Trigger Thumb (Stenosing Flexor Tenosynovitis)

What is Trigger Thumb (Stenosing Flexor Tenosynovitis)?

The thumb is quite different from the rest of our fingers. It has a bone in the palm of your hand (a metacarpal bone), and two segments (proximal and distal phalanges). Interestingly, unlike the other fingers, the thumb can also have extra small bones known as sesamoid bones. What makes the thumb really unique is that it can do two special movements that other fingers can’t: opposition (touching the other fingers) and apposition (bringing it across the palm). Moreover, it can move up and down, and sideways at the joint where it joins the palm, giving it great flexibility and use.

‘Trigger thumb’, also known as stenosing flexor tenosynovitis of the thumb, is a condition characterized by the narrowing of the protective covering of the tendon in the thumb. This means that the tendon, which helps the thumb move, gets caught when trying to glide through this too narrow sheath. This is typically due to a size mismatch between the sheath and the swollen tendon where the thumb meets the palm. This can lead to a noticeable clicking or popping sensation when you try to extend, or straighten, your thumb.

Thumb movement is driven by two main muscles: the flexor pollicis longus (FPL) muscle, which is outside the thumb, and the flexor pollicis brevis (FPB) muscle, which is inside the thumb. These muscles move the thumb and contribute to bending it. These tendons slide through a tunnel, or sheath, secured by a system of pulleys along the length of the finger bone. This system helps the tendon work efficiently. The FPL tendon slides through three pulleys, the most important being the A1 pulley, which is located on the palm-side bone of the thumb, over the joint and the base of the thumb bone.

Trigger thumb usually results from the A1 pulley becoming thicker, which hampers the smooth movement of the FPL tendon. This can lead to pain, difficulty in moving the thumb, and a clicking or popping sound when trying to extend the thumb. Both adults and kids can experience trigger thumb, but it’s pretty rare in kids. Treatment usually starts with wearing a splint and doing physical therapy. If that doesn’t help, a steroid injection can be administered. In cases where these measures don’t bring relief, a minor surgical procedure to release the A1 pulley may be needed.

What Causes Trigger Thumb (Stenosing Flexor Tenosynovitis)?

The exact cause of the condition known as ‘trigger thumb’ isn’t clear, but several factors are known to increase the risk of it developing. These include using the hands heavily, repeatedly gripping objects, and conditions that cause general growth of the tendon lining. People with diabetes, amyloidosis (an abnormal protein build-up disease), hypothyroidism (underactive thyroid), gout, and rheumatoid arthritis (a long-term immune system disorder) are more likely to develop trigger thumb.

While certain jobs that involve a lot of gripping and hand bending have been linked to trigger thumb, research has not consistently shown a direct link between occupation and this condition. Trigger thumb is complex and is likely caused by multiple factors.

The likely cause of trigger thumb is a mismatch in size between the A1 pulley (a small loop at the base of the thumb that helps secure the tendon) and the FPL tendon (tendon that helps bend your thumb). In kids, this could be because the tendon swells or the pulley gets thicker. Other possible causes include injury, diabetes, mucopolysaccharidosis (an enzyme deficiency disease), and abnormal thumb structures.

In adults, the size mismatch could be due to the border of the A1 pulley growing because of pressure. The most pressure is applied when the thumb is fully bent and gripping tightly. This leads to growth and a change of cells at the spot where the tendon and pulley meet, causing the tendon to swell and thicken, forming something called a Notta’s nodule. Once this nodule gets big enough, it causes triggering. While the strong muscles that bend the thumb can overcome this, the weaker muscles that straighten the thumb may struggle, causing the thumb to get stuck in a bent position. Although injury can speed up the development of trigger thumb in people who are already prone to it, it likely doesn’t cause it to develop in the first place.

Risk Factors and Frequency for Trigger Thumb (Stenosing Flexor Tenosynovitis)

Trigger fingers and thumbs affect over 200,000 people in the United States each year, making it a common issue. The condition is most commonly seen in women aged 40 to 60. Overall, the risk of developing a trigger finger in one’s lifetime is 2% to 3%. However, this risk increases to 10% for those with diabetes.

