PELVIS
17 .02. 2014
Kaan Yücel
M.D., Ph.D.
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Dr.Kaan Yücel
yeditepeanatomyfhs122.wordpress.com
Pelvis
In common usage, the pelvis (L. basin) is the part of the trunk inferoposterior to the abdomen and is the area
of transition between the trunk and the lower limbs. The bones of the pelvis consist of the right and left pelvic (hip)
bones, the sacrum, and the coccyx.
The pelvic girdle is a basin-shaped ring of bones that connects the vertebral column to the two femora. The
pelvic girdle is strong and rigid, especially compared to the pectoral (shoulder) girdle.
In the mature individual, the pelvic girdle is formed by three bones:
Right and left hip bones (coxal bones; pelvic bones): large, irregularly shaped bones, each of which develops
from the fusion of three bones, the ilium, ischium, and pubis.
Sacrum: formed by the fusion of five, originally separate, sacral vertebrae.
The ilium is the superior, fan-shaped part of the hip bone. The ala iliaca, wing of the ilium represents the
spread of the fan, and the body of the ilium, the handle of the fan.
On its external aspect, the body participates in formation of the acetabulum. The entire superior margin of the ilium
is thickened to form a prominent crest (iliac crest), which is the site of attachment for muscles and fascia of the
abdomen, back, and lower limb and terminates anteriorly as the anterior superior iliac spine and posteriorly as the
posterior superior iliac spine.
The ischium has a body and ramus. The body of the ischium helps form the acetabulum and the ramus of the
ischium forms part of the obturator foramen. The large posteroinferior protuberance of the ischium is the ischial
tuberosity. The small pointed posteromedial projection near the junction of the ramus and body is the ischial spine.
The pubis is an angulated bone with a superior ramus, which helps form the acetabulum, and an inferior
ramus, which helps form the obturator foramen.
The pelvis is divided into greater (false) and lesser (true) pelves by the oblique plane of the pelvic inlet
(superior pelvic aperture). The bony edge (rim) surrounding and defining the pelvic inlet is the pelvic brim.
The pelvic inlet is the circular opening between the abdominal cavity and the pelvic cavity. Through the
pelvic inlet structures traverse between the abdomen and pelvic cavity. It is completely surrounded by bones and
joints. The pelvic outlet is diamond shaped, with the anterior part of the diamond defined predominantly by bone
and the posterior part mainly by ligaments.
The pelvic cavity is a body cavity that is bounded by the bones of the pelvis. Its oblique roof is the pelvic inlet
(the superior opening of the pelvis). Its lower boundary is the pelvic floor. The pelvic cavity primarily contains
reproductive organs, the urinary bladder, the pelvic colon, and the rectum.
The linea terminalis consists of the the arcuate line, the pecten pubis or pectineal line, and the pubic crest. It is part
of the pelvic brim, which is the edge of the pelvic inlet.
The primary joints of the pelvic girdle are the sacroiliac joints and the pubic symphysis. The sacroiliac joints
link the axial skeleton (skeleton of the trunk, composed of the vertebral column at this level) and the inferior
appendicular skeleton (skeleton of the lower limb). The lumbosacral and sacrococcygeal joints, although joints of
the axial skeleton, are directly related to the pelvic girdle. Strong ligaments support and strengthen these joints.
The sacroiliac joints are strong, weight-bearing compound joints, consisting of an anterior synovial joint
(between the earshaped auricular surfaces of the sacrum and ilium, covered with articular cartilage) and a posterior
syndesmosis (between the tuberosities of the same bones). Weight is transferred from the axial skeleton to the ilia
via the sacroiliac ligaments, and then to the femurs during standing, and to the ischial tuberosities during sitting.
The sacrum is actually suspended between the iliac bones and is firmly attached to them by posterior and
interosseous sacroiliac ligaments.
The pubic symphysis is a secondary cartilaginous joint which consists of a fibrocartilaginous interpubic disc
and surrounding ligaments uniting the bodies of the pubic bones in the median plane. The ligaments joining the
bones are thickened at the superior and inferior margins of the symphysis, forming superior and inferior pubic
ligaments.
