Slide 1

BONY PELVISBONY PELVIS: BONES & JOINTSComposed of 4 bones in the adult:2 hip bonesSacrumCoccyx

The joints of the pelvis include the:Sacroiliac JointsPubic SymphysisSacrococcygeal joint

2HIP BONESynonyms: coxal, pelvic bone

Formed by the fusion of 3 bones:IliumIschiumPubis

Acetabulum: Cup-like depression in the lateral surfaceArticulates with the head of femurFusion of above bones takes place in this region

HIP BONE: ILIUMSuperior flattened fan-shaped part:1) Ala (wing): expanded upper part2) Body: helps to form the acetabulum

Arcuate line: ridge medially separating both parts

HIP BONE: ILIUMALA PARTSIliac crest: Convex superior edge Runs between the ASIS & PSISAnterior part has outer & inner lipsTubercle projects outwards from the outer lip ~5cm behind ASIS

AIIS: rounded protuberance inferior to ASIS

Gluteal surface posteriorly: origin of glutei muscles

HIP BONE: ILIUMALA PARTS CONTDIliac fossa: internal concavity anteriorly

Sacropelvic surface:Iliac Tuberosity: posterior thickened part of iliac crest

Auricular surface: articulation with sacrum (sacroiliac joint)PIIS: posterior prominence

6HIP BONE: ILIUMBODYHelps to form the acetabulum

Greater Sciatic Notch:Notched posteriorly

HIP BONE: ISCHIUML-shaped inferior part:BodyInferior ramus

HIP BONE: ISCHIUMBODY (Upper part)Contributes to formation of acetabulumIschial spine: provides attachment for the sacrospinous ligamentNotched posteriorly: lesser sciatic notch

BODY (Lower part)Ischial tuberosity: palpable landmark that supports the sitting weightProvides attachment for the sacrotuberous ligament

9HIP BONE: ISHIUMISCHIAL RAMUS:Forms an acute angle with the bodyFuses with the inferior pubic ramus..Forms the inferior boundary of the obturator foramen

HIP BONE: PUBISMost anterior part:1) Body 2) Superior Ramus3) Inferior Ramus

Both pubic bones articulate via the pubic symphysis

HIP BONE: PUBISBODYMedial surface: pubic symphysis Upper border:Pubic crest: convex part medially Pubic tubercle: prominent bump laterally

HIP BONE: PUBISINFERIOR RAMUSFuses with ischial ramus

HIP BONE: PUBISSUPERIOR RAMUSContributes to the acetabulumPecten pubis (Pectineal line): oblique ridgeMeets the arcuate lineObturator crest: anteriorlyObturator groove: posteriorlyConverted to a canal by the upper borders of the obturator membrane & obturator muscles

14HIP BONE: PUBIS & ILIUMIliopubic /Iliopectineal Eminence/Tubercle:Junction of ilium (body) & pubis (superior ramus) Acetabular region (1/5)

Medial border: arcuate line meets pectineal line (iliopectineal line)

15SACRUMFusion of 5 sacral vertebrae

Inverted triangleSacral base: superior surface of S1Apex: articulates with the coccyx

Ala (wing): the fused transverse processes

Lateral surfaces: Articular facet: articulation with ilium

There are 4 pairs of anterior & posterior sacral foramina

SACRUMAnterior surface: concaveSacral promontory: Projecting anterior edge of the body of S1

SACRUMPosterior surface: convexMedian sacral crest: the fused spinous processesMedial (intermediate) sacral crest: fused articular surfacesLateral sacral crest: fused transverse processes

Sacral hiatus: Inverted U shaped openingTermination of sacral canal Resulting from absence of laminae & spinous processes of S4 & S5

Sacral Cornu: inferior articulating surface of S5

18COCCYXSmall triangular bone: 4 fused vertebrae (3-5)2 cornu: project upwards to articulate with sacral cornu

SACRUM & COCCYX

PELVIC JOINTS & LIGAMENTSPELVIC JOINTSThe joints of the pelvis include the:2 Sacroiliac JointsPubic SymphysisSacrococcygeal joint

SACROILIAC JOINTSynovial joint:Between the sacrum & ilium (auricular surfaces)

Jagged interlocking articulating surfaces:Limit movement

Obliteration of joint space with age

SACROILIAC JOINTSurrounding ligaments:Anterior Sacroiliac LigamentInterosseous Sacroiliac LigamentPosterior Sacroiliac Ligament

ANTERIOR SACROILIAC LIGAMENTRuns anterior-inferiorlyWell developed inferiorly

INTEROSSEOUS SACROILIAC LIGAMENTMost significant ligamentIt fills the irregular space postero-superior to the jointFibers run to the iliac tuberosity

POSTERIOR SACROILIAC LIGAMENTOverlies the interosseous ligamentSome fibers run from the intermediate & lateral sacral crestsSome fibers from S3 & S4 ascend to the PSIS

SACROILIAC JOINT ASSOCAITED LIGAMENTSThere are 3 associated ligaments:IliolumbarSacrotuberousSacrospinous

ILIOLUMBAR LIGAMENTInverted V shaped

2 components:Upper band: passes to the iliac crestLower band (lumbosacral ligament): passes to blend with the anterior sacroiliac ligament

SACROTUBEROUS LIGAMENTWide origin not only from the sacrum:Ilium: from the PSIS to the PIISPosterior sacroiliac ligament: lateral aspectLower sacrum & upper coccyx: lateral margins

