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FEMALE PELVIS
AND
PELVIMETRY
AYMAN SHEHATA
MD Obstetrics and Gynecology
TANTA UNIVRSITY
2015
BY
P’S IN LABOR & DELIVERY
1.Passenger= The fetus
2. Passageway= The birth canal
3. Power of labor= Force of uterine contract...
Pelvic anatomy
• Bony pelvis
• Pelvic diameters
• Pelvic planes
• Pelvic axes
• Pelvic types
• Pelvimetry
The bony pelvis
”four bones“:
• two hip bones(ileum, ischium & pubis) laterally &
anteriorly
• sacrum & coccyx posteriorly...
Sacrum
• consists of 5 rudimentary vertebrae fused together to form
a single wedge-shaped bone with a forward concavity
• ...
Coccyx
• consists of 4 vertebrae fused together to form a small
triangular bone
• articulates at its base with the lower e...
Hip Bone
In children:
each hip bone consists of :
• the ilium, which lies superiorly
• the ischium, which lies posteriorly...
The ilium,
 the upper flattened part of the hip bone
• iliac crest runs between the anterior and posterior superior
iliac...
The ischium
 the inferior and posterior part of the hip bone
• ischial spine
• ischial tuberosity
3-The pubis
 the anterior part of the hip bone
• Body bears pubic crest & pubic tubercle and articulates
with the pubic b...
False pelvis: above the pelvic brim and has no
obstetric importance.
True pelvis: below the pelvic brim and related
to the...
False Pelvis
bordered by:
• lumbar vertebrae posteriorly
• iliac fossa bilaterally
• abdominal wall anteriorly.
supports ...
True Pelvis
bony canal and is formed by:
• the sacrum and coccyx posteriorly
• the ischium and pubis laterally and anterio...
The Pelvic Inlet (Brim)
Boundaries
 Sacral promontory,
 alae of the sacrum,
 sacroiliac joints,
 iliopectineal lines,
...
Pelvic anatomy
• Bony pelvis
• Pelvic diameters
• Pelvic planes
• Pelvic axes
• Pelvic types
• Pelvimetry
Pelvic Inlet
Diameters
(A) Antero -posterior diameters:
 Anatomical antero-posterior diameter (true conjugate) = 11cm
 f...
Pelvic Inlet
(B) Transverse diameters:
 Anatomical transverse diameter =13cm
 between the farthest two points on the
ili...
Pelvic Inlet
(C) Oblique diameters:
 Right oblique diameter =12 cm
from the right sacroiliac joint to the left iliopecti...
4) Anatomical Transverse Diameter (13 cm)
5) Obstetric Transverse Diameter
ATD
OTD
6) Oblique Diameter (12 cm)
7) Sacrotyloid Diameter (9.5 cm)
SI Joint
Iliopubic eminence
Pelvic cavity
The Cavity..!!!
• Round cavity of greatest dimensions.
• Anteroposterior diameter
• Oblique diameter
• Transverse diameter...
Anatomical outlet
It is lozenge-shaped bounded by;
 the lower border of symphysis pubis,
 pubic arch,
 ischial tuberosi...
It is a segment, the boundaries of which are:
Obstetric outlet
• the roof is the plane of least pelvic dimension,
• the fl...
•Antero - posterior diameters:
o Anatomical antero-posterior diameter =11cm
 from the tip of the coccyx to the lower bord...
Pelvic anatomy
• Bony pelvis
• Pelvic diameters
• Pelvic planes
• Pelvic axes
• Pelvic types
• Pelvimetry
Pelvic Planes
• imaginary, flat surfaces that extend across the
pelvis at different levels.
four planes :
1. The pelvic in...
1-The plane of the inlet:
bordered by:
• pubic crest anteriorly
• iliopectineal line of the innominate bones laterally
• p...
Pelvic Inlet
• Plane
Plane of mid cavity
(plane of greatest pelvic dimensions(
 pass between the middle of the posterior surface of the
symphy...
Plane of obstetric outlet
(plane of least pelvic dimensions(:
passes from the lower border of the symphysis pubis anterior...
THOM᾿S DICTUM
IF THE SUM OF TRANSVERSE DIAMETER OF OUTLET AND
POSTERIOR SAGITAL DIAMETER IS LESS THAN 15 CM THE
OULET IS C...
