“MRI of the thumb: anatomy and spectrum of findings in asymptomatic volunteers”

Hirschmann A, Sutter R, Schweizer A, Pfirrmann CW.
American Journal of Roentgenology 2014;202(4):819-27.

For this study MRI of the thumb was performed on a dedicated 1.5-T extremity MRI system in 34 asymptomatic volunteers. Study summary:

  • The ligaments and pulleys of the thumb show considerable variability on MRI in healthy volunteers.
  • The ulnar collateral ligament of the metacarpophalangeal joint is typically striated and less than 3 mm thick.
  • A full-thickness synovial recess at the base of the dorsal plate of the metacarpophalangeal joint is a normal finding and should not be misdiagnosed as a tear.

BACKGROUND. MRI of the thumb was obtained in 34 asymptomatic volunteers (mean age, 33.9 ± 9.2 years). MRI was performed with a 1.5-T extremity MRI scanner (Optima MR 430s, GE Healthcare) in a dedicated 100-mm standard coil. The volunteer was seated next to the scanner, the hand was placed in a neutral position, and the thumb was fixated with two positioning pads (Multipad, Pearltec) on each side.
Two radiologists independently assessed visibility and signal intensity (SI) and thickness of the following structures of the metacarpophalangeal and interphalangeal joints: proper and accessory radial and ulnar collateral ligaments, volar and dorsal plates, adductor pollicis aponeurosis, and annular pulleys. The presence and size of a synovial recess at the base of all plates was assessed.

RESULTS. On intermediate-weighted fat-saturated images, the ulnar collateral ligament of the metacarpophalangeal joint (reader 1, 79%; reader 2, 62%) and the adductor pollicis aponeurosis (reader 1, 50%; reader 2, 82%) commonly had a striated appearance. The radial collateral ligament of both joints was mainly of low SI (metacarpophalangeal joint, 53% for reader 1 and 85% for reader 2; interphalangeal joint, 59% for reader 1 and 82% for reader 2).
All four pulleys were visible in each volunteer. An intermediate SI was observed in almost all pulleys, whereas the variable annular pulley had predominantly a low SI (reader 1, 50%; reader 2, 74%). The ulnar collateral ligament of the metacarpophalangeal joint is typically less than 3 mm thick, and the radial collateral ligament is less than 2 mm thick. A full-thickness synovial recess at the base of the dorsal plate of the metacarpophalangeal joint was seen in almost all volunteers (reader 1, 97%; reader 2, 100%).

CONCLUSION. The ligaments and pulleys of the thumb show considerable variability on MRI in healthy volunteers. The ulnar collateral ligament of the metacarpophalangeal joint is typically striated and less than 3 mm thick. A full-thickness synovial recess at the base of the dorsal plate of the metacarpophalangeal joint is a normal finding and should not be misdiagnosed as a tear.

Read more: http://www.ajronline.org/doi/full/10.2214/AJR.13.11397

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