Anna Hirschmann MD, Presenter: Nothing to Disclose

Reto Sutter MD, Abstract Co-Author: Nothing to Disclose

Andreas Schweizer MD, Abstract Co-Author: Nothing to Disclose

Christian W. A. Pfirrmann MD, MBA, Abstract Co-Author: Nothing to Disclose

Characterization of normal MR appearance of the ulnar collateral ligament (UCL) and adductor pollicis aponeurosis (ADP) of the first metacarpophalangeal joint (MCP) and the thumb pulley system.

This study had institutional review board-approval, informed consent was obtained. MR scans of the thumb in 34 asymptomatic volunteers (17 women, 17 men; mean age 34 years, SD 9 years) were obtained on a dedicated 1.5T extremity scanner. Morphological characteristics were quantified on a 4-point scale (hypointense, intermediate, striated, not visible) for the UCL and ADP of the MCP joint and pulley system (A1, Av, oblique and A2 pulley) of the thumb. Thickness was measured for the UCL and the A1 and Av pulleys. The Mann-Whitney U test was used.

All structures could be identified in asymptomatic volunteers. The UCL had commonly a striated appearance (79%) in intermediate weighted fat-suppressed images while only a few had an intermediate (15%) or low (6%) SI. The UCL showed no significant difference in thickness between sexes (p=0.2). Striation was present in 50% of the ADP. The oblique and A2 pulley ligaments showed an intermediate SI in all volunteers (100% for each), the Av pulley had a low SI in 50% and an intermediate SI in 44%, the A1 pulley had a commonly intermediate SI (62%). The Av pulley was significantly thicker in men (2.2mm) than in women (1.3mm; p=0.004), the A1 showed no significantly difference between sexes (p=0.5).

Contrary to most reports in the literature each of the 4 pulleys as well as the UCL and ADP were visible in all volunteers. Most of the UCL and half of the ADP have a striated appearance. Intermediate signal intensity is normal for the oblique and A2 pulleys.

Striation of the UCL is a normal finding at MR imaging and should not be mistaken for a tear when evaluating patients with suspected gamekeeper`s thumb.

Hirschmann, A, Sutter, R, Schweizer, A, Pfirrmann, C, MR Variants of the Ulnar Collateral Ligament and Pulley System of the Thumb in Asymptomatic Volunteers.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12033680.html