Trigger fingers or thumbs are a common issue that affects over 200,000 people per year in the United States.
This condition is often seen in women aged between 40 to 60.
The overall lifetime risk for developing a trigger finger is 2% to 3%.
For individuals with diabetes, this risk increases to 10%.

On another note, the occurrence of congenital trigger thumb in infants is quite rare, with just about 3.3 cases in every 1000 live births noted when they reach the age of 1. Importantly, 25% to 30% of these patients have the condition on both sides. This underscores the need for a thorough examination of both sides.

Congenital trigger thumb is rare in infants, with usually 3.3 cases in every 1000 live births when they reach the age of 1.
Of these patients, 25% to 30% have the condition on both sides.
This highlights the need for a thorough examination of both sides.

Signs and Symptoms of Trigger Thumb (Stenosing Flexor Tenosynovitis)

Trigger thumb is a condition that can present differently in individuals, with mild to moderate symptoms. It typically starts with a soreness at the base of the thumb, near the joint that connects the thumb to the palm of the hand. As the condition progresses, the thumb may become painful and stiff when flexed, and a swollen or tender lump might appear on the palm side of the thumb’s main joint (metacarpal head). In severe cases, the thumb might get stuck in a bent position and can be difficult to straighten out. It might need assistance to unbend, and a popping or snapping sound could be heard when it is released from this locked position.

In children, the most common symptom is a thumb locked in a bent state, though the thumb can normally be stretched back to its original position. Triggering of the thumb (getting stuck and then released) does not commonly occur in children, and sometimes, the thumb might even get locked in a fully stretched position.

During a doctor’s examination, adults may display pain at the thumb joint and might resist any attempts to stretch out the thumb. When they do extend the thumb, a distinct popping sensation could be felt and a snap can be noticed. To better understand and grade the severity of a trigger thumb, doctors might use the Quinnell or Sugimoto grading systems.

Quinnell Grading System:
- 0 – Normal thumb movement
- I – Uneven thumb movement
- II – Thumb can actively be unlocked
- III – Thumb can passively be unlocked
- IV – Thumb is permanently bent or deformed
Sugimoto Classification System:
- Stage I – Normal thumb movement but a lump can be felt
- Stage II – Active triggering of the thumb
- Stage III – Thumb triggering can be caused by passive movement
- Stage IV – Thumb locked in a bent position
Grading in Pediatric Trigger Thumb:
- Type I – Trigger thumb with thumb joint hyperextension
- Type II – Trigger thumb without thumb joint hyperextension

Testing for Trigger Thumb (Stenosing Flexor Tenosynovitis)

If your doctor suspects you have trigger thumb, they will diagnose this based on what you tell them about your symptoms and through a physical check. During the examination, they will let your hand rest with your palm facing upwards and ask you to slowly move your thumb to see if it gets stuck or ‘catches’. If these symptoms aren’t noticeable at first, the doctor might put their fingers on the base of your thumb (the MCP joint) and ask you to move your thumb again. During this, the doctor will notice if there is any unusual clicking feeling or if the motion isn’t smooth. You might not experience this with every movement, and it doesn’t happen in all cases. An imaging test isn’t usually needed to determine if you have trigger thumb.

There have been some studies using ultrasound scans to understand trigger thumb better. One study found that trigger thumb occurs when there is a change in the size of the tendon at the base of the thumb (FPL tendon) compared to the A1 pulley, a structure that helps the tendon slide smoothly. When the sizes matched again, the trigger thumb symptoms went away. People who had trigger thumb in one hand and a certain ratio of the size of the tendons in the two hands (known as a trigger ratio) were more prone to getting trigger thumb in the other hand as well.

Another study that also used ultrasound scans looked at the size of the FPL tendon in two different places in the thumb. They found that in a healthy thumb, the ratio of these two measurements is pretty stable, but if the ratio is above a certain number, it suggests that the person has trigger thumb. Different numbers were found to be the cutoff for children and adults. Some other signs of trigger thumb that can be seen on a type of imaging scan called an MRI include swelling of the FPL tendon and a thickening of the A1 pulley. In some cases, there were also changes to other structures in the thumb.