Pelvic anatomy
• Bony pelvis
• Pelvic diameters
• Pelvic planes
• Pelvic axes
• Pelvic types
• Pelvimetry
V) Pelvic Axes:
1-Anatomical axis (curve of Carus):
It is an imaginary line joining the centre points of the planes of the...
Pelvic Axes…!!!
• Anatomical Axis of Carus…
Curved axis formed by joining the axis of inlet,
cavity and outlet.
Obstetric axis
N.B. At the Level of Ischial
Spines:
1. The plane of obstetric outlet (plane of the
least pelvic dimensions) is at this le...
N.B. At the Level of Ischial
Spines:
5. Forceps is applied only when the head at this
level (mid forceps) or below it (low...
Pelvic anatomy
• Bony pelvis
• Pelvic diameters
• Pelvic planes
• Pelvic axes
• Pelvic types
• Pelvimetry
Caldwell- Moloy Classification of
Pelvic Types
• Gynaecoid pelvis(50%)
• Anthropoid pelvis (25%)
• Android pelvis (20%)
• ...
Comparison of pelvic
types
Pelvic Types
Gynecoid Pelvis
• The classic female type.
• Found in approximately 50% of women.
• Characteristics:
1. Round inlet, with ...
• These features create a cylindrical
shape that is spacious throughout.
• The fetal head generally rotates
into the occip...
Android Pelvis
• The typical male type
• Found in less than 30% of women
• Characteristics:
1. Triangular inlet with a fla...
• Limited space at the inlet &
progressively lessens down the
pelvis, owing to the funneling effect
of the side walls, sac...
Anthropoid Pelvis
• Resembles anthropoid ape pelvis.
• Found in approximately 20% of women
• Characteristics:
1. A much la...
• The fetal head can engage only in
the AP diameter and usually does so
in the occipitoposterior position,
because there i...
Platypelloid Pelvis
• Flattened gynecoid pelvis.
• Found in only 3% of women
• Characteristics:
1. A short AP & wide trans...
PELVIMETRY
• Pelvimetry is the assessment of the
dimensions & capacity of adult female pelvis
in relation to the birth of ...
Pelvic anatomy
• Bony pelvis
• Pelvic diameters
• Pelvic planes
• Pelvic axes
• Pelvic types
• Pelvimetry
Types of Pelvimetry
 Clinical pelvimetry:
 Internal pelvimetry (manually)
 pelvic inlet
 mid-cavity
 pelvic outlet
 ...
Internal Pelvimetry
• Through vaginal examination
• At first prenatal visit screen for obvious
contractions.
• In late pre...
Pelvic Inlet
1. Palpation of pelvic brim:
• The index & middle fingers are moved
along the pelvic brim.
• Note whether rou...
2) Diagonal conjugate:
• Measured from the lower border of the
pubis to the sacral promontory using the tip
of the second ...
The Midpelvis
1) Symphysis:
– Height, thickness & curvature
2) Sacrum:
– Shape & curvature
– Concave usually.
– Flat or co...
4) Ischial spines prominence:
– The ischial spines can be located by
following the sacrospinous ligament to its
lateral en...
6) Sacrospinous ligament:
– Its length is assessed by placing one
finger on the ischial spine & one finger
on the sacrum i...
Pelvic Outlet
1) Subpubic angle:
– Assessed by placing a thumb next to each
inferior pubic ramus and then estimating the
a...
2) Mobility of the coccyx.
– by pressing firmly on it while an
external hand on it can determine its
mobility.
3) Anteropo...
4) Bituberous diameter:
– Done by first placing a fist between
the ischial tuberosities.
– An 8.5 cm distance (4 knuckles)...
Adequate Pelvis
Data Finding
Forepelvis (pelvic brim) Round.
Diagonal conjugate ≥ 11.5 cm.
Symphysis Average thickness, pa...
Radiological Pelvimetry
• X-ray:
– Limited value. No role in guiding management.
• CT:
– Ease of performance, interpretati...
Indications
1. Clinical evidence or obstetric
history suggestive of pelvic
abnormalities.
2. A history of pelvic trauma.
CT pelvimetry.
• Breech presentation.
A. Anteroposterior view is used to measure the transverse
diameter of the pelvic inl...
MRl pelvimetry with AP inlet and outlet
measurements.
Cephalometry
• Ultrasonography: is the safe, accurate and easy
method and can detect:
– The biparietal diameter (BPD).
