The purpose of this study was to identify surface landmark ratios to locate the A1 pulley and clarify the controversy of differing anatomic descriptions of the A1, C0, and A2 pulleys. Minimally invasive and percutaneous approaches to A1 pulley release may be facilitated with surface landmark ratios, which identify and predict the proximal and distal margins of the A1 pulley. Two-hundred fifty-sixty fingers were dissected in 64 preserved cadaver hands. Measurements of A1 pulley lengths and pulley margins in relation to surface landmarks were obtained. We found that the distance from the palmar digital crease to the proximal interphalangeal crease (mean, 2.42 ± 0.03 cm) corresponds to the distance of the proximal edge of the A1 pulley from the palmar digital crease (mean, 2.45 ± 0.03 cm). The mean absolute difference between these two measured distances in each finger was 0.13 cm, with a 95 percent confidence interval of 0.11 to 0.14 cm. Thus, the distance between the palmar digital crease and the proximal interphalangeal crease can be used to predict the distance between the palmar digital crease and the A1 pulley proximal edge with reasonable accuracy. A1 pulley length averaged 0.98 ± 0.02 cm for the small finger and 1.17 ± 0.02 cm for the index, middle, and ring fingers. The length of the A1 pulley was significantly shorter (p < 0.001) for the small finger than for the index, middle, and ring fingers. Additionally, a cruciate (C0) pulley was consistently located between the A1 and A2 pulleys, an average of 0.46 cm proximal to the palmar digital crease, which can serve as guide for concluding the release of the A1 pulley. Clinically, hand surface landmark ratios were used to release 32 trigger fingers with a minimally invasive technique, without a complication during 4- to 30-week follow-up. We conclude that hand surface landmark ratios can serve to locate the proximal A1 pulley edge, thus facilitating complete trigger finger release by either open or minimally invasive techniques. Additionally, our study clarifies the discrepancy of prior smaller reports of the pulley system anatomy regarding the existence of the CO pulley between the A1 and A2 pulleys. The cruciate fibers of this CO pulley can serve as the distal boundary for release of trigger finger.
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