The Story of Two Tendons and 20,000 Miles apart: From Anatomical and Functional Perspectives in Education

With the emergence of social media, two college friends were able to reconnect again across the globe and to talk about the good old times. One has become an anatomist and asked the other about an old cut on her right 5 th finger. The objective of this presentation is to compare and contrast the anatomical and functional perspectives of this unique injury versus normal hand and finger function. It accidentally happened 45 years ago while grabbing a broken sink, during one of the college field trips in a rural region of Thailand. She was rushed to an emergency room and was treated at a local hospital with a couple stitches on the skin. At the time, she was told that her tendons were cut, but no loss of sensation. A tetanus shot and antibiotics were administered, but she did not recall having any x‐rays done. She reports no splint was applied for protection or any physical therapy treatment. The patient consulted with an orthopedic doctor later, but elected against surgical intervention to reconnect the tendons because it did not heavily interfere with her normal hand functions. The patient sent videos for evaluation on the extent of the loss of function in her hand movements. The deep laceration was in zone II of the grading scale used for hand injury, just above the crease at the base of the right 5 th finger and the palm. This zone is located between the opening of the flexor sheath (the distal palmar crease) and the insertion of the flexor digitorum superficialis tendon. While curling her hand to make a fist, she can only flex the metarcarpophalangeal joint, but not the proximal and distal interphalangeal joints. It indicates that both tendons of flexor digitorum superficialis and profundus to that finger were cut and never re‐connected for repair. The muscle bellies of these two tendons in the forearm have extensively atrophied over time, and can be seen as a long hollowed‐out area on the ulnar side of the distal forearm, proximal to the wrist. The palmaris longus muscle and tendon seems to be more prominent, as part of a compensatory hypertrophy for the loss of function of the other muscles. The patient is still able to flex the metacarpophalangeal joint and to adduct that finger, indicating that the lumbrical and interosseous muscles and tendons are still intact. Due to the loss of the palmar flexor tendons connecting to the 5 th digit, this finger is in a constant stage of hyper‐extension (‘sticking out’), as there is no longer any counterbalance between the flexor and extensor tendons of the finger. In conclusion, this is a very unique interesting injury to emphasize the structures and movement of the muscles and tendons in the hand and finger. It can be a good teaching tool, used as a problem solving case incorporated into the teaching and learning of the hand anatomy and function.