Ligament of head of femur

The ligament of the head of the femur (round ligament of the femur, foveal ligament, or Fillmore's ligament) is a weak^[1] ligament located in the hip joint. It is triangular in shape and somewhat flattened. The ligament is implanted by its apex into the anterosuperior part of the fovea capitis femoris and its base is attached by two bands, one into either side of the acetabular notch, and between these bony attachments it blends with the transverse ligament.^[2]

Ligament of head of femur
Left hip-joint, opened by removing the floor of the acetabulum from within the pelvis (Ligament of head of femur labeled as ligt. teres at cente.)
Hip-joint, front view. The capsular ligament has been largely removed (ligament visible at center labeled as ligam teres)
Details
From	Femur head
To	Acetabular notch
Identifiers
Latin	ligamentum capitis femoris, ligamentum teres femoris
MeSH	D000069593
TA98	A03.6.07.010
TA2	1882
FMA	43235
Anatomical terminology [edit on Wikidata]

Anatomy

Development

Initially, the ligament contains a small artery (the acetabular branch of the obturator artery^{[citation needed]}) which becomes obliterated in late childhood.^[3]

Variation

It is ensheathed by the synovial membrane, and varies greatly in strength in different subjects; occasionally only the synovial fold exists, and in rare cases even this is absent.^[2]

Function

The ligament becomes taut when the thigh is both flexed and either adducted or laterally/externally rotated. The ligament is usually too weak to actually function as a ligament^[4] past childhood;^[5] excessive movement at the hip joint is instead primarily limited by the three capsular ligament of the hip joint.^[4] Nevertheless, more recent research suggests the ligament may have a number of functions, including a significant biomechanical role on the basis of cadaveric studies where increases of range of motion were seen after sectioning of the ligament.^[6]

Other animals

It has been suggested that some animals, such as the orangutan and Indian elephant, lack a ligamentum teres.^[7][8] However, the presence of a ligamentum teres, albeit with a morphology different from the human version, has been found upon dissection in both these animals. In the orangutan, it is believed to play a significant role in preventing dislocation of the femoral head within extreme ranges of motion. In the Indian elephant, it is the primary support of the hip joint when the hind limbs are abducted.^[9]

• 
  A human femur head with some synovium attached at the bottom and the ligament of the head of the femur attached at the top. A blue suture wire is drawn through the ligament. Ruler in centimetres at left side.
• 
  Structures surrounding right hip-joint
• 
  Hip joint. Lateral view. Ligament of head of femur

References

This article incorporates text in the public domain from page 336 of the 20th edition of Gray's Anatomy (1918)

1. Palastanga, Nigel; Soames, Roger (2012). Anatomy and Human Movement: Structure and Function. Physiotherapy Essentials (6th ed.). Edinburgh: Churchill Livingstone/Elsevier. p. 290. ISBN 978-0-7020-3553-1.
2. Gray's Anatomy (1918), see infobox
3. Palastanga, Nigel; Soames, Roger (2012). Anatomy and Human Movement: Structure and Function. Physiotherapy Essentials (6th ed.). Edinburgh: Churchill Livingstone/Elsevier. pp. 290–291. ISBN 978-0-7020-3553-1.
4. Palastanga, Nigel; Soames, Roger (2012). Anatomy and Human Movement: Structure and Function. Physiotherapy Essentials (6th ed.). Edinburgh: Churchill Livingstone/Elsevier. pp. 290–291. ISBN 978-0-7020-3553-1.
5. Tan CK, Wong WC (August 1990). "Absence of the ligament of head of femur in the human hip joint". Singapore Medical Journal. 31 (4): 360–3. PMID 2124003.
6. O'Donnell JM, Pritchard M, Salas AP, Singh PJ (July 2014). "The ligamentum teres-its increasing importance". Journal of Hip Preservation Surgery. 1 (1): 3–11. doi:10.1093/jhps/hnu003. PMC 4765261. PMID 27011796.
7. Femur article, Encyclopædia Britannica.
8. Ishida, Hidemi (2006). "Current Thoughts on Terrestrialization in African Apes and the Origin of Human Bipedalism". In Ishida, Hidemi; Tuttle, Russell; Pickford, Martin; Ogihara, Naomichi; Nakatsukasa, Masato (eds.). Human Origins and Environmental Backgrounds. Developments in Primatology: Progress and Prospects. pp. 259–66. doi:10.1007/0-387-29798-7_20. ISBN 9780387296388.
9. Crelin ES (1988). "Ligament of the head of the femur in the orangutan and Indian elephant". Yale J Biol Med. 61 (5): 383–8. PMC 2590443. PMID 3201784.