Ultrasound visualization of the thumb annular pulleys: A cadaveric validation study.

Background: The thumb annular pulley system is unique from the other digits and is integral to normal thumb function. Injuries to this pulley system can present a diagnostic challenge. No prior study has evaluated the ability of ultrasound (US) to evaluate all four thumb pulleys.

Objective: To validate the sonographic visualization of all four thumb pulleys.

Design: Prospective cadaveric laboratory investigation.

Setting: Academic center procedural skills laboratory.

Participants: Twelve unembalmed cadaveric hands from seven adult male donors ages 78-89 years with body mass index 21.9-26.6 kg/m .

Interventions: Based on anatomic descriptions, a single examiner used a standardized protocol and high-frequency linear transducers to identify the A1, variable (Av), oblique (Ao), and A2 pulleys of the thumb in 10 cadaveric hands. As part of the validation process, the presumed Ao pulley was injected with diluted colored latex using US guidance. Two additional cadaveric specimens were dissected for detailed study of the thumb pulley system.

Main Outcome Measures: Correlation between the four anatomic pulleys as revealed by dissection and the US findings, including identification of latex location with respect to the Ao pulley.

Results: US correctly identified all four thumb pulleys as distinct anatomic structures and the sonographic appearance of the pulleys correlated with the dissection in all 10 specimens. Latex was observed in the Ao pulley in 100% of the cadavers.

Conclusions: Ultrasound can be used to accurately identify all four thumb pulleys, including distinct Ao and Av pulleys, and should be considered in the evaluation of thumb pulley injuries. This is the first study to validate the US visualization of the annular pulley system of the thumb.