How to Treat Flexor Tendon Injury

There are two tendons that flex digits 2-5: flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP). The thumb is flexed by the flexor pollicis longus (FPL)                                                             .                                                                               

The FDS splits into two and is attached  to the proximal area of the middle phalynx. It flexes the PIP and MCP. The FDP runs in between and attaches to the base of the distal phalynx. It flexes the DIP, PIP, and MCP.

Unlike the extensor tendons, the flexor tendons are deep in the finger and encircled by muscle, fascia, vascular, and nerve structures. This makes it them difficult to visualize and evaluate for injury.

According to one study, 30% of flexor tendon injuries are missed by emergency physicians and orthopedic residents when outside the OR.

Furthermore, the flexor tendons are enclosed by synovial sheaths (unlike the extensors), which make them prone to deep space infection as well as long-term complications due to the precise nature of their flexion action.

Anesthetize the finger with a digital block. (Remember to evaluate sensation and motor function before you do so.)

Limit blood loss from obscuring the wound with a finger tourniquet. Milk the finger distal to proximal by wrapping the finger circumferentially with an elastic tourniquet and unraveling it towards the palm.

21 gauge needles can be attached on to 3mL syringes and bent to make small soft tissue retractors. 

Use a cotton-tipped applicator to probe the tendon as fully as possible. Make sure you evaluate the tendon throughout its full ROM as the site of injury can be hidden in the soft tissue. However, do not extend the laceration with an incision.                                    

Obtain an x-ray to look for any foreign bodies, fractures or avulsions. Give a tetanus shot if applicable. If the wound is open, flush it with sterile water. Consider antibiotics if wound is dirty or if there is a fracture. While only flexor tendon injuries > 25% need to be repaired by a hand surgeon, it is extremely difficult to assess this in the emergency department. Closed tendon injuries may be splinted with a dorsal splint and sent to hand clinic as soon as possible. However, if there is an open wound obtain a orthopedics/hand consult if there is any suspicion of a tendon injury given location, exam and evaluation.

References:

Davenport M.and P. Tang. “Chapter 268. Lithium.”Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e. Eds. Judith E. Tintinalli, et al. New York, NY: McGraw-Hill, 2015. n. pag. AccessMedicine.Web. 28 Nov. 2016.

Taecker M., Bosch D., Broderick K.A. and M. Breyer. How to Treat Open Injury to Flexor Compartment of  Fingers and Hands. EP Monthly. 2014 Oct