Abstract
BackgroundNon-invasive imaging techniques such as magnetic resonance imaging (MRI) provide the ability to evaluate the complex anatomy of bone and soft tissues of the wrist without the use of ionizing radiation. Dynamic instability of wrist – occurring during joint motion – is a complex condition that has assumed increased importance in musculoskeletal medicine. The objective of this study was to develop an MRI protocol for evaluating the wrist during continuous active motion, to show that dynamic imaging of the wrist is realizable, and to demonstrate that the resulting anatomical images enable the measurement of metrics commonly evaluated for dynamic wrist instability.MethodsA 3-Tesla “active-MRI” protocol was developed using a bSSFP sequence with 475 ms temporal resolution for continuous imaging of the moving wrist. Fifteen wrists of 10 asymptomatic volunteers were scanned during active supination/pronation, radial/ulnar deviation, “clenched-fist”, and volarflexion/dorsiflexion maneuvers. Two physicians evaluated distal radioulnar joint (DRUJ) congruity, extensor carpi ulnaris (ECU) tendon translation, the scapholunate (SL) interval, and the SL, radiolunate (RL) and capitolunate (CL) angles from the resulting images.ResultsThe mean DRUJ subluxation ratio was 0.04 in supination, 0.10 in neutral, and 0.14 in pronation. The ECU tendon was subluxated or translated out of its groove in 3 wrists in pronation, 9 wrists in neutral, and 11 wrists in supination. The mean SL interval was 1.43 mm for neutral, ulnar deviation, radial deviation positions, and increased to 1.64 mm during the clenched-fist maneuver. Measurement of SL, RL and CL angles in neutral and dorsiflexion was also accomplished.ConclusionThis study demonstrates the initial performance of active-MRI, which may be useful in the investigation of dynamic wrist instability in vivo.
Highlights
The wrist is considered unstable clinically if it exhibits symptomatic dysfunction, is not able to bear loads, and does not exhibit normal kinematics during any portion of the wrist’s arc of motion [1,2]
Active-magnetic resonance imaging (MRI) Protocol Representative snapshots obtained from the active-MRI protocol are shown in Figure 3 and 4
During wrist rotation from supination to neutral to pronation, the ulna tended to translate in the dorsal direction relative to the sigmoid notch of the radius, with a slight increase in the distal radioulnar joint (DRUJ) subluxation ratio
Summary
The wrist is considered unstable clinically if it exhibits symptomatic dysfunction, is not able to bear loads, and does not exhibit normal kinematics during any portion of the wrist’s arc of motion [1,2]. In order to diagnose static and dynamic instability at these sites, numerous radiographic measurements have been proposed, including SL interval, SL angle, capitolunate (CL) angle, radiolunate (RL) angle and DRUJ subluxation ratio [3,4]. These measurements are commonly applied to static examinations (i.e., with the wrist immobilized in the imaging system), radiography in multiple positions or with stress may be needed to diagnose instability [6]. Non-invasive imaging techniques such as magnetic resonance imaging (MRI) provide the ability to evaluate the complex anatomy of bone and soft tissues of the wrist without the use of ionizing radiation. The objective of this study was to develop an MRI protocol for evaluating the wrist during continuous active motion, to show that dynamic imaging of the wrist is realizable, and to demonstrate that the resulting anatomical images enable the measurement of metrics commonly evaluated for dynamic wrist instability
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