Computer-Aided Assessment of Three-Dimensional Standard Bone Morphology of the Distal Radius

Abstract

The present study attempted to define the three-dimensional (3D) locations of reference points and standard measures of the distal radius of a normal wrist joint. One hundred wrists from 50 males and 50 females who matched the age distribution (19−95 years old, mean: 56.0 years old) were evaluated. Computed tomography (CT) images of normal wrist joints acquired for comparison with the affected side were used. The absence of a previous history and complaints in the unaffected wrist was confirmed in an interview and with medical records. Three-dimensional images of the distal radius were reconstructed using the data obtained from CT scans. The site at which the major axis of the radial diaphysis contacted the distal radius joint surface was defined as the origin. The 3D coordinates of reference points for the radial styloid process (1), sigmoid notch volar edge (2), and sigmoid notch dorsal edge (3) as well as the barycenter for the joint surface and joint surface area were evaluated. A slope of the line connecting coordinates 1−2 in the coronal plane was evaluated as the 3D radial inclination (3DRI) and that connecting coordinates 2−3 in the sagittal plane as the 3D palmar tilt (3DPT). Each measurement value was compared between males and females. The positions of each reference point from the origin were as follows: (1) 14.2 ± 1.3/12.6 ± 1.1 mm for the distal-palmar-radial position; (2) 19.3 ± 1.3/16.9 ± 1.3 mm for the proximal-palmar-ulnar position; (3) 15.6 ± 1.4/14.1 ± 0.9 mm for the proximal-dorsal-ulnar position; and (barycenter) 4.1 ± 0.7/3.7 ± 0.7 mm for the proximal-volar-ulnar position for males and females, respectively. The areas of the radius articular surface were 429.0 ± 67.9/347.6 ± 44.6 mm2 for males and females, respectively. The 3DRI and 3DPT were 24.2 ± 4.0/25.7 ± 3.1° and 10.9 ± 5.1/13.2 ± 4.4° for males and females, respectively. Significant differences were observed in all measurement values between males and females (p < 0.01). The reference points and measured values obtained in the present study will serve as criteria for identifying the dislocation direction and reduction conditions of distal radius fractures in 3D images.

Keywords: computed tomography; computer-aided diagnosis; distal radius; osteosynthesis; three dimensions.

Figure 1

Three reference points on 3D images. (a) The oblique view from the distal ulnar side and (b) the axial view. Red dots indicate the three reference points: (1) the radial styloid process; (2) sigmoid notch volar edge; and (3) sigmoid notch dorsal edge. The long axis of the radius was marked by the green dots and bar.

Figure 2

Articular surface and the position of barycentric coordinates. (a) The articular surface of the 3D model was identified with the bony prominence of the distal radius, (b) the articular surface was extracted, and (c) the surface area and position of the barycentric coordinates (red dots) were calculated. The bar indicates the long axis of the radius.

Figure 3

Measurements of 3DRI and 3DPT. (a) 3DRI was defined as the angle between the line connecting reference point (1) to reference point (2) and the line perpendicular to the longitudinal axis of the radius. (b) 3DPT was defined as the angle between the line connecting reference point (2) to the reference point (3) and the line perpendicular to the longitudinal axis of the radius. Red lines show the angles for the 3DRI and 3DPT.

Figure 4

Coordinates of three reference points in the axial plane. (a) Results of coordinates for males. (b) Results of coordinates for females. Orange dots indicate the radial styloid process: reference point (1). Gray dots indicate the sigmoid notch volar edge: reference point (2). Blue dots indicate the sigmoid notch dorsal edge: reference point (3). Black dots indicate average positions for each reference point.

Figure 5

Coordinates of three reference points in the sagittal plane. (a) Results of coordinates for males. (b) Results of coordinates for females. Orange dots indicate the radial styloid process: reference point (1). Gray dots indicate the sigmoid notch volar edge: reference point (2). Blue dots indicate the sigmoid notch dorsal edge: reference point (3). Black dots indicate average positions for each reference point.

Figure 6

3DRI and 3DPT. Both 3DRI and 3DPT were significantly larger in females than in males (*: p < 0.01).

Figure 7

The area of the radius articular surface. The area was significantly larger in males than in females (*: p < 0.01).