High-resolution ultrasound evaluation of the trapeziometacarpal joint with emphasis on the anterior oblique ligament (beak ligament)

The anterior oblique ligament is one of the main stabilizers of the trapeziometacarpal joint. Insufficiency of this ligament is closely linked to degenerative joint disease. High-resolution musculoskeletal ultrasound has advantages over magnetic resonance imaging (availability, dynamic nature, cost, patient comfort). This study evaluates the feasibility of ultrasound of the anterior oblique ligament. Ten cadaveric thumb specimens and 10 volunteers with normal trapeziometacarpal joints underwent imaging with high-frequency ultrasound. An ultrasound-guided, progressive dissection technique was used to confirm the ultrasound findings. Two radiologists reviewed the images in consensus. The detectability of the ligament was rated. The anterior oblique ligament was identified and measured in 90% of the specimens and 100% of the volunteers. The ultrasound findings correlated well with the dissections. This ligament appeared as a thin hypoechogenic structure in the ulnar-most part of the trapeziometacarpal joint, with a thickness that varied from 1.0 to 2.0 mm. Detectability of this ligament was good in 66% of the specimens and 100% of the volunteers. Ultrasound evaluation of the anterior oblique ligament of the trapeziometacarpal joint is feasible with state of the art equipment.