The origin structure of each finger in the flexor digitorum superficialis muscle



The flexor digitorum superficialis muscle (FDS) is considered the most important of the forearm flexors for maintaining elbow valgus stability. However, the relationships between the origin structure of each finger of the FDS and the anterior oblique ligament (AOL) of the ulnar collateral ligament and the common tendon (CT) in the proximal part, and morphological features are unclear. The purpose of this study was to clarify the relationships between the origin structure of each finger of the FDS and the AOL and the CT, as well as to clarify the morphological features of the muscle belly of each finger of the FDS.


This study examined 20 elbows. The origin of each finger was examined. Muscle mass, muscle fiber bundle length, and the pennation angle of each finger were also measured.


In all cases, the third and fourth digits originated from the radius, the anterior common tendon (ACT), and the posterior common tendon (PCT). The second and fifth digits (18 elbows) or an independent fifth digit (2 elbows) originated from the ACT, the PCT, the AOL, and other soft tissues of the elbow. Muscle mass and muscle fiber bundle length in the muscle belly of the third and fourth digits were significantly heavier and longer, respectively, than in the muscle belly of the second and fifth digits.


Because the second and fifth digits or an independent fifth digit originated from the AOL, their contraction may cause tension in the AOL.

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The authors would like to acknowledge and thank those anonymous individuals who generously donated their bodies and so enabled this study to be performed. This study was supported by a Grant-in-Aid for Scientific Research (19K11358) from the Japan Society for the Promotion of Science (JSPS) and a Grant-in-Aid program from Niigata University of Health and Welfare (H30B05).

Author information




KM: protocol/project development, data collection, data analysis, manuscript, writing/editing. ME: protocol/project development, data collection, data analysis, manuscript writing/editing. MI: data collection, manuscript writing/editing. FK: data collection, manuscript writing/editing. RH: data collection and manuscript writing/editing. IK: protocol/project development, data collection, data analysis, and manuscript writing/editing.

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Correspondence to Kanta Matsuzawa.

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All methods were carried out in accordance with the 1964 Declaration of Helsinki, and all cadavers were legally donated for research purposes to the Nippon Dental University of Life Dentistry at Niigata, Japan.

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Informed consent was obtained from the families of all subjects.

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Matsuzawa, K., Edama, M., Ikezu, M. et al. The origin structure of each finger in the flexor digitorum superficialis muscle. Surg Radiol Anat (2020).

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  • Ulnar collateral ligament
  • Baseball
  • Valgus
  • Anatomy
  • Rehabilitation