Evaluation of Flexor Digitorum Superficialis-Small Function: A Novel Dynamic Assessment Technique in Professional...

The flexor digitorum superficialis of the little finger (FDS-small) exhibits anatomical variation, with absence reported in 2% to 30% of individuals. As FDS is the only flexor of the proximal interphalangeal joint (PIPJ), its absence may affect finger dexterity, particularly in professional musicians who depend on precise finger control. This study evaluates the impact of FDS-small presence or absence on the technical abilities of pianists and string musicians using novel dynamic assessment tools.

Thirty-one Bachelor of Music students (21 string players, 10 pianists) were assessed for FDS-small function and classified as "independent," "common," or "absent." Tests included grip strength, static gap, and stretch tests, and a novel assessment method comprising custom-composed double-stop trill etudes for piano and strings. Technical performance was evaluated by 2 professional musicians using predefined criteria. Statistical analyses were conducted using Fisher's exact tests, t tests, analysis of variance, and nonparametric equivalents.

Ten participants had absent FDS-small function in at least 1 hand. Pianists with bilateral absent FDS-small demonstrated superior coordination and regularity compared with those with FDS-small presence, while FDS-small absence did not significantly affect string players. Female pianists excelled in dynamic tests despite male musicians' higher grip strength and trill speed.

Absence of FDS-small does not impair, and may even enhance, fine motor performance in pianists. For string musicians, FDS-small status does not influence technique. These findings may contribute to evaluating the risk versus benefits of FDS-small surgical repair and have implications for instrument selection and pedagogy.