Evaluation of the modified radio-ulnar line in correlation with imaging features of the distal radio-ulnar joint osteoarthritis, using a 4D CT examination

Abstract

Purpose: Modified Radio-Ulnar line (mRU) is a previously defined index of the Distal RadioUlnar Joint (DRUJ) and ulnar head alignment. The purpose of our study was to evaluate the association between mRU measurements using Four-Dimensional Computed Tomography (4DCT) examination with clinical symptoms and imaging features of DRUJ osteoarthritis (OA). Methods: In this IRB approved HIPAA compliant study, we scanned 18 wrists (10 patients with unilateral wrist pain and instability). Imaging of the contralateral asymptomatic side was also performed to aid the diagnosis in the symptomatic side. The 4DCT was obtained using a 320-row detector scanner (Aquilion One, Toshiba Medical Systems) in active pronation-supination. Our previous study confirmed the reliability of mRU measurements using 4DCT examination. The mRU measurements were performed in pronation, midpoint and supination by a fellowship trained MSK radiologist. Presence of symptoms (yes vs. no) and the Kellgren-Lawrence grade of OA (0-4) were assessed in correlation with mRU measurements in active motion. Results: The mRU values showed a significantly greater volar motion of the ulnar head in asymptomatic wrists (mRU mean values (P<0.001) in supination. Changes in the mRU measurements from pronation to midpoint (mean change: 0.11 (0.03), P:0.002) and to supination (0.19 (0.03), P<0.001) were significant only in the asymptomatic wrists. Unlike wrists with KL grade >=2, wrists with KL grade <2 had significant changes in the mRU values while moving from pronation to midpoint (mean change: 0.09, P:0.004) and from pronation to supination (0.14, P:0.059). The mRU values in pronation were not associated with the presence of symptoms or DRUJ OA. However, mRU values in supination were significantly correlated with both the presence of symptoms (correlation coefficient: 0.796, P<0.001) and KL grade of DRUJ OA (correlation coefficient: 0.647, P:0.005). Conclusions: while moving from pronation to supination, we observed that presence of clinical symptoms and imaging features of DRUJ OA severity were associated with restricted volar motion of the ulnar head (assessed by the mRU line).