Download Dr. Kaan Yücel http://yeditepeanatomy1.wordpress.com Yeditepe

Dr. Kaan Yücel
http://yeditepeanatomy1.wordpress.com
Yeditepe Anatomy
8. December.2011 Thursday
Joints of the Vertebral Column
The joints of the vertebral column include the:
1) Joints of the vertebral bodies
2) Joints of the vertebral arches
3) Craniovertebral (atlanto-axial and atlanto-occipital) joints
4) Costovertebral joints
5) Sacroiliac joints
A typical vertebra has a total of six joints with adjacent vertebrae, four synovial joints (two above and
two below) and two symphyses (one above and one below). Each symphysis includes an intervertebral disc.
1. JOINTS OF VERTEBRAL BODIES
The joints of the vertebral bodies are symphyses (secondary cartilaginous joints) designed for weightbearing and strength. The articulating surfaces of adjacent vertebrae are connected by intervertebral discs and
ligaments
The intervertebral disc consists of an outer anulus fibrosus, which surrounds a central nucleus pulposus.
The anulus fibrosus consists of an outer ring of collagen surrounding a wider zone of fibrocartilage arranged in
a lamellar configuration. This arrangement of fibers limits rotation between vertebrae.
The nucleus pulposus (L. pulpa, fleshy) is the core of the intervertebral disc. The nucleus pulposus fills the
center of the intervertebral disc, is gelatinous, and absorbs compression forces between vertebrae. At birth,
these pulpy nuclei are about 88% water and are initially more cartilaginous than fibrous. Their semifluid nature
is responsible for much of the flexibility and resilience of the intervertebral disc and of the vertebral column as
a whole.
The intervertebral discs provide strong attachments between the vertebral bodies, uniting them into a
continuous semirigid column and forming the inferior half of the anterior border of the intervertebral foramen.
In aggregate, the discs account for 20-25% of the length (height) of the vertebral column.
There is no intervertebral disc between C1 and C2 vertebrae; the most inferior functional disc is between L5
and S1 vertebrae. The discs vary in thickness in different regions. The thickness of the discs increases as the
vertebral column descends. However, their thickness relative to the size of the bodies they connect is most
clearly related to the range of movement, and relative thickness is greatest in the cervical and lumbar regions,
where the movements of the vertebral column are greatest. Their thickness is most uniform in the thoracic
region. The discs are thicker anteriorly in the cervical and lumbar regions, their varying shapes producing the
secondary curvatures of the vertebral column.
Function of the Intervertebral Discs
The semifluid nature of the nucleus pulposus allows it to change shape and permits one vertebra to rock
forward or backward on another, as in flexion and extension of the vertebral column.
A sudden increase in the compression load on the vertebral column causes the semifluid nucleus pulposus to
become flattened. The outward pushing of the nucleus is accommodated by the resilience of the surrounding
anulus fibrosus. Sometimes, the outward push is too great for the anulus fibrosus and it ruptures, allowing the
nucleus pulposus to herniate and protrude into the vertebral canal, where it may press on the spinal nerve roots,
the spinal nerve, or even the spinal cord.
With advancing age, the water content of the nucleus pulposus diminishes and is replaced by fibrocartilage. The
collagen fibers of the anulus degenerate and, as a result, the anulus cannot always contain the nucleus pulposus
under stress. In old age the discs are thin and less elastic, and it is no longer possible to distinguish the nucleus
from the anulus.
2. JOINTS OF VERTEBRAL ARCHES (Zygapophysial joints)
The joints of the vertebral arches; the zygapophysial joints are often called facet joints. These
articulations are plane synovial joints between the superior and inferior articular processes (G.
zygapophyses) of adjacent vertebrae. A thin articular capsule attached to the margins of the articlar facets
encloses each joint. Those in the cervical region are especially thin and loose, reflecting the wide range of
http://www.youtube.com/yeditepeanatomy
1
Dr. Kaan Yücel
http://yeditepeanatomy.wordpress.com
Yeditepe Anatomy
movement. Accessory ligaments unite the laminae, transverse processes, and spinous processes and help
stabilize the joints.
