What is a flexor tendon?
The flexor tendons are the long tendons that run from the mid-forearm to the fingertip; each finger has two flexor tendons, and the thumb has one. The muscles that connect to these tendons originate in the forearm even though their action is in the hand. Their actions are complex, and injuries to them are devastating.
How does one get a flexor tendon injury?
The most common flexor tendon injury mechanism is a laceration from a sharp object like a knife, saw, or glass. You can also rupture a tendon when grabbing something or trying to tackle an opponent, hence the common name for an avulsion injury: “jersey finger.” Frequently, an avulsion injury is thought to be a “sprain” as the finger hurts and swells but can still partially flex.
Why are injuries to flexor tendons so challenging to treat?
Shortly after an injury, the pulley system in the finger starts to shrink, and the injured tendon swells. These anatomical changes make surgical repair after two weeks very unlikely. In a successful surgical repair, the tendons that are lacerated or injured will heal back to each other. In addition to healing where they cut, lacerated tendons can fuse together (two tendons adherent) as well as to the surrounding tissues.
Before the mid-1970s, surgeons treated all tendon injuries with grafts with minimal success. These initial attempts at early repair resulted in a large scar along the tendon, resulting in little function. In the 1970s, a few pioneering surgeons came up with a postoperative protocol relying on dynamic passive motion. The result was a significant increase in active range of motion and function, a development which ultimately changed the treatment of flexor tendon injuries throughout the world.
How do we repair flexor tendon injuries today?
Researchers have published thousands of papers about operative repair of flexor tendons, and surgeons have trialed numerous methods and implants. Today, the preferred method for repairing lacerations is multiple sutures crossing the gap (the area where the tendon is lacerated). Unfortunately, the treatment of choice for avulsions is less clear; if possible, surgeons fix the tendon to the bone with added sutures.
We utilize local anesthesia in our repairs of flexor tendons. Allowing the patient to move their fingers in the operating room before completing the procedure enables the surgeon to make sure the tendon will pass underneath the pulley system. Visualizing the repair passing underneath the pulley is very important for rehabilitation.
Physical therapy with a Certified Hand Therapist (CHT) is mandatory for anyone recovering from a flexor tendon injury. Often, patients will be sent to see the hand therapist before surgery. Depending on the nature of the damage and the method of the repair, patients will start therapy one or two days after surgery. If there is a bad wound (i.e., from a table saw, hatchet, etc.), sometimes we will have to wait to begin treatment. In any case, the therapist is essential in pushing the patient enough to try and prevent adhesions.
Many, many factors affect the outcome of a flexor tendon repair. The most important variables in determining surgical outcomes are the age of the patient–young-good, older-not so good–and the type of injury. Very sharp lacerations will have much better results than a table saw injury or a mutilating injury with corresponding fractures of the fingers.
The location of the laceration in the hand is also significant. The hand has been described in zones. Zone II, which runs from the middle of the palm to the end of the first phalanx, is called “No man’s land” because of the bad results early on with tendon repairs here. These poor outcomes are the result of the pulley system. Finally, positive outcomes are highly dependent on a motivated patient as well.
What is a flexor tenolysis?
If a patient has not regained an adequate range of motion (ROM) following surgery, they can elect to have an additional surgical procedure, called flexor tenolysis, to ‘loosen’ or break up the scar tissue between the tendons and the surrounding tissue. For this procedure to work, a patient must have a full passive ROM, meaning they must be able to make a fist with the injured hand using the other hand.