L5 and S1 vertebrae articulate at the anterior intervertebral (IV) joint formed by the L5/S1 IV disc between
their bodies and at two posterior zygapophysial joints (facet joints) between the articular processes of these
vertebrae as lumbosacral joints.
The sacrococcygeal joint is a secondary cartilaginous joint with an intervertebral disc.
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Pelvis
1. PELVIS
In common usage, the pelvis (L. basin) is the part of the trunk inferoposterior to the abdomen and is
the area of transition between the trunk and the lower limbs. The pelvic cavity is the inferiormost part of the
abdominopelvic cavity. The bones of the pelvis consist of the right and left pelvic (hip) bones, the sacrum, and
the coccyx.
2 PELVIC GIRDLE
The pelvic girdle is a basin-shaped ring of bones that connects the vertebral column to the two femora.
In the mature individual, the pelvic girdle is formed by three bones:
Right and left hip bones (coxal bones; pelvic bones): large, irregularly shaped bones, each of which
develops from the fusion of three bones, the ilium, ischium, and pubis.
Sacrum: formed by the fusion of five, originally separate, sacral vertebrae.
The internal (medial or pelvic) aspects of the hip bones bound the pelvis, forming its lateral walls.
In infants and children, the hip bones consist of three separate bones that are united by a triradiate
cartilage at the acetabulum, the cup-like depression in the lateral surface of the hip bone, which articulates
with the head of the femur. After puberty, the ilium, ischium, and pubis fuse to form the hip bone. The two
hip bones are joined anteriorly at the pubic symphysis (L. symphysis pubis) and articulate posteriorly with the
sacrum at the sacroiliac joints to form the pelvic girdle.
The primary functions of the pelvic girdle are to:
bear the weight of the upper body when sitting and standing.
transfer that weight from the axial to the lower appendicular skeleton for standing and walking.
provide attachment for the powerful muscles of locomotion and posture and those of the abdominal
wall, withstanding the forces generated by their actions.
Consequently, the pelvic girdle is strong and rigid, especially compared to the pectoral (shoulder)
girdle. Other functions of the pelvic girdle are to:
Contain and protect the pelvic viscera (inferior parts of the urinary tracts and the internal reproductive
organs) and the inferior abdominal viscera (intestines), while permitting passage of their terminal parts (and,
in females, a full-term fetus) via the perineum.
Provide support for the abdominopelvic viscera and gravid (pregnant) uterus.
Provide attachment for the erectile bodies of the external genitalia.
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Pelvis
Provide attachment for the muscles and membranes that assist the functions listed above by forming the
pelvic floor and filling gaps that exist in or around it.
Figure 1. Pelvic girdle- hip bones (os coxae) & sacrum
Pelvic girdle –anterior view
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3. HIP (PELVIC) BONES
Each pelvic bone is formed by three elements: the ilium, pubis, and ischium. At birth, these bones are
connected by cartilage in the area of the acetabulum; later, at between 16 and 18 years of age, they fuse into
a single bone.
Pelvic bone (Hip bone) separated by an oblique line on the medial surface
FALSE PELVIS (PELVIS MAJOR, GREATER PELVIS)
pelvic bone above this line lateral wall of the false pelvis.
part of the abdominal cavity
Part of the abdominal cavity
Occupied by abdominal viscera
TRUE PELVIS (PELVIS MINOR, LESSER PELVIS)
contains the pelvic cavity.
major obstetrical and gynecological significance
pelvic bone above this line lateral wall of the true pelvis
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Pelvis
ILIUM
Latin (ile, ilis), meaning "groin-kasık" or "flank-böğür"
Figure 2. Ilium
Acetabulum
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Ala iliaca (Wing of the ilium)
Anterior inferior iliac spine
Anterior superior iliac spine
Auricular surface
Body of the ilium
Greater sciatic notch
Iliac crest
Iliac fossa
Posterior inferior iliac spine
Posterior superior iliac spine
Tuberculum of iliac crest
Of the three components of the pelvic bone, the ilium is the most superior in position. The upper fanshaped part of the ilium is associated on its inner side with the abdomen and on its outer side with the lower
limb.
