Trigger Finger is a common condition which may cause significant functional impairment. It is a tenosynovitis in the flexor sheaths of the fingers and thumb as a result of repetitive use. A narrowing of flexor pulley sheaths combined with hypertrophy and inflammation of the tendon/sheath interface causes trigger finger or stenosing tenosynovitis. The inflammation may cause the tendon to become nodular.  It most commonly occurs in the ring finger and the thumb but can present in any finger. It classically involves the A1 pulley sheath (at the metacarpal-phalangeal joint) which is the proximal portion of the tendon sheath.  It can also occur at A2 (at the proximal interphalangeal joint) or A3 (at the distal interphalangeal joint). Patients complain of locking of the digits during either flexion or extension. Usually, the extension is more problematic.

Trigger finger is painful. It usually begins as an odd ache in the palm during movement of the affected finger. Gradually there is snapping sound of the flexor tendon as the individual extends and flexes the digit. Trigger finger commonly affects the dominant hand and the most common digit involved is the thumb. 

The etiology of trigger finger is multifactorial. There are some associations with specific comorbid diseases in adult patients with trigger finger, for example, diabetes, amyloidosis, carpal tunnel syndrome, gout, thyroid disease, and rheumatoid arthritis. Traumatic forces result in hypertrophy and narrowing of the tendon and its sheath, leading to the tendon being unable to slide smoothly within its sheath. This results in catching and locking.

In children, the etiology appears to be developmental, with a mismatch in the size of the flexor tendon of the thumb and its tendon sheath. The fibroblast proliferation results in a discrepancy in the size of the tendon and the A1 pulley sheath. Although the majority of the cases are idiopathic at this age, it is more commonly associated with congenital metabolic (e.g., Hurler syndrome) and inflammatory conditions (e.g., juvenile rheumatoid arthritis)

The diagnosis of trigger finger is clinical, and it is presumed in a patient whose finger locks during flexion, clicks painfully, and catches upon extension. It is also presumed when an inflamed nodule at the base of the affected finger is present.

Ultrasound can be obtained in assessing this condition. Ultrasound may demonstrate thickening of the pulley as well as inflammation and irregularity of the underlying flexor tendon. However, it may not reliably predict the site. Ultrasound can be used dynamically to demonstrate the catching and clicking during tendon sliding.

Plain radiographs are useful to rule out other conditions, such as an occult fracture. In general, MRI and CT scans may not be required.

The management of trigger finger can be divided into the following two classes:

Non-surgical

Treatment of trigger finger usually is nonoperative particularly especially if it is uncomplicated and of a short duration of symptoms. It includes steroids injection and splinting.

Steroid injection

Injection of steroids is often successful and first-line treatment strategy for patients with trigger finger. It is inexpensive, easily performed, and less invasive than surgery. Delivery of steroid into the tendon sheath is important for its effectiveness. A steroid injection may be helpful in many patients, although recurrence of symptoms can occur. Steroid injections may cause tissue atrophy, skin discoloration, hypopigmentation or even infection. Patients with prolonged symptoms are less likely to have a resolution.

Splinting

It is based on the concept that is limiting tendon gliding; inflammation can be reduced. In an MCP blocking splint, at 10 to 15 degree of flexion for 6 to 10 weeks. However, it .is less likely to benefit those patients who suffer from severe or prolonged symptoms.

Surgical

Open release of the A1 pulley is considered the gold standard for surgical management of trigger finger. A surgical release should be considered when there is

• No improvement with splinting and/or injection treatment

• Irreducibly locked trigger finger

• Trigger thumb during infancy: it is believed that at this age, without surgical release, these infants are likely to develop a fixed flexion deformity of the interphalangeal (IP) joint. Since the causes of trigger finger in children are more varied than merely from a thickened A1 pulley, the outcomes of conservative treatment are unpredictable.

Percutaneous release of the A1 pulley is an alternative management strategy. This requires understanding and recognition of certain specified landmarks. Although the percutaneous technique has been shown effective and safe for the thumb, many physicians advocate avoiding the use of this approach on the thumb, because of the digital nerve courses over the A1 pulley. Incomplete pulley release and damage to the flexor tendons and digital nerves constitute possible concerns with this approach.

Prognosis

With treatment, the prognosis is good. Most patients do respond to corticosteroid injection. A few cases do resolve spontaneously when the primary condition is treated. However, even with steroid injection, full recovery can take months. Diabetics tend to have the least favorable response to corticosteroids and often require surgery. Surgery for release of trigger finger is successful and is a reasonable choice for patients who have failed steroid injections.

Enhancing Healthcare Team Outcomes

The diagnosis and management of trigger finger is best done with an interprofessional team that consists of a hand surgeon, orthopedic surgeon, plastic surgeon, nurse practitioner, physical therapist and the primary care provider. The diagnosis of trigger finger is clinical. In most cases, the initial treatment is non-surgical and may involve splinting or injection of a corticosteroid. Patients should be made aware that after a steroid injection, pain may be significant for a few days. To minimize the risk of tendon rupture after a steroid injection, patients should be warned not to perform strenuous activity for a few weeks.

Surgery is recommended when conservative treatments fail. However, surgery is not 100% effective and complications are not unheard of. In addition, surgery may fail to resolve the trigger finger. It is vital to educate the patient on non-surgical methods before surgery is contemplated. Damage to the digital nerves and incomplete release are relatively common with the surgical approach. With open communication between members of the team, the patient should be provided with realistic expectations. This helps improve treatment satisfaction.