Your fingers are moved or bent by the flexor muscles that pull or push on tendons that attach the muscle to the bone being moved. The flexor muscles begin up near the elbow or upper forearm and become tendons halfway down the middle of the forearm. They ultimately run into the hand and attach to the bones in the fingers.
Inside the finger, the tendons run through rings of fiber called pulleys that keep the tendons in place, close to the bones. This arrangement lets the tendons move the joints very efficiently and permits the fingers to make the fine motions we expect.
If the wrist, hand, or fingers get a deep cut on the palm side of the hand, the flexor tendon, nerves and blood vessels that are near it can also sustain injury. The injury may appear minor on the surface, however, under the skin it can be rather complex. If the tendon is completely severed, the ends that are still attached will pull away from each other. If the tendon isn't completely detached, it can still enable the fingers to move with some pain initially. Ultimately, however, it may end up tearing in half. If the tendon is completely cut, the fingers won't be able to move.
Since tendons are made out of living cells, if the cut ends are brought back together, they will heal. As long as the ends can be held in place, the tendon can heal from the inside through cell growth, right along with the tissue on the outside. Because the ends of a tendon usually snap apart if the tendon is cut, it's rare for the tendon to heal without surgery.
If one of your flexor tendons has been cut, your hand surgeon will let you know how soon surgery should take place to heal the damage. The type of repair depends on the type of cut, and there is no particular procedure to fix them all. If the injury caused a cut in the tendon of a finger, the pulleys will also need to be saved. In such a case, your hand surgeon will also make sure that blood vessels and nerves near the area injured remain healthy.
After the tendon has been repaired through surgery, the injured area will be either slightly or completely restricted from for several weeks, depending on the type of cut. After the surgery, hand therapy may be necessary.
If the fingers aren't held in place after the surgical procedure and are, instead, left to move on their own the tendon is likely to pull apart again. Four to six weeks after the surgery, the fingers may be able to be moved slowly and against no resistance, but healing of the tendon takes place during a full three months after the procedure.
Even after surgery, patients do not necessarily regain full and normal use of the injured area. If the tendon has pulled apart again after surgery or is hampered in its movements by surrounding scar tissue, it may be extremely difficult for the muscles to move the finger. It is common for the tendon to be scarred when repaired and scarring may make it difficult to bend or straighten the finger. You may be given a set of exercises to loosen any scar tissue that interferes with finger movement as part of a therapy program. If therapy isn't helpful, surgical intervention aimed at removing scar tissue around the repaired tendon may be needed.
A therapy program of limited and controlled hand or finger movement usually follows surgery and lasts for several weeks. A hand therapist, and a hand surgeon, will help you understand the therapy and follow appropriate guidelines. If the hand is used too soon after surgery, or if the guidelines of the therapy program aren't carefully followed, the repaired tendon may pull back apart. Therapy will help soften any scar tissue and increase grip strength, and its benefits aren't just limited to restoring hand or finger motion.