RESUMO
STUDY DESIGN: A descriptive study of the anatomical characteristics of the upper serratus anterior. OBJECTIVES: To delineate the upper serratus anterior with comparison to classical descriptions of the anatomy of the muscle as a whole. BACKGROUND: Although the serratus anterior has a major role in scapulothoracic stability, description of the separate function and anatomy of the upper, middle, and lower portions of the muscle has been limited. METHODS AND MEASURES: Bilateral anatomical dissection of 8 cadavers (3 female and 5 male) exposed 13 serratus anterior and surrounding structures for review. The number of serrations, attachment sites, length, and girth of the upper serratus anterior were measured. RESULTS: The upper serratus anterior presented with dual serrations and single serrations in 7 (54%) and 6 (46%) of 13 observations, respectively. Attachments to both first and second ribs were noted in 6 (46%) of the 13 observations. The remaining proximal attachments were to the second rib only, the first rib only, and dual attachments to the second and third ribs. In all cases, cranial attachments were to the superior scapular angle blending with the levator scapulae attachment. Length ranged from 4.8 to 9.0 cm (mean +/- SD, 6.9 +/- 1.2 cm). The girth ranged from 3.0 to 8.5 cm (mean +/- SD, 6.1 +/- 1.5 cm). One or more branches of the long thoracic nerve were observed to consistently innervate the upper serratus anterior fibers. CONCLUSION: The upper serratus anterior demonstrated wide variation in anatomy and was noted to be distinct in appearance and peripheral innervation from the middle and lower serratus anterior.