Method for Registering Articulated Anatomical Structures

Abstract

The present invention relates to a method for registering a first anatomical structure ( 1 ) which is articulately coupled to a second anatomical structure ( 2 ), the method being constituted to be executed by a computer and comprising the steps of: acquiring second structure correlation data describing the spatial position of at least one correlation feature ( 3 ) relative to the second anatomical structure ( 2 ); acquiring coupling data describing a positional fixation ( 6 ) of the first anatomical structure ( 1 ) relative to the second anatomical structure ( 2 ), which is set by the articulated coupling ( 4 ) between the first anatomical structure ( 1 ) and the second anatomical structure ( 2 ); determining, based on the second structure correlation data and the coupling data, first structure correlation data describing the spatial position of the at least one correlation feature ( 3 ) relative to the first anatomical structure ( 1 ). The present invention further relates to a corresponding computer program and system.

1 .- 15 . (canceled) 
     
     
         16 . A computer implemented method for providing surgical guidance information, comprising:
 acquiring second structure correlation data describing the spatial position of at least one correlation feature relative to the second anatomical structure;   acquiring coupling data. describing a positional fixation of the first anatomical structure relative to the second anatomical. structure, which is set by the articulated coupling between the first anatomical structure and the second anatomical structure;   determining, based on the second structure correlation. data and the coupling data, first structure correlation data describing the spatial position of the at least one correlation feature relative to the first anatomical structure;   wherein   a pelvis of the patient constitutes a first anatomical structure;   a femur of the patient constitutes a second anatomical structure;   a midsagittal plane constitutes the at least one correlation feature;   detecting, using a detection device, an object having a marker device and associated with the patient;   outputting guidance information to an indicating device based on the first structure correlation data to provide the spatial position of the object in relation to the correlation feature.   
     
     
         17 . The method according to  claim 16 , wherein determining first structure correlation data involves defining
 a first coordinate system positionally assigned to the first anatomical structure and a second coordinate system positionally assigned to the second anatomical structure; and   at least one reference feature for which an invariant spatial position relative to the positional fixation is determined within the first coordinate system, and for which the spatial position is determined within the second coordinate system;   and wherein   the spatial position of the at least correlation feature relative to the first anatomical structure is determined based on establishing within the second coordinate system the spatial position of the at least one reference feature relative to the positional fixation, that has been determined within the first coordinate system.   
     
     
         18 . The method according to  claim 16 , Wherein acquiring the second structure correlation data comprises determining the spatial position of at least one geometrical feature of the second anatomical structure and defining the spatial position of the at least one correlation feature relative to the at least one geometrical feature. 
     
     
         19 . The method according to  claim 16 , wherein at least one image showing at least the first anatomical structure is acquired, and wherein the position and/or positional relationship of at least one feature, particularly of at least one of:
 the positional fixation;   at least one geometrical feature;   at least one correlation feature; and/or   at least one reference feature;   is determined based on the at least one image.   
     
     
         20 . The method according to  claim 19 , wherein said at least one image is an X-ray-image that has been taken in an anterior-posterior direction. 
     
     
         21 . The method according to  claim 19 , Wherein the position and/or positional relationship of the at least one feature is determined via direct measurements. 
     
     
         22 . The method according to  claim 17 , wherein establishing within the second coordinate system said spatial relationship of the at least one reference feature relative to the positional fixation involves altering the spatial position of the second anatomical structure relative to the first anatomical structure. 
     
     
         23 . The method according to  claim 17 , wherein a computational algorithm is used to establish within the second coordinate system the spatial relationship of the at least one reference feature relative to the positional fixation, by virtually altering the spatial position of the second anatomical structure relative to the first anatomical structure. 
     
     
         24 . The method according to  claim 16 , wherein the method is used to register the pelvis via the femur-registration, and wherein
 a mechanical axis of the femur constitutes the geometrical feature;   an anatomical landmark of the pelvis, such as an anterior superior iliac spine or a most lateral point of the iliac crest constitutes a reference feature; and/or   a centre of rotation of a hip joint constitutes a positional fixation.   
     
     
         25 . The method according to  claim 24 , wherein the midsagittal plane is defined within the second coordinate system as being parallel to the mechanical axis of the femur, running through the centre of rotation of the hip joint, and as being spaced from said mechanical axis in a medial direction by a predetermined distance, said predetermined distance being equal to the distance between the centre of rotation of the hip joint and the midsagittal plane within the first coordinate system. 
     
     
         26 . The method according to  claim 17 , wherein at least one spatial direction determined within the second coordinate system, particularly by registering the second. anatomical structure, is transferred to the first coordinate system. 
     
     
         27 . The method according to  claim 24 , further comprising the step of defining the functional coronal pelvis plane, by
 determining the spatial position of at least one landmark of the pelvis;   acquiring anatomical data of the pelvis from an anatomical atlas;   acquiring anatomical data from further images taken from different directions.   
     
     
         28 . A non-transitory computer implemented program which, when running on the computer, causes the computer to:
 acquire second structure correlation data describing the spatial position of at least one correlation feature relative to the second anatomical structure;   acquire coupling data describing a positional fixation of the first anatomical structure relative to the second anatomical structure, which is set by the articulated coupling between the first anatomical structure and the second anatomical structure;   determine, based on the second structure correlation data and the coupling data, first structure correlation data describing the spatial position of the at least one correlation feature relative to the first anatomical structure,   detect, using a detection device, an object having a marker device and associated with the patient;   output guidance information to an indicating device including an indication signal, based on the first structure correlation data to provide the spatial position of the object in relation to the correlation feature.   
     
     
         29 . A system for registering a first anatomical structure which is articulately coupled to a second anatomical structure, comprising a computer with a program storage medium on which the program according to  claim 28  is stored.