Ultrasound may not predict those who will spontaneously recover from trigger thumb

Issue: August 2011

The reasons why certain patients with pediatric trigger thumb resolve spontaneously while others require surgery remains unclear, and a recently presented study was unable to show whether ultrasound could reliably predict which patients would resolve on their own.

“It may be that there is a certain crucial mismatch difference that will prevent this [condition] from resolving spontaneously,” study researcher Clifford L. Craig, MD, a clinical associate professor in the department of orthopedic surgery at University of Michigan Health System, Ann Arbor, told Orthopedics Today. Michelle S. Caird, MD, a co-author of the study, presented the results at the 2011 Annual Meeting of the Pediatric Orthopaedic Society of North America.

Pediatric trigger thumb is a developmental condition, Craig noted, and trauma is not a contributing factor.

“There does not appear to be any injury to the tendon,” he said. “There was also no evidence of inflammation.”

Pediatric trigger thumb is the result of a size disparity between the flexor pollicis longus tendon and the tendon sheath at the A1 pulley. The condition resolves when the size difference is corrected, Craig said, either spontaneously through developmental changes in the local anatomy or through surgical release of the A1 pulley.

For their study, Craig and colleagues conducted a prospective analysis of 33 children who presented to the University of Michigan Health System from May 2008 through June 2010. They excluded five patients with a pre-existing history of trigger thumb release or an inability to obtain an ultrasound. Twenty-one patients had unilateral triggering, and seven had bilateral thumb triggering.

Initially, all children were treated with nighttime splinting with a custom-measured flexible, neoprene thumb splint.

Each patient received a bilateral dynamic ultrasound of the thumb at presentation and at each follow-up visit until clinical resolution or the end of data collection. The investigators chose ultrasound for their study because “it’s a dynamic study, as opposed to just taking a photograph,” Craig said.

Surgeons performed surgical release of the A1 pulley in eight patients (nine thumbs).

At the conclusion of the study, 11 patients with unilateral trigger thumb had resolved (7 with splinting and 4 with surgery); 10 children continued to have thumb triggering. Two children in this group eventually developed bilateral triggering.

In the bilateral group, one patient had bilateral resolution by the conclusion of the study, five patients had unilateral resolution, and one patient had persistent bilateral triggering.

Craig and colleagues also used ultrasound to see how trigger thumb resolves. “We wanted to see what happens when they get better spontaneously and if we could figure out a way to prospectively predict which children were going to get better. … [This way] we could save some children from surgery.”

The answer to that question is incomplete, Craig said. From their study, Craig and colleagues were unable to show whether ultrasound could reliably predict which patients would resolve spontaneously and which would require surgery.

“We don’t have the numbers who have gotten better spontaneously,” he said. “We have about three or four, and we don’t think that’s enough to comment on yet.”

This study is not complete, Craig said. “We’re still hoping that we can get enough data so that we can make a prediction.” — by Colleen Owens

Reference:

Craig C. Verma, M, Dipietro, M, Caird, M. Serial ultrasound evaluation of pediatric trigger thumb. Paper # 72. Presented at the 2011 Annual Meeting of the Pediatric Orthopaedic Society of North America. May 11-14. Montreal.

Clifford L. Craig, MD, can be reached at A. Alfred Taubman Health Care Center, 1500 East Medical Center Drive, Reception B, Ann Arbor, MI 48109; 734-936-5780; email: clcraig@umich.edu.

Disclosure: Craig has no relevant financial disclosures.