Application of Soft Tissue Artifact Compensation Using Displacement Dependency between Anatomical Landmarks and Skin Markers

Table 1

Definition of anatomical coordinate frame (ACF) of lower extremities.

Segment	Definition
Pelvis	Origin: the mid-point of left and right anterior superior iliac spine
	𝑧: connecting left anterior superior iliac spine to right anterior superior iliac spine
	𝑦: orthogonal to the plane defined with left and right anterior superior iliac spine and the midpoint left and right posterior superior iliac spine
	𝑥: the cross vector of 𝑌 and 𝑍
Thigh	Origin: the midpoint of lateral and medial epicondyles
	𝑦: connecting the origin to femoral head
	𝑥: orthogonal to the plane defined with lateral epicondyle, medial epicondyle, and femoral head
	𝑧: the cross vector of 𝑋 and 𝑌
Shank	Origin: the midpoint of lateral and medial malleolus
	𝑦: intersection of the plane defined by lateral malleolus, medial malleolus, and head of fibula and the plane defined by tibial tuberosity and the midpoint of lateral and medial malleolus; positive direction is proximal
	𝑥: orthogonal to the plane defined by lateral malleolus, medial malleolus, and head of fibula
	𝑧: the cross vector of 𝑋 and 𝑌
Foot	Origin: calcaneus
	𝑦: intersection of the plane defined by calcaneus, first metatarsal head and fifth metatarsal head, and the plane defined by calcaneus and second metatarsal head; positive direction is proximal
	𝑥: orthogonal to the plane defined by calcaneus, first metatarsal head, and fifth metatarsal head
	𝑧: the cross vector of 𝑋 and 𝑌