# Functional absence of flexor digitorum superficialis of the 5th digit and its association with agenesis of palmaris longus

## TL;DR

This study found that about 35% of people lack a certain hand muscle, and this absence is not linked to handedness or another missing muscle.

## Contribution

The study reports the prevalence of FDS agenesis and its lack of association with PL agenesis and handedness.

## Key findings

- Functional agenesis of FDS for the 5th digit occurred in 35.7% of cases.
- Agenesis of PL was observed in 33.7% of cases.
- No significant association was found between FDS agenesis and PL agenesis or handedness.

## Abstract

To determine the prevalence of absence of Flexor digitorum superficialis and its association with gender, handedness, and agenesis of Palmaris Longus

A cross-sectional descriptive study was carried out at Bahria University Health Sciences Campus (BUHSC), Karachi from August 2022 to September 2024 that included both males and females. Standard and Modified Tests for Flexor digitorum superficialis (FDS) while Schaffer’s and Thompson’s Test for Palmaris longus PL were used to check prevalence. By SPSS version 27, statistical analysis was done. Frequencies and percentages were used to show categorical variables. To determine the association of the absence of FDS superficialis with gender, handedness, and agenesis of PL, the Chi-square test was used. A P-value of ≤0.05 was considered as significant.

Five hundred and four limbs were observed for functional agenesis of FDS for the 5th digit and agenesis of PL. Overall, functional agenesis of FDS for the 5th digit was 35.7% while PL agenesis was 33.7%. Functionality of FDS showed highly significant results (p<0.001) depicting variability on two sides in terms of dependent and independent function. When handedness was compared, results were not statistically significant for FDS absence (p=0.73). When agenesis of FDS was compared with PL, results were not statistically significant (p=0.527). Bilateral agenesis of both PL and FDS was 3.2% while unilateral agenesis of both muscles was 10%.

FDS functionality showed variability on two sides in terms of dependent and independent function. Both genders showed a higher prevalence of right-sided agenesis. Females showed more unilateral agenesis while males had higher bilateral prevalence. We found no association between agenesis of the FDS of 5th digit with handedness and PL agenesis.