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, extension is more problematic.
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).
Trigger finger has a bimodal incidence, with a first peak before eight years of age and the second peak in patients in their 40s and 50s. Overall, trigger finger is more common in adults. When children get trigger finger, it affects boys and girls equally and is most common in the thumb. In adults, women are much more likely to be affected by trigger finger, and typically, in their dominant hand.
Microtrauma, whether through repetitive use or compression forces, results in inflammation and injury of the flexor tendon-sheath complex. The greatest degree of force occurs on the A1 pulley, and hence, this is the one that is most commonly affected. Inflammation, over time, results in the tendon sticking within its sheath and is perceived by the patient as locking. Because the flexor tendon apparatus has superior strength, compared to the extensor tendon apparatus, patients classically do not have difficulty flexing their fingers. However, the inflammation causes the flexor tendon to catch in the flexor sheath during extension, and patients will notice locking when they attempt to extend their fingers.
The diagnosis of this disease is clinical. However, histopathology has demonstrated that fibro-cartilaginous metaplasia occurs at the tendon-pulley interface and is accompanied by both hypertrophy and inflammation.
Patients typically present with either discomfort or functional limitations in the affected digit. Patients may note progressive discomfort on the palmar aspect of the affected digit when flexed, and there may also be swelling or a nodule present. Patients frequently complain of a painful click in the digit. Patients may also present with locking of the finger during extension, or inability to move a finger from a fixed flexed position. Symptoms may develop gradually or may be acute. Patients may present with stiffness or discomfort if trigger finger involves their dominant hand and interferes with their work.
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:
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.
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. 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.
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.
Open release of the A1 pulley is considered the gold standard for surgical management of trigger finger. Surgical release should be considered when there is
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.
Trigger finger is less common than trigger thumb in children. Consider evaluation for JRA in recurrent cases.
The diagnosis and management of trigger finger is best done with a multidisciplinary 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 steroid. 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. (Level V)
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