Flexor Tendon Injury


Tendons are the long, strong linear structures connecting the contracting muscle of the forearm to the fingers.

They are required to glide back and forth as the fingers bend or straighten.

When tendons are injured they require repair or loss of strength, motion or dexterity may occur. The photograph below illustrates an individual trying to bend his small finger but it won't bend because the tendons are cut.

Tendons should be repaired as soon as possible after they are severed.  Prolonged delay may impact outcome.
After surgery to repair the tendons a splint will be devised to protect from excessive uses of the injured hand.

The splint uses a rubber band to protect the tendon repair and the rubber band may be attached to a suture that is place through the finger nail plate.    The rubber band lets one straighten the finger but the rubber band bends the finger. Trying to bend the finger, or make a fist on your own may result in having the sutures cut through the tendon like a cheese cutter or just breaking the sutures that are holding the tendon together because your muscles are stronger than the sutures.
Tendons when cut are repaired with sutures that are not as strong as the power you can exert using your muscles. After tendon repairs follow therapy instructions carefully or your tendons will pull apart at the repair site and have to be repaired a second time. After cutting a tendon and having it repaired it will be necessary to restrict the the use of the injured hand for a period of 4-6 weeks to allow the tendon to heal sufficiently to handle the forces it has to pull against. Tendons like other body structures heal by producing scar tissue if excessive the scar tissue will anchor the tendon so that it doesn't glide back and forth. When this occurs a second operation will be required to free the tendon from the scar tissue surrounding it and preventing it from gliding. It can be expected that severe, blunt, saw and contaminated tendon injuries will increase the incidence of needing a second operation. Proper surgical care combined with supervised hand therapy provide the best chance of avoiding a second procedure following tendon injury. Tendon injuries usually don't permanently alter hand function unless there are associated injuries.

The fingers have tunnels that work as pulleys. Because they are constricted repaired tendons may not be able to glide through the tunnels and that will block movement of the fingers.  The pulleys are labeled on this photograph

Because of the tunnels the areas where injury to flexor tendons can occur are designated. Injuries to flexor tendons in zone II are difficult to repair and still have them glide through the pulleys.

This photograph shows the tendon cut and one of them is outside its sheath.  The tendon is put back in the sheath and then repaired. 
There are two tendons to each finger that need to be repaired.

When the cut to the tendon occurs while one is gripping into a flexion position the cut tendon ends retract away from the site of injury. This will make it necessary for the surgeon to make additional incisions to retrieve and repair the tendons.  When the tendons are cut and the fingers were in a straight extension position it is easier to retrieve the retracted tendons ends and then repair them.

Following  a repair of flexor tendons it is easy to break the repair by gripping or clinching fingers.   The power of the muscles can easily disrupt a new repair.  The hand therapy and protective devices will restrict use of the injured hand for 8 weeks following injury and repair.  Because of the difficulty of repairing tendons injured in zone 2 there is at least a 15% chance that a second surgery will be required.   Also remember that tearing, crush, and dirty injuries are more likely to require additional surgery compared to sharp injuries.   Ask your surgeon what your prognosis is for additional surgery when you are seeing him at your follow-up visit.   It is also recommended that a hand therapist guide you through the process of recovery.

This image show the pulley after a surgery to release scars around the tendon (tenolysis) that developed because the tendon had been cut with a saw.   This operation weakens the tendon at the time of surgery and will result in restricted use of the finger and hand after surgery

Additional Information

Dr. Allen L. Van Beek, MD
7373 France Ave. South, Edina, MN 55435