The ilium is separated into upper and lower parts by a ridge on the medial surface. Anteriorly, the
ridge separating the upper and lower parts of the ilium is rounded and termed the arcuate line (The arcuate
line forms part of the linea terminalis and the pelvic brim).
The portion of the ilium lying inferiorly to the arcuate line is the pelvic part of the ilium and contributes
to the wall of the lesser or true pelvis.
The ala iliaca, wing of the ilium represents the spread of the fan, and the body of the ilium, the handle
of the fan. On its external aspect, the body participates in formation of the acetabulum.
The upper part of the ilium expands to form a flat, fan-shaped "wing," “ala iliaca” provides bony
support for the lower abdomen, or false pelvis. This part of the ilium provides attachment for muscles
functionally associated with the lower limb. The anteromedial surface of the wing is concave and forms the
iliac fossa.
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Pelvis
The entire superior margin of the ilium is thickened to form a prominent crest (iliac crest), which is the
site of attachment for muscles and fascia of the abdomen, back, and lower limb. The iliac crest terminates
anteriorly as the anterior superior iliac spine and posteriorly as the posterior superior iliac spine.
A less prominent posterior inferior iliac spine occurs along the posterior border of the sacral surface of
the ilium, where the bone angles forward to form the superior margin of the greater sciatic notch.
A prominent lateral expansion of the crest just posterior to the anterior superior iliac spine is the
tuberculum of iliac crest. The posterior end of the iliac crest thickens to form the iliac tuberosity.
The anteromedial concave surface of the ala forms the iliac fossa. Posteriorly, the sacropelvic surface
of the ilium features an auricular surface and an iliac tuberosity, for synovial and syndesmotic articulation
with the sacrum, respectively. The anterior inferior iliac spine is on the anterior margin of the ilium, and
below this, where the ilium fuses with the pubis, is a raised area of bone; iliopubic eminence (or iliopectineal
eminence).
ISCHIUM
From the Greek ἰσχίον ischion, meaning “hip”
Figure 3. Ischium
http://www.lollylegs.com/injuries/ischial_tuberosity.aspx
Acetabulum
Body of ischium
Greater sciatic notch
Ischial spine
Ischial tuberosity
Lesser sciatic notch
Obturator foramen
Ramus ossis ischii (ramus of ischium)
The ischium is the posterior and inferior part of the pelvic bone. It has:
a large body that projects superiorly to join with the ilium and the superior ramus of the pubis; and
a ramus (L. branch) that projects anteriorly to join with the inferior ramus of the pubis.
The body of the ischium helps form the acetabulum and the ramus of the ischium forms part of the
obturator foramen.
The most prominent feature of the ischium is a large tuberosity; ischial tuberosity on the
posteroinferior aspect of the bone. This tuberosity is an important site for the attachment of lower limb
muscles and for supporting the body when sitting. The small pointed posteromedial projection near the
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Pelvis
junction of the ramus and body is the ischial spine. The concavity between the ischial spine and the ischial
tuberosity is the lesser sciatic notch. The larger concavity, the greater sciatic notch, is superior to the ischial
spine and is formed in part by the ilium.
PUBIS
from Latin pubes "genital area, groin," related to pubes "full-grown"
Figure 4. Pubis
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Acetabulum
Inferior ramus of pubis
Obturator foramen/groove
Pecten pubis (pectineal line of pubis)
Pubic crest
Pubic tubercle
Superior ramus of pubis
The anterior and inferior part of the pelvic bone is the pubis. It has a body and two arms (rami).
The pubis is an angulated bone with a superior ramus, which helps form the acetabulum, and an
inferior ramus, which helps form the obturator foramen. A thickening on the anterior part of the body of the
pubis is the pubic crest, which ends laterally as a prominent swelling; pubic tubercle. The lateral part of the
superior pubic ramus has an oblique ridge; pecten pubis (pectineal line of pubis). The superior pubic ramus is
marked on its inferior surface by the obturator groove, which forms the upper margin of the obturator canal.
