What is an Extensor Tendon Injury?
Extension by simple definition means to straighten, so when relating to an extensor tendon injury of the hand, it specifically relates to the muscles, tendons, and ligaments that help with straightening the fingers. So, what does this mean?
The design of hands is complex. Within each hand, there are 29 bones, 29 ligaments and numerous arteries, tendons, and nerves. These bones and tissue together make the shape and function of the hands. They are interconnected functioning to help move and feel with our hands; therefore, understanding the functional anatomy of the hand is important to understanding an extensor tendon injury.
Bones provide structure, and when two bones connect, they form a joint. Joints are held together by fibrous tissue called ligaments. The main job of a ligament is to keep the bones together throughout the movement.
Muscles attach to bones by way of tendons, which helps with the movement of bones and joints. When a muscle contracts or relaxes, it pulls on the tendon which in turn pulls on the bone enacting movement.
Within the main body of the hand, the palm area, there are five metacarpal bones extending from the wrist to each of phalanges, or fingers. Each finger has three phalanxes (finger bones) and three joints. The knuckle joints are called the metacarpophalangeal joints (MCP). The joints in the middle of the fingers are called proximal interphalangeal joints (PIP). The furthest joints of the fingers are the distal interphalangeal joints (DIP).
The thumb has a slightly different structure. The base of the wrist and thumb forms a joint called the carpometacarpal joint (CMC). The joint that forms the knuckle of the thumb is called the metacarpophalangeal (MP). The final joint of the thumb is the interphalangeal (IP).
The nervous system also plays a key role in the sensation and function of the hand. To know how small to pinch something, how tight to grasp something, or to know if something is hot, cold, sharp, or dull, we need our nervous system. The nerves are a pathway of how the brain communicates with our bodies. Constantly sending signals back and forth as we interact with our world around us.
There are many nerves in the hands, but there is three main nerves-ulnar, median, and radial. Each originates from the neck and travels down the arm to the hand. The ulnar nerve innervates with the little and ring fingers to help with sensation and flexion. The median nerve innervates with the thumb, 1st and 2nd fingers. It also helps with flexion and sensation of these fingers. The radial nerve innervates at the back of our hand which specifically corresponds to the muscles, tendons, and ligaments related to extension movements.
Understanding this basic anatomy is important as all medical providers use this terminology to navigate and describe the hand. Specifically related to an extensor tendon injury, a medical provider will quickly diagnose and describe the injury based on the function and sensory system within each zone or area of the hand. In other words, extensor injuries are specific to lacerations (cuts) or trauma to the dorsal (back of) hand and forearm area.
This dorsal area of the hand is complex. To simplify the anatomy, here is a high-level summary of muscles and tendons related to the extensor tendon injury.
- Extension and deviation of the wrist
- Extensor Carpi Radialis Brevis (ECRB)
- Extensor Carpi Radialis Longus (ECRL)
- Extensor Carpi Ulnaris (ECU)
- Extension of the fingers
- Extensor Digitorum Communis
- Extensor Indicis Proprius
- Extensor Digiti Minimi
- Lumbrical Muscles
- Extension of the thumb
- Abductor Pollicis Longus
- Extensor Pollicis Brevis
- Extensor Pollicis Longus
- Abduction of fingers (pulling them apart)
- Dorsal Interossei
What causes extensor tendon injuries?
The two most common causes of extensor tendon injuries are lacerations or trauma like “jamming” your finger. If not properly treated, it can cause limit or prevent the extension of the finger(s) involved in the injury.
One of the more common causes for an extensor injury is a cut to the back of the forearm or hand; however, there are three common forms of trauma to an extensor tendon:
- Mallet Finger-this is when the tip of the finger (DIP) is jammed into an object (e.g. a basketball). When the extensor tendon is injured, the tip of the finger will sag or droop.
- Boutonniere Deformity-when the middle of the finger (PIP) is cut or jammed into an object, it can cause the PIP to flex down and the DIP to extend upwards.
- Swan Neck Deformity-with trauma, the PIP joint is hyperextended, and the DIP joint is flexed.
Symptoms of an Extensor Tendon Injury
Extensor tendon injuries are the result of a traumatic event or laceration. Immediately after the injury, symptoms may include:
- Bruising (if closed wound)
- Loss of ability to straighten a finger(s)
- Loss of sensation (when nerve injury involved)
- Open wound, bleeding
- Pain with attempt to extend finger(s)
How is an extensor tendon injury diagnosed?
As with any tendon injury of the hand, this is a serious injury. If not properly diagnosed and treated, loss of movement and function may occur. Often the injury occurs after a laceration or traumatic event. If you have a significant cut to the back of your arm or hand, seek immediate medical attention.
In some cases, the injury to the extensor tendon is minimal. With these rare cases, you can directly access a physical or occupational therapist (PT or OT) to customize a splint for your finger(s). The goal is to immobilize the finger(s) for several weeks while the tendon heals.
Unfortunately for most, surgical intervention is needed. Often when a laceration or jarring impact (like jamming) to a finger occurs, there is damage to other surrounding tissue like ligaments. In severe cases, the nerve(s) may also be affected.
To determine the best course of action, your medical provider will complete a full exam on the forearm and hand. Based on the findings, he or she will advise you on your options for treatment of the injury.
Treatment of an Extensor Tendon Injury
For those cases with minimal tendon damage (closed injury), immobilizing the finger(s) is the best conservative option. Once the tendon has healed, starting hand therapy with a physical or occupational therapist is recommended. Your therapist will work with you on safely restoring range of motion and strength so you can get back to the activities you love to do.
When surgery is indicated, your surgeon will repair the damaged tendon(s) and any other damage to the area. Unfortunately for most cases, despite this repair coupled with rehab, a full range of motion is never fully regained. Damaged tendons need medical attention, even in mild cases. Quickly getting medical attention coupled with completing the full course of care, gives the best chance for a full recovery. Have patience and take the time to follow through on the recommendations rehabilitation as healing time can be slow.
As a consumer of health care, you have a choice in finding the right provider for you. If this is a non-emergency injury, do your homework and search for a health care provider, like a physical or occupational therapist, with excellent outcomes, great customer reviews, and can provide you the care you need for a reasonable cost.
Most states have direct access to a physical therapist, meaning you can go directly to a physical therapist without a physician order. To determine if your state has direct access, please visit the American Physical Therapy Association’s website Physical Therapy Direct Access By State.
Occupational therapists typically work under the direction of a doctor. If your doctor has recommended hand therapy, you do have a choice on where you go.
If you are a surgical candidate, once you’ve had surgery, it is recommended you do your homework then to find the highest qualified hand PT or OT in your area. You can find a highly qualified PT or OT in your area by clicking on Find A Clinic. This link will help you find a PT or OT that has top national rankings for treating hand injuries.