The zygapophysial joints permit gliding movements between the articular processes; the shape and
disposition of the articular surfaces determine the types of movement possible. The range (amount) of
movement is determined by the size of the intervertebral disc relative to that of the vertebral body. In the
cervical and lumbar regions, these joints bear some weight, sharing this function with the intervertebral discs,
particularly during lateral flexion.
"Uncovertebral" joints
The lateral margins of the upper surfaces of typical cervical vertebrae are elevated into crests or lips
termed uncinate processes. These may articulate with the body of the vertebra above to form small
"uncovertebral" synovial joints.
Uncovertebral “joints” or clefts (of Luschka) commonly develop between the unci of the bodies of C3 or
4-C6 or 7 vertebrae and the inclined inferolateral surfaces of the vertebral bodies superior to them after 10 years
of age. The joints are at the lateral and posterolateral margins of the intervertebral discs. They are considered
synovial joints by some; others consider them to be degenerative spaces (clefts) in the discs occupied by
extracellular fluid.
LIGAMENTS
Joints between vertebrae are reinforced and supported by numerous ligaments, which pass between
vertebral bodies and interconnect components of the vertebral arches.
Anterior and posterior longitudinal ligaments
The anterior and posterior longitudinal ligaments are on the anterior and posterior surfaces of the vertebral
bodies and extend along most of the vertebral column.
The anterior longitudinal ligament is attached superiorly to the base of the skull and extends inferiorly
to attach to the anterior surface of the sacrum. Along its length it is attached to the vertebral bodies and
intervertebral discs.
The posterior longitudinal ligament is on the posterior surfaces of the vertebral bodies and lines the
anterior surface of the vertebral canal. Like the anterior longitudinal ligament, it is attached along its length to
the vertebral bodies and intervertebral discs. The upper part of the posterior longitudinal ligament that connects
C2to the intracranial aspect of the base of the skull is termed the tectorial membrane.
Ligamenta flava
The ligamenta flava, on each side, pass between the laminae of adjacent vertebrae. These thin, broad
ligaments consist predominantly of elastic tissue and form part of the posterior surface of the vertebral canal.
Each ligamentum flavum runs between the posterior surface of the lamina on the vertebra below to the anterior
surface of the lamina of the vertebra above. The ligamenta flava resist separation of the laminae in flexion and
assist in extension back to the anatomical position.
Supraspinous ligament and ligamentum nuchae
The supraspinous ligament connects and passes along the tips of the vertebral spinous processes from
vertebra C7 to the sacrum. From vertebra C7 to the skull, the ligament becomes structurally distinct from more
caudal parts of the ligament and is called the ligamentum nuchae.
The ligamentum nuchae is a triangular, sheet-like structure in the median sagittal plane:
 base of the triangle is attached to the skull, from the external occipital protuberance to the foramen magnum;
 apex is attached to the tip of the spinous process of vertebra C7;
 deep side of the triangle is attached to the posterior tubercle of vertebra C1 and the spinous processes of the
other cervical vertebrae.
The ligamentum nuchae supports the head. It resists flexion and facilitates returning the head to the anatomical
position. The broad lateral surfaces and the posterior edge of the ligament provide attachment for adjacent
muscles.
Interspinous ligaments
Interspinous ligaments pass between adjacent vertebral spinous processes. They attach from the base to
the apex of each spinous process and blend with the supraspinous ligament posteriorly and the ligamenta flava
anteriorly on each side.
3. CRANIOVERTEBRAL JOINTS
http://www.youtube.com/yeditepeanatomy
2
Dr. Kaan Yücel
http://yeditepeanatomy1.wordpress.com
Yeditepe Anatomy
There are two sets of craniovertebral joints, the atlanto-occipital joints, formed between the atlas (C1
vertebra), and the occipital bone of the cranium, and the atlanto-axial joints, formed between the atlas and
axis (C2 vertebra). The craniovertebral joints are synovial joints that have no intervertebral discs. Their design
gives a wider range of movement than in the rest of the vertebral column. The articulations involve the occipital
condyles, atlas, and axis.
Atlanto-occipital Joints
The articulations are between the superior articular surfaces of the lateral masses of the atlas and the
occipital condyles. They are synovial joints of the condyloid type and have thin, loose joint capsules. The
atlanto-occipital joints are synovial joints of the condyloid type and have thin, loose joint capsules.These joints
permit nodding of the head, such as the flexion and extension of the head occurring when indicating approval
(the “yes” movement). These joints also permit sideways tilting of the head. The main movement is flexion,
with a little lateral flexion and rotation.
