Defining the Digit-Specific Confluence of the A1 Pulley

Abstract

Purpose: Variations in the description of the flexor pulley system exist, particularly in whether the A1 and A2 pulleys represent discrete or confluent entities. This has potentially important clinical relevance at the time of A1 pulley release for symptomatic trigger finger, given the goal of adequate release without overrelease. The purpose of this study was to determine the relative prevalence of confluent A1 pulleys on a digit-by-digit basis employing 2.5× loupes alone, thereby simulating a clinical surgical environment.

Methods: Cadaveric anatomic specimens underwent flexor pulley system dissection under 2.5× loupe magnification by 2 hand surgeons. The presence of pulley confluence and length (measured from the proximal aspect to the distal aspect) was recorded and compared on a digit-to-digit basis.

Results: Forty-five digits, comprising 9 adult forearm or hand specimens (5 right and 4 left) obtained from 6 donors (4 men and 2 women, age: 67 ± 8 years), were dissected. A total of 19 confluent A1 pulleys were encountered, with notable digit-by-digit variation in the prevalence of confluent pulleys. There were 0 confluent pulleys observed in the thumb, compared with 6 confluent pulleys observed in the middle finger. The average overall A1 pulley length was 5.0 ± 1.5 mm, with a similar pulley length observed between the digits.

Conclusions: A1 pulley confluence varies on a digit-to-digit basis, with no observed confluence in the thumb and the most common confluence observed in the middle finger.

Clinical relevance: In the setting of intraoperatively observed pulley confluence, we suggest pulley release under traction in order to develop the plane between the A1 and A2 pulleys and, thus, confirm the complete and isolated release of the A1 pulley.

Keywords: A1 pulley; flexor pulley system; hand; palmar aponeurosis.