1. Pelvis: structure, diameters, static
Ákos Lukáts MD. Ph.D

2. os coxae (pelvic bone) 2x!
Osseous pelvis
Sacroiliac joint
sacrum
os coxae (pelvic bone) 2x!
coccyx (tail bone)
Ring, composed of 3 (+1) bones
Limited movements, great forces and shear stress
Coccyx has no major mechanical role
Pubic symphysis

3. Os coxae
ilium
pubic bone
ischium

4. Iliac crest
ant. sup.
iliac spine
post. sup.
Iliac spine
ant. inf. iliac spine
post. Inf. Iliac spine
Acetabulum
Symphyseal surface
Ischiac spine
Obturator foramen
Tuber ishiadicum.

5. Importance of palpation: intramuscular injection
Triangular technique
(trochanter major, anterior superior iliac spine, iliac crest)
NOT to hit: superior gluteal
a., v., n.
Sobota - Atlas of Human Anatomy

6. Lesser sciatic foramen : They enter the ischiorectal fossa!
Gluteal region
Suprapiriform hiatus :
superior gluteal a., v., n.
Infrapiriform hiatus:
inferior gluteal a., v., n.
sciatic n.
posterior femoral cut. n.
internal pudendal a., v.
pudendal n.
Lesser sciatic foramen :
internal pudendal a., v.
pudendal n.
They enter the ischiorectal fossa!
Sobota - Atlas of Human Anatomy

7. 3 bones ossify together near puberty to form an 8-shaped structure
Firs centers of ossifications already visible at 3rd fetal month
Common body of the bones forms the acetabulum – extremely strong
Force acting from proper direction in utero is inevitable for the normal development of acetabulum.
(hip dysplasia)
pecten
Symphyseal surface

8. Hip dysplasia, hip dislocation
Causes: intrauterine developmental defect of acetabular fossa, not deep enough, can dislocate to relatively small forces.
(twins, oligohydramnion, ??)
Screening (physical examination, ultrasound)

9. Hip dysplasia, hip dislocation
Therapy: proper positioning of femur after birth:
Pavlik harness
(anteflexion, abduction)
Forces acting on the head of femur deppen the acetabular fossa!
Operations rarely needed today.
Greater degrees in small children!

10. Sacrum, coccyx
5 sacral and 2-4 coccygeal vertebrae ossify together (synostosis).
Coccyx fairly rudimental, can ossify together with sacrum.
Problems at birth.
Auricular surface
(fibrous cartilage)

11. Sacroiliac joint, pubic symphysis
Structures holding osseous ring together:
Sacroiliac joint (plane joint)
great shear stress: fibrous cartilage
symphysis (synchondrosis – almost proper joint)
Sacroiliac joint
Pubic symphysis

12. Ligaments of Sacroiliac joint
Sacro-iliac ligaments dorsal
inerosseal
ventral
Functionally belong to here:
Ileolumbal lig. ,
Sacrospinous lig.
Sacrotuberous lig.
(two-armed lever)

14. Pubic symphysis

15. Bones and ligaments Greater schiatic foramen Obturator canal
Subinguinal hiatus
Sacrospinous lig.
Sacrotuberous lig.
Inguinal lig.
Lesser schiatic foramen
Obturator membrane (+ m. obt. Ext, int.)

16. Pelvis minor Superior aperture : 60-65º - inclinatio pelvis
Terminal line (linea terminalis):
Promontory
Lateral mass
Arcuate line
Pecten ossis pubis
Symphysis, upper border
Inferior aperture:
10-15º
Coccyx
Sacrotuberous lig.
Rami of pubic and schiatic bones
Symphysis, inf. border

17. Diameters of the lesser pelvis
a: superior aperture
b: cavity (amplitudo pelvis)
(greatest diameter)
c: angustia pelvis
(smallest diameter)
d: inferior aperture a b
HOUR-GLASS FORM c d

18. distantia spinarum (25-26 cm) distantia cristarum (28-29 cm)
Diameters: superior aperture
Greatest: transverse diameter
Median diameter
11 cm
Oblique diameter
12 cm
Transverse diameter
13,5 cm
distantia spinarum (25-26 cm)
distantia cristarum (28-29 cm)

19. Conjugates a b c a: conjugata anatomica vera
anatomical conjugate 12 cm
b: conjugata anatomica obstetrica
obstetric conjugate
11.5 cm
c: conjugata diagonalis
diagonal conjugate
13 cm
Diagonal conjugate can be measured by intravaginal examination. a b c

20. Diameters: amplitudo pelvis
Almost circular
Greatest diameter: oblique (approx.14 cm)
All diameters >13cm

21. Diameters: angustia pelvis
Almost circular
Smallest diameters of pelvis
Greatest diameter: oblique (approx.10 cm)

22. Diameters: inferior aperture
11,5-12 cm
Coccyx bends away: 2 cm

23. Greatest diameters Superior aperture: transverse: 13-13.5 cm
Amplitudo pelvis:
oblique: 14 cm
Inferior aperture:
sagittal: cm

24. A bit of gynecology oblique transverse sagittal
At birth, the head of the baby must always fit to the greatest diameters: rotates 90 degrees!

25. Axis pelvis
Bent tube

26. Sexual differences
Arcus pubis
Angulus pubis
Female
Male

27. Female
Male

28. Static of pelvis: center of gravity
Passing through the following structures:
atlantooccipital joint
lower lumbar vertebrae, anterior to promontory
head of femur - acetabulum
talus (highest point of longitudinal lantar arch)
Weight and support in the same plane! – Can stay in equilibrium without continuous muscle work.
It is only possible if the superior aperture of pelvis is bent degrees! – Pelvic inclination

29. Pelvic inclination Approximately 60-65 degree.
(male – 60, female – 65)
Ant. Sup iliac Spine and symphysis lies approximately in the same frontal plane.
Position of sacrum: almost horizontal.

30. Leonardo da Vinci
Vesalius (1538)

31. Flexible support, energy absorption
Two-armed lever
F1 x d1 = F2 x d2 F1 F2 d1 d2
Flexible support, energy absorption

33. Double arch

34. Aqueduct, Pont du Gard, France

35. Sitting position Force/weight is transferred to tuber ischiadicum.
„Sitting tubercule”!

36. Normal AP. X-ray.

37. Fracture with dislocation (open book)

38. Post-partum pubic diastasis

40. Always to think about pelvic deformity
Trauma (car accidents)
Vertebral deformity
Vit D deficiency (rachitis)
Any disease requiring long-term inbed therapy in children
Some genetic diseases
(fetal size)

41. Dog: pelvic fracture

42. Literature
Szentagothai J, Réthelyi M: Funkcionális anatómia, Medicina, 1989
Sobota - Atlas of Human Anatomy, 20th edition, Urban and Schwarzenberger, 1993
Renner Antal: Traumatológia, 2nd edition, Medicina, Budapest, 2003
Vízkelety Tibor: Az ortopédia tankönyve, 2nd edition, Semmelweis Kiadó, 1999
Radiologic images: