Flexor digitorum profundus tendon injuries are categorized into how many finger zones (I–V)?

• A. Three zones
• B. Seven zones
• C. Nine zones
• D. Five zones

Answer: (D)

Flexor digitorum profundus (FDP) tendon injuries are organized along five distinct finger zones, starting at the fingertip and extending toward the forearm. This five-zone system reflects changes in anatomy along the tendon’s path—differences in where the tendon travels relative to the FDS tendon, the pulley system, and the carpal tunnel—that influence how the injury heals and how rehab is planned.

In the most distal zone, the FDP portion beyond the FDS insertion lies at the fingertip, affecting tip flexion. Moving proximally, the next zone covers the region where the tendons run together within a tight sheath, a historically challenging area often called “no man’s land” because adhesions are common and careful repair is crucial. The more proximal zones correspond to the areas around the proximal phalanx with the pulley system and into the palm and carpal tunnel, continuing to the forearm in the final zone.

So, FDP tendon injuries are categorized into five zones I–V. This classification helps clinicians plan the repair approach and rehabilitation because each zone presents different anatomical constraints and healing considerations.