Flexor profundus tendon avulsion injuries occur when the fingertip is
suddenly pulled into extension while being actively flexed. The tendon
may retract all the way into the palm at the metacarpal neck level (1).
Lesser degrees of tendon retraction are more likely when the injury
results in an avulsion fracture, which may lodge at the A2 or A4 flexor
tendon pulley (2,3) or be minimally displaced (4). Retraction proximal
to the proximal interphalangeal joint disrupts the vincular arteries,
ischemic tendon damage, and a worse outcome.