New Orleans, LA LSU Health New Orleans anatomists and their colleagues have shown that centuries-old knowledge about the musculature that assists with human walking and running was correct after all. Though the information was known many years earlier, Henry Grays detailed studies of the human thigh in the 1858 Anatomy: Descriptive and Surgical identified the iliopsoas, the most powerful hip flexor, as two separate and distinct muscles. Somewhere along the line, though, that information was simplified and combined in most modern textbooks. Students have been being taught that the two muscles combine into a single tendon that inserts on a bony bump known as the lesser trochanter. Research led by Jayc Sedlmayr, PhD and Emma Schachner, PhD, both associate professors of cell biology and anatomy at LSU Health New Orleans School of Medicine, and their colleagues, found the early anatomists were right. These muscles do not join into a single tendon but attach to very different regions of the lesser trochanter in different ways. Their results are published online in The Anatomical Record, available here.

We did 3D digital modeling comparing the textbook idea of the two muscles inserting as a common tendon and our finding of them inserting separately in different areas, and found it completely changes how each works in flexing the hip, notes Dr. Sedlmayr. The models show that they function independently due to the different attachment sites.

Adds Dr. Schachner, Separate insertions. Separate innervations. Separate muscles. Their fibers interconnect but they have different moment arms in flexion than assumed before.

Besides showing, contrary to previously published descriptions, that the iliacus tendon does not fuse with the psoas tendon, the research team also found that the pectineus, adductor brevis, and magnus muscles have insertions into the lesser trochanter, too. This research makes it clear that the lesser trochanter is more important than previously identified.

They conclude that understanding the real anatomy is key. They conclude that since these muscles can be injured during activities like walking, running, and falls, their rediscovery has important implications about how to correctly approach them clinically.

These findings could also significantly affect our understanding of the evolution of human upright gait and bipedal locomotion, concludes Sedlmayr.

Other members of the research team included Drs Karl T. Bates of the University of Liverpool, and Jonathan J. Wisco of the Boston University School of Medicine.

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LSU Health Sciences Center New Orleans educates Louisiana's health care professionals. The state's flagship health sciences university, LSU Health New Orleans includes a School of Medicine with branch campuses in Baton Rouge and Lafayette, the state's only School of Dentistry, Louisiana's only public School of Public Health, and Schools of Allied Health Professions, Nursing, and Graduate Studies. LSU Health New Orleans faculty take care of patients in public and private hospitals and clinics throughout the region. In the vanguard of biosciences research in a number of areas in a worldwide arena, the LSU Health New Orleans research enterprise generates jobs and enormous economic impact. LSU Health New Orleans faculty have made lifesaving discoveries and continue to work to prevent, advance treatment, or cure disease. To learn more, visit http://www.lsuhsc.edu, http://www.twitter.com/LSUHealthNO, or http://www.facebook.com/LSUHSC.

The Anatomical Record

Observational study

Human tissue samples

Revision of hip flexor anatomy and function in modern humans, and implications for the evolution of hominin bipedalism

26-Sep-2021

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