Effect of pulley excision on flexor tendon biomechanics

TLDR

Tendon excursion and work of flexion can assess pulley loss effects and are applicable to other flexor tendon studies, including pulley reconstruction. The study measured tendon excursion and work of flexion—defined as the force–excursion area resisting flexion, including counterweight and frictional forces—using a tensile testing machine to evaluate flexor tendon function after excising portions of the fibro‑osseous pulley system. Pulley loss affected work of flexion more than tendon excursion, indicating work of flexion is a more sensitive metric; the A2 pulley was the most critical, followed by A4, and both must be present for near‑normal hand function, whereas sacrificing A1 had little impact, with skin and soft tissue also mitigating bow‑stringing.

Abstract

Abstract Flexor tendon function following excision of various portions of the fibro‐osseous pulley system was measured biomechanically using a tensile testing machine. The biomechanical parameters measured were tendon excursion (the excursion of the tendon required to fully flex the digit) and work of flexion (the area under the force‐excursion curve, representing all the forces that resist tendon flexion). In this experiment, work of flexion included the forces necessary to accomplish full digital flexion against a 15‐g counterweight, as well as the frictional forces that resist tendon gliding. The results indicate that the work of flexion was affected to a greater degree by pulley loss than was tendon excursion, suggesting that it is a more sensitive measurement of tendon function. A 2 was found to be the single most important pulley for flexor tendon function, followed by A 4 . However, both A 2 and A 4 had to be present if near‐normal hand function was to be achieved; sacrificing the A 1 pulley was not associated with a significant loss of flexion. The “pulley effect” of the skin and soft tissue as a supplement to the fibro‐osseous pulleys in reducing tendon bow‐stringing was also noted. Although the parameters of tendon excursion and work of flexion were used in this study to determine the effect of pulley loss on tendon function, they can also be used to evaluate other flexor tendon studies, such as pulley reconstruction.