The ligament then slopes inferiorly to the medial surface of the ischial tuberosity

30SACROSPINOUS LIGAMENTExtends from:Ischial spine to..Lateral margins of the sacrum & coccyx Lies anterior to the sacrotuberous ligament With which it blends in part

SACROILIAC JOINT MOVEMENT & STABILITYThe joint has:Considerable strengthLittle mobility

This is important wrt weight transmission:From the vertebral column (trunk) to..Hip bones (lower limbs)

SACROILIAC JOINT MOVEMENT & STABILITYBody weight transmitted through L5 tends to..Push the sacrum down & cause its forward rotation

STABILITY:Forward rotation:Resisted by the sacrotuberous & sacrospinous ligaments

33SACROILIAC JOINT MOVEMENT & STABILITYSTABILITY:Downward movement:Resisted by the iliolumbar & interosseous sacroiliac ligaments

SCIATIC FORAMINAThe sacrotuberous & sacrospinous ligaments convert..The lesser & greater sciatic notches into foramina:Greater sciatic foramenLesser sciatic foramen

SCIATIC FORAMINAGreater sciatic foramenLesser sciatic foramen

SCIATIC FORAMINALesser Sciatic ForamenProvides an entrance into the perineum from the gluteal regionPudendal nerve & internal pudendal vessels

SACROCOCCYGEAL JOINTSymphysis (2 cartilaginous)

Associated ligaments:Anterior ligament 2 Posterior ligaments: Superficial & DeepLateral ligament

Movement: some flexion & extension possible

39PUBIC SYMPHYSIS2 cartilaginous: Intervening fibrocartilage often contains a non-synovial cavity

Associated Ligaments: Anterior pubic ligamentPosterior pubic ligament (less well developed)Superior pubic ligamentInferior (Arcuate) pubic ligament

Movement: none significant

40PELVIC JOINTS & LIGAMENTSPREGNANCY CHANGESDuring pregnancy:Pelvic joints and ligaments relaxPelvic movements increase

This permits a small increase in size of the pelvis during childbirth

PELVISORIENTATION, PLANES, SEGMENTS, DIAMETERsPELVIS: ORIENTATIONAnatomical position:The top of the pubic symphysis & ASIS..Are in the same vertical plane

Pelvic inlet: faces anteriorlyPubic arch: nearly horizontal

PELVISPLANES SEGMNETS DIAMETERS A number of planes have been described as it relates to the pelvis:Pelvic inletPelvic outlet

The pelvis is thus divided into segments:Greater pelvisLesser pelvis

Additionally various measurements (diameters) have been describedThese are especially useful in obstetrics

PLANE: PELVIC INLET (BRIM)

Plane bounded by:Superior margin of pubic symphysisPubic crestPectineal lineIlium arcuate lineAnterior border sacral alaSacral promontory

45PLANE: PELVIC OUTLET

Plane bounded by:Inferior margin of pubic symphysisInferior pubic ramusIschial ramus & tuberositySacrotuberous ligamentCoccygeal tip

SEGMENTSPelvis may be divided into:Greater (false) pelvis: above the pelvic inlet

Lesser (true) pelvis: between the pelvic inlet & outlet

SEGMENTSLesser (true) pelvis = Pelvic cavity

DIAMETERSPELVIC INLET DIAMETERSAnteroposterior (True conjugate) (~ 11cm):

Transverse (~ 13 cm):Between arcuate lines

Oblique (~12.5cm):Iliopubic ramus & opposite SI joint

DIAMETERSPELVIC INLET DIAMETERSDiagonal Conjugate: An indirect measurement of the True conjugateDone on vaginal examination

DIAMETERSPELVIC INLET DIAMETERSDiagonal Conjugate:Estimation on vaginal examination

DIAMETERSPELVIC OUTLET DIAMETERSAnteroposterior (~12.5cm)

Transverse (midplane) (~ 9.5cm): Smallest diameterIschial spines

Transverse (bituberous) (~12 cm):Diameter influenced by pubic arch/ subpubic angle

DIAMETERSPELVIC OUTLET DIAMETERSTransverse (bituberous) diameter:Estimation on obstetric examination

PELVIS SEXUAL DIFFERENCESPELVIS SEXUAL DIFFERENCESThe pelvis provides the most marked skeletal differences between sexesDifferences are linked to functionIn both the primary function is locomotion

In women the pelvis (lesser pelvis) is adapted to childbearing:Female pelvis generally is: wider, shallower & has a larger pelvic inlet & outlet

Males are more muscular & more heavily built:Men: pelvic dimensions are greater, markings for muscles & ligaments more pronounced, & general architecture heavierPELVIS SEXUAL DIFFERENCESWOMENPelvic Inlet:Circular: less distinct promontoryBroader alae

Lesser Pelvis:Wide & shallow

Pubic arch/ subpubic angle:Obtuse

Ischial spines:Less prominent

MENPelvic InletHeart shaped: distinct promontory

Lesser Pelvis:Narrow & Deep

Pubic arch/ subpubic angle:Acute

Ischial Spines:Prominent

PELVES CLASSIFICATIONThere are usually clear cut differences between the pelves of males & females

However the pelvis of any person may have some features of the opposite sex

Pelves have been classified according the shape of the pelvic inlet

PELVES CLASSIFICATIONGynecoid: typical femaleAndroid: typical male funnel shaped Anthropoid: oval (more common in males)Platypelloid: wide flattened (uncommon in both sexes)