– T...
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
Pelvis and pelvimetry
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Pelvis and pelvimetry

pelvis and pelvimetry

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Pelvis and pelvimetry

  1. 1. FEMALE PELVIS AND PELVIMETRY AYMAN SHEHATA MD Obstetrics and Gynecology TANTA UNIVRSITY 2015 BY
  2. 2. P’S IN LABOR & DELIVERY 1.Passenger= The fetus 2. Passageway= The birth canal 3. Power of labor= Force of uterine contractions
  3. 3. Pelvic anatomy • Bony pelvis • Pelvic diameters • Pelvic planes • Pelvic axes • Pelvic types • Pelvimetry
  4. 4. The bony pelvis ”four bones“: • two hip bones(ileum, ischium & pubis) laterally & anteriorly • sacrum & coccyx posteriorly ‘3 joints’ • symphysis pubis anteriorly • sacroiliac joints posteriorly
  5. 5. Sacrum • consists of 5 rudimentary vertebrae fused together to form a single wedge-shaped bone with a forward concavity • The upper border ( base) articulates with the L5 • The narrow inferior border articulates with the coccyx. • Laterally, the sacrum articulates with the two iliac bones • The anterior and upper margins of the first sacral vertebra bulge forward sacral promontory
  6. 6. Coccyx • consists of 4 vertebrae fused together to form a small triangular bone • articulates at its base with the lower end of the sacrum • It’s vertebrae consist of bodies only, but the first vertebra possesses a rudimentary transverse process and cornua. The cornua are the remains of the pedicles and superior articular processes and project upward to articulate with the sacral cornua
  7. 7. Hip Bone In children: each hip bone consists of : • the ilium, which lies superiorly • the ischium, which lies posteriorly and inferiorly • the pubis, which lies anteriorly and inferiorly  joined by cartilage at the acetabulum  At puberty, >>> fuse together to form one large, irregular bone.  articulate with the sacrum at the sacroiliac joints >>>>form the anterolateral wall of the pelvis  articulate with one another anteriorly at the symphysis pubis.
  8. 8. The ilium,  the upper flattened part of the hip bone • iliac crest runs between the anterior and posterior superior iliac spines • Below these spines are the corresponding anterior and posterior inferior iliac spines • The iliopectineal line runs downward and forward around the inner surface of the ilium and serves to divide the false from the true pelvis.
  9. 9. The ischium  the inferior and posterior part of the hip bone • ischial spine • ischial tuberosity
  10. 10. 3-The pubis  the anterior part of the hip bone • Body bears pubic crest & pubic tubercle and articulates with the pubic bone of the opposite side at the symphysis pubis • superior and inferior pubic rami
  11. 11. False pelvis: above the pelvic brim and has no obstetric importance. True pelvis: below the pelvic brim and related to the child -birth.
  12. 12. False Pelvis bordered by: • lumbar vertebrae posteriorly • iliac fossa bilaterally • abdominal wall anteriorly. supports the abdominal contents after 1st trimester helps support the gravid uterus.
  13. 13. True Pelvis bony canal and is formed by: • the sacrum and coccyx posteriorly • the ischium and pubis laterally and anteriorly  It’s internal borders are solid and relatively immobile.  The posterior wall is twice the length of the anterior wall.  The area of concern to the obstetrician because its dimensions are sometimes not adequate to permit passage of the fetus.
  14. 14. The Pelvic Inlet (Brim) Boundaries  Sacral promontory,  alae of the sacrum,  sacroiliac joints,  iliopectineal lines,  iliopectineal eminencies,  upper border of the superior pubic rami,  pubic tubercles,  pubic crests and  upper border of symphysis pubis.
  15. 15. Pelvic anatomy • Bony pelvis • Pelvic diameters • Pelvic planes • Pelvic axes • Pelvic types • Pelvimetry
  16. 16. Pelvic Inlet Diameters (A) 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.  External conjugate = 20 cm  from the depression below the last lumbar spine to the upper anterior margin of the symphysis pubis measured from outside by the pelvimeter . It has not a true obstetric importance.
  17. 17. Pelvic Inlet (B) Transverse diameters:  Anatomical transverse diameter =13cm  between the farthest two points on the iliopectineal lines.  It lies 4 cm anterior to the promontory and 7 cm behind the symphysis.  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.