The cranium and C1 are also connected by anterior and posterior atlanto-occipital membranes, which
extend from the anterior and posterior arches of C1 to the anterior and posterior margins of the foramen
magnum. The atlanto-occipital membranes help prevent excessive movement of the atlanto-occipital joints.
Ligaments
Anterior atlanto-occipital membrane: This is a continuation of the anterior longitudinal ligament, which runs
as a band down the anterior surface of the vertebral column. The membrane connects the anterior arch of the
atlas to the anterior margin of the foramen magnum.
Posterior atlanto-occipital membrane: This membrane is similar to the ligamentum flavum and connects the
posterior arch of the atlas to the posterior margin of the foramen magnum.
Atlanto-axial Joints
There are three atlanto-axial articulations: two (right and left) lateral atlantoaxial joints (between the
inferior facets of the lateral masses of C1 and the superior facets of C2), and one median atlantoaxial joint
(between the dens of C2 and the anterior arch of the atlas). The lateral atlanto-axial joints are gliding-type
synovial joints, whereas the median atlanto-axial joint is a pivot joint.
Movement at all three atlanto-axial joints permits the head to be turned from side to side, as occurs
when rotating the head to indicate disapproval (the “no” movement). During this movement, the cranium and
C1 rotate on C2 as a unit. During rotation of the head, the dens of C2 is the axis or pivot that is held in a socket
or collar formed anteriorly by the anterior arch of the atlas and posteriorly by the transverse ligament of the
atlas, a strong band extending between the tubercles on the medial aspects of the lateral masses of C1 vertebrae.
Ligaments
Superior and inferior longitudinal bands pass from the transverse ligament to the occipital bone superiorly
and to the body of C2 inferiorly.
Apical ligament: This median-placed structure connects the apex of the odontoid process to the anterior
margin of the foramen magnum.
Alar ligaments: These lie one on each side of the apical ligament and connect the odontoid process to the
medial sides of the occipital condyles. The alar ligaments attach the cranium to the C1 vertebra and act as
check ligaments in preventing excessive rotation at the joints.
Cruciate ligament: The cruciate ligament of the atlas, so named because of its resemblance to a cross,
consists of the transverse ligament of the atlas plus the longitudinal (vertical) bands.T he transverse part is
attached on each side to the inner aspect of the lateral mass of the atlas and binds the odontoid process to the
anterior arch of the atlas. The vertical part runs from the posterior surface of the body of the axis to the anterior
margin of the foramen magnum.
Tectorial membrane (Membrana tectoria): The tectorial membrane is the strong superior continuation of
the posterior longitudinal ligament that broadens and passes posteriorly over the median atlantoaxial joint and
its ligaments. It runs superiorly from the body of C2 through the foramen magnum to attach to the central part
of the floor of the cranial cavity, formed by the internal surface of the occipital bone. It covers the posterior
surface of the odontoid process and the apical, alar, and cruciate ligaments.
Movements of the Vertebral Column
http://www.youtube.com/yeditepeanatomy
3
Dr. Kaan Yücel
http://yeditepeanatomy.wordpress.com
Yeditepe Anatomy
The range of movement of the vertebral column varies according to the region and the individual. The
mobility of the vertebral column results primarily from the compressibility and elasticity of the intervertebral
discs. The normal range of movement possible in healthy young adults is typically reduced by 50% or more as
they age.
Although the movement between any two vertebrae is limited, the summation of movement among all
vertebrae results in a large range of movement by the vertebral column.
Movements by the vertebral column include flexion, extension, lateral flexion, rotation, and
circumduction. Movements by vertebrae in a specific region (cervical, thoracic, and lumbar) are determined by
the shape and orientation of joint surfaces on the articular processes and on the vertebral bodies.
The range of movement of the vertebral column is limited by the:
 Thickness, elasticity, and compressibility of the IV discs
 Shape and orientation of the zygapophysial joints
 Tension of the joint capsules of the zygapophysial joints
 Resistance of the back muscles and ligaments (e.g., the ligamenta flava and the posterior longitudinal
ligament)
 Attachment to the thoracic (rib) cage
 Bulk of surrounding tissue.
