Metrics associated with wrist instability that were derived from standardized measurements on active-MR images.

<p>(a) <b>DRUJ subluxation ratio</b> – the subluxation ratio for the DRUJ was determined on axial images by connecting the palmar and dorsal aspects of the sigmoid notch and drawing perpendicular lines. The subluxation ratio was computed as a ratio between CD and AB; (b) <b>SL interval and ulnar variance</b> – the measurement of SL interval (two-sided arrow) and ulnar variance (distance between the dots with white centers on the solid red lines) was performed on the coronal images. The solid red lines represent the most distal aspect of the distal ulna and most proximal aspect of the distal radius articular surfaces; (c) <b>SL, RL and CL angles</b> – the axis of the scaphoid (S) was drawn by connecting the proximal and distal poles along the volar cortex (dotted line) on sagittal images. Similarly, the axis of the lunate was determined by connecting the distal dorsal and distal palmar corners and creating a perpendicular line. The SL angle (SLA) was determined by measuring the angle between the scaphoid and the lunate (L) axes. Similarly, the axes of the capitate and the radial shaft were determined and the CL angle was measured as the angle between the capitate and the lunate axes (not shown). The RL angle was measured as the angle between the long axis of the radial shaft and the lunate (not shown).