Longer Tendon-Bone Distances of the A2 and A4 Annular Pulleys in Experienced High-Level Sport Climbers: Injury or Adaptation?

Abstract

Experienced high-level climbers are subject to a number of bone and soft tissue changes over the years and are also among the most exposed to pulley injuries. One of the main consequences of pulley rupture is the separation of the flexor tendons from the subjacent phalanges, also known as bowstringing. The purpose of this study was to determine whether this population has asymptomatic bowstringing of the A2 and/or A4 pulleys as determined by tendon-bone distance (TBD) values when compared to nonclimbers. High-resolution ultrasound TBD measurements in active forced flexion were made for the A2 and A4 pulley of the ring finger bilaterally. Participants were 21 asymptomatic sport climbers who had 21 consecutive years of climbing at a level above 9.66 in the International Mountaineering and Climbing Federation difficulty metric scale. Control subjects were 21 age-matched nonclimbers. A significantly longer TBD-25% (0.3 mm) and 35% (0.4 mm) for the A2 and A4 pulleys, respectively-was found in the experienced climbers group (experienced climbers group: A2 1.6±0.5 mm and A4 1.6±0.4 mm; nonclimbers group: A2 1.2±0.1 mm and A4 1.2±0.2 mm). Our results suggest that bowstringing of A2 and A4 pulleys occurs in asymptomatic experienced high-level climbers, which could be interpreted as either an adaptive mechanism to workloads endured over years of climbing or a consequence of underdiagnosed pulley ruptures.