Ultrasonographical assessment of absence of palmaris longus muscle: a cross-sectional study in the Turkish population

Abstract

Introduction: The palmaris longus is one of the most variable muscles of the human body. The decision of existence of palmaris longus in individuals is often made by clinical tests, but detection of agenesis of this muscle trough ultrasound is rare in literature.Aim: The aim of this study is to evaluate the frequency of the palmaris longus and variations when available in healthy volunteers by ultrasonography.Materials and Methods: In this cross-sectional descriptive study, forearms of 220 healthy volunteers examined by ultrasonography. A physiatrist and a radiologist, both trained in musculoskeletal ultrasound performed all ultrasound evaluations by using a linear probe (7-12 MHz). Volunteers between 18-35 years old, having any acute or chronic disease and having normal sensory examination results, are included to this study.Results: The results of 125 women and 95 men were recorded. The prevalence of bilaterally absence of palmaris longus muscle was 38.9% in our study population. The unilateral presence of palmaris longus mostly on the left side and percentage of unilaterality was 5.55%. The absence of the muscle was found statistically more common in women. No significant difference in palmaris longus agenesis was found for laterality. In addition to these results, we define four different types of palmaris longus muscle shape. Conclusion: In discordance with the literature, the prevalence of the absence of palmaris longus muscle was significantly higher than the previous studies` results. But ultrasound in experienced hands is the gold standard method for detecting the absence of palmaris longus muscle. Also, further studies will be needed in bigger population to define the absence, size, shape and other variations of the palmaris longus muscle.