The forearm of a healthy volunteer in the wrist harness.

<p>The harness has been slid outwards for better visualization of both the harness and the MR coil.</p

Active-MRI of the wrist during active ulnar-radial deviation.

<p>Snapshots of the coronal images of the wrist in the ulnar deviation (a), neutral (b) and radial deviation (c) positions during the continuous radial-ulnar deviation maneuver. SL interval and ulnar variance (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084004#pone-0084004-g002" target="_blank">Figure 2</a> for these definitions) were measured from the resulting images.</p

Quantitative metrics derived from active-MRI images of the wrist during the pronation/supination maneuver.^*

<p>One volunteer unable to complete the pronation/supination motion protocol.</p><p>DRUJ subluxation ratio, as described by <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084004#pone.0084004-Park1" target="_blank">[20]</a>.</p

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).</p

Quantitative metrics derived from active-MRI images of the wrist during radial/ulnar deviation.

<p>Quantitative metrics derived from active-MRI images of the wrist during radial/ulnar deviation.</p

MRI sequence (true-FISP) parameters used for the study.

<p>MRI sequence (true-FISP) parameters used for the study.</p

Extensor carpi ulnaris (ECU) tendon translation during wrist rotation.

<p>The relationship of the ECU tendon (arrow) to its groove as the forearm is rotated from (a) pronation, through (b) neutral to (c) supination – on axial images of the DRUJ using the active-MRI scan. In this volunteer, the ECU tendon was located within its groove in pronation, while in the neutral position, the tendon is subluxated eccentrically at the margin of the ulnar groove. In supination, the tendon is dislocated. Also visualized is the trajectory of the ulnar styloid process (white star) during the supination/pronation maneuver. Lister's tubercle (white triangle) at the dorsal aspect of the radius is shown as an anatomical reference point.</p

Quantitative metrics derived from active-MRI images of the wrist during the clenched fist maneuver.

<p>Quantitative metrics derived from active-MRI images of the wrist during the clenched fist maneuver.</p