Treatment Options for Trigger Thumb (Stenosing Flexor Tenosynovitis)

The treatment for trigger thumb depends on how severe and long-lasting the symptoms are. Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen are often used to manage pain. Some home care strategies may include resting for 3 to 4 weeks, avoiding repetitive hand movements or prolonged use of vibrating hand-held machinery, applying ice to the palm several times a day, warm-water soaks (especially in the morning), and using a splint at night to keep the finger straight. Gentle movements to maintain mobility are also beneficial.

For children with trigger thumb, the first approach usually involves using a thumb splint, keeping an eye on the condition and doing gentle exercises to stretch the thumb. This nonoperative care is usually recommended for at least 6 months. In one study, almost one-third of children’s conditions resolved on their own.

If these methods don’t work, healthcare providers might recommend a minor invasive procedure or even surgery. The most common treatment for adults involves injecting corticosteroids like methylprednisolone or triamcinolone into the tendon sheath (the protective layer around the tendon). These steroids reduce inflammation, which helps the tendon move smoothly. However, this treatment is not recommended for children with trigger thumb present at birth.

People with diabetes need to keep a close eye on their blood sugar levels after these injections, as steroids can cause high blood sugar. Although a second injection is an option, it should be done with caution because repeated injections can potentially damage the tendon.

For more severe or resistant cases, healthcare providers may perform a percutaneous release of the A1 pulley, a structure in the hand that the tendon slides through. This is done using local anesthesia and involves cutting the pulley with a needle. Lastly, if all other methods are unsuccessful, an open surgical procedure is the final option. The surgery usually involves an outpatient procedure where the A1 pulley is cut to free up the tendon and allow it to move without catching. Early movement of the thumb after surgery is encouraged to reduce the risk of scar tissue forming and the condition recurring.

For children born with trigger thumb, if the nonoperative methods don’t work, surgical release of the A1 pulley is usually recommended. In some cases where symptoms appear after the age of 2, surgery may be the first option due to the lower success rate of nonoperative treatments. In more severe stages of the disease, immediate surgery may be recommended without a period of observation, especially if it is safe for the patient to undergo anesthesia.

Various studies have explored different surgical techniques and the optimal timing for surgical intervention. For instance, one trial found that a certain technique of A1 pulley release offered faster pain relief and functional recovery after surgery. However, having three or more steroid injections before surgery, or having a steroid injection within 3 months prior to surgery, may increase the risk of complications after surgery.

In fact, a Chinese study found that a modified acupotomy procedure, a type of percutaneous release, resulted in better long-term outcomes and satisfaction compared to the regular percutaneous release. However, in the short term, the regular percutaneous release resulted in less residual pain and higher satisfaction.

When a person experiences symptoms similar to trigger thumb, doctors need to consider other conditions that might cause those symptoms. These conditions might include:

Abnormalities in the thumb’s extension mechanism
Spasticity or tightness in the muscles
De-Quervain’s tenosynovitis, an inflammation of the tendons on the thumb side of the wrist
Dupuytren’s contracture, a thickening and tightening of the layer of tissue underneath the skin of the hand
Diabetic hand syndrome, a disorder caused by diabetes that leads to tightened skin and stiff joints
Diseases resulting in calcium buildup in or around the tendons
Infections within the tendons
MCP sprain, a sprain in the main joint of the thumb
Noninfectious tenosynovitis, inflammation of the protective sleeve around the tendons

Doctors should always take special care with infectious tenosynovitis. Its symptoms include severe pain, swelling, redness, and loss of movement in the thumb. This quick diagnosis is crucial to prevent possible complications such as tendon rupture, which restricts thumb motion. Similar symptoms can also be seen in noninfectious tenosynovitis, commonly linked to certain forms of arthritis. Treatment for this type of arthritis may include anti-inflammatory drugs, medications to slow down the disease, and steroids to help relieve symptoms.

