eMedicine Specialties > Orthopedic Surgery > Hand & Upper Extremity
Trigger Finger
Updated: May 8, 2008
Introduction
One of the most common upper limb problems to be encountered in orthopedic practice, trigger finger (TF), also known as trigger digit or stenosing tendovaginitis, has remained a mystery with regard to its formation.
History of the Procedure
In the past, triggering of the digits was treated by splinting in extension, which caused stiffness and consequently loss of metacarpophalangeal and interphalangeal flexion. Due to dissatisfaction with this form of treatment, researchers used intrasheath steroid injections, which resulted in a high proportion of good results.1
Surgery, in the form of release of the A1 pulley, became popular when splinting and/or injection therapy failed or in the presence of other pathology, such as rheumatoid arthritis, in which injection treatment proved futile or there was a risk of tendon rupture or infection.
In an uncomplicated case of trigger digit, the first-line therapy is still generally agreed to be injection into the tendon sheath, with surgical release of the A1 pulley as second-line treatment.
Problem
TF is one of the most common causes of hand pain and disability. The condition begins as discomfort in the palm during movements of the involved digit(s). Gradually or, in some cases, acutely, the flexor tendon causes painful popping or snapping as the patient flexes and extends the digit. The patient may present with a digit locked in a particular position, more often flexion, which may require gentle, passive manipulation into full extension.2
The phenomenon is due to a mismatch between the size of the flexor tendon and the retinacular pulley. This is usually caused by the formation of a nodule in the flexor digitorum superficialis (FDS) tendon, in the region of the metacarpal head where the tendon glides under the A1 pulley; in rare instances, a nodule distal to it in the tendon of the flexor digitorum profundus could be the culprit.
A few case reports have documented rare causes of TF, including tenosynovitis that itself resulted from a Mycobacterium kansasii infection in an immunocompetent patient; triggering following the development of calcific tendonitis has been reported in a child. Such cases should invoke a high degree of suspicion.
Frequency
Stenosing tendovaginitis is much more common in women, with a frequency 2-6 times than that observed in men.
Several series found the peak incidence of trigger digit to be in individuals aged 55-60 years. Age distribution has not changed significantly despite an increase in computing activities and repetitive tasks.
Increased incidence in the dominant hand is observed. The involvement of several fingers is not unusual. The most commonly affected digit is the thumb, followed by the ring, long, little, and index fingers.
Triggering seems to occur more frequently in patients with rheumatoid arthritis (RA) or diabetes mellitus (DM). These patients also seem to be more resistant to injection treatment.3,4
Etiology
Trauma/local
Systemic causes of TF are collagen-vascular diseases, including RA, DM, psoriatic arthritis, amyloidosis, hypothyroidism, sarcoidosis, and pigmented villonodular synovitis.
Septic causes of TF are secondary infections (eg, tuberculosis).
Idiopathic
The etiology of TF is unknown or uncertain; suspect nodule or pulley morphology change.
Other causes that can simulate locking include the following:
- Collateral ligaments of the metacarpophalangeal (MCP) joint catch on a bony prominence on the side of the metatarsal head (osteophyte).
- Localized swelling in the flexor digitorum profundus (FDP) gets entrapped at the decussation of the FDS.
- A partially lacerated flexor tendon catches against the A1 pulley or the FDS decussation.
- A nodule in the FDS catches against the A3 pulley.
- Locking is simulated by abnormal sesamoids.
- A loose body is present in the MCP joint.
- Snapping or subluxation of the extensor digitorum communis (EPC) occurs.
Pathophysiology
A mismatch between the flexor tendon and the proximal pulley mechanism occurs in most cases. Several studies have demonstrated a correlation between this condition and activities that require exertion of pressure in the palm while a powerful grip is employed or that involve repetitive, forceful digital flexion (eg, arc welding, use of heavy shears). Proximal phalangeal flexion in power-grip activities causes high annular loads at the distal edge of the A1 pulley. Hueston and Wilson have suggested that bunching of the interwoven tendon fibers causes the reactive intratendinous nodule observed at surgery.5
Presentation
Symptoms of TF are as follows:
- Locking or catching during active flexion-extension activity (Passive manipulation may be needed to extend the digit in the later stages.)
- Stiff digit, especially in long-standing or neglected cases
- Pain over the distal palm
- Pain radiating along the digit
Signs of TF are as follows:
- Triggering on active or passive extension by the patient
- Palpable snapping sensation or crepitus over the A1 pulley
- Tenderness over the A1 pulley
- Palpable nodule in the line of the FDS, just distal to the MCP joint in the palm
- Fixed-flexion deformity in late presentations, especially in the proximal interphalangeal (PIP) joint
- Evidence of associated conditions (eg, RA, gout)
- Early signs of triggering in other digits (may be bilateral)
Indications
The chief indications for surgical management of this condition are as follows:
- Failure of splinting and/or injection treatment
- Irreducibly locked TF
- Trigger thumb in infants (Without surgical release, these infants are likely to develop a fixed flexion deformity of the interphalangeal joint.)
Relevant Anatomy
Tendon sheaths of the long flexors run from the level of the metacarpal heads (distal palmar crease, superficial; volar plate, deep) to the distal phalanges. They are attached to the underlying bones and volar plates, which prevent the tendons from bowstringing. Predictable and efficient thickenings in the fibrous flexor sheath act as pulleys, directing the sliding movements of the fingers.
The 2 types of pulleys are annular (A) and cruciate (C). Annular pulleys are composed of single fibrous bands (ie, rings), while cruciate pulleys have 2 crossing fibrous bands.
The order of the pulleys from proximal to distal is as follows:
- The A1 pulley overlies the MCP joints. It is released during surgery for TF.
- The A2 pulley overlies the proximal end of the proximal phalanx.
- The C1 pulley overlies the middle of the proximal phalanx.
- The A3 pulley lies over the PIP joint.
- The C2 pulley lies over the proximal end of the middle phalanx.
- The A4 pulley lies over the middle of the middle phalanx.
- The C3 pulley lies over the distal end of the middle phalanx.
- The A5 pulley lies over the proximal end of the distal phalanx.
The A2 and A4 pulleys are vital in preventing bowstringing of the flexor tendons and have to be preserved or reconstructed following any damage to them.
Contraindications
No absolute contraindications exist for surgical management.
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References
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Further Reading
Keywords
TF, trigger digit, trigger thumb, snapping digit, locking digit, stenosing tendovaginitis, peritendinitis stenosans, digitus saltans
