Biomechanical aspects of trigger finger - which changed first, the pulley or the tendon?

Although trigger finger is a relatively common hand disorder, its exact cause remains unknown. Whether the etiology of the abnormality resides in the tendon or in the pulley continues debate. The purpose of this review is to summarize what is known about the clinical and biomechanical presentation of trigger finger. While the A1 pulleys are more accessible for examination than the flexor tendons during surgery and have been more extensively studied, it should not yet be assumed that the tendons are any less responsible for the entrapment symptom. Previous assessments of these tissues include testing of their compliance, friction coefficient, and contact angle. Kinematic and kinetic performance of trigger fingers has been evaluated in vivo. Thickening and changes in gene expression have also been identified in trigger finger tendons. Further investigation into the role of flexor tendons in trigger finger should be performed to facilitate the understanding of the etiology and mechanism of trigger finger development. Future studies could incorporate non-invasive medical imaging in order to understand the appearance and material properties of the involved pulley and tendons, and to combine these characteristics with finger kinematics. Furthermore, understanding the mechanism of biologic adaptations of the A1 pulley and the flexor tendons in response to the mechanical loading might be helpful in providing clues and evidence for effective, novel treatment for trigger finger.