Length and Landmark of A1 Pulley in Hand: An Anatomical Study
Yolchai Jongjirasiri MD*
Affiliation : * Department of Orthopaedic Surgery, Bangkok Metropolitan Administration General Hospital, Bangkok, Thailand
Objective : The purpose of the present study was to identify length and landmark of proximal of A1 pulley in
hand.
Material and Method: An anatomical study of the length and landmark of A1 pulley in hand was performed in
510 fingers and thumbs from 51 preserved cadavers. There were 25 females and 26 males whose ages at the
time of death ranged from 48 to 89 years.
Results : The lengths of A1 pulley were 5.30 + 0.53 mm in average of thumbs and 6.32 + 0.17, 6.58 + 0.19, 6.32
+ 0.20, and 5.30 + 0.49 for the index, middle, ring, and small finger respectively. The average of all fingers
were 6.13 + 0.17 mm. The margin from the proximal edge of A1 pulley related to the perpendicular line from
posterior superior prominent of metacarpal head to the volar aspect of its fingers, which was in the same line
for 327 (64.1%) fingers and thumbs, and for 464 (91.0%) fingers and thumbs were differences < 1 mm, and for
509 (99.8%) were differences < 2mm to proximal edge of A1 pulley of its finger and thumb.
Conclusion : The posterior superior prominent of metacarpal head line in perpendicular to the volar aspect of
its finger and thumb may be used as an anatomical landmark to predict of the proximal edge of A1 pulley with
reasonable accuracy. The length of A1 pulley can serve as an important guide for the distal termination of A1
pulley release.
Keywords : A1 pulley, Landmark, Anatomy, Trigger finger