Clinical Notes
Disc Hernia & Back Pain
A tear can occur within the anulus fibrosus through which the material of the nucleus pulposus can
track. After a period of time, this material may track into the vertebral canal or into the intervertebral foramen
to impinge on neural structures. This is a common cause of back pain.
Discectomy/laminectomy
A prolapsed intervertebral disc may impinge upon the meningeal (thecal) sac, cord, and most commonly
the nerve root, producing symptoms attributable to that level. In some instances the disc protrusion will undergo
a degree of involution that may allow symptoms to resolve without intervention. In some instances pain, loss of
function, and failure to resolve may require surgery to remove the disc protrusion.
There are a number of ways in which the surgeon may approach the disc within the vertebral canal, and
there are a number of procedures that can be performed to relieve the patient's symptoms.
It is of the utmost importance that the level of the disc protrusion is identified before surgery. This may
require MRI scanning and on-table fluoroscopy to prevent operating on the wrong level. In some instances
removal of the lamina will increase the potential space and may relieve symptoms. Some surgeons perform a
small fenestration (windowing) within the ligamentum flavum. This provides access to the canal. The
meningeal sac and its contents are gently retracted, exposing the nerve root and the offending disc. The disc is
dissected free, removing its effect on the nerve root and the canal.
PELVIS
Introduction to 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 pelvis is subdivided into greater and lesser pelves. The greater pelvis is surrounded by the superior
pelvic girdle. The greater pelvis is occupied by inferior abdominal viscera, affording them protection similar to
the way the superior abdominal viscera are protected by the inferior thoracic cage. The lesser pelvis is
surrounded by the inferior pelvic girdle, which provides the skeletal framework for both the pelvic cavity and
the perineum—compartments of the trunk separated by the musculofascial pelvic diaphragm.
PELVIC GIRDLE
The pelvic girdle is a basin-shaped ring of bones that connects the vertebral column to the two femurs. 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.
http://www.youtube.com/yeditepeanatomy
4
Dr. Kaan Yücel
http://yeditepeanatomy1.wordpress.com
Yeditepe Anatomy
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.
 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.
The pelvic bone is irregular in shape and has two major parts separated by an oblique line on the medial surface
of the bone:
 the pelvic bone above this line represents the lateral wall of the false pelvis, which is part of the
abdominal cavity;
 the pelvic bone below this line represents the lateral wall of the true pelvis, which contains the pelvic
cavity.
The linea terminalis is the lower two-thirds of this line and contributes to the margin of the pelvic inlet.
Bones and Features of Pelvic 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 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.
Ilium
The ilium is the superior, fan-shaped part of the hip bone. The ala, or 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 iliac crest which is the rim of the fan has a curve that
follows the contour of the ala between the anterior and posterior superior iliac spines.
A prominent tubercle, tuberculum of iliac crest, projects laterally near the anterior end of the crest; the
posterior end of the crest thickens to form the iliac tuberosity.
Inferior to the anterior superior iliac spine of, on the anterior margin of the ilium, is a rounded protuberance
called the anterior inferior 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.
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. Medial to the anterior inferior iliac spine is a broad, shallow groove which is bounded
medially by the iliopubic eminence (or iliopectineal eminence), which marks the point of union of the ilium
and pubis. It constitutes a lateral border of the pelvic inlet.The iliopectineal line is the border of the eminence.
Ischium
The ischium has a body and ramus (L. branch). 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 concavity between the ischial spine and the ischial tuberosity is the lesser
http://www.youtube.com/yeditepeanatomy
5
Dr. Kaan Yücel
http://yeditepeanatomy.wordpress.com
Yeditepe Anatomy
sciatic notch. The larger concavity, the greater sciatic notch, is superior to the ischial spine and is formed in
part by the ilium.
Pubis
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, the pubic tubercle. The lateral part of the superior pubic
ramus has an oblique ridge, the pecten pubis (pectineal line of pubis).
The lateral surface of the pelvic bone has a large articular socket, the acetabulum, which, together with the
head of the femur, forms the hip joint.
