Trigger finger, also known as stenosing tenosynovitis, is a disorder characterized by catching or locking of the involved

finger A finger is a prominent digit (anatomy), digit on the forelimbs of most tetrapod vertebrate animals, especially those with prehensile extremities (i.e. hands) such as humans and other primates. Most tetrapods have five digits (dactyly, pentadact ...

in full or near full

flexion Motion, the process of movement, is described using specific anatomical terminology, anatomical terms. Motion includes movement of Organ (anatomy), organs, joints, Limb (anatomy), limbs, and specific sections of the body. The terminology used de ...

, typically with force. There may be tenderness in the palm of the hand near the last skin crease (distal

palmar crease A palmar crease is a type of crease on the palm. A single transverse palmar crease also called simian crease is sometimes associated with Down syndrome. Other types of creases include the Sydney crease and the Suwon, or double transverse palmar ...

). The name "trigger finger" may refer to the motion of "catching" like a trigger on a gun. The

ring finger The ring finger, third finger, fourth finger, leech finger, or annulary is the fourth digit of the human hand, located between the middle finger and the little finger. Sometimes the term ring finger only refers to the fourth digit of a left-ha ...

and

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

are most commonly affected. The problem is generally

idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent spontaneous origin. For some medical conditions, one or more causes are somewhat understood, but in a certain percentage of people with the condition, the cause ...

(no known cause). People with

diabetes Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...

might be relatively prone to trigger finger. The pathophysiology is enlargement of the flexor

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

and the

A1 pulley In human anatomy, the annular ligaments of the fingers, often referred to as A pulleys, are the annular part of the fibrous sheathes of the fingers. Four or five such annular pulleys, together with three cruciate pulleys, form a fibro-osseous t ...

of the

tendon sheath A tendon sheath is a layer of synovial membrane around a tendon. It permits the tendon to stretch and not adhere to the surrounding fascia. It contains a lubricating fluid (synovial fluid) that allows for smooth motions of the tendon during muscl ...

. While often referred to as a type of stenosing tenosynovitis (which implies

inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

) the pathology is

mucoid Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood, or bone. The interactions between mesenchyme and epithelium help to form nearly ever ...

degeneration. Mucoid degeneration is when fibrous tissue, such as tendon, has less organized

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

, more abundant

extracellular matrix In biology, the extracellular matrix (ECM), also called intercellular matrix (ICM), is a network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and bio ...

, and changes in the cells (

fibrocyte A fibrocyte is an inactive mesenchymal cell, that is, a cell showing minimal cytoplasm, limited amounts of rough endoplasmic reticulum, and lacks biochemical evidence of protein synthesis. The term ''fibrocyte'' contrasts with the term ''fib ...

s) to act and look more like

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

cells (chondroid metaplasia). Diagnosis is typically based on symptoms and signs after excluding other possible causes. Trigger digits can resolve without treatment. Treatment options that are disease modifying include

steroid A steroid is an organic compound with four fused compound, fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes t ...

injections and surgery. Splinting immobilization of the finger may or may not be disease modifying.

Signs and symptoms

Symptoms include catching or locking of the involved finger when it is forcefully flexed. There may be tenderness in the palm of the hand near the last skin crease (distal palmar crease). Often a nodule can be felt in this area. There is some evidence that idiopathic trigger finger behaves differently in people with

Causes

It is important to distinguish association and causation. The vast majority of trigger digits are

, meaning there is no known cause. However, recent publications indicate that diabetes and high blood sugar levels increases the risk of developing trigger finger. Some speculate that repetitive forceful use of a digit leads to narrowing of the fibrous digital sheath in which it runs, but there is little scientific data to support this theory. The relationship of trigger finger to work activities is debatable and there are arguments for and against a relationship to hand use with no experimental evidence supporting a relationship.

Diagnosis

20230326 Trigger finger - right middle finger

Diagnosis is made on interview and physical examination. More than one finger may be affected at a time. It is most common in the thumb and ring finger. The triggering more often occurs while gripping an object firmly or during sleep when the palm of the subject’s hand remains closed for an extended period of time, presumably because the enlargement of the tendon is maximum when the finger is not being used. Upon waking, the affected person may have to force the triggered fingers open with their other hand. In some, this can be a daily occurrence.

Treatment

Post-operative photo of trigger finger release surgery

Depending on the number of affected digits and the clinical severity of the condition,

Corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invo ...

injections can cure trigger digits. Treatment consists of injection of a corticosteroid such as

methylprednisolone Methylprednisolone (Depo-Medrol, Medrol, Solu-Medrol) is a synthetic glucocorticoid, primarily prescribed for its anti-inflammatory and immunosuppressive effects. It is either used at low doses for chronic illnesses or used at high doses durin ...

often combined with a local anesthetic (

lidocaine Lidocaine, also known as lignocaine and sold under the brand name Xylocaine among others, is a local anesthetic of the amino amide type. It is also used to treat ventricular tachycardia and ventricular fibrillation. When used for local anae ...

) at the A1 pulley in the palm. The infiltration of the affected site is straightforward using standard anatomic landmarks. There is evidence that the steroid does not need to enter the sheath. The role of sonographic guidance is therefore debatable. Injection of the tendon sheath with a corticosteroid is effective over weeks to months in more than half of people. Steroid injection is not effective in people with Type 1 diabetes. If triggering persists 2 months after injection, a second injection can be considered. Most specialists recommend no more than 3 injections because corticosteroids can weaken the tendon and there is a possibility of tendon rupture. Triggering is predictably resolved by a relatively simple surgical procedure under local anesthesia. The surgeon will cut the sheath that is restricting the tendon. The patient should be awake in order to confirm adequate release. On occasion, triggering does not resolve until a slip of the FDS (flexor digitorum superficialis) tendon is resected. One study suggests that the most cost-effective treatment is up to two corticosteroid injections followed by open release of the first annular pulley. Choosing surgery immediately is an option and can be affordable if done in the office under local anesthesia.

Surgery

Trigger digits can be released percutaneously using a needle. This is not used for the thumb where the digital nerves are at greater risk.

Postoperative outcome

In some trigger finger patients, tenderness is found in the dorsal proximal interphalangeal (PIP) joint. Dorsal PIP joint tenderness is more common in trigger fingers than previously thought. It is also associated with higher and prolonged levels of postoperative pain after A1 pulley release. Therefore, patients with pre-existing PIP tenderness should be informed about the possibility of sustaining residual minor pain for up to 3 months after surgery.

References

External links

Video of Trigger Finger Release Surgery on YouTube

American Academy of Orthopaedic Surgeons information on trigger finger

Information from the Mayo Clinic
{{DEFAULTSORT:Trigger Finger Ailments of unknown cause Fingers Inflammations Disorders of synovium and tendon Wikipedia medicine articles ready to translate