Back to the Anatomy Lab to Redefine the Pulley System of the Thumb: Is There an A0 Pulley?

The presence of an A0 pulley in greater than 80% of the studied thumbs serves as an important anatomic finding that should be considered in surgical treatment. An additional finding of importance is that the pulley system anatomy demonstrated variability in laterality. Based on these anatomic findings, not only can the A0 pulley be defined as a unique anatomic structure of the thumb, but its repair also has implications for successful surgical treatment of thumb pulley system pathologies.