Inferior to the acetabulum is the large obturator foramen, most of which is closed by a flat connective tissue
membrane, the obturator membrane. A small obturator canal remains open superiorly between the membrane
and adjacent bone, providing a route of communication between the lower limb and the pelvic cavity.
The posterior margin of the pelvic bone is marked by two notches separated by the ischial spine:
 greater sciatic notch;
 lesser sciatic notch.
The posterior margin terminates inferiorly as the large ischial tuberosity.
The irregular anterior margin of the pelvic bone is marked by the anterior superior iliac spine, the anterior
inferior iliac spine, and the pubic tubercle.
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 which
structures traverse between the abdomen and pelvic cavity. It is completely surrounded by bones and joints. The
promontory of the sacrum protrudes into the inlet, forming its posterior margin in the midline. The pelvic inlet
is formed anteriorly by the pubic symphysis, posteriorly by the sacrum, and laterally by the iliopectineal line.
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,
 anteriorly the lower border of symphysis pubis,
 posteriorly the coccyx.
 laterally the ischial spines.
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 greater pelvis (false pelvis) is the part of the pelvis:
http://www.youtube.com/yeditepeanatomy
6
Dr. Kaan Yücel
http://yeditepeanatomy1.wordpress.com
Yeditepe Anatomy
 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
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.
Joints and Ligaments of Pelvic Girdle
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.
SACROILIAC 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). The sacroiliac joints differ from most
synovial joints in that limited mobility is allowed, a consequence of their role in transmitting the weight of most
of the body to the hip 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. As long as tight apposition is maintained
between the articular surfaces, the sacroiliac joints remain stable. Unlike a keystone at the top of an arch, the
sacrum is actually suspended between the iliac bones and is firmly attached to them by posterior and
interosseous sacroiliac ligaments.
The thin anterior sacroiliac ligaments are merely the anterior part of the fibrous capsule of the
synovial part of the joint. The abundant interosseous sacroiliac ligaments (lying deep between the tuberosities
of the sacrum and ilium) are the primary structures involved in transferring the weight of the upper body from
the axial skeleton to the two ilia of the appendicular skeleton.
The posterior sacroiliac ligaments are the posterior external continuation of the same mass of fibrous
tissue. Because the fibers of the interosseous and posterior sacroiliac ligaments run obliquely upward and
outward from the sacrum, the axial weight pushing down on the sacrum actually pulls the ilia inward (medially)
so that they compress the sacrum between them, locking the irregular but congruent surfaces of the sacroiliac
joints together. The iliolumbar ligaments are accessory ligaments to this mechanism.
Inferiorly, the posterior sacroiliac ligaments are joined by fibers extending from the posterior margin of
the ilium (between the posterior superior and posterior inferior iliac spines) and the base of the coccyx to form
http://www.youtube.com/yeditepeanatomy
7
Dr. Kaan Yücel
http://yeditepeanatomy.wordpress.com
Yeditepe Anatomy
the massive sacrotuberous ligament. This ligament passes from the posterior ilium and lateral sacrum and
coccyx to the ischial tuberosity, transforming the sciatic notch of the hip bone into a large sciatic foramen. The
sacrospinous ligament, passing from lateral sacrum and coccyx to the ischial spine, further subdivides this
foramen into greater and lesser sciatic foramina. The sacrospinous and sacrotuberous ligaments are major
components of the lateral pelvic walls that help define the apertures between the pelvic cavity and adjacent
regions through which structures pass.
Most of the time, movement at the sacroiliac joint is limited by interlocking of the articulating bones and
the sacroiliac ligaments to slight gliding and rotary movements. By allowing only slight upward movement of
the inferior end of the sacrum relative to the hip bones, resilience is provided to the sacroiliac region when the
vertebral column sustains sudden increases in force or weight.
PUBIC SYMPHYSIS
This secondary cartilaginous joint consists of a fibrocartilaginous interpubic disc and surrounding
ligaments uniting the bodies of the pubic bones in the median plane. The interpubic disc is generally wider in
women. The ligaments joining the bones are thickened at the superior and inferior margins of the symphysis,
forming superior and inferior pubic ligaments. The superior pubic ligament connects the superior aspects
of the pubic bodies and interpubic disc, extending as far laterally as the pubic tubercles. The inferior (arcuate)
pubic ligament is a thick arch of fibers that connects the inferior aspects of the joint components, rounding off
the subpubic angle as it forms the apex of the pubic arch.
