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Triqutral Rotational Index: A Measure of Ulnocarpal Instability
Christopher J. Dy; Hospital for Special Surgery; Arianna Trionfo, MD; UMDNJ; Anna-Lena Makowski; Physicians For The Hand/The Hand Place; Edward Milne, BS; Max Biedermann Institute for Biomechanics/Mt Sinai Medical Center; Loren Latta, PhD, PE; Max Biedermann Inst for Biomech/ Univeristy of Miami; E. Anne Ouellette; Physicians For The Hand
Physicians For The Hand, Miami, FL, USA

Introduction:Fluoroscopy video can be used a diagnostic tool for Ulnocarpal Instability (UCI) by utilizing image analysis. The difference of the length of the triquetrum in points of max volar vs. dorsal excursion of the carpus in relation to the forearm forms an indication of instability, termed triquetral rotational index, (TRI).

Material & Methods:106 wrists from volunteer subjects were included in this study. Dynamic testing of ulnocarpal instability was performed using the supination test (ST), a maneuver performed by stabilizing the DRUJ with a firm grasp while stressing the wrist in volar/dorsal excursion.1 Rotation of the carpus off the distal ulna and/or reproduction of ulnar-sided wrist pain constitutes a positive supination test. Live fluoroscopy with the subjects hand in anterior-posterior view was performed during the supination test to evaluate and visualize movement of the bones. The length of the triquetrum was measured while in max dorsal versus volar position. TRI was calculated as the percentage of triquetral length change. Statistical analysis was performed using the students T-test, odds ratio and relative risk.

Results:Based on the supination test, 64 wrists were found to have ulnocarpal instability, while 42 were found to be stable. A students t-test comparing wrists with a stable versus unstable supination test, confirmed a statistically significant difference in the triquetral rotation index (p<0.001). In this population, wrists with a TRI between 1 and 3 were more likely to be stable than unstable (Relative risk 10.0). Wrists with a TRI greater than 21 were more likely to be unstable than stable (Relative risk 5.67).


  • dynamic, real-time fluoroscopy allows evaluation of UCI
  • This diagnostic technique can be used to assess extent of impairment as well as response to treatment
  • TRI quantifies the amount of UCI.


  1. Dy, CJ, Ouellette, EA.. Makowski, A-L.: Extensor retinaculum capsulorraphy for ulnocarpal and distal radioulnar instability – the Herbert Sling. Techniques in Hand and Upper Extremity Surgery. 13;19-22, 2009

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