Obsteritric Anatomy overview for obs and gyn

Gives a brief overview for anatomy

1. OBSTETRIC ANATOMY Group B CONTENTS Introduction Female pelvis Pelvimetry Cephalopelvic disproportion Contracted pelvis

2. Objectives To learn about: Applied anatomy of female pelvis - Basic anatomy - Classification - Pelvic inlet & outlet - Pelvic measurement - Variation in pelvis

3. Introduction Obstetric anatomy refers to the anatomical structures of the female reproductive system and the pelvis that are involved in conception, pregnancy, labor and delivery. Landmarks Ischeal spine Sacral prominent Illiac crest Anterior superior iliac spine Symphysis pubis

4. Landmarks Pubic crest Pubic tubercle Pectineal line iliopectineal eminence Sacral ala or wing Sacral promontory

5. Bony Pelvis Bony pelvis is formed by 1) 2 Hip bones formed by fusion of 3 bones – ilium, ischium and pubis 2) Sacrum formed by fusion of 5 sacral vertebrae 3) Coccyx formed by fusion of 4-5 coccygeal vertebrae Pelvic girdle = hip bones + sacrum

6. Function Of Bony Pelvis 1) To protect pelvic viscera 2) To support the weight of the body - transfer the weight of the upper body from the axial to the lower appendicular skeleton 3) Provides attachment for muscles 4) In females, it provide bony support for the birth canal

7. HIP BONE 2 hip bones are joined at the pubic symphysis Hip bones articulate with the sacrum at the sacroiliac joints Ilium, ischium and pubis fused at acetabulum

8. CLASSIFICATION OF PELVIS Divided into: 1) False pelvis (pelvis major; greater pelvis) Part of abdominal cavity 2) True pelvis (pelvis minor; lesser pelvis ) Is the true pelvic cavity Lies inferior to pelvic brim/pelvic inlet

9. PELVIMETRY Measurement of the dimensions of the bony pelvis undertaken chiefly to help determine whether a woman can give birth normally or requires C-section Types : clinical (by VE) and Radiological .

10. PELVIC INLET Pelvic inlet is bounded by: 1. Superior margin of pubic symphysis 2. Pubic crest 3. Iliopectineal line 4. Anterior border of ala of sacrum 5. Sacral promontory

11. MEASUREMENTS OF PELVIC INLET Four diameters of pelvic inlets 1) Anteroposterior (true conjugate) 2) Diagonal conjugate – can be measured clinically 3) Obstetric conjugate 4) Transverse diameter

12. Anterior posterior diameters True conjugate (anatomical conjugate) : sacral promontory to upper border of the pubic symphysis (11cm) Obstetric conjugate : sacral promontory to posterior surface of the pubic symphysis(10.5cm) Diagonal conjugate: sacral promontary to lower border of the pubic symphysis (12.5-13cm ) this is what is used clinically to estimate obstetric conjugate by subtracting 1.5cm

13. Obstetric conjugate is clinically important – It is shortest AP diameter through which the head must pass. But cannot be measured clinically Diagonal diameter can be measured clinically For clinical purposes, obstetric conjugate is estimated indirectly by subtracting 1.5 to 2 cm from diagonal conjugate

14. Vaginal Examination to Determine Diagonal Conjugate

15. THE MID CAVITY It is bounded anteriorly by the mid point of the pubic symphysis , posteriorly by the junction of 4th and 5th sacral vertebrae and laterally by the ischial spines. The most important diameter is the interspinous diameter between the two ischial spines =10cm

16. Diamond shaped Is bounded by: 1) Inferior margin of the pubic symphysis 2) Inferior rami of the pubis 3) Ischial tuberosities 3) Sacrotuberous ligaments 4) Tip of coccyx

17. Measurement Extension Diameter Anteroposterior diameter From lower margin of pubic symphysis  sacrococcygeal joint 12.5 cm Transverse diameter ( intertuberous ) Between the ischial tuberosities (Diameter > 8 cm – normal) 11 cm

18. Pelvic outlet The pelvic outlet assessed clinically by the fist test (if 4 knuckles can fit then it is adequate

19. CALDWELL MOLOY CLASSIFICATION Female pelvis shapes may be subdivided as follows (after Caldwell and Moloy ) 1. Normal and its variants - Gynaecoid – most common type , suited for delivery - Android – the masculine type of pelvis - Platypelloid – flat pelvis; short AP diameter & wide transverse diameter - Anthropoid – resembling that of anthropoid ape, AP diameter is greater than the transverse 2. Symmetrically contracted pelvis - That of a small women but with a symmetrical shape

20. GYNAECOID PELVIS Is a typical female pelvis. Ideal for vaginal delivery Found in 80 % of Asian women; 50-70 % white women Rounded or slightly oval inlet Straight pelvic sidewalls with roomy pelvic cavity Ischial spines are not prominent - wide interspinous diameter Good sacral curve Subpubic arch is wide

21. ANDROID PELVIS Present in most male and also in few females 0.6 % in Asian women; 2-8% in white women Heart shaped (or triangular) pelvic inlet - due to prominent sacrum Pelvis funnels from above downwards (convergent sidewalls) Prominent ischial spines Sacrum inclining forward Narrow subpubic arch

22. ANTHROPOID PELVIS Present in some males and females 15% in Asian women; 15-30% in white women Pelvic inlet is long oval AP diameter > tranverse diameter Long & narrow sacrum (often with 6 sacral segments) Straight pelvic sidewalls

23. PLATYPELLOID PELVIS Uncomon in both sexes 6 % of Asian women; 8-13% in white women Pelvic inlet appears slightly flattened ( kidney shape) Transverse diameter is greater than AP diameter Sacral promontory pushed forwards Straight pelvic sidewalls Subpubic angle & interspinous diamater are wide

24. Normal Pelvic Variations

25. DIFFERENCES BETWEEN MALE & FEMALE PELVIS

26. Contracted pelvis This is a pelvis with one or more diameters reduced below normal making vaginal delivery difficult or impossible Types inlet contraction mid pelvis contraction outlet contraction