US 12,148,080 B2
Method for locating a center of rotation of an articulated joint
Xia Du, Velizy Villacoublay (FR); Pinghan Chen, Velizy Villacoublay (FR); Mickael Brossard, Velizy Villacoublay (FR); and Sarath Reddi, Bengaluru (IN)
Assigned to DASSAULT SYSTEMES, Velizy Villacoublay (FR)
Filed by DASSAULT SYSTEMES, Velizy Villacoublay (FR)
Filed on Jan. 29, 2021, as Appl. No. 17/163,201.
Claims priority of application No. 20305112 (EP), filed on Feb. 6, 2020.
Prior Publication US 2021/0248802 A1, Aug. 12, 2021
Int. Cl. A61B 5/00 (2006.01); A61B 5/103 (2006.01); G06T 3/10 (2024.01); G06T 13/40 (2011.01); G06V 40/20 (2022.01); A61B 34/10 (2016.01)
CPC G06T 13/40 (2013.01) [A61B 5/103 (2013.01); A61B 5/4528 (2013.01); A61B 5/6828 (2013.01); G06T 3/10 (2024.01); G06V 40/23 (2022.01); A61B 2034/105 (2016.02)] 20 Claims
OG exemplary drawing
 
1. A method for locating a center of rotation of an articulated joint connecting two bones or set of bones of an upper or lower limb of a user, comprising:
a) simultaneously acquiring 3D positions of the bone or set of bones during a series of repetitive movements of sweeping one of the two bones or set of bones around the articulated joint by the user, thereby obtaining a 3D cloud of points;
b) computing, in a 3D searching space comprising a 3D position of a termination of a second bone or set of bones, a point referred to as a center point being a searching point of the 3D searching space for which a standard deviation is the lowest considering a set of distances between the searching point and each point of the 3D cloud of points;
c) transforming the 3D cloud of points into a single plane for all the points of the 3D cloud of points; and
d) projecting the center point on said plane, thereby obtaining the center of rotation of the joint,
wherein in step a), the series of repetitive movements are performed while the user is holding a first one of two hand-held trackers, referred to as mobile tracker, a second one of the two hand-held trackers, referred to as reference tracker, being maintained against a termination of the second bone or set of bones, and
wherein step b) includes subs-steps of recursively subdividing the 3D searching space by:
b1) defining the 3D searching space as a cube of predefined edge length, and which is centered on the 3D position of the reference tracker, referred to as reference point,
b2) receiving, from the user, an input identifying a set of points of the cube constituting, with said reference point, a set of searching points,
b3) for each searching point, computing the distance between said searching point and each point of the 3D cloud of pints, and deriving a standard deviation for each searching point,
b4) identifying, among the set of searching points, at least one searching point, for which standard deviation is the lowest, and
b5) reiterate steps b1), b2), b3) and b4) by also halving the edge length of the cube and centering the cube on the identified searching point, until the edge length of the cube is lower or equal to a predefined threshold, the center point corresponding then to the identified searching point.