Abstract

A device for digitizing a center of rotation of a hip joint implant component with respect to a bone element in computer-assisted surgery. The device comprises a detectable member trackable for position and orientation by a computer-assisted surgery system. A body is connected to the detectable member in a known geometry. The body has a coupling portion adapted to be coupled to the hip joint implant component in a predetermined configuration. The center of rotation of the hip joint implant component is calculable in the predetermined configuration as a function of the known geometry and of the position and orientation of the detectable member.

1 . A device for digitizing a center of rotation of a hip joint implant component with respect to a bone element in computer-assisted surgery, comprising: 
 a detectable member trackable for position and orientation by a computer-assisted surgery system; and    a body connected to the detectable member in a known geometry, the body having a coupling portion adapted to be coupled to the hip joint implant component in a predetermined configuration, the center of rotation of the hip joint implant component being calculable in the predetermined configuration as a function of the known geometry and of the position and orientation of the detectable member.    
   
   
       2 . The device according to  claim 1 , wherein the implant is a femoral implant, and the coupling portion of the body is a cylindrical receptacle in the body adapted to be releasably fitted in said predetermined configuration to a neck of the femoral implant prior to a ball head of the femoral implant being fixed to the neck of the femoral implant.  
   
   
       3 . The device according to  claim 1 , wherein the implant is a femoral implant, and the coupling portion of the body is a hemispherical receptacle in the body adapted to be releasably fitted in said predetermined configuration to a ball head of the femoral implant.  
   
   
       4 . The device according to  claim 1 , wherein the implant is a pelvic implant, and the coupling portion is a hemispherical member received in any one of a shell and a liner of the pelvic implant in said predetermined configuration.  
   
   
       5 . The device according to  claim 4 , wherein the hemispherical member has a flange at a periphery thereof, the flange being adapted to abut a rim of the pelvic implant in said predetermined configuration, the flange being in a known geometric relation with the detectable member such that an orientation of the pelvic implant is calculable with respect to said known geometric relation, as a function of said predetermined configuration.  
   
   
       6 . A method for digitizing a center of rotation of a pelvic implant component with a computer-assisted surgery system, comprising the steps of: 
 providing a device being trackable for position and orientation by the computer-assisted surgery system, the device being releasably coupled in a known configuration to the pelvic implant component;    tracking a position and orientation of a pelvis implanted with the pelvic implant component and a position and orientation of the device; and    calculating a center of rotation of the pelvic implant component with respect to the position and orientation of the pelvis by relating the known configuration of the device with the position and orientation tracking of the pelvis and of the device.    
   
   
       7 . The method according to  claim 6 , further comprising the step of calculating an orientation of the pelvic implant component with respect to the position and orientation of the pelvis by relating the known configuration of the device with the position and orientation tracking of the pelvis and of the device.  
   
   
       8 . The method according  claim 6 , wherein the method is performed on an anatomical bone model or on a cadaver.  
   
   
       9 . A method of doing surgical treatment with a position tracking system in computer-assisted surgery for guiding an operator in inserting a femoral implant of a hip joint implant in a resected femur tracked for position and orientation, comprising the steps of: 
 positioning a trackable device on the femoral implant in a predetermined configuration, the trackable device being trackable in space for position and orientation;    registering implant geometry information for the femoral implant with respect to the trackable device as a function of said predetermined configuration between the femoral implant and the trackable device; and    inserting the femoral implant in the femur by obtaining implant position and orientation information, the implant position and orientation information being calculated from said implant geometry information as a function of the tracking for position and orientation of the trackable device with respect to a frame of reference of the femur.    
   
   
       10 . The method according to  claim 9 , wherein the step of registering implant geometry information includes obtaining a center of rotation of the femoral implant and a neck axis of the implant as a function of said predetermined configuration between the femoral implant and the trackable device, whereby the implant position and orientation information with respect to the frame of reference is any one of a femoral anteversion and a limb length discrepancy.  
   
   
       11 . The method according to  claim 10 , wherein the step of registering implant geometry information includes registering surface information on the femoral implant, said surface information being used to calculate a longitudinal axis of the femoral implant, whereby the implant position and orientation information with respect to the frame of reference is any one of a femoral anteversion, a limb length discrepancy and a varus/valgus angle.  
   
   
       12 . A method according to  claim 9 , wherein the method is performed on an anatomical bone model or on a cadaver.  
   
   
       13 . A computer-assisted surgery system for guiding an operator in inserting a femoral implant of a hip joint implant in a resected femur tracked for position and orientation, comprising: 
 a trackable reference device positionable onto the femoral implant in a predetermined configuration and trackable in space for position and orientation;    a registration device trackable in space for position and orientation and handled by the operator to register surface information;    a sensing apparatus, for tracking any one of the devices for position and orientation;    a controller connected to the sensing apparatus, the controller being provided to:    i) calculate a position and orientation of the devices as a function of the tracking by the sensing apparatus;    ii) digitize surface information of the femoral implant as a function of the tracking of the registration device by the sensing apparatus; and    an implant geometry information calculator connected to the controller, for calculating geometry information of the femoral implant from said predetermined configuration with respect to the trackable reference device, as a function of said surface information of the femoral implant;    whereby the geometry information is used to provide implant position and orientation information related to a frame of reference of the femur, so as to guide the operator in subsequently inserting the femoral implant in the resected femur.    
   
   
       14 . The computer-assisted surgery system according to  claim 13 , wherein the geometry information is at least one of a center of rotation of the femoral implant, a neck axis of the femoral implant, and a longitudinal axis of the femoral implant.  
   
   
       15 . The computer-assisted surgery system according to  claim 14 , wherein the surface information is a plane digitized from points on the femoral implant, and a tip of the femoral implant.  
   
   
       16 . The computer-assisted surgery system according to  claim 13 , wherein the implant position and orientation is at least one of limb length discrepancy, femoral anteversion and varus/valgus angle.  
   
   
       17 . The computer-assisted surgery system according to  claim 13 , wherein the controller stores a digital model of the femoral implant, said geometry information calculated by the implant geometry information calculator being associated to the digital model through a tracking of the trackable reference device.  
   
   
       18 . A controller computer program product comprising code means recorded in a computer readable memory for executing the method defined in  claim 13.