RADIOGRAPHIC ANATOMY OF PELVIS, HIP AND SI JOINTS

1. Radiographic Anatomy
of Pelvis, Hip and SI
Joints
DR. SHRAVANI SHINDE
JR I RADIOLOGY
BHARATI HOSPITAL
References
Chiamil SM, Abarca CA. Imaging of the hip: a systematic approach to the young
adult hip. Muscles Ligaments Tendons J. 2016;6(3):265–280. Published 2016
Dec 21. doi:10.11138/mltj/2016.6.3.265
Lim SJ, Park YS. Plain Radiography of the Hip: A Review of Radiographic
Techniques and Image Features. Hip Pelvis. 2015;27(3):125–134.
doi:10.5371/hp.2015.27.3.125

2. PELVIS
 Primary function is to allow
movement of the body, while
walking, running, sitting and
kneeling. The pelvis contains
and protects the reproductive
organs as well as the bladder
and rectum.
 The pelvis is formed by the
two innominate bones and
the sacrum (the innominate
bones are themselves formed
from the ilium, ischium and
pubis).

3. PELVIC JOINTS
 The symphysis pubis (< 5mm): A slightly movable joint
at the junction of the two pubic bones, united by a pad of
cartilage.
 The sacroiliac joints(2-4mm): are the strongest joints in
the body. They are formed where the ilium joins with the
first two sacral vertebrae thus connecting the spine to the
pelvis.
 The sacrococcygeal joint: is a hinge joint between the
sacrum and the coccyx, which, at the end of labour, allows
the coccyx to be deflected backwards facilitating delivery
of the fetus.

5. HIP JOINT
 Ball-and-socket type of
synovial joint.
 The head of the femur
articulates with the
acetabulum (formed by
the union of ilium,
ischium & pubis in early
adulthood).
 Joint space: 3-5mm.

6. HIP JOINT CAPSULE
 The hip joint capsule attaches to the
edge of the acetabulum proximally.
Distally, it attaches to the
intertrochanteric line (anteriorly) and
the femoral neck (posteriorly).
 Ligamentum teres attaches to fovea
capitis (in femur) and the cotyloid
fossa (in acetabulum) and acts as a
secondary stabilizer.
 Acetabular labrum is a ring
of cartilage that surrounds
the acetabulum of the hip. It
provides an articulating surface for
the acetabulum.

7. OSSIFICATION OF HIP BONE
Three primary:
 Ilium: 2 months in utero
 Ischium: 4-6 months in utero
 Pubis: 4-6 months in utero
Five secondary:
 The crest of the ilium (one each).
 The anterior inferior spine (one each).
 The tuberosity of the ischium (one each).
 The pubic symphysis (one each).
 The Y-shaped piece at the bottom of the acetabulum (one or more).
The ilium, ischium and pubis all fuse at 7-9 years. Acetabulum fusion(i.e. replacement
of triradiate cartilage) occurs at 18-20 years of age.

8. OSSIFICATION OF PROXIMAL
FEMUR
 Shaft: 7 weeks in utero
 Femoral head: 4-6 months
 Greater trochanter: 2-4 years
 Lesser trochanter: puberty
All of the femoral ossification centres fuse at the age of 14 -18 years.

9. MALE PELVIS

10. FEMALE PELVIS

12. Lines (Pelvis)
Iliopectineal/ Iliopubic line:
Determines the inner margin of the pelvic ring
and the anterior column of acetabulum.
Fractures extending through the anterior column
disrupt this line.
Ilioischial line:
This defines the posterior column of the pelvis.
Tear drop:
Radiographic projection of bony ridge running along
the floor of the acetabular fossa.
The distance of the tear drop to medial aspect of
femoral should be < 11 mm on both sides.
Displacement of tear drop indicates occult acetabular
fracture.

13. Lines (Hip)
 Line of Kline is a line drawn along the long axis of the femoral
neck, which normally will intersect the epiphysis. It is useful in
detecting early SCFE.

14. The Shenton arc extends from the undersurface of
superior pubic ramus to medial aspect of femoral
neck. If disrupted, can indicate fracture of femoral
neck or DDH.

15. Hilgenreiner line is a horizontal line
connecting the triradiate cartilages

16. Perkins line is a perpendicular to the
hilgenreiner line through the lateral edge
of the acetabular roof. They both define
four quadrants in which, in normal hips, the
femoral head should be in the lower inner
quadrant.

17. Fat pads
Gluteus minimus,
Iliopsoas, Obturator fat
pads.
 These pads define
respective muscles.
They must be
rectilinear and well
defined.
 If they have a
convexity, implies
distension of the
hip joint with fluid
(hematoma/effusio
n).
Gluteal (white arrow), Iliopsoas (blue
arrow), Obturator fat pad (black arrow).

