Digital Flexor Injection Technique

Updated: Jul 01, 2016
  • Author: Jennifer Moriatis Wolf, MD; Chief Editor: Erik D Schraga, MD  more...
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Steroid Injection Into Digital Flexor Sheath

The author’s preferred technique is quite similar to that described by Murphy. [13]  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 angled 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. The patient is generally much less tender distal to the lesion at the A1 pulley.

Digital flexor injection. Needle is placed at 50º 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. [14]  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, 11, 10]

Infection after corticosteroid injection is unusual. Whereas mycobacterial infection has been reported after corticosteroid injection for De Quervain tenosynovitis, [15]  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. [16]  In another, Fitzgerald et al reported a case of flexor digitorum profundus and superficialis rupture that presented 11 months after two corticosteroid injections. [17]  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. [18]

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. [19, 20]  The results of these studies showed decreased collagen synthesis, lower cell viability, and fragmentation of collagen bundles.