Classification of pelvis

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

4. ANATOMICAL FEATURES OF PARENT PELVIC TYPES

5. GYNECOID (50%) ANTHROPOID (25%) ANDROID (20%) PLATYPELLOID (5%)

6. 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.

7. 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

8. OBSTETRIC OUTCOME IN PARENT PELVIC TYPE

9. INLET GYNECOID ATHROPOID ANDROID PLATYPELLOID 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

10. GYNECOID ATHROPOID ANDROID PLATYPELLOID 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

11. 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.

12. 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.

13. 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.