Congenital trigger thumb in children

Abstract

Although numerous studies have been performed on congenital trigger thumb (CTT), the pathogenesis is still unknown. Cytocontractile proteins and myofibroblasts are present during soft-tissue contraction, and they may have a role in CTT. The aim of the study is to clarify the immunohistochemical and the electron microscopy characteristics of the first annular (A-1) pulley in CTT. The specimens from the A-1 pulleys were collected from 22 children with CTT. Electron microscopy was used to study the last five specimens. Immunohistochemistry staining demonstrated that all specimens stained positively for vimentin and for α-smooth muscle actin, and stained negatively for desmin. Electron microscopy showed fibroblasts in collagenous matrix, which contain vimentin-like material and associated at the surface with elastin-like tubular matrix filaments and elastin fibers. In two specimens, a few cells showed markers of myofibroblastic differentiation. The presence of the cytocontractile proteins and myofibroblasts suggests proliferation of fibrous tissues during either the intrauterine or extrauterine phase of development and may account for the presence of congenital stenosis at the level of the A-1 pulley. We believe that CTT may be developmental; if the process started in the intrauterine phase it might present as a fixed flexion contracture and will show mature fibroblasts. If the process started in the extrauterine phase, it might present as triggering first and will show myofibroblastic changes, then with the maturation of the fibrous tissue, result in a fixed flexion contracture.

Changes in flexor pollicis longus tendon cross-sectional dimensions after A1 pulley release for paediatric trigger thumb

“…Paediatric trigger thumb was previously thought to be a congenital condition with several studies having reported pathological changes to the A1 pulley or FPL tendon. Some authors (Buchman et al., 1999; Khoshhal et al., 2012) found that patients with paediatric trigger thumb have pathologic fibrous tissue in and around the FPL tendon and A1 pulley, including proliferation of fibroblasts and surrounding collagen. However, a number of neonatal surveys (Kikuchi and Ogino, 2006; Moon et al., 2001; Rodgers and Waters, 1994) failed to demonstrate a convincing incidence of paediatric trigger thumb at birth, indicating this is more likely to be an acquired condition.…”

Common Pediatric Hand Anomalies

“…13 While ultrasound has identified a larger-than-normal size of FPL compared with the contralateral uninvolved FPL tendon, both ultrasound and electron microscopy of the flexor tendon have not demonstrated inflammatory or degenerative changes of the tendon. 14 15 16…”

“…13 While ultrasound has identified a larger-than-normal size of FPL compared with the contralateral uninvolved FPL tendon, both ultrasound and electron microscopy of the flexor tendon have not demonstrated inflammatory or degenerative changes of the tendon. [14][15][16] The most common classification system used is that of Sugimoto, in which stages range from a palpable Notta's nodule without triggering of the thumb to a locked IP joint without active or passive extension (►Table 1). 17 Pediatric trigger thumb is diagnosed based on physical exam with no need for imaging.…”

Current concepts in the management of pediatric trigger thumb

“…Fahey and Bollinger found collagenous degeneration and synovial proliferative changes within the flexor tendon [11] . More recently, both ultrasound and electron microscopy of the flexor tendon have not demonstrated inflammatory or degenerative changes [15,16] . Electron microscopy identified cytocontractile proteins and myofibroblasts within the tendon, further suggesting a developmental process [16] .…”