Patent ID: 8118818

Claim:
A method for computer assisted distal locking of intramedullary nails comprising the steps of: A) establishing a virtual geometric representation at least of the distal part ( 5 ) of an intramedullary nail ( 1 ) comprising at least one distal locking hole ( 3 , 4 ); B) acquiring a first medical image ( 28 ) using a radioscopic unit ( 25 ) with its focal line ( 23 ) adjusted at an angle between 0° and 30° to the axis ( 8 , 9 ) of the at least one distal locking hole ( 3 , 4 ), said first medical image ( 28 ) showing a contour of the radiopaque distal part ( 5 ) including a pictorial outline ( 14 ″) of the pictorial distal part ( 5 ″) and at least one lens shaped inner element with a pictorial first and a second arc ( 16 ″, 48 ″) representing the visible edges of the at least one distal locking hole ( 3 , 4 ) projected onto the image plane ( 24 ); C) acquiring a second medical image using a radioscopic unit ( 25 ) with its focal line ( 23 ) adjusted at an angle between 60° and 90° to the axis ( 8 , 9 ) of the at least one distal locking hole ( 3 , 4 ), said second medical image ( 29 ) showing a contour of the radiopaque distal part ( 5 ) including a pictorial outline ( 14 ″) of the pictorial distal part ( 5 ″), said pictorial outline ( 14 ″) including a pictorial first and second intersection curve ( 15 ″, 49 ″) representing the visible edges of the at least one distal locking hole ( 3 , 4 ) projected onto the image plane ( 24 ); D) computing the position of the longitudinal axis ( 2 ) of the distal part ( 5 ) of the intramedullary nail ( 1 ) using said first and second medical image and said virtual geometric representation by means of a computer ( 40 ); E) computing the position of the axis ( 8 , 9 ) of the at least one distal locking hole ( 3 , 4 ) using said first and second medical image ( 28 , 29 ) by means of the computer ( 40 ) in a manner that said contours visible in said first and second image ( 28 , 29 ) are matched with said virtual geometric representation; F) transferring information related to the positions of the distal part ( 5 ) and the at least one distal locking hole ( 3 , 4 ) from a central processing unit of the computer ( 40 ) to an external guide means ( 41 ) for drilling a hole in a bone ( 30 ) which is aligned with said at least one distal locking hole ( 3 , 4 ), whereby G) said pictorial outline ( 14 ″) and said pictorial first and second arc ( 16 ″, 48 ″) visible in said first medical image ( 28 ) and said pictorial outline ( 14 ″) including said pictorial first and second intersection curve ( 15 ″, 49 ″) visible in said second medical image ( 29 ) are matched with the virtual geometric representation by means of the computer ( 40 ) under step E).