Figure 4. Hip bones
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Pelvis
4. PELVIC INLET & PELVIC OUTLET
The pelvis is divided into greater (false) and lesser (true) pelves by the oblique plane of the pelvic inlet
(superior pelvic aperture). The bony edge (rim) surrounding and defining the pelvic inlet is the pelvic brim,
formed by the:
Promontory and ala of the sacrum (superior surface of its lateral part, adjacent to the body of the
sacrum).
A right and left linea terminalis (terminal line)
The pubic arch is formed by the ischiopubic rami (conjoined inferior rami of the pubis and ischium) of
the two sides. These rami meet at the pubic symphysis, their inferior borders defining the subpubic angle. The
width of the subpubic angle is determined by the distance between the right and the left ischial tuberosities,
which can be measured with the gloved fingers in the vagina during a pelvic examination.
PELVIC INLET (SUPERIOR PELVIC APERTURE)
The pelvic inlet is the circular opening between the abdominal cavity and the pelvic cavity. Through
the pelvic inlet structures traverse between the abdomen and pelvic cavity. It is completely surrounded by
bones and joints.
The pelvic inlet is formed:
anteriorly by the pubic symphysis
posteriorly by the sacrum
laterally by the iliopectineal line
The promontory of the sacrum protrudes into the inlet, forming its posterior margin in the midline.
PELVIC OUTLET (INFERIOR PELVIC APERTURE)
The pelvic outlet is diamond shaped, with the anterior part of the diamond defined predominantly by
bone and the posterior part mainly by ligaments.
Anatomical outlet is bounded by;
pubic arch,anteriorly
ischial tuberosities, laterally
sacrotuberous and sacrospinous ligaments, posterolaterally
tip of the coccyx, posteriorly
Obstetric outlet is bounded by:
the roof is the plane of least pelvic dimension,
the floor is the anatomical outlet,
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Pelvis
anteriorly the lower border of symphysis pubis,
posteriorly the coccyx.
laterally the ischial spines.
The greater pelvis (false pelvis) is the part of the pelvis:
Superior to the pelvic inlet.
Bounded by the iliac alae posterolaterally and the anterosuperior aspect of the S1 vertebra posteriorly.
Occupied by abdominal viscera (e.g., the ileum and sigmoid colon).
The lesser pelvis (true pelvis) is the part of the pelvis:
Between the pelvic inlet and the pelvic outlet.
Has an inlet, an outlet, and a cavity.
The pelvic inlet is bounded posteriorly by the sacral promontory, laterally by the iliopectineal lines, and
anteriorly by the symphysis pubis.
Bounded by the pelvic surfaces of the hip bones, sacrum, and coccyx.
That is of major obstetrical and gynecological significance.
PELVIC CAVITY
The pelvic cavity is a body cavity that is bounded by the bones of the pelvis. Its oblique roof is the
pelvic inlet (the superior opening of the pelvis). Its lower boundary is the pelvic floor. The pelvic cavity
primarily contains reproductive organs, the urinary bladder, the pelvic colon, and the rectum.
It is a segment, the boundaries of which are:
the roof is the plane of pelvic brim,
the floor is the plane of least pelvic dimension,
anteriorly the shorter symphysis pubis,
posteriorly the longer sacrum.
The terms pelvis, lesser pelvis, and pelvic cavity are commonly used incorrectly, as if they were
synonymous terms.
The linea terminalis consists of the the arcuate line, the pecten pubis or pectineal line, and the pubic
crest. It is part of the pelvic brim, which is the edge of the pelvic inlet. The pecten pubis forms part of the
pelvic brim and the continuation on the superior ramus pubis of the linea terminalis, forming a sharp ridge.
The arcuate line of the ilium is a smooth rounded border on the internal surface of the ilium. It is immediately
inferior to the iliac fossa. It forms part of the border of the pelvic inlet. The pecten pubis forms part of the
pelvic brim.
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Figure 5. Pelvic inlet & outlet
Pelvis
Figure 6. Pelvic cavity, lesser (true) pelvis and greater (false) pelvis
http://kullamilowski.files.wordpress.com/2012/08/pelvic-cavity.jpeg
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VARIATIONS IN MALE AND FEMALE PELVES
The pelvic girdles of males and females differ in several respects. These sexual differences are related
mainly to the heavier build and larger muscles of most men and to the adaptation of the pelvis (particularly
the lesser pelvis) in women for parturition (childbearing).
