A method for carpal motion hysteresis quantification in 4-dimensional imaging of the wrist

• Dynamic or predynamic carpal instabilities of the wrist only demonstrate abnormalities during motion.
• Carpal bones motions exhibit hysteresis that is dependent on the direction of wrist motion.
• To measure the true dynamic motion of the wrist, the specimen was moved and scanned continuously in RUD direction.
• We have demonstrated that our approach of using 4DCT imaging can be used to assess the carpal hysteresis.
• We have achieved good reliability in both intra- and inter-rater assessment.

IntroductionCarpal bones motions exhibit hysteresis that is dependent on the direction of wrist motion, which can be seen during 4-dimensional (3D plus time) imaging of the wrist. In vitro studies have demonstrated the phenomenon of carpal hysteresis and have reported that hysteresis area increases with carpal instabilities. However, their techniques required implantation of bone markers and thus cannot be used clinically. The objective of this study is to use noninvasive 4-dimensional computed tomography (4DCT) technique to quantify carpal hysteresis, and to determine the reliability of this method.MethodA cadaveric wrist mounted on a custom motion simulator was imaged using a dual-source CT scanner while undergoing periodic radioulnar deviation. Ten image phases of this motion was reconstructed through retrospective cardiac gating. The rotational angles of scaphoid, lunate and triquetrum in each phase were derived through manual registration using Matlab after segmenting the bones in Analyze 8.1. These angles were then plotted against global wrist positional angles to produce the hysteresis curves and the area was calculated. The image segmentation and measurements were repeated by 2 raters to derive intra- and inter-rater reliability assessments.ResultsThe hysteresis area was found to be larger in the lunate (96.5 deg2) followed by triquetrum (92.3 deg2) and scaphoid (67.5 deg2). The measurement of the total hysteresis area of the scaphoid had the highest reliability with intra- and inter-rater reliability of 95.5% and 95.4% respectively.DiscussionWe have demonstrated that our approach of using 4DCT imaging can be used to assess and quantify the hysteresis of the carpal motion with good reliability.