Trigger Thumb Treatment & Management

Conservative treatment of trigger thumb is aimed toward the irritation surrounding the tendon through immobilization and anti-inflammatory medication. This includes oral nonsteroidal anti-inflammatory drugs, steroid injection, and judicious use of a hand-based splint that prevents motion of the metacarpophalangeal (MP) and interphalangeal (IP) joints of the thumb (each maintained in 15 degrees of flexion).^{[3, 9]} The splint most commonly is worn at night and prevents the excessive flexing and locking that occurs during sleep. Patients with severe symptoms may need to wear the splint for daytime activities as well. The splint should not be worn for more than 10-14 days on a constant basis; after that period, wean the patient from the splint to avoid permanent stiffness.^[10]

Patients with a history of triggering for more than 4-6 months or who present with locking are less likely to respond to medical treatment. Most patients who improve with corticosteroid injection do so after the first injection; some may require a second or even third injection after an appropriate interval.^[11]

The outcome of conservative treatment for pediatric trigger thumb is somewhat controversial.^[12] A recent report on the natural history of this condition by Baek et al^[13] demonstrated complete resolution of flexion deformity in 63%, and partial improvement in the flexion deformity in another 31% of patients without any treatment over a two year (minimum) observation period. Another study by Lee et al^[14] reported that extension splinting for 12 weeks led to improvement in 71% of thumbs, compared to 23% improvement in patients not receiving any treatment. See also the current recommendations described by Ogino.^[15]

Surgical decompression of the trigger thumb is performed best under tourniquet using local anesthesia with or without additional intravenous sedation. Loupe magnification greatly assists in visualization of important structures.

• The A1 pulley is approached through a transverse incision in the flexion crease overlying the MP joint. See the image below.Incision for trigger thumb release placed in MP flexion crease, centered over flexor tendon nodule.
• Palpate the FPL to ensure that the incision is centered appropriately.
• Bluntly dissect through subcutaneous tissue; identify and gently retract radial and ulnar neurovascular bundles.
• Expose the A1 pulley, identify its proximal and distal edges, and incise it longitudinally.^[16] See the image below. Trigger thumb. A1 pulley exposed within surgical field (arrow). Digital neurovascular bundles behind retractors.
• Avoid injury to the underlying tendon. See the image below.Trigger thumb. A1 pulley has been released; flexor pollicis longus tendon now exposed. Retractors have been removed to demonstrate proximity of neurovascular bundles (arrows) to tendon.
• Inspect the tendon nodule during full passive motion of the IP joint; ensure that no further restrictions to excursion are present. A band of tissue proximal to A1 may exist that also requires release.
• Observe FPL excursion while the patient actively flexes the thumb to verify a complete surgical decompression.
• Deflate the tourniquet, obtain hemostasis, and close the incision with nylon.
• Dress the wound with a soft compressive bandage.

Encourage active motion as soon as the patient is comfortable. Unless the patient develops a prominent tender scar or a stiff thumb due to adhesions, formal hand therapy is rarely required.

If the surgeon maintains a careful surgical technique, the incidence of complications should be low.^[4] The most common complication reported after trigger thumb surgery is transection of a digital nerve. The radial digital nerve is injured more frequently because of its superficial location and oblique course over the flexor sheath. Adhesions and subsequent stiffness may develop with excessive handling of the tendon or delayed postoperative mobilization. Flexor tendon sheath infection is a rare but potentially devastating complication of A1 release. Compared to trigger thumb surgery, painful scars are more likely to occur after trigger finger surgery.

Idiopathic

Splinting alone may lead to resolution in 50% of individuals with trigger thumb. Corticosteroid injection may be successful in as many as 90% of thumbs, although it may require as many as 3 treatments. Surgical release of the A1 pulley results in more than 95% relief of symptoms, with approximately a 3% recurrence rate.^[17]

Pediatric

Triggering may resolve spontaneously in 23-63% of cases. If patients are not treated by the time they are aged 4 years, some may be left with permanent flexion contractures. Surgical release of the A1 pulley prior to this age leads to excellent results.^{[18, 19]}

While historically referred to as congenital trigger thumb, recent studies have called into question the natural history of this process in the pediatric population. This condition actually is rarely seen in newborns and infants; pediatric trigger thumb appears to develop in young children sometime during the first few years of life. As indicated in the above discussion, the exact roles of observation, splinting, and surgical release are being reevaluated.

Percutaneous release of the A1 pulley has been advocated for some individuals with trigger finger. This procedure should not be attempted in persons with trigger thumbs because of the significant risk of iatrogenic digital nerve injury.^[20]