Fig 1.
3D model alignment and model registration process.
(A) We imported 3D models of the radius and ulna. (B) The left forearm bones were geometrically reflected, and all forearm bones were aligned to an anatomical coordination system. (C) The radii and ulnae were overlapped.
Fig 2.
Measurement of forearm bone bowing.
The a-b line is defined as ‘bow length’, the location of point c on the a-b line is defined as ‘bow location’, and the distance from line a-b to point c is defined as ‘bow depth’. (A) Coronal bowing measurement of the radius. a, the most ulnar aspect of the bicipital tubercle; b, the most ulnar aspect of the articular surface; c, the farthest radial concavity point from the a-b line. (B) Coronal bowing measurement of the ulna. a, the most prominent ulnar point on the olecranon process; b, the most ulnar aspect of the ulnar head; c, the farthest ulnar concavity point from the a-b line. (C) Sagittal bowing measurement of the radius. a, the most bolar aspect of the bicipital tubercle; b, the most bolar aspect of the articular surface; c, the farthest radial concavity point from the a-b line. (D) Sagittal bowing measurement of the ulna. a, the tip of the olecranon; b, the most dorsal aspect of the ulnar styloid process; c, the farthest ulnar concavity point from the a-b line.
Fig 3.
Landmark points on the forearm bones.
(A) RH, the radial head; RT, the radial tuberosity; RSP, the radial styloid process; RUNA, ulnar notch anterior lip of the radius; RUNP, ulnar notch posterior lip of the radius. (B) UOC, olecranon tip of the ulna; UCP, coronoid process of the ulna; UF, the ulnar fovea; UH, the ulnar head.
Fig 4.
Measurement method of regional shape differences.
(A) The 3D bone model was divided into 10 equal parts to obtain 9 cross-sectional images. (B) Cross-sectional image of overlapped 3D bone models of the original and reflected sides. (B-1) Measurement of distance from the right-side centroid to original (right) bone cortical outline. (B-2) Measurement of distance from the right-side centroid to reflected bone cortical outline. To characterize the asymmetry of the left and right bones, both bones were measured using centroids from the original side.
Table 1.
Length and volume of the radius and ulna.
Table 2.
Differences of length and volume between sides.
Table 3.
Twisting and bending measurement of the forearm bones.
Fig 5.
Regional shape difference of the radius and ulna.
Angles with significant shape differences between bilateral bones are marked with dotted red lines on each cross-sectional image. P, proximal; C, central; D, distal; Pu, upper section of the proximal part; Pm, middle section of the proximal part; Pl, lower section of the proximal part; Cu, upper section of the central part, Cm, middle section of the central part, Cl, lower section of the central part, Du; upper section of the distal part, Dm; middle section of the distal part, Dl; lower section of the distal part.