what is the name of the hip bone

what is the name of the hip bone

The left and proper hip bones (innominate bones, pelvic bones) are two irregularly formed bones that kind a part of the pelvic girdle – the bony construction that attaches the axial skeleton to the decrease limbs.

The hip bones have three primary articulations:

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  • Sacroiliac joint – articulation with the sacrum.
  • Pubic symphysis – articulation between the left and proper hip bones.
  • Hip joint – articulation with the pinnacle of femur.

On this article, we will take a look at the anatomy of the hip bones – their composition, bony landmarks, and medical relevance.

Fig 1 – Overview of the anatomical place of the hip bones.

Composition of the Hip Bone

The hip bone is comprised of the three elements; the ilium, pubis and ischium. Previous to puberty, the triradiate cartilage separates these elements – and fusion solely begins on the age of 15-17.

Collectively, the ilium, pubis and ischium kind a cup-shaped socket often known as the acetabulum (literal that means in Latin is ‘vinegar cup’). The top of the femur articulates with the acetabulum to kind the hip joint.

We will now take a look at the person elements of the hip bone, and their respective bony landmarks.

Fig 2 – The hip bone of a 5 yr previous, with triradiate cartilage nonetheless current.

The Ilium

The ilium is the widest and largest of the three elements of the hip bone, and is situated superiorly. The physique of the ilium types the superior a part of the acetabulum (acetabular roof). Instantly above the acetabulum, the ilium expands to kind the wing (or ala).

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The wing of the ilium has two surfaces:

  • Internal floor – has a concave form, which produces the iliac fossa (website of origin of the iliacus muscle).
  • Exterior floor (gluteal floor) – has a convex form and supplies attachments to the gluteal muscular tissues.

The superior margin of the wing is thickened, forming the iliac crest. It extends from the anterior superior iliac backbone (ASIS) to the posterior superior iliac backbone (PSIS).

On the posterior facet of the ilium there’s an indentation often known as the higher sciatic notch.

Fig 3 – The bony landmarks of the ilium.

Scientific Relevance: Anterior Superior Iliac Backbone

The anterior superior iliac backbone (ASIS) is a crucial anatomical landmark:

  • Mid-inguinal level – midway between the ASIS and the centre of the pubic symphysis. The femoral artery could be palpated right here.
  • Mid-point of the inguinal ligament – midway between the ASIS and the pubic tubercle.

In medical follow, a affected person’s “true” leg size is measured from the ASIS to the medial malleolus on the ankle joint. That is distinct from “obvious” leg size, which is measured from the umbilicus to the medial malleolus.

True leg size discrepancy is a function of varied hip issues, in addition to being a possible complication of hip joint alternative (arthroplasty).


The Pubis

The pubis is essentially the most anterior portion of the hip bone. It consists of a physique, superior ramus and inferior ramus (ramus = department).

  • Pubic physique – situated medially, it articulates with the other pubic physique on the pubic symphysis. Its superior facet is marked by a rounded thickening (the pubic crest), which extends laterally because the pubic tubercle.
  • Superior pubic ramus – extends laterally from the physique to kind a part of the acetabulum.
  • Inferior pubic ramus – tasks in the direction of the ischium.

Collectively, the superior and inferior rami enclose a part of the obturator foramen – via which the obturator nerve, artery and vein cross via to achieve the decrease limb.

Fig 4 – Bony landmarks of the pubis.
Fig 5 – The orientation of the hip bones inside the pelvis.

Scientific Relevance – Pubic Rami Fractures

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Pubic rami fractures can typically be noticed on x-rays in aged sufferers who’re investigated after easy low power falls from standing peak. On this context and offered they’re the one harm a affected person has sustained, these fractures are normally handled with out surgical procedure.

Therapeutic could be anticipated inside 6-8 weeks and sufferers are inspired to totally weight bear straightaway.


The Ischium

The ischium types the posteroinferior a part of the hip bone. Very like the pubis, it’s composed of a physique, an inferior ramus and superior ramus.

The inferior ischial ramus combines with the inferior pubic ramus forming the ischiopubic ramus, which encloses a part of the obturator foramen. The posterorinferior facet of the ischium types the ischial tuberosities and when sitting, it’s these tuberosities on which our physique weight falls.

Close to the junction of the superior ramus and physique is a posteromedial projection of bone; the ischial backbone.

Two essential ligaments connect to the ischium:

  • Sacrospinous ligament – runs from the ischial backbone to the sacrum, thus creating the higher sciatic foramen via which decrease limb neurovasculature (together with the sciatic nerve) transcends.
  • Sacrotuberous ligament – runs from the sacrum to the ischial tuberosity, forming the lesser sciatic foramen.

Fig 6 – Bony landmarks of the ischium.

Scientific Relevance: Pelvic Fractures

There are two broad teams of pelvic fractures:

  • Low power accidents:
    • For instance, a easy fall from standing peak in an osteoporotic affected person leading to pubic rami fracture.
    • These are normally ‘steady’ accidents, not requiring surgical procedure.
  • Excessive power accidents with direct or transmitted trauma:
    • For instance, after a excessive velocity highway visitors accident. These lead to extra in depth fractures which can embrace the acetabulum and sacroiliac joint.
    • These could be ‘unstable’ accidents and should require pressing surgical procedure.
    • Increased power accidents could be related to comfortable tissue and vascular harm. Particularly, the bladder and urethra are at excessive danger of injury. Vascular harm can lead to life threatening haemorrhage.

Within the context of a excessive power main trauma affected person, the pelvis is usually a main supply of bleeding as a result of fracture. Consequently, main trauma sufferers are assumed to have a pelvic fracture till confirmed in any other case and a ‘pelvic binder’ is used to stabilise the pelvis and minimise additional bleeding. Circumferential stress is utilized by the binder on the stage of the higher trochanters – an essential anatomical landmark.

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Fig 7 – X-Ray demonstrating an acetabular fracture (arrow).