A2 and A4 flexor pulley biomechanical analysis: comparison among gender and digit.

Rock climbing has become increasingly more popular in the USA over the past two decades. Accordingly, with increased participation comes an increase in climbing-related injuries. Rooks et al noted that three-quarters of elite and recreational climbers will suffer upper extremity injuries, approximately 60% involving the hand or wrist and 40% divided evenly between the shoulder and elbow. Most of these injures will be strains, microtrauma, and tendonitis; however, 30-50% represent trauma to the proximal interphalangeal region. The purpose of this study was to investigate the biomechanical properties of the A2 and A4 pulley and compare biomechanical properties among gender and digit. A specially designed materials testing machine, shown in the included figure, measured maximum breaking load, displacement and stiffness of the A2 and A4 pulleys of ten cadaveric hands using an S hook to apply a steady force until complete pulley rupture. The A2 and A4 biomechanical properties of breaking load, displacement, and stiffness did not significantly differ among the index, middle, ring, and little fingers. Additionally, there was no significant difference in A2 or A4 pulley biomechanics between male and female specimens. The A2 and A4 pulleys among differing digits and genders have similar biomechanical properties in regards to maximum breaking load, displacement, and stiffness.