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 annular (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]
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Ring and small finger locking with trigger finger.
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.
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]
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 be treated with surgical drainage of the flexor sheath to treat the infection.[9]
A previous allergic reaction to some component of the planned injection is also a contraindication for steroid injection. Allergies to corticosteroids[10] and multiple local anesthetics[11] 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.[12] 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.[13]
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.[14] The highest glucose level spike occurred the morning after injection, when average glucose levels were 72% higher than average preinjection levels.
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.
The equipment needed for a single trigger finger injection includes the following (see the image below):
Syringe, 3 mL
Needle, 16 or 18 gauge, to withdraw the lidocaine and steroid - This is particularly important when multidose vials are used, so as to decrease any chance of cross-contamination
Needle, 25 or 27 gauge - The needle from a 1-mL insulin syringe is the right size and length (5/8 in., or ~16 mm)
Lidocaine 1% (without epinephrine)
Corticosteroid - The author uses either 0.25 mL (10 mg) of triamcinolone (40 mg/mL) or 0.25 mL (1.5 mg) of betamethasone (Celestone Soluspan 6 mg/mL)
Povidone-iodine solution
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Equipment needed for injection of digital flexor tendon sheath.
Digital flexor injection is usually performed with only local anesthesia. Various anesthetic techniques for this procedure have been described. The author’s preferred technique is to mix 1% lidocaine without epinephrine with the corticosteroid of choice and to inject this mixture directly into the flexor sheath. Other authors have described placing a wheal of local anesthetic at the skin and separately injecting the steroid preparation through this site. For more information on local anesthetic injections, see Local Anesthetic Agents, Infiltrative Administration.
Positioning
The patient is seated, and the affected hand is supinated on a table or another flat surface (the foot support portion of a standard examination table works well for this). The provider is seated across from the patient so that the volar surface of the extended fingers is closest to the provider. The patient is asked to keep the hand as flat as possible; this assists the provider with placing the needle in the midline of the finger.
In a study evaluating high-resolution ultrasonography (US) as a potentially useful adjunct for assessing the response to treatment of trigger finger with steroid injection,[15] Mifune et al found that US was able to reveal that the thickened A1 pulley and flexor tendon significantly improved after steroid injection, thereby facilitating confirmation of the therapeutic effects of the steroid injection.
The author’s preferred technique is quite similar to that described by Murphy.[16] The injection is placed at the base of the digit, through the flexor crease where the digit meets the hand.
Prepare the site in a sterile fashion with povidone-iodine solution. Using a 16- or 18-gauge needle attached to the 3-mL syringe, draw up a combination of 0.5 mL of lidocaine and 0.25 mL of corticosteroid (either triamcinolone or betamethasone).
Next, change to a 25-gauge needle. Place the needle in the midline of the finger, through the finger flexion crease at the base of the finger, and angle it approximately 50° proximally, with the bevel of the needle facing proximally (see the image below). This places the needle distal to the A1 pulley in the hand and is far easier than inserting the needle right at the A1 pulley. Generally, there is much less tenderness distal to the lesion at the A1 pulley.
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Digital flexor injection. Needle is placed at 50º angle at base of finger flexion crease.
Advance the needle through both flexor tendons until it contacts bone. Slowly withdraw the needle, with forward pressure on the barrel of the syringe, until the resistance encountered by the needle is decreased, indicating that the needle is within the flexor sheath. This injection should not require any force, and the solution should be quite easily injected into the flexor sheath.
With a 25-gauge needle, injection into the flexor tendon (as opposed to the flexor sheath) requires a very large amount of force. Thus, if the flexor sheath injection seems to require a great deal of force, it is likely that the needle is positioned inappropriately in the flexor tendon.
The provider often visualizes or palpates the tendon sheath filling during injection to confirm that the needle is placed well within the sheath. The provider should warn the patient that he or she may note pressure in the finger during this step. When the injection is complete, withdraw the needle slowly from the sheath, and place an adhesive bandage over the injection site.
Warn the patient that the area injected is likely to be tender and painful for a day or two. In addition, remind the patient that steroids take some time to have effect; often, patients wait 3-5 days to experience a difference in clinical symptoms.
Subcutaneous injections for trigger finger have also been described and have been shown to have effect.[17] If the injectate escapes the sheath and subcutaneous fluid is seen, the injection may still have effect.
The most common complication is recurrence of the triggering of the finger. In a 2006 study, trigger fingers in patients without diabetes who were treated with one or two injections showed a 57% success rate with complete resolution.[3] Patients with diabetes had a 32% success rate. Predicting triggering recurrence is difficult, though it is clear that the failure rate of injection is higher in patients with diabetes than in the general population.[3, 13, 12]
Infection after corticosteroid injection is unusual. Whereas mycobacterial infection has been reported after corticosteroid injection for De Quervain tenosynovitis,[18] most articles about digital flexor injections have shown no evidence of infection as a complication.
A few cases of flexor tendon rupture after corticosteroid injection have been reported. In one, the flexor pollicis longus ruptured 4 years after two corticosteroid injections.[19] In another, Fitzgerald et al reported a case of flexor digitorum profundus and superficialis rupture that presented 11 months after two corticosteroid injections.[20] In a third, Oh et al described rupture of the flexor digitorum profundus tendon that occurred in a 57-year-old male golfer after a single corticosteroid injection.[21]
The deleterious effect of corticosteroid on tendon has been shown previously. Researchers have studied the effects of corticosteroid treatment on tenocytes both in culture and in animal rotator cuff tendons.[22, 23] The results of these studies showed decreased collagen synthesis, lower cell viability, and fragmentation of collagen bundles.
Jennifer Moriatis Wolf, MD, Associate Professor, Department of Orthopedic Surgery, University of Connecticut Health Center
Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: The Journal of Hand Surgery; American Society for Surgery of the Hand<br/>Received research grant from: Dept of Defense.
Specialty Editors
Mary L Windle, PharmD, Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Nothing to disclose.
Chief Editor
Erik D Schraga, MD, Staff Physician, Department of Emergency Medicine, Mills-Peninsula Emergency Medical Associates
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