Pelvic girdle: Bones & ligaments

Lumbosacral joint

...

What is the function of the pelvic girdle?

1) *Transference of weight* from the *vertebrae* via the *sacrum* - Towards the *lower limbs* when *standing* - Towards the *ischial tuberosity* when *sitting* 2) Shock absorption - dissipate forces protecting the lumbar spine during gait 3) Dynamic *stress relieving* function in gait - The pelvis *swings from side to side* by a *rotatory movement. - This occurs at the *hip joint* coupled with small movements in the *lumbar spine* - This *prevents the onset of trauma to the hip* 4) Provides *attachment* for *muscles* 5) Provides bony support for the *birth canal*

Sacroiliac joint - What are the articular surfaces of this joint?

1) Auricular surface of the ilium 2) Auricular surface of the sacrum These articulating surfaces are L shaped, being *broader above* and *narrower below* The central aspect of the *sacral auricular surface* is *concave* centrally with raised crests on either side The ilial auricular surface presents with a *central crest* between two furrows

Sacroiliac joint - The articular surfaces of the two bones are covered by different structures. State what they are on the: 1) Sacrum 2) Ilium

1) Hyaline cartilage 2) Fibrocartilage

What are the ligaments of the pubic symphysis? -Arcuate pubic ligament 1) Where are the attachments of this ligament 2) what is the function of this ligament?

1) Inferior pubic rami of the two pubic bones 2) Stabilizes the pubic symphysis.

Ligaments of the sacroiliac joint - What ligaments are known as the posterior sacroiliac ligaments?

1) Interosseous sacroiliac ligament 2) Long posterior sacroiliac ligament 3) Short posterior sacroiliac ligament

What are the ligaments of the pubic symphysis? -Superior pubic ligament 1. Where is the origin? 2. Where is the insertion? 3. What is the function of this ligament?

1) Pubic crests 2) Pubic tubercles 3) Strengthen the anterosuperior aspect of the joint.

Bony landmarks of the sacrum - The Sacral canal is enclosed by different structures. State what structures do so: 1) Anteriorly 2) Posteriorly 3) Laterally

1) Sacral vertebral bodies 2) Laminae, spinous processes + ossified ligamentum flava 3) Transverse processes

What joints are present at the pelvic girdle

1) Sacroiliac Joints (x2) - Between the ilium of the hip bones, and the sacrum 2) Sacrococcygeal symphysis - Between the sacrum and the coccyx. 3) Pubic symphysis - Between the pubis bodies of the two hip bones. 4) Lumbosacral joint - Between L5 and the superior aspect of the sacrum

What ligaments are known as the accessory ligaments of the sacroiliac joint?

1) Sacrotuberous ligament 2) Sacrospinous ligament 3) Iliolumbar ligament

What are the ligaments of the pubic symphysis?

1) Superior pubic ligament 2) Arcuate pubic ligament

Bony landmarks of the sacrum - Lateral sacral crest 1) Describe the structure of this landmark 2) This landmark provides attachment for several muscles . State which ones and where they attach.

1) The tips of these transverse tubercles on the posterior surface of the sacrum forms the *lateral sacral crest* 2) a) Multifidus attaches medially b) Erector spinae laterally to the upper three-quarters c) Gluteus maximus attaches to the lower quarter.

Ligaments of the sacroiliac joint - Anterior sacroiliac ligament Answer the following questions regarding this structure: 1. Where is it located? 2. Where is the origin? 3. Where is the insertion?

1) This is a broad and flat ligament consists of *numerous thin bands* on the anterior aspect of the joint 2) Ala and anterior surface of the sacrum 3) The margin of the auricular surface of the ilium

Ligaments of the sacroiliac joint - Interosseous sacroiliac ligament Answer the following questions regarding this structure: 1. Where is it located? 2. Where are the attachments of this ligament? 3. What is the function of this ligament?

1) This is the *deepest posterior ligament*. It is also short, thick and extremely strong 2) This ligament fills the *narrow irregular space* between the areas of bone above and behind the auricular surfaces *posterior and inferior* to the sacro-iliac joint. - This ligament consists of deep and superficial bands that cross between the bones. This acts to *strongly bind the surfaces* 3) a) The major function of this ligament is to keep the *sacrum and ilium together*, therefore preventing *abduction or distraction* of the sacroiliac joint. b) It also helps to bear the weight of the thorax, upper limbs, head, and neck. This is performed by the nearly horizontal direction of the fibers running perpendicular from the sacrum to the ilium.

Bony landmarks of the sacrum - Median sacral crest and spinous processes 1) Describe the structure of this landmark 2) This landmark provides attachment for several muscles . State which ones and where they attach.

