Presentation and diagnosis
Trigger finger may be idiopathic, but it is common in early and late rheumatoid arthritis. It can affect any or all of the flexor tendons of the fingers in the palm. A tender nodule in the palm is usually palpated over the line of the flexor tendon just proximal to the metacarpophalangeal joint crease. Injection will be into the tendon sheath and not into this nodule.
The patient complains of an uncomfortable locking of the affected finger spontaneously occurring in flexion – only with difficulty can the finger be released by manipulating or forcefully extending the affected joint. Naturally, this condition is an occupational hazard for anyone undertaking machine or intricate work involving the hands and fingers.
Functional anatomy
This condition is a tenosynovitis affecting any of the flexor tendons (superficial and deep) in the palm. These tendons are enveloped by synovial sheaths as they traverse the carpal tunnel. They extend for about 2.5cm above the flexor retinaculum to about halfway along each metacarpal, except for the little finger in which the sheath is continuous and extends to the terminal phalanx and the thumb (flexor pollicis longus), where the sheath is continuous to the tip of the finger. The fibrous synovial sheaths of the terminal parts of the tendons are thinner over the joints.
Injection technique
Use 1ml steroid mixed with 1ml lidocaine 1% plain in a 2ml syringe with a 1.6cm needle. Insert the needle over the crease overlying the metacarpophalangeal joint and advance it proximally into the flexor tendon. Ask the patient to flex that finger, which will move the needle and confirm the needle point is in the tendon. There will be some resistance to the plunger. Slowly withdraw the needle while maintaining pressure on the plunger until resistance to injection disappears, when the contents may easily be injected into the tendon sheath. A slow injection of the solution will expand the part of the tendon sheath proximal to the injection, a confirmatory sign that the steroid is in the correct place.
It is important to emphasise that one should never attempt to inject steroid into the substance of a tendon. As stated previously, these injections should be easy with no force required, and the solution should just glide in. Trigger fingers respond well to steroid injection, but do recur and may be injected two to three times in a year if clinically required. However, further recurrences may need a surgical release.1
References
- Nimigan A et al. Steroid injections in the management of trigger fingers. Am J Phys Med Rehabil 2006;85:36-43
This extract is taken from Joint and Soft Tissue Injection 5th Edition, by Dr Trevor Silver which is now available to purchase from Radcliffe Publishing with an exclusive 20% discount available until 30th September – simply quote PULSETS12.
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