This anatomic and clinical evaluation of the flexor pulley system in the finger attempts to outline reliable surface landmarks that will allow for safe and minimally invasive A1 pulley release in trigger fingers, as well as direct surgical approaches in other relevant hand surgical procedures. The authors dissected 256 fingers in 64 preserved cadaver hands. Identification and measurements of the A1 pulleys were performed with calipers under 4x loupe magnification. The authors also measured the distances from the proximal edge of the A1 pulley to the palmar digital crease (PDC), the PIP crease, and the distance from proximal edge of the first cruciform pulley to the PDC. In all dissections the authors identified five annular pulleys and four cruciform pulleys. The origins and locations of the pulleys were reliable, with a first cruciform pulley located between the fibers of the A1 and A2 pulleys in all specimens. The authors found that the distance from the PDC to the PIP crease (2.42 +/-0.03 cm) closely duplicated the distance from the PDC to the proximal edge of the A1 pulley (2.45 +/- 0.03 cm), thus serving as a useful anatomic measure for locating the A1 pulley during minimal incision surgery. The average length of the A1 pulleys measured 1.17 +/- 0.02 cm for the index, middle, and ring fingers, and 0.98+/- 0.02 cm for the small finger. The authors used their findings to perform trigger finger releases through a minimal transverse incision approach in 32 fingers with complete correction of triggering and no complications after a follow-up of 4-30 weeks.
This paper lends important information to the literature relating to the flexor tendon pulley system. There has been some debate regarding the number, location, size, and nature of the pulleys in the digits, as reflected in the authors’ depiction of five separate descriptions from the existing literature. The existence of a first cruciform pulley between the fibers of the A1 and A2 pulleys serves as a useful landmark in terminating A1 pulley release without injury to the A2 pulley. By delineating the location of the proximal edge of the A1 pulley, its average length, and the distance from the PDC, the authors provide an easily reproduced measurement system for guiding safe and complete pulley release in all digits, except the thumb. Other uses for this measurement system are described, such as locating the proximal digital sheath for treatment of suppurative tenosynovitis and tendon retrieval proximal to the sheath in the palm.