1) This landmark is an *irregular raised ridge* in the *midline* of the posterior aspect of the sacrum - It typically represents the four fused spinous processes of the upper four sacral vertebrae. 2) a) The erector spinae medially b) Multifidus laterally.

Ligaments of the sacroiliac joint - Long posterior sacroiliac ligament Answer the following questions regarding this structure: 1. Where is it located? 2. Where is the origin? 3. Where is the insertion? 4. What is its funtion?

1) This ligament is superficial to the interosseous ligament and runs between the sacrum and ilium 2) The *first and second transverse tubercles* on the *posterior* aspect of the *sacrum* 3) The tuberosity of the ilium. 4) This ligament resists sacral counternutation

Ligaments of the sacroiliac joint - Short posterior sacroiliac ligament Answer the following questions regarding this structure: 1. Where is it located? 2. Where is the origin? 3. Where is the insertion?

1) This ligament is superficial to the interosseous ligament and runs between the sacrum and ilium - This ligament is *oblique in direction* 2) The *third transverse tubercle* of*posterior* aspect of the *sacrum* 3) The *PSIS* 4) This ligament resists sacral counternutation

Iliolumbar ligament Answer the following questions regarding this structure: 1. Where is the origin? 2. Where is the insertion?

1) Tranverse process of L5 2) Deep into anterior margin of iliac crest 3) An important role in restraining movement in lumbosacral and the sacroiliac joints

What bones form the pelvic girdle?

1) x2 hip bones 2) Sacrum 3) Coccyx

Sacrotuberous ligament Answer the following questions regarding this structure: 1. Where is it located? 2. Where is the origin? 3. Where is the insertion?

1. i. The posterior superior and posterior inferior iliac spines ii. The posterior surface of the sacrum iii. The lateral aspect of the lower sacrum iiii. The upper surface of the coccyx. 2. The medial margin of the ischial tuberosity and the lower margin of the ischial ramus. 3. The presence of this ligament along with the Sacrospinous ligament converts the greater and lesser sciatic notches to foramina

Pubic symphysis - What type of joint is this?

A secondary cartilaginous joint

Bony landmarks of the sacrum - What is likely to occur to the sacrum whilst standing erect as a result of the curvature

As a result of the curvature, the sacrum would *tilt anteriorly* as a result of the weight from the verterbra

Bony landmarks of the coccyx - The fused second to fourth vertebrae

In both the male and female the second, third, and fourth coccygeal vertebrae: • Decrease in size from above downwards and are usually fused. • Consist of rudimentary vertebral bodies. • Have the following muscle attachments: levator ani (centrally) and coccygeus (laterally).

Bony landmarks of the sacrum - Intermediate sacral crest

On the posterior aspect of the sacrum, *lateral* to the *spinous tubercles*, the junction of *consecutive laminae* is marked by a *tubercle* that represents a *fused sacral zygapophyseal joint*. This line of articular processes forms the intermediate crest, which serves as an attachment site for multifidus.

Sacroiliac joint - With increasing age, changes occur at the SIJ. State what occurs.

Over time the joint cavity becomes either *patially* or *completely* obliterated by *fibrous bands* or *fibrocartlaginous adhesions* between the surfaces.

Sacroiliac joint - Briefly describe the structure of the joint capsule and the synovial membrane.

The joint capsule completely surrounds the joint, attaching to the *anterior margins* of both bones. The synovial membrane lines the *non-articular* surfaces of the joint

Pubic symphysis - What are the articular surfaces of this joint?

The medial, oval articulating surfaces of the two *pubic bones*, joined together by a *fibrocartilaginous interpubic disc*

Sacrospinous ligament Answer the following questions regarding this structure: 1. Where is it located? 2. Where is the origin? 3. Where is the insertion?

The sacrospinous ligament lies deep to the sacrotuberous ligament. 1. The edge of the lower sacrum and coccyx and the 2. The ischial spine. 3. The presence with this ligament along with the Sacrotuberous ligament converts the greater and lesser sciatic notches to foramina

Bony landmarks of the sacrum -Anterior sacral foramen

There are typically four pairs of this structure in both males and females These communicate with the sacral canal (vertebral foramen) via the intervertebral foramina. These structures transmit the *ventral rami* of the *first to fourth sacral spinal nerves*, *lateral sacral arteries*, and *venous plexuses*.

