Radiological features of achondroplasia, pseudochondroplasia and hypochondroplasia with explanation with the help of images.

1. ACHONDROPLASIA,
PSEUDOCHONDROPLASIA &
HYPOCHONDROPLASIA
DR.ANKIT BENIWAL

2. ACHONDROPLASIA
• Autosomal dominant disturbance in epiphyseal chondroblastic
growth and maturation. Homozygous achondroplasia is lethal. It is
most common skeletal dysplasia and leads to rhizomelic dwarfism
i.e. dwarfism where the dominant feature is proximal limb
shortening (i.e. femoral, humeral).
• The major abnormality is failure of normal enchondral cartilage
growth at the physis. Periosteal and membranous ossification are
normal. Some enchondral ossification centres are affected more
than others, particularly those at the base of skull and at the ends of
long bones.
• Its prevalence is approx 1 in 25,000 to 50,000 births with males
more frequently affected. It is most common type of
disproportionate dwarfism.

3. ANTENATAL ULTRASOUND
• Antenatal detectable sonographic features include:
Short femur length measurement: often well below 5th
centile.
The femur length (FL) to biparietal diameter (BPD) is taken as
a useful measurement.
Trident hand: 2nd ,3rd and 4th fingers appears similar in length.
Protruding forehead: frontal bossing.

4. RADIOLOGICAL FEATURES
SKULL
• These changes are mandatory to the diagnosis of
achondroplasia.
• Narrowing of the spinal canal is the pathologic hallmark of
achondroplasia.
• The base of the skull (which is formed by enchondral
ossification) is small, often with a stenotic foramen magnus.
• Basilar impression is frequent.
• The cranium is large, though short in its antero-posterior
dimension (Brachycephaly)

5. • The frontal bones are prominent and the nasal bones are
small.
• The mandible forms normally and, therefore gives the
impression of prognathism.
• Cervico medullary kink is seen.
• Relative elevation of the brainstem resulting in a large
suprasellar cistern and vertically-oriented straight sinus.
• Communicating hydrocephalus.

6. Relativelylarge
cranialvault
withsmall
skullbase.
Prominent
foreheadwith
depressed
nasalbridgeis
seen.Narrow
foramen
magnumis
noted

7. • Cranial vault is relatively large with small
base.
• Prominent forehead with depressed nasal
bridge.
• Narrow foramen magnum.
• Cervico-medullary kink.
• Relative elevation of the brainstem gives
rise to a large suprasellar cistern and a
vertically oriented straight sinus.

8. • The clivus is short such that the tip of
the odontoid is elevated to the level of
the posterior lip of foramen magnum.
At this point, the AP diameter of the
bony cranio-cervical junction
measures only 7mm.
• The cord fills the available
subarachnoid space at this level, and
there is impingement on the cord by
the posterior lip of foramen magnum.
Subtle T2 hyperintensity (shown by
arrow) is seen in the medulla and in
the upper cord down to the level of
junction of odontoid with body of C2.

9. • LIMBS
• There is symmetric shortening of all long bones. The
femur and humerus are particularly shortened.
• Metaphyseal flaring: can give a trumpet bone type
appearance.
• The bone ends are often splayed, with metaphyseal
cupping.