classification of bony pelvis

1. CLASSIFICATION OF
PELVIS
POOJA SANALKUMAR

2. Size and shape of female pelvis differs widely due to
morphological factors (developmental, sexual, racial, etc.)

3. CALDWELL-MOLOY
CLASSIFICATION
• On the basis of the shape of the inlet, female pelvis is divided into
four parent types:
• Gynecoid
• Android
• Anthropoid
• Platypelloid

5. ANATOMICAL FEATURES OF
PARENT PELVIC TYPES

6. GYNECOI
D
(50%)
ANTHROP
OID
(25%)
ANDROI
D
(20%)
PLATYPELL
OID
(5%)

7. INLET
GYNECOID ANTHROPOID ANDROID PLATYPELLOID
Shape Round Antero-
posteriorly oval
Triangular Transversely oval
Anterior
&
posterior
segments
Almost equal
& spacious
Both increased
with slight
anterior
narrowing
Posterior
segment short
& anterior
segment
narrow.
Both reduced-
flat
Sacrum Sacral angle
>90⁰
Inclined
backwards.
Well curved
from above
down and side
to side
Sacral angle
>90⁰
Inclined
posteriorly.
Long and
narrow
Sacral angle
<90⁰
Inclined
forwards and
straight.
Sacral angle >90⁰
Inclined
posteriorly.

8. CAVITY AND OUTLET
Gynecoid Anthropoid Android Platypelloid
Sacrosciatic
notch
Wide &
shallow
More wide &
shallow
Narrow &
deep
Slightly
narrow &
small
Sidewalls Straight or
slightly
divergent
Straight or
divergent
Convergent Divergent
Pubic arch Curved Long &
curved
Long &
straight
Short &
curved
Subpubic
angle
Wide (85⁰) Slightly
narrow
narrow Very wide
(>90⁰)
Bituberous
diameter
Normal Normal or
short
Short Wide

9. OBSTETRIC OUTCOME IN PARENT
PELVIC TYPE

10. INLET
GYNECOID ATHROPOID ANDROID PLATYPEL
LOID
Position Occipito-
lateral or
oblique
Occipito-
anterior
Direct
Occipito-
anterior or
posterior
Occipito-
lateral or
oblique
Occipito-
posterior
Occipito-
lateral
Diameter of
engagement
Transverse or
oblique
Antero-
posterior
Transverse or
oblique
Transverse
Engagement No difficulty
Usual
mechanism
No difficulty
except flexion
is delayed
Delayed and
difficult
Difficult by
exaggerated
parietal
presentation

11. GYNECOID ATHROPOI
D
ANDROID PLATYPEL
LOID
Internal
rotation
Easy anterior
rotation
Non-rotation
common
Difficult
anterior
rotation. Not
occurs early
above the
ischial spine,
chances of
arrest
Anterior
rotation
occurs late in
the perineum
Delivery No difficulty More
incidence of
face to pubis
delivery.
Difficult
delivery with
increased
chances of
perineal
injuries
No difficulty
CAVITY AND OUTLET

12. INTERMEDIATE OR MIXED TYPE
OF PELVIS
• Apart from these parent forms, intermediate forms with
combination of features are found more commonly.
• Based on the type of posterior & anterior segments of inlet.
• Posterior segment determines the type of pelvis.

14. CLINICAL SIGNIFICANCE
SMALL GYNECOID PELVIS:
• Shape is normal
• Diameters are proportionately reduced. Hence, there is delay
at every stage of labour due to lack of space.
• Powerful uterine contractions are required to push the
presenting part downwards.

15. CLINICAL SIGNIFICANCE (CONT.)
ANDROID PELVIS:
• Occipito-posterior position is common
• Due to the funnel shape of the pelvis
• Progressive difficulty is faced.
• Rotation fails to occur.
• Transverse arrest is common.
PLATYPELLOID PELVIS:
• Difficulty in engagement of foetal head.