  18. 18. Pelvic Inlet (C) 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.  Sacro-cotyloid diameters = 9-9.5 cm  from the promontory of the sacrum to the right and left iliopectineal eminence, so the right diameter ends at the right eminence and vice versa.
  19. 19. 4) Anatomical Transverse Diameter (13 cm) 5) Obstetric Transverse Diameter ATD OTD
  20. 20. 6) Oblique Diameter (12 cm) 7) Sacrotyloid Diameter (9.5 cm) SI Joint Iliopubic eminence
  21. 21. Pelvic cavity
  22. 22. The Cavity..!!! • Round cavity of greatest dimensions. • Anteroposterior diameter • Oblique diameter • Transverse diameter 12cm
  23. 23. Anatomical outlet It is lozenge-shaped bounded by;  the lower border of symphysis pubis,  pubic arch,  ischial tuberosities,  sacrotuberous and sacrospinous ligaments and,  tip of the coccyx. The Pelvic Outlet
  24. 24. It is a segment, the boundaries of which are: Obstetric outlet • 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.
  25. 25. •Antero - posterior diameters: o Anatomical antero-posterior diameter =11cm  from the tip of the coccyx to the lower border of symphysis pubis. o 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: o Bituberous diameter = 11 cm  between the inner aspects of the ischial tuberosities. o Bispinous diameter = 10.5 cm  between the tips of ischial spines. Diameters of pelvic outlet
  26. 26. Pelvic anatomy • Bony pelvis • Pelvic diameters • Pelvic planes • Pelvic axes • Pelvic types • Pelvimetry
  27. 27. Pelvic Planes • imaginary, flat surfaces that extend across the pelvis at different levels. four planes : 1. The pelvic inlet 2. The plane of greatest diameter 3. The plane of least diameter 4. The pelvic outlet
  28. 28. 1-The plane of the inlet: bordered by: • pubic crest anteriorly • iliopectineal line of the innominate bones laterally • promontory of the sacrum posteriorly. fetal head enters the pelvis through this plane in the transverse position.
  29. 29. Pelvic Inlet • Plane
  30. 30. Plane of mid cavity (plane of greatest pelvic dimensions(  pass between the middle of the posterior surface of the symphysis pubis and the junction between 2nd and 3rd sacral vertebrae. Laterally, it passes to the centre of the acetabulum and the upper part of the greater sciatic notch.  It is a round plane with diameter of 12.5 cm.  Internal rotation of the head occurs when the biparietal diameter occupies this wide pelvic plane while the occiput is on the pelvic floor i.e. at the plane of the least pelvic dimensions.
  31. 31. Plane of obstetric outlet (plane of least pelvic dimensions(: passes from the lower border of the symphysis pubis anteriorly, to the ischial spines laterally, to the tip of the sacrum posteriorly. Plane of anatomical outlet: passes with the boundaries of anatomical outlet and consists of 2 triangular planes with one base which is the bituberous diameter.  Anterior sagittal plane: its apex at the lower border of the symphysis pubis.  Posterior sagittal plane: its apex at the tip of the coccyx.  Anterior sagittal diameter: 6-7 cm o from the lower border of the symphysis pubis to the centre of the bituberous diameter. •* Posterior sagittal diameter: 7.5-10 cm ofrom the tip of the sacrum to the centre of the bituberous diameter.
  32. 32. THOM᾿S DICTUM IF THE SUM OF TRANSVERSE DIAMETER OF OUTLET AND POSTERIOR SAGITAL DIAMETER IS LESS THAN 15 CM THE OULET IS CONTRACTED
  33. 33. Pelvic anatomy • Bony pelvis • Pelvic diameters • Pelvic planes • Pelvic axes • Pelvic types • Pelvimetry
  34. 34. V) Pelvic Axes: 1-Anatomical axis (curve of Carus): It is an imaginary line joining the centre points of the planes of the inlet, cavity and outlet. It is C shaped with the concavity directed forwards. It has no obstetric importance. 2-Obstetric axis: It is an imaginary line represents the way passed by the head during labour. It is J shaped passes downwards and backwards along the axis of the inlet till the ischial spines where it passes downwards and forwards along the axis of the pelvic outlet.
  35. 35. Pelvic Axes…!!! • Anatomical Axis of Carus… Curved axis formed by joining the axis of inlet, cavity and outlet.