18. Pelvic Inlet
 The pelvic inlet is oval shaped and is widest transversely. It divides
the bony pelvis into the false pelvis above (made up mainly of the
ala of the ilium on each side), and the true pelvis below (the pelvic
cavity). The boundaries of the pelvic inlet include:

19. Types of pelvis

20. Acetabular Angle
 Angle measured from
Hilgenreiner’s line (in children) or
teardrop sign (in adults) to a line
intersecting most superolateral
aspect of acetabular roof.
Children: <28º at birth,
>22º after 1 year
 Decreased angle: Down syndrome,
achondroplasia
 Increased angle: DDH
Adults: 33 - 38º

21. Suspicion for dislocation
based on image results
 Posterior dislocation: Femoral head is superolateral
to joint space and appears smaller than C/L; can lead
to sciatic nerve damage.

22. Anterior dislocation: Femoral head is
inferomedial to joint space and appears
larger than C/L side; anterior dislocations
can damage the femoral nerve and artery.

23. AP – pelvis and both hips
(basic projection)
Used as a first assessment of the pelvic bones and hip
joints.
Position of patient and cassette
• Patient lies supine with median sagittal plane perpendicular to the
table.
• To avoid pelvic rotation, both the ASIS must be equidistant from
the tabletop. The coronal plane should be parallel to the table.
• The limbs are slightly abducted and internally rotated to bring the
femoral necks parallel to the cassette.
The center of the cassette is placed level with the upper border of
the symphysis pubis for the hips and upper femur.

24. Essential image
characteristics
 Both iliac crests and
proximal femur,
including both the
trochanters, should
be visible.
 No rotation.
 Pubic symphysis
and coccyx in
middle with approx.
1-3 cm distance in
between.
 It should be
possible to identify
Shenton’s line

25. Anatomical appearances
with Position of limb
 Neutral – Long axis of foot vertical, femoral neck
oblique. Lesser trochanter just visible.
 Internal rotation: Femoral neck appears elongated
but the lesser trochanter obscured by shaft of femur.
 External rotation: Femoral neck appears shortened.
Lesser trochanter clearly visible.

27. Posterior oblique (Lowenstein’s
projection)
Position of patient and cassette
• Patient lies supine, legs extended, the median sagittal
plane coincides with long axis of table.
• The patient rotates 45 degrees on to the affected side,
with the hip abducted and flexed 45 degrees.
• The knee is flexed to bring the lateral aspect of the thigh
into contact with the table.
• The cassette is centered at the level of the femoral pulse
in the groin and should include the upper third of the
femur. The upper border of the cassette should be level
with the ASIS.

28. Posterior oblique (Lowenstein’s
projection)

29. True lateral – neck of femur
(basic)
Position of patient and cassette
• Patient supine, legs extended, the median sagittal plane
perpendicular to the table.
• The unaffected limb is then raised until the thigh is vertical,
with the knee flexed.
• The cassette is positioned vertically, with the shorter edge
pressed firmly against the waist, just above the iliac crest on
the affected side.
• The longitudinal axis of the cassette should be parallel to
the neck of femur.

30. True lateral – neck of femur
(basic)
• Routinely used for suspected
neck of femur fracture

31. Anterior oblique (Judet’s
projection)
Position of patient and cassette
• Patient prone
• The trunk is rotated 45 degrees on to the unaffected
side and the affected side is raised.
• Centre just distal to the coccyx, with the central beam
directed 12 degrees towards the head.

32. Anterior oblique (Judet’s
projection)
Judet view (LPO - right hip elevated)
• Used in cases of suspected
acetabular fracture.
• Although the acetabulum is seen
on the AP pelvis, the anterior and
posterior rims are superimposed
over the head of the femur and the
ischium

33. Posterior oblique (reverse
Judet’s projection)
Position of patient and cassette
• Patient supine.
• Affected side is raised approximately 45 degrees.
• Centre to the femoral pulse on the raised side, with the
central ray directed 12 degrees towards the feet.

34. Posterior oblique (reverse
Judet’s projection)
Used in trauma cases to demonstrate
fractures of the pelvis and acetabulum.

35. Lateral - both hips (frog’s legs position
 Position of patient and cassette
 Patient supine with equidistant ASIS from table to
avoid rotation.
 The hips and knees are flexed and the limbs rotated
laterally through approximately 60 degrees.
 Centre in the midline at the level of the femoral pulse,
with the central ray perpendicular to the table.

36. Lateral - both hips (frog’s
legs position)

37. SI Joints - Postero-anterior
Position of patient and cassette
 Patient prone.
 The posterior superior iliac spines should be
equidistant from the tabletop to avoid rotation.
 Centre in the midline at the level of the posterior
superior iliac spines.
 The central ray is angled 5–15 degrees caudally from
the vertical. The oblique rays coincide with the
direction of the joints.

38. SI Joints - Postero-anterior

39. Questions

40. Identify the view

41. Thank you