The Pelvic Girdle and Pelvic Fractures
by Robert Tallitsch, PhD | April 14, 2022
Video with Real 3D Visualizations of the Pelvic Girdle and a Multi-fractured Pelvis + Patient Case Example!
Written by: Robert Tallitsch, PhD
The adult pelvic girdle is composed of the paired pubic, ischial, and iliac bones. Closely associated with the pelvic girdle is the sacrum, which is joined to the pelvic girdle at the sacro-iliac joint.
The bones of the pelvic girdle develop independently by endochondral (intracartilaginous) ossification. Fusion of the ossification centers within these bones begins between 15 to 17 years of age and is typically complete between 20 to 25 years of age.
The right and left pubic, ischial, and iliac bones all contribute to the formation of the acetabulum on each side of the pelvic girdle. The acetabulum is a large articular socket that participates in the formation of the hip joint with the femur.
The pubis forms the anteroinferior parts of the pelvis. The two pubic bones join anteriorly at the pubic symphysis. During delivery and under the influence of hormones, the joints of the pelvis, including the pubic symphysis, loosen, thereby allowing passage of the fetus through the birth canal. Other conspicuous parts of the pubic bones are:
- anterior and inferior pubic rami
- pubic crest
- pubic tubercle
- body of the pubis
The paired iliac bones form the superior element of the pelvic girdle. The lateral projection of each ilium forms the wing (ala) of the ilium. The smooth inner and outer surfaces of each wing serve as attachment sites for muscles of the lower limb. Other conspicuous parts of each ilium are:
- iliac crest
- anterior superior and inferior iliac spines (ASIS)
- posterior superior and inferior iliac spines (PSIS)
- greater sciatic notch
- lesser sciatic notch
The ischium forms the most posterior portion of the right and left halves of the pelvic girdle. Conspicuous parts of each ischium are:
- ischial tuberosity
- ischial ramus
- obturator foramen
- ischial spine
The sacrum is typically composed of 5 sacral vertebrae. These vertebrae begin to fuse at puberty and are completely fused between the ages of 25 to 30. Complete fusion of these vertebrae forms the sacrum. Each sacro-iliac joint is formed at the articulation of the sacrum and the right and left iliac bones. This joint possesses a very small joint cavity and several very strong ligaments connect the sacrum to the two lateral iliac bones.
Fractures to the bones of the pelvic girdle are termed pelvic fractures. Often times a fracture of the neck, trochanters, or head of the femur is termed a hip fracture, which is anatomically incorrect. These types of fractures are actually femoral fractures.
Pelvic fractures are often the result of any number of injuries. The most common causes of pelvic fractures are:
- anteroposterior compression of the pelvis
- lateral compression of the pelvis
- crushing injuries to one or more bones of the pelvis
- forces transmitted to the pelvic bones through the lower limbs as a result of a fall onto the feet
The pelvic bones, like any other bones of the body, have areas of weakness that are more susceptible to injury. Areas of weakness include the pubic rami, pubic symphysis, areas immediately surrounding the acetabula, the sacro-iliac joint, and the wing of the ilium.
Pelvic fractures may also cause injuries to soft tissues associated with the pelvis, such as pelvic organs, nerves, and blood vessels.
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Pelvic girdle - The structure formed by the paired iliac, ischial, and pubic bones.
Pubic symphysis - The joint formed by the union of the right and left pubic bones of the pelvic girdle.
Acetabulum - A structure formed by the union of the ilium, ischium, and pubic bones of the pelvic girdle.
Ischium - One of the bones of the pelvis that forms the most posterior portion of the right and left halves of the pelvic girdle.
Ala - Another term for the wing of the ilium.
Anteroposterior compression - Compression to a part of the body oriented from the anterior to the posterior surfaces.
Femoral fracture - A fracture to any part of the femur. Fractures of the head, neck, and/or trochanters of the femur are often (and incorrectly so) referred to as hip fractures.
- At what age do the various endochondral ossification centers of the bones of the pelvic girdle begin to fuse?
A: 15 to 17 years of age
- What is the anatomical term of the joint formed by the union of the right and left pubic bones?
A: Pubic symphysis
- The smooth internal and external surfaces of the wings of the ilium serve as attachment sites for what other structures?
A: Muscles of the lower limbs
- What is the name of the structure that participates with the femur in the formation of the hip joint?
- How many vertebrae fuse together to form the sacrum?
A: Typically five
- What bones contribute to the formation of acetabulum?
A: The right and left pubic, ischial, and iliac bones all contribute to the formation of the acetabulum on each side of the pelvic girdle.
- Which pelvic bones have “wings”?
A: The paired iliac bones or the ilium
- The bones of the pelvic girdle are formed through what process?
A: Endochondral Ossification
- What joint attaches the sacrum to the pelvis?
A: Sacro-iliac joint
- Name three areas of weakness within the pelvic girdle.
A: Any three of the following areas of weakness would be correct:
Wing of the ilium
Acetabulum (acetabuli is the pleural term)
Areas surrounding the acetabuli
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