  36. 36. Obstetric axis
  37. 37. N.B. At the Level of Ischial Spines: 1. The plane of obstetric outlet (plane of the least pelvic dimensions) is at this level. 2. The levator ani muscles are situated at this level and its ischio-coccygeous part is attached to the ischial spines. 3. The obstetric axis of the pelvis changes its direction. 4. The head is considered engaged when the vault is felt vaginally at or below this level. www.freelivedoctor.com
  38. 38. N.B. At the Level of Ischial Spines: 5. Forceps is applied only when the head at this level (mid forceps) or below it (low and outlet forceps). 6. Pudendal nerve block is carried out at this level. 7. The external os of the cervix is located normally. 8. The vaginal vault is located nearly. 9. The ring pessary should be applied above this level for treatment of prolapse. www.freelivedoctor.com
  39. 39. Pelvic anatomy • Bony pelvis • Pelvic diameters • Pelvic planes • Pelvic axes • Pelvic types • Pelvimetry
  40. 40. Caldwell- Moloy Classification of Pelvic Types • Gynaecoid pelvis(50%) • Anthropoid pelvis (25%) • Android pelvis (20%) • Platypelloid pelvis (5%) www.freelivedoctor.com
  41. 41. Comparison of pelvic types
  42. 42. Pelvic Types
  43. 43. Gynecoid Pelvis • The classic female type. • Found in approximately 50% of women. • Characteristics: 1. Round inlet, with the widest transverse diameter only slightly greater than the AP diameter 2. Side walls straight 3. Ischial spines of average prominence . 4. Well-rounded sacrosciatic notch 5. Well-curved sacrum 6. Spacious subpubic arch, with an angle of approximately 90 degrees
  44. 44. • These features create a cylindrical shape that is spacious throughout. • The fetal head generally rotates into the occipitoanterior position in this type of pelvis.
  45. 45. Android Pelvis • The typical male type • Found in less than 30% of women • Characteristics: 1. Triangular inlet with a flat posterior segment & the widest transverse diameter closer to the sacrum than in the gynecoid type . 2. Convergent side walls with prominent spines 3. Shallow sacral curve 4. Long and narrow sacrosciatic notch 5. Narrow subpubic arch
  46. 46. • Limited space at the inlet & progressively lessens down the pelvis, owing to the funneling effect of the side walls, sacrum, and pubic rami. • Restricted space at all levels. • The fetal head is forced to be in the occipitoposterior position to conform to the narrow anterior pelvis. • Arrest of descent is common at the midpelvis.
  47. 47. Anthropoid Pelvis • Resembles anthropoid ape pelvis. • Found in approximately 20% of women • Characteristics: 1. A much larger AP than transverse diameter, creating a long narrow oval at the inlet 2. Side walls that do not converge 3. Ischial spines that are not prominent but are close, owing to the overall shape 4. Variable, but usually posterior, inclination of the sacrum 5. Large sacrosciatic notch 6. Narrow, outwardly shaped subpubic arch
  48. 48. • The fetal head can engage only in the AP diameter and usually does so in the occipitoposterior position, because there is more space in the posterior pelvis.
  49. 49. Platypelloid Pelvis • Flattened gynecoid pelvis. • Found in only 3% of women • Characteristics: 1. A short AP & wide transverse diameter creating an oval- shaped inlet 2. Straight or divergent side walls 3. Posterior inclination of a flat sacrum 4. A wide bispinous diameter 5. A wide subpubic arch • The fetal head has to engage in the transverse diameter.
  50. 50. PELVIMETRY • Pelvimetry is the assessment of the dimensions & capacity of adult female pelvis in relation to the birth of a baby. • Pelvimetry was heavily used in leading the decision of natural, operative vaginal delivery or CS.
  51. 51. Pelvic anatomy • Bony pelvis • Pelvic diameters • Pelvic planes • Pelvic axes • Pelvic types • Pelvimetry
  52. 52. Types of Pelvimetry  Clinical pelvimetry:  Internal pelvimetry (manually)  pelvic inlet  mid-cavity  pelvic outlet  External pelvimetry ( Pelvimeter )  pelvic inlet  pelvic outlet  Imaging pelvimetry:  X-ray  Computerised tomography (CT)  Magnetic resonance imaging (MRI)
  53. 53. Internal Pelvimetry • Through vaginal examination • At first prenatal visit screen for obvious contractions. • In late pregnancy (preferred) – After 37 weeks GA or at the onset of labour – the soft tissues are more distensible – more accurate – less uncomfortable
  54. 54. Pelvic Inlet 1. Palpation of pelvic brim: • The index & middle fingers are moved along the pelvic brim. • Note whether round or angulated, causing the fingers to dip into a V-shaped depression behind the symphysis.