Although anatomical differences between male and female pelves are usually clear cut, the pelvis of
any person may have some features of the opposite sex. The gynecoid pelvis is the normal female type; its
pelvic inlet typically has a rounded oval shape and a wide transverse diameter. An android (masculine or
funnel-shaped) pelvis in a woman may present hazards to successful vaginal delivery of a fetus.
In forensic medicine (the application of medical and anatomical knowledge for the purposes of law),
identification of human skeletal remains usually involves the diagnosis of sex. A prime focus of attention is the
pelvic girdle because sexual differences usually are clearly visible. Even fragments of the pelvic girdle are
useful in determining sex.
1) The pelvic inlet in women is circular in shape compared with the heart-shaped pelvic inlet in men. The
more circular shape is partly caused by the less distinct promontory and broader alae in women.
2) The angle formed by the two arms of the pubic arch is larger in women (80-85°) than it is in men (50-60°).
3) The ischial spines generally do not project as far medially into the pelvic cavity in women as they do in
men.
In 1933, Caldwell and Moloy classified pelves into four groups: gynecoid, android, anthropoid, and
platypelloid.
a. Gynecoid type is present in about 41% of women, the typical female pelvis
b. Android type is the male or funnel-shaped pelvis with a contracted outlet.
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c. Anthropoid type is long, narrow, and oval shaped.
d. Platypelloid type is present in only about 2% of women, is a wide pelvis flattened at the brim, with the
promontory of the sacrum pushed forward.
Figure 11. Male and female pelves
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PELVIC DIAMETERS (CONJUGATES)
The size of the lesser pelvis is particularly important in obstetrics because it is the bony canal through
which the fetus passes during a vaginal birth. To determine the capacity of the female pelvis for childbearing,
the diameters of the lesser pelvis are noted radiographically or manually during a pelvic examination.
Diameters of pelvic outlet
Antero - posterior diameters
Anatomical antero-posterior diameter
Obstetric antero-posterior diameter
Transverse diameters
Bituberous diameter
Bispinous diameter
Diameters of pelvic inlet
Antero -posterior diameters
Anatomical antero-posterior diameter (true conjugate) = 11cm
from the tip of the sacral promontory to the upper border of the symphysis pubis
Obstetric conjugate = 10.5 cm
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from the tip of the sacral promontory to the most bulging point on the back of symphysis pubis which is about 1 cm below its upper border. It
is the shortest antero-posterior diameter
Diagonal conjugate = 12.5 cm
i.e. 1.5 cm longer than the true conjugate. From the tip of sacral promontory to the lower border of symphysis pubis (or inferior pubic
ligament)
Transverse diameters
Anatomical transverse diameter
Obstetric transverse diameter
Oblique diameters
Right oblique diameter
Left oblique diameter
The minimum anteroposterior (AP) diameter of the lesser pelvis, the true (obstetrical) conjugate –
conjugata vera-, is the narrowest fixed distance through which the baby's head must pass in a vaginal delivery.
This distance, however, cannot be measured directly during a pelvic examination because of the presence of
the bladder. Consequently, the diagonal conjugate (from inferior pubic lig. to promontory) is measured by
palpating the sacral promontory with the tip of the middle finger, using the other hand to mark the level of
the inferior margin of the pubic symphysis on the examining hand. After the examining hand is withdrawn,
the distance between the tip of the index finger (1.5 cm shorter than the middle finger) and the marked level
of the pubic symphysis is measured to estimate the true conjugate, which should be 11.0 cm or greater.
During a pelvic examination, if the ischial tuberosities are far enough apart to permit three fingers to
enter the vagina side by side, the subpubic angle is considered sufficiently wide to permit passage of an
average fetal head at full term.
Anatomy for Forceps http://emedicine.medscape.com/article/263603-overview#a04
http://www.gfmer.ch/Obstetrics_simplified/anatomy_of_the_female_pelvis.htm
Figure 12. Pelvic conjugates
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