Bony landmarks of the sacrum - Sacral lateral masses

These are enlarged parts of the sacral vertebrae - These are formed by the *embryonic transverse processes, pedicles* and *embryonic costal elements* which are fused with the *vertebral bodies*

Bony landmarks of the coccyx - Coccygeal cornua

These landmarks are *superior projections* that arise from the *base of the coccyx*. - This is where the coccyx articulates with the *sacral cornua*.

Surface anatomy of the sacrum - Transverse ridges

These landmarks are located on the anterior surface of the sacrum. There are typically four of these structures and they act to *separate* the *original bodies* of the *5 sacral vertebrae*

Bony landmarks of the sacrum - Transverse tubercles

These landmarks are located on the posterior surface of the sacrum. - The tips of these landmarks form the *lateral sacral crest*

Bony landmarks of the sacrum - Superior articular process

These landmarks form the *superior surface* of the sacrum and bear *concave articular facets*. - These typically face *posteromedially* in both male and females • These facets are covered in *hyaline cartilage* and articulate with the *inferior articular facets* of the *L5* at the *L5/S1 zygapophyseal joints*.

Bony landmarks of the sacrum - Ala of sacrum

These structures are *large triangular surfaces* found either side of *sacral base* - This is formed by the fusion of the *costal + transverse processes of S1*. - When the sacrum articulates with the hip bone, the *ala of the ilium* is continuous with this structure

What is the pelvic girdle

This is a *ring of bone* that provides *articulation* for the *lower limbs* and *trunk*

Bony landmarks of the sacrum - Cornu of sacrum

This is a horn-like projection is located on the *caudal end* of the *intermediate crest* - It represents the *inferior articular process* of *S5*. This process articulates with the *ascending cornu of the coccyx*.

Bony landmarks of the sacrum - Sacral canal / vertebral foramen

This is formed by the *vertebral foramina* of the sacral vertebrae. This is *triangular* in cross section and contains the following: 1) Internal venous plexus 2) Spinal nerves 3) Fat 4) Lower dural sac*- (this contains the cauda equina) 5) Film terminale 6) Spinal meninges 7) CSF

Bony landmarks of the sacrum - Body of the sacrum

This is landmark is located on the superior surface of the sacrum and articulates with L5

Bony landmarks of the sacrum - Auricular surface

This is the *lateral surface* of the sacrum which bears *auricular surfaces* that articulate with the *auricular surfaces* of the *ilium* at the SIJ. • There are *reciprocal irregularities* between the two bones, allowing them to *increase form closure* • The surfaces have well defined *anterior and inferior borders*. - These give attachment to the anterior sacro-iliac ligaments. • *Superoposteriorly* to this landmark are *roughened areas* for the attachment of the *strong interosseous sacro-iliac ligaments*.

Sacroiliac joint - What type of joint is this?

This joint is considered to be a *synovial joint anteriorly* and a *fibrous joint posteriorly* - This is because the region behind the synovial joint is united by *powerful interosseous ligaments*.

Bony landmarks of the coccyx - The first coccygeal vertebra 1) Describe the structure of this landmark 2) This landmark provides attachment for several muscles . State which ones and where they attach.

This landmark has an *oval facet* on its *supeior surface* that articulates with *apex of the sacrum* - It does so via the *sacrococcygeal intervertebral disc* At the *posterolateral* aspect of this facet are the *coccygeal cornua* - These project *upwards* to articulate with the *sacral cornu* . • Provides attachment for the sacrotuberous ligaments, sacrospinous ligaments, gluteus maximus, levator ani, and coccygeus.

Bony landmarks of the sacrum - Facet for coccyx

This landmark is located on the *apex of the sacrum* It is *a flat, oval facet*, which articulates with the *coccyx*. - It does so via the *sacrococcygeal intervertebral disc*

Bony landmarks of the sacrum - Sacral hiatus

This landmark is the *inferior opening* of the *sacral canal*. It is located below the *fourth spinous tubercle*. It is a *U shaped* defect in the posterior wall of the *sacral canal* where the *laminae* of S5 has not been fused

Bony landmarks of the coccyx - Transverse process

This landmark projects *superolaterally* from each side of the *first coccygeal body*. This articulates with the *inferolateral sacral angle* .

Bony landmarks of the sacrum - Sacral promontory

This structure is an anterior projection of the upper anterior margin of the body of S1 in both male and female.

Bony landmarks of the sacrum - Describe the structure of this bone.

• This is a *traingular bone* which consists of *5 fused vertebrae* - It has dorsal, pelvic (ventral) and lateral surfaces • It has an *inferior apex* that articulates with *coccyx* • It has a *superior base* that articulates with *L5* at the *lumbosacral angle* • The upper aspect of this bone is *anteriorly inclined* at *35-45°* and the lower aspect is *almost vertical*