  55. 55. 2) Diagonal conjugate: • Measured from the lower border of the pubis to the sacral promontory using the tip of the second finger and the point where the index finger of the other hand meets the pubis • Normally 12.5 cm & cannot be reached. • If it is felt the pelvis is contracted • True conjugate = diagonal conjugate – 1.5 • Not done if the head is engaged.
  56. 56. The Midpelvis 1) Symphysis: – Height, thickness & curvature 2) Sacrum: – Shape & curvature – Concave usually. – Flat or convex shape may indicate AP constriction throughout the pelvis. 3) Side walls: – Straight, convergent or divergent starting from the pelvic brim down to the base of ischial spines. – Normally almost parallel or divergent
  57. 57. 4) Ischial spines prominence: – The ischial spines can be located by following the sacrospinous ligament to its lateral end. – Blunt (difficult to identify at all), – Prominent (easily felt but not large) or – Very prominent (large and encroaching on the mid-plane). 5) Interspinous diameter: – If both spines can be touched simultaneously, the interspinous diameter is 9.5 cm i.e. inadequate for an average- sized baby.
  58. 58. 6) Sacrospinous ligament: – Its length is assessed by placing one finger on the ischial spine & one finger on the sacrum in the midline. – The average length is 3 fingerbreadths. 7) Sacrosciatic notch: – If the sacrospinous ligament is 2.5 fingers, the sacrosciatic notch is considered adequate. – Short ligament suggests forward curvature of the sacrum & narrowed sacrosciatic notch.
  59. 59. Pelvic Outlet 1) Subpubic angle: – Assessed by placing a thumb next to each inferior pubic ramus and then estimating the angle at which they meet. – Normally, it admits 2 fingers. (90o ) – Angle ≤ 90 degrees suggests contracted transverse diameter in the midplane and outlet.
  60. 60. 2) Mobility of the coccyx. – by pressing firmly on it while an external hand on it can determine its mobility. 3) Anteroposterior diameter of the outlet: – From the tip of the sacrum to the inferior edge of the symphysis. (>11cm)
  61. 61. 4) Bituberous diameter: – Done by first placing a fist between the ischial tuberosities. – An 8.5 cm distance (4 knuckles) is considered to indicate an adequate transverse diameter.
  62. 62. Adequate Pelvis Data Finding Forepelvis (pelvic brim) Round. Diagonal conjugate ≥ 11.5 cm. Symphysis Average thickness, parallel to sacrum. Sacrum Hollow, average inclination. Side walls Straight. Ischial spines Blunt. Interspinous diameter ≥ 10.0 cm. Sacrosciatic notch 2.5 -3 finger - breadths. Subpubic angle 2fingerbreadths (90o). Bituberous diameter 4 knuckles (> 8.0 cm). Coccyx Mobile. Anterposterior diameter of outlet ≥ 11.0 cm.
  63. 63. Radiological Pelvimetry • X-ray: – Limited value. No role in guiding management. • CT: – Ease of performance, interpretation, & 10% less radiation exposure to the fetus . – Can evaluate fetal lie & position. • MRI (method of choice): – Lack of ionizing radiation, higher resolution & contrast but also higher cost.
  64. 64. Indications 1. Clinical evidence or obstetric history suggestive of pelvic abnormalities. 2. A history of pelvic trauma.
  65. 65. CT pelvimetry. • Breech presentation. A. Anteroposterior view is used to measure the transverse diameter of the pelvic inlet (≥ 11.5 cm). B. Lateral view is used to measure the anteroposterior diameter of the inlet (≥10 cm) & midpelvis. C. Axial view at the level of the fovea of the femoral heads is used to measure the bi-ischial diameter (≥ 9.5 cm)
  66. 66. MRl pelvimetry with AP inlet and outlet measurements.
  67. 67. Cephalometry • Ultrasonography: is the safe, accurate and easy method and can detect: – The biparietal diameter (BPD). – The occipito-frontal diameter. – The circumference of the head.

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