Background
Injection of a flexor tendon in the hand is most commonly performed for the treatment of stenosing tenosynovitis. Stenosing tenosynovitis, also known as trigger finger, involves a size mismatch between a thickened or stenotic first anular (A1) pulley in the hand and the flexor tendon trying to glide through the pulley. As the patient attempts to extend the finger, the flexor tendon catches, causing clunking or locking at the proximal interphalangeal (PIP) joint of the involved digit. This locking is termed triggering (see the image below). [1]
In 1972, corticosteroid injection into the flexor tendon sheath for the treatment of trigger finger was advocated by Lapidus, who noted resolution of triggering in most fingers treated with steroid injection. [2] Since then, corticosteroid injection for trigger finger has become the first-line conservative treatment in most patients who present with stenosing tenosynovitis. [3, 4] A 2013 retrospective review that included 577 trigger digits found corticosteroid injection to be safe and effective (79.7% success rate). [5]
Injection of hyaluronic acid for trigger finger has also been described, but additional study is required to establish its role in treatment. [4, 6]
Nonoperative treatment of stenosing tenosynovitis is more likely to be successful if initiated relatively early (eg, before 3 months). [7] For information on surgical treatment of trigger finger that does not respond to conservative treatment, see Trigger Finger.
Indications
Trigger finger or stenosing tenosynovitis is the usual indication for injection into the digital flexor sheath. Some patients present with pain over the A1 pulley without demonstrable locking or catching. When this is clinically suspected as pretriggering, corticosteroid injection is appropriate. Trigger finger is commonly graded according to the classification outlined by Wolfe (see Table 1 below). [8]
Table 1. Wolfe's Classification of Trigger Finger (Open Table in a new window)
Grade |
Type |
Description |
I |
Pretriggering |
Pain in the palm; possible history of catching, but not seen on examination; tenderness over A1 pulley |
II |
Active |
Patient demonstrates catching but can actively extend the finger |
III |
Passive |
Patient demonstrates locking that requires passive extension (IIIa); may be unable to flex the finger (IIIb) |
IV |
Contracture |
A locked trigger finger with a fixed flexion contracture of the proximal interphalangeal joint |
Studies by Girolimetto et al have shown steroid injection into the digital flexor tendon sheath to be effective in improving clinical aspects of hand psoriatic dactylitis. [9, 10]
Contraindications
The main contraindication for injection into the digital flexor sheath is preexisting infection. Patients who present with suppurative flexor tenosynovitis or infection that extends throughout the flexor sheath in the finger and hand should undergo surgical drainage of the flexor sheath to treat the infection. [11]
A previous allergic reaction to some component of the planned injection is also a contraindication for steroid injection. Allergies to corticosteroids [12] and multiple local anesthetics [13] have been reported.
A patient who presents with diabetes and trigger finger may present a relative contraindication for offering a corticosteroid injection as the first-line treatment.
Baumgarten et al published a randomized blinded study comparing corticosteroid injections with placebo injections in patients with diabetes, which found no significant differences in response between placebo and steroid. [14] More important, symptomatic relief and the need for surgery were not decreased by the use of corticosteroid injections in patients with diabetes. Griggs et al also demonstrated a poorer response to corticosteroid injections in patients with diabetes as compared with the general population. [15]
Patients with diabetes who choose to undergo corticosteroid injection into the flexor tendon sheath must be educated about the effects of such injections on blood glucose levels. Wang and Hutchinson studied the effects of corticosteroid injection for trigger finger on blood glucose levels in diabetic patients and found that in all patients, blood glucose levels rose after injection; those with type I diabetes were most affected. [16] The highest glucose level spike occurred the morning after injection, when average glucose levels were 72% higher than average preinjection levels.
Technical Considerations
Anatomy
The palmar fascia consists of resistant fibrous tissue arranged in longitudinal, transverse, oblique, and vertical fibers. The longitudinal fibers originate at the wrist from the palmaris longus tendon, when present. These fibers spread out to the base of each digit, where minor fibers extend distally and attach to tissues.
This arrangement of fibers forms the fibrous flexor sheath and pulley system of each digit. The A1 pulley arises from the palmar plate and proximal portion of the proximal phalanx, overlies the membranous sheath at the level of the metacarpophalangeal (MCP) joint, and is approximately 8 mm in width.
For more information about the relevant anatomy, see Flexor Tendon Anatomy and Hand Anatomy.
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Equipment needed for injection of digital flexor tendon sheath.
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Lidocaine and triamcinolone used for injection of digital flexor tendon sheath.
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Ring and small finger locking with trigger finger.
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Digital flexor injection. Needle is placed at 50º angle at base of finger flexion crease.
Tables
Grade |
Type |
Description |
I |
Pretriggering |
Pain in the palm; possible history of catching, but not seen on examination; tenderness over A1 pulley |
II |
Active |
Patient demonstrates catching but can actively extend the finger |
III |
Passive |
Patient demonstrates locking that requires passive extension (IIIa); may be unable to flex the finger (IIIb) |
IV |
Contracture |
A locked trigger finger with a fixed flexion contracture of the proximal interphalangeal joint |
