Diagnosis of A3 Pulley Injuries Using Ultrasound

Pulley ruptures are the most common injuries in sport climbing. Ruptures of the A2 and A4 pulleys have been studied extensively, and ultrasound has proven to be a highly sensitive and specific tool for their diagnosis. However, the correct diagnosis of A3 pulley ruptures continues to be a challenge. Therefore, we investigated a novel approach to this pathology.

Eighteen fingers from nine different human cadavers were examined using high-resolution, dynamic ultrasound before and after being subjected to different combinations of singular and multiple iatrogenic pulley ruptures in a standardised fashion. Special attention was paid to the behaviour of the volar plate (VP) with respect to the proximal interphalangeal joint (PIP) and the flexor tendons before and after pulley rupture.

Injuries to the A2 and A4 pulleys were diagnosed via ultrasound with sensitivities of 90 % and 94 % and specificities of 100 % and 97 %, respectively. A direct visualisation of the A3 pulley was achieved in 61 % of the fingers. The VP became significantly thicker and shorter during finger flexion as well as after A3 pulley rupture. The distance between tendon and VP became significantly more pronounced after A3 pulley rupture. For distances greater than 0.9 mm between VP and tendon, a sensitivity of 76 % and a specificity of 94 % were achieved for determining A3 pulley ruptures.

The distance measurement between VP and tendon was found to be a valid indirect method for the diagnosis of A3 pulley ruptures. This approach is the first ultrasound method for accurately diagnosing A3 pulley ruptures.