1. Altered bone density and stress distribution patterns in long-standing cubitus varus deformity and their effect during early osteoarthritis of the elbow 
S. Miyamura, K. Oka, S. Abe, A. Shigi, H. Tanaka, K. Sugamoto, H. Yoshikawa, T. Murase 
Osteoarthritis and Cartilage 
Volume 26, Issue 1, Pages (January 2018)
DOI: /j.joca
Copyright © 2017 Osteoarthritis Research Society International Terms and Conditions

2. Fig. 1
Three-dimensional (3-D) bone models of both normal and affected sides of the humerus, radius, and ulna are extracted from CT data in the first instance. The proximal part of the affected humerus is superimposed onto the mirror image of the corresponding part on the contralateral, normal side. The deformity of the distal humerus is quantified three-dimensionally (varus, extension, and internal rotation). An orthogonal coordinate system, which is a modified form of the International Society of Biomechanics reference system, is applied for the distal humerus47. The origin is the midpoint of the line (Y-axis) connecting the lateral and medial epicondyle tips. Z-axis, the line connecting the origin and the center of the humeral head perpendicular to the Y-axis; X-axis, the line perpendicular to the Y- and Z-axes3,18. Using the Euler angles method, rotations around the X-, Y- and Z-axes were indicated as varus, extension, and internal rotation, respectively.
Osteoarthritis and Cartilage  , 72-83DOI: ( /j.joca )
Copyright © 2017 Osteoarthritis Research Society International Terms and Conditions

3. Fig. 2
Definition of regions. (A) Distal humerus: the anterior part is divided into Capitellum, Anterolateral trochlea, and Anteromedial trochlea, and the posterior part is divided into Posterolateral trochlea and Posteromedial trochlea. See text for definition of each plane. The humerus planes are as follows: (1) coronal plane (cor-h), (2) axial plane (axi-h), (3) sagittal plane passing the lateral verge of the capitellum (sag-hL), (4) sagittal plane passing the lateral trochlear ridge (sag-hLTR), (5) sagittal plane passing the trochlear groove (sag-hTG), (6) sagittal plane passing the medial verge of the trochlea (sag-hM), and (7) sagittal plane passing the capitello-trochlear groove (sag-hCTG). (B) The proximal ulna is divided into quadrants (Lateral coronoid, Lateral olecranon, Medial coronoid, and Medial olecranon) by (i) the sagittal plane of the ulna (sag-u) and (ii) the axial plane (axi-u). The radial head is divided into quadrants (Anterolateral, Anteromedial, Posterolateral, and Posteromedial) by (I) the sagittal plane of the radial head (sag-r), (II) the coronal plane (cor-r), and (III) the axial plane (axi-r).
Osteoarthritis and Cartilage  , 72-83DOI: ( /j.joca )
Copyright © 2017 Osteoarthritis Research Society International Terms and Conditions

4. Fig. 3
Diagram of the normal side (beige, right elbow) and the affected side (purple, right elbow) showing the boundary conditions. An 80 N load (multiple red arrows) is applied to one-third of the proximal part of the radius and ulna in the direction of the loading axis (red dashed lines), which was defined by a line drawn from the humeral head center to the wrist joint center. The distal humerus is fully restrained and displacement constraint (planes) was applied to the radius–ulna region.
Osteoarthritis and Cartilage  , 72-83DOI: ( /j.joca )
Copyright © 2017 Osteoarthritis Research Society International Terms and Conditions

5. Fig. 4
Distribution patterns of HDV when assessing bone density. (A) Distribution in the distal humerus. HDV is distributed along the capitello-trochlear groove and trochlear groove on the normal side (beige, right elbow); however, it is distributed on the medial side of the distal humerus on the affected side (purple, right elbow). (B) Distributions in the proximal ulna and radial head. On the normal side (beige, right elbow), HDV is distributed in the middle of the proximal ulna and in the posteromedial radial head; however, it is distributed on the medial side of the proximal ulna and the anterolateral part of the radial head on the affected side (purple, right elbow).
Osteoarthritis and Cartilage  , 72-83DOI: ( /j.joca )
Copyright © 2017 Osteoarthritis Research Society International Terms and Conditions

6. Fig. 5
Contours of the stress distributions that describe the equivalent stress. (A) Loading caused stress to concentrate on the medial side of the affected humerus (purple, right elbow) when compared with the normal humerus (beige, right elbow). (B) Loading caused stress to concentrate on the medial side of the affected ulna (purple, right elbow) compared with the normal ulna (beige, right elbow). However, no obvious regional difference was found in the stress distribution patterns in the radial heads between the affected (purple, right elbow) and normal (beige, right elbow) sides.
Osteoarthritis and Cartilage  , 72-83DOI: ( /j.joca )
Copyright © 2017 Osteoarthritis Research Society International Terms and Conditions