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Orthopedics and Sports Medicine Case of the Month

April 2013: Why Won’t My Thumb Straighten?

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Cheryl Parker PA-C COTM  

Cheryl Parker, a physician assistant with Orthopedics and Sports Medicine, reviews the stages for classifying trigger thumb.

For more general information about pediatric trigger thumb, visit our Hand and Upper Extremity Program.

Patient History

Trigger Thumb COTM  

A 2-year-old boy was referred to our orthopedic clinic after falling on an outstretched hand. Parents noted that after the fall he could not straighten his right thumb. Patient was taken to an outside Emergency Department (ED). Radiographs revealed no fracture, but the parents were told his thumb was dislocated. He was splinted by the ED and referred to orthopedics. Parents report their child removed the splint as soon as they left the ED. Patient is right-handed. There has been no decline in daily activities. He only feels pain when his thumb suddenly straightens, but is relieved of pain when the tip flexes again. Parents report no fevers, upper respiratory infections or discoloration. They do feel a small lump by his thumb; otherwise, he is happy.

Physical Exam

Patient’s thumb is flexed at the interphalangeal (IP) joint. Skin is warm, moist and intact. Neuromotor is intact. Patient able to abduct thumb (median nerve), fully extend index finger (radial nerve), spread fingers (ulnar nerve) and give “OK” sign (anterior interosseus nerve – median nerve). Neuro sensation is intact. Patient is able to feel over the first webspace (radial nerve) and the tips of the index (median) and small (ulna) fingers. There is a palpable firm nodule (Notta’s node) at the base of the first metacarpophalangeal (MCP) joint that can be felt to move when the patient tries to further flex and extend the thumb. Radial pulse is palpable. Capillary refill is less than two seconds. Patient has full range of motion to other digits and wrist with no tenderness to palpation.

Imaging

No imaging was needed. 

Differential Diagnosis

Occult fracture of thumb

Dislocation of thumb

Congenital difference

Pediatric trigger thumb

Discussion

The patient has a pediatric trigger thumb. The true incidence in the United States is not known, but others report it to be approximately 3.3 cases per 1,000 live births. This is a stenosing tenosynovitis of the flexor pollicis longus tendon. A classic nodule, Notta’s node, develops in the tendon, and this is the bump that can be felt at the MCP joint. The flexor tendon is held in place by thickened areas of the tendon sheath called pulleys, and this nodule gets large enough so that it gets caught on one of the pulleys, thus preventing smooth motion. As the nodule becomes stuck in the flexor tendon sheath proximal to the pulley, it causes the IP joint to remain flexed. More rarely, it can cause the thumb to remain extended if the nodule is stuck distal to the pulley. There is debate as to whether trigger thumb is congenital or acquired, but recent studies suggest that this is an acquired condition. It is not usually associated with other medical conditions. Trigger thumb is different from trigger finger in children, in that trigger finger is often due to accessory or abnormally positioned slips of tendon and not just a nodule that requires different treatment.

Four stages to classify trigger thumb

  • Stage 1: Palpable nodule with no triggering
  • Stage 2: Active triggering that can be seen with extension of IP joint by the patient
  • Stage 3: Active extension of IP joint not possible by the patient, but one can extend the IP joint passively, often with a “pop”
  • Stage 4: Fixed flexion deformity – unable to extend IP joint actively or passively

Treatment

There is much debate in regard to treatment, and there are several current studies exploring this question. It is generally agreed that initial treatment is observation with stretching and perhaps splinting, especially if the thumb is still triggering and not stuck in a fixed position, as many cases will resolve on their own. However, if the thumb remains in a fixed flexed position for a prolonged period, this could lead to altered shape of the IP joint as the child grows, hyperextension of the MCP joint as the child accommodates to extend their thumb during activity and development of contracture of other tissues about the joint. Surgical release is considered if there is no improvement after a period of observation, stretching or splinting for these reasons, or if there is painful triggering of the digit. Since this can develop in the contralateral thumb in up to 25% of patients, surgery is most often delayed until after the age of 2 to make sure it does not become bilateral.

Surgical treatment is done as an outpatient procedure in which the pulley that the nodule is stuck on is opened. A small incision is made at the flexor crease at the base of the thumb so as it heals, the incision blends well with the naturally occurring skin lines. The incision is closed with absorbable sutures, and when the dressing is removed, the child is allowed to return to regular activities without the need of therapy. The swollen nodule (Notta’s node) takes approximately three to four months to dissipate after surgery, but may not resolve completely.

Comments

It is unclear what causes a pediatric trigger thumb. This is typically discovered incidentally. It is characterized by either the thumb sticking in a flexed position or by the clicking/snapping of the digit, with a thickened nodule noted in the palm of the hand. If persistent and untreated, it can lead to a fixed flexion deformity.

References

  1. Shah AS, Bae DS. “Management of Pediatric Trigger Thumb and Trigger Finger.” Journal of the American Academy of Orthopedic Surgeons. 2012; 20(4): 206–213
  2. Ogino, T. (2008). “Trigger Thumb in Children: Current Recommendations for Treatment.” The Journal of Hand Surgery. 2008; 33(6): 982–984.
  3. Baek et al. The Natural History of Trigger Thumb. The Journal of Bone and Joint Surgery. 2008; 90:980–985.

Contact Orthopedics and Sports Medicine

For more information, please contact Orthopedics and Sports Medicine.