LUMBOSACRAL JOINTS
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. The facets on the S1 vertebra face posteromedially, interlocking with the anterolaterally facing
inferior articular facets of the L5 vertebra, preventing the lumbar vertebra from sliding anteriorly down the
incline of the sacrum. These joints are further strengthened by fan-like iliolumbar ligaments radiating from the
transverse processes of the L5 vertebra to the ilia.
SACROCOCCYGEAL JOINT
The sacrococcygeal joint is a secondary cartilaginous joint with an intervertebral disc. Fibrocartilage and
ligaments join the apex of the sacrum to the base of the coccyx. The anterior and posterior sacrococcygeal
ligaments are long strands that reinforce the joint.
Clinical Notes
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 funnelshaped) 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.
 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.
 The angle formed by the two arms of the pubic arch is larger in women (80-85°) than it is in men (50-60°).
 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.
 The gynecoid type, present in about 41% of women, is the typical female pelvis, which was previously
described.
 The android type, present in about 33% of white females and 16% of black females, is the male or funnelshaped pelvis with a contracted outlet.
http://www.youtube.com/yeditepeanatomy
8
Dr. Kaan Yücel
http://yeditepeanatomy1.wordpress.com
Yeditepe Anatomy
 The anthropoid type, present in about 24% of white females and 41% of black females, is long, narrow, and
oval shaped.
 The platypelloid type, present in only about 2% of women, is a wide pelvis flattened at the brim, with the
promontory of the sacrum pushed forward.
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 =11cm
from the tip of the coccyx to the lower border of symphysis pubis.
Obstetric antero-posterior diameter = 13 cm
from the tip of the sacrum to the lower border of symphysis pubis as the coccyx moves backwards during the
second stage of labour.
Transverse diameters:
Bituberous diameter = 11 cm
between the inner aspects of the ischial tuberosities.
Bispinous diameter = 10.5 cm
between the tips of ischial spines.
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
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 =13cm
between the farthest two points on the iliopectineal lines.
It is the largest diameter in the pelvis.
Obstetric transverse diameter:
It bisects the true conjugate and is slightly shorter than the anatomical transverse diameter.
Oblique diameters:
Right oblique diameter =12 cm
from the right sacroiliac joint to the left iliopectineal eminence.
Left oblique diameter = 12 cm
from the left sacroiliac joint to the right iliopectineal eminence.
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.
http://www.youtube.com/yeditepeanatomy
9
Dr. Kaan Yücel
http://yeditepeanatomy.wordpress.com
Yeditepe Anatomy
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 Delivery @ the following link: http://emedicine.medscape.com/article/263603-overview#a04
http://www.gfmer.ch/Obstetrics_simplified/anatomy_of_the_female_pelvis.htm
Pelvic Fractures
Anteroposterior compression of the pelvis occurs during crush accidents (as when a heavy object falls
on the pelvis). This type of trauma commonly produces fractures of the pubic rami. When the pelvis is
compressed laterally, the acetabula and ilia are squeezed toward each other and may be broken.
Fractures of the bony pelvic ring are almost always multiple fractures or a fracture combined with a joint
dislocation. Pelvic fractures can result from direct trauma to the pelvic bones, such as occurs during an
automobile accident, or be caused by forces transmitted to these bones from the lower limbs during falls on the
feet. Weak areas of the pelvis, where fractures often occur, are the pubic rami, the acetabula (or the area
immediately surrounding them), the region of the sacroiliac joints, and the alae of the ilium.
Pelvic fractures may cause injury to pelvic soft tissues, blood vessels, nerves, and organs. Fractures in
the pubo-obturator area are relatively common and are often complicated because of their relationship to the
urinary bladder and urethra, which may be ruptured or torn. Falls on the feet or buttocks from a high ladder may
drive the head of the femur through the acetabulum into the pelvic cavity, injuring pelvic viscera, nerves, and
vessels.
Pelvic Fractures in Emergency Medicine @ http://emedicine.medscape.com/article/825869-overview
http://www.youtube.com/yeditepeanatomy
10