Introduction:
Muscles are connected to the bone by the tendons. These tendons transfer the forces generated by the muscles to the bones, which move the joint. A group of muscles and tendons are responsible for the arm, hands, wrist, and fingers movement. The flexor tendon is located between the forearm and the fingers across the wrist and is responsible for the movement of our fingers, like bending, pinching, making a fist, gripping, etc. Any injury to the flexor tendon results in the restriction of these movements called flexor tendon injuries. These are relatively more common in males than females. The tendon of the fifth finger (little finger) is usually injured in isolation.
What Are Flexor Tendon Injuries?
Tendons which are cord-like connective tissue connecting the muscles of the forearm and the finger bones across the palm side, allowing the bending or flexing movement of the fingers, are called flexor tendons. Tendons pass through ring-like structures called pulleys in the fingers, which help them to attach closely to the bones, facilitating easy movement at the joints. The flexor tendons include; Flexor digitorum superficialis (FDS) and Flexor digitorum profundus (FDP). Any injuries to these tendons cause loss of flexion or inability to bend the fingers and are termed flexor tendon injuries. Flexor tendon injuries can be classified into various zones:-
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Zone 1: The injury is located distal to FDS insertion, avulsion injuries come under this category.
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Zone 2: It is also called no man’s land; the injury is located between the FDS insertion to the palmar creases. Both the tendons FDP and FDS are in the same tendon sheath.
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Zone 3: The injury is in the palm, associated with neuromuscular involvement, and has a poor prognosis.
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Zone 4: The injury is in the carpal tunnel area, usually a complicated injury.
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Zone 5: The injury is between the carpal tunnel and forearm, is associated with neuromuscular involvement, and has a poor prognosis.
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Thumb: The injury to the tendons of the thumb, the prognosis is usually poor as it is associated with re-rupture compared to other fingers.
What Are the Causes of Flexor Tendon Injuries?
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Laceration, cuts, or any trauma to the tendon from broken glass, burns, or crush injuries.
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Avulsion injuries occur during sports activities like football, rugby, wrestling, etc. pull the tendons away from the bone. It is also called a Jersey's finger.
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Outdoor activities like rock climbing.
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Patients with chronic conditions like rheumatoid arthritis are susceptible to flexor tendon injuries.
What Are the Signs and Symptoms of Flexor Tendon Injuries?
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Open injuries or cuts are seen in the fingers, wrist, or forearm, restricting movement.
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Inability to bend the fingers in case of a complete tear of tendons or severe pain in bending one or more finger joints in case of partial injury.
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The corresponding finger is in a relatively extended position.
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Numbness or tingling sensation at the fingertips, as the nerves and arteries are in close proximity with the tendons.
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Tenderness is present along the palm side of the hand.
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Severe bleeding at the lacerated site of the tendon.
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Excessive blood loss leads to white or purple discoloration of the skin.
What Are the Immediate Measures to Be Taken After the Injury?
First aid treatment is necessary immediately after the injury. Irrigation with saline or clean water is recommended to wash away the debris and prevent infection. A bandage or a clean cloth should be wrapped to arrest bleeding. A cold pack can be applied to reduce swelling. The hand should be kept raised to prevent swelling. A doctor should be consulted as soon as possible; tetanus injections and antibiotics are advised to prevent infection.
How Are Flexor Tendon Injuries Diagnosed?
After recording the history, the doctor examines the injury site for any cuts or lacerations. The exact location of the injury can be determined by assessing the full range of motion. The patient is asked to bend the finger while the other fingers are held flat. A cut or injury in this area also affects the nerves and blood vessels, so the doctor checks for sensation or numbness. An X-ray is advised to confirm the diagnosis. In some severe cases, an ultrasound or magnetic resonance imaging (MRI) may be preferred.
How Are Flexor Tendon Injuries Managed?
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Partial tendon or mild injuries may be managed by non-surgical treatment but after a careful evaluation, splinting for around four to six weeks, followed by physical exercises. Surgery is the treatment of choice, in most cases, as the tendons that are torn apart need to be joined together to facilitate healing from inside and outside the tendon.
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Surgery is advised within seven to ten days, as early management is said to have a good prognosis. If the injury restricts blood flow to the hands or finger, immediate surgery should be performed, or it can lead to complications.
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Tendons usually get pulled in various ways like straight, across, at an angle, or away from the bone. Therefore the outcome depends on the severity of the injury.
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Surgery is usually performed under local anesthesia. An incision is made at the injured site to enlarge the area, and the cut ends of the tendon are pulled together and sutured. The forearm and the hand are immobilized by splinting with plaster or special braces for around four to six weeks; fingers are kept in a slightly bent position, which causes a reduction in tension on the tendon and protects the repair of the tissues.
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Physical exercises are advised after the surgery to regain movement and function and a better prognosis. Hand therapy is advised, which helps restore the fingers' dexterity. During hand therapy, the plaster splint is replaced by a light plastic splint, followed by exercises crucial for the tendon's healing. However, it takes about three to six months to recover back to normal.
What Are the Complications of Surgery?
Significant complications of the surgery include:
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Infection is a common complication in most surgeries, usually seen in crush injuries. Redness, fever, swelling, and pain at the site are some of the features. It is treated with antibiotics.
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Scar formation and tendon adhesion are also seen in some cases where the tendons get attached to nearby tissues leading to loss of movement. Most of the cases are treated by re-surgery.
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Re-rupture or tendon snap can occur a few days post-surgery if proper care is not taken or due to accidental falls, often treated by a re-surgery.
Conclusion:
Flexor tendon injuries are due to avulsion or crush injuries leading to restriction in the movement of fingers. It is associated with cuts, pain, and numbness. These injuries are treated surgically, followed by hand therapy. The outcome of the surgery is good; by following the post-operative instructions and a healthy lifestyle, the patient usually recovers in three to six months.
