Flexor Tendon Injuries
Tendons in the hand and forearm
The muscles that bend or flex the fingers are found in the forearm and are
called flexor muscles. The flexor muscles are able to move the fingers through
cord-like extensions called tendons, which attach the muscle to bone. The tendons
of the flexor muscles that lead to the fingers and the thumb begin just beyond
the middle of the forearm.
The thumb has one long flexor muscle, and the fingers each have two flexor
muscles. One tendon attaches to the middle bone of each finger on the palm side
of the hand and bends the fingers at the base and second joints. The other tendon
attaches to the bone at the tip of each finger on the palm side and bends all
three finger joints (see Diagram 1).
Deep cuts on the palm side of the wrist, hand, or fingers can injure the flexor
tendons and nearby nerves and blood vessels. The injury may appear simple but
is acually more complex. When a tendon is cut, it acts like a rubber band and
its cut ends pull away from each other. Because many cuts happen while the fingers
are bent, the cut ends of the tendon move even further apart as the fingers
are straightened. A tendon that has not been cut completely through may still
allow the fingers to bend, but can cause pain or catching and may rupture. When
both tendons are cut completely through, the finger joints cannot bend on their
own (see Diagram 2).
Tendon Healing
Tendons are made of living cells and connective tissue. If the cut ends of
the tendon can be brought back together, healing be-gins through the cells inside
as well as the tissue outside of the tendon. Because the cut ends of a tendon
usually separate after an injury, it is not likely that a cut tendon will heal
without surgery.
Your doctor can advise you on how soon surgery is needed after a flexor tendon
is cut. There are many ways to repair a cut tendon, and certain types of cuts
need a specific type of repair. After surgery and depending on the type of cut,
the injured area can either be protected from movement or started on a very
specific limited movement program for several weeks (see Diagram 3). If unprotected
finger motion begins too soon, the tendon repair is likely to pull apart. After
four to six weeks, the fingers are allowed to move slowly and without resistance.
Healing takes place during the first three months after the repair.
In most cases, full and normal movement of the injured area does not return
after surgery. If it is hard to bend the finger using its own muscle power,
it could mean that the repaired tendon has pulled apart or is bogged down in
scar tissue. Scarring of the tendon repair is a normal part of the healing process.
But in some cases, the scarring can make bending and straightening of the finger
very difficult. Depending on the injury, your doctor may prescribe therapy to
loosen up the scar tissue and prevent it from interfering with the finger’s
movement. If therapy fails to improve motion, surgery to release scar tissue
around the tendon may be required.
Therapy
If a program of controlled, limited motion is selected as therapy for the first
three or four weeks after surgery, it is important to work closely with a hand
therapist and your surgeon to understand the therapy and follow set guidelines.
The tendon repair can pull apart if your hand is used too soon or if therapy
guidelines are not followed. In addition to regaining motion of the finger after
a tendon injury, therapy can be helpful in softening scars and building grip
strength.
Diagram 1
The tendons of the hand extend from the flexor muscle in the forearm.
Diagram 2
When a flexor tendon is completely cut, the affected finger cannot be bent.
Diagram 3
After surgery, the area of the injured tendon must be protected from movement.
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