5 Key Takeaways

• 1

  Among 130 patients undergoing primary ACL reconstruction with peroneus longus autografts, 2 developed new flatfoot by Arch Index criteria, an incidence of 1.5%.

• 2

  Both cases occurred in the operated foot, and neither patient reported pain, instability, or limitations in daily activities or sports.

• 3

  Flatfoot classification varied by measure: the Chippaux-Smirak Index identified 2 patients, the Staheli Index 24, and the Clarke angle 61.

• 4

  Exploratory analyses found no significant associations with Beighton score, body mass index, weight, or height; the 2 cases were older than other participants.

• 5

  The single-center study had no alternative-graft comparison group, and its small number of cases limited risk-factor analyses and generalizability.