Patients with an MCP sprain usually report tenderness along with a loss of full flexion after an injury. Unlike trigger thumb, however, there is no associated clicking sensation. Likewise, patients with diabetic hand syndrome often display limited movement in the joints of their fingers, usually affecting all fingers similarly and appearing tight and waxy on the back of the hand. Unlike trigger digits, Dupuytren’s contracture is often painless and causes chronic problems with extending the affected finger or fingers. Patients may notice hard bumps or a tough string-like cord in the palm.

What to expect with Trigger Thumb (Stenosing Flexor Tenosynovitis)

The outlook for trigger thumb, a condition where your thumb catches or sticks in a bent position, is usually good. In children, trigger thumb often improves on its own, while adults and children under 2 usually find relief through non-surgical treatments. Nearly half (45%) of patients find relief from symptoms for at least 10 years after receiving a glucocorticoid injection, a type of anti-inflammatory medicine. However, if these steps don’t work, surgery to release the A1 pulley (a band of tissue causing the thumb to stick or lock) could be necessary, and this generally gives positive results. Fortunately, the chance of trigger thumb returning after surgery is very low, with only about 1.4% of cases seeing a recurrence.

Possible Complications When Diagnosed with Trigger Thumb (Stenosing Flexor Tenosynovitis)

Possible issues following a corticosteroid injection may include an infection, a tear in the tendon, or the symptoms coming back.

Potential problems after surgery might include a procedure that didn’t fully release tension, a cut tendon, bowstringing, infection, rigidity, weakened strength, a false aneurysm in the digital artery, a digital nerve injury, and the symptoms coming back.

Corticosteroid Injection Complications:

Infection
Tendon rupture
Recurrence of symptoms

Surgery Complications:

Insufficient tension release
Tendon cuts
Bowstringing
Infection
Stiffness
Weakness
Digital artery pseudoaneurysm, a false aneurysm of the digital artery.
Digital nerve damage
Recurrence of symptoms

Preventing Trigger Thumb (Stenosing Flexor Tenosynovitis)

Trigger thumb, also known as stenosing flexor tenosynovitis, is a condition where the tendon in the thumb becomes too big for its protective casing. The usual symptoms include feelings of the thumb catching, snapping, or locking when bending it. As the condition progresses, it becomes increasingly painful and may prevent the individual from fully extending their thumb.

People with certain conditions, such as diabetes, rheumatoid arthritis, and amyloidosis, have a higher chance of developing trigger thumb. It can also affect children but is less common. The initial treatment usually involves conservative approaches like resting the affected thumb, applying ice, and using a splint for about 4 to 6 weeks. The treatment plan for children may be extended depending on their age.

If these conservative treatments do not bring relief, adults can choose to have a glucocorticoid or steroid injection. Sometimes, a second injection may be necessary. In cases where other treatments don’t work or if the child’s symptoms are severe, surgery could be considered.

While there are some risks associated with surgery and corticosteroid injections, the number of complications is typically low. The good news is that most people with trigger thumb have a positive outcome and get better with time.

Frequently asked questions

The prognosis for Trigger Thumb (Stenosing Flexor Tenosynovitis) is generally good. In children, trigger thumb often improves on its own, while non-surgical treatments can provide relief for both adults and children under 2. Glucocorticoid injections can provide symptom relief for at least 10 years in 45% of patients. If non-surgical treatments are not effective, surgery to release the A1 pulley can be performed, which generally has positive results. The chance of trigger thumb returning after surgery is very low, with only about 1.4% of cases experiencing a recurrence.

The exact cause of trigger thumb is not clear, but several factors can increase the risk of developing it. These include using the hands heavily, repeatedly gripping objects, and conditions such as diabetes, amyloidosis, hypothyroidism, gout, and rheumatoid arthritis. In children, trigger thumb can be caused by tendon swelling or thickening of the A1 pulley. In adults, a size mismatch between the A1 pulley and the FPL tendon, along with pressure and growth of the A1 pulley, can lead to trigger thumb. Injury can also contribute to the development of trigger thumb in individuals who are already prone to it.

Signs and symptoms of Trigger Thumb (Stenosing Flexor Tenosynovitis) include: - Soreness at the base of the thumb, near the joint that connects the thumb to the palm of the hand. - Pain and stiffness in the thumb when flexed. - Swollen or tender lump on the palm side of the thumb's main joint (metacarpal head). - Thumb getting stuck in a bent position and difficulty in straightening it out. - Needing assistance to unbend the thumb. - Popping or snapping sound when the thumb is released from the locked position. - In children, the most common symptom is a thumb locked in a bent state, which can be stretched back to its original position. - Triggering of the thumb (getting stuck and then released) does not commonly occur in children, and sometimes, the thumb might even get locked in a fully stretched position. - During a doctor's examination, adults may display pain at the thumb joint and might resist any attempts to stretch out the thumb. - A distinct popping sensation and a snap can be felt when the thumb is extended. - Severity of trigger thumb can be graded using the Quinnell or Sugimoto grading systems. - Quinnell Grading System: 0 – Normal thumb movement, I – Uneven thumb movement, II – Thumb can actively be unlocked, III – Thumb can passively be unlocked, IV – Thumb is permanently bent or deformed. - Sugimoto Classification System: Stage I – Normal thumb movement but a lump can be felt, Stage II – Active triggering of the thumb, Stage III – Thumb triggering can be caused by passive movement, Stage IV – Thumb locked in a bent position. - Grading in Pediatric Trigger Thumb: Type I – Trigger thumb with thumb joint hyperextension, Type II – Trigger thumb without thumb joint hyperextension.

No imaging test is usually needed to determine if you have trigger thumb. However, in some cases, an ultrasound scan or an MRI may be used to further evaluate the condition. These tests can help assess the size of the tendon and the A1 pulley, as well as identify any swelling or thickening. The ultrasound scan can also be used to measure the ratio of the tendon size in different places in the thumb, which can indicate the presence of trigger thumb.

The other conditions that a doctor needs to rule out when diagnosing Trigger Thumb (Stenosing Flexor Tenosynovitis) include: - Abnormalities in the thumb's extension mechanism - Spasticity or tightness in the muscles - De-Quervain's tenosynovitis, an inflammation of the tendons on the thumb side of the wrist - Dupuytren's contracture, a thickening and tightening of the layer of tissue underneath the skin of the hand - Diabetic hand syndrome, a disorder caused by diabetes that leads to tightened skin and stiff joints - Diseases resulting in calcium buildup in or around the tendons - Infections within the tendons - MCP sprain, a sprain in the main joint of the thumb - Noninfectious tenosynovitis, inflammation of the protective sleeve around the tendons

The side effects when treating Trigger Thumb (Stenosing Flexor Tenosynovitis) can vary depending on the treatment method used. Here are the potential side effects for each treatment option: Corticosteroid Injection Complications: - Infection - Tendon rupture - Recurrence of symptoms Surgery Complications: - Insufficient tension release - Tendon cuts - Bowstringing - Infection - Stiffness - Weakness - Digital artery pseudoaneurysm, a false aneurysm of the digital artery. - Digital nerve damage - Recurrence of symptoms

You should see an orthopedic surgeon or a hand surgeon for Trigger Thumb (Stenosing Flexor Tenosynovitis).

Trigger fingers or thumbs affect over 200,000 people per year in the United States.

The treatment for Trigger Thumb (Stenosing Flexor Tenosynovitis) depends on the severity and duration of the symptoms. Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen are commonly used to manage pain. Home care strategies may include resting, avoiding repetitive hand movements, applying ice, warm-water soaks, and using a splint at night. For children, the first approach usually involves using a thumb splint and doing gentle exercises. If these methods don't work, healthcare providers may recommend corticosteroid injections or minor invasive procedures. In more severe or resistant cases, a percutaneous release or open surgical procedure may be performed. The optimal timing and technique for surgical intervention may vary.

Trigger Thumb, also known as Stenosing Flexor Tenosynovitis, is a condition characterized by the narrowing of the protective covering of the tendon in the thumb. This narrowing causes the tendon to get caught when trying to glide through the sheath, leading to a clicking or popping sensation when trying to extend the thumb. Treatment usually involves wearing a splint, physical therapy, and in some cases, a minor surgical procedure to release the A1 pulley.

Joint Muscle and Bone Pain at Base of Thumb Thickening of the Flexor Tendon Sheath