Grasping the Grasp: The A1 Pulley as a Fulcrum for Flexor Tendon Excursion – A Histopathological Study

Objective: Stenosing tenosynovitis of the flexor tendons which readily causes the alleged “trigger finger” is a common and yet not completely understood phenomenon. The A1 Pulley is the pivot point at which

the force protracted by the flexors of the digits acts upon the fulcrum at the leading edge of the pulley.

Method: We performed a histopathological study aimed at assessing the A1 Pulley of digits 2 through 5 in cadaver hands in an effort to delineate the changes the A1 pulley undergoes through the cycle of life

and its repetitive motion tasks. Thirty-Nine A1 Pulley specimens were included in the study. These

specimens were assessed as to physical width utilizing a caliper and as to histological characteristics

following embedment and pertinent staining.

Results: Our findings suggest the proximal leading edge of the A1 Pulley to be significantly (p<0.05) thicker than the more distal aspect of the A1 pulley when pulley data were stratified for handedness and gender. We found insignificant differences within each digit as to differences between the radial and ulnar aspects of the denoted numerated digit.

Conclusions: We believe our study sheds further light on the mechanism leading to digital triggering and that further studies may substantiate our preliminary findings as to the differences in radial versus ulnar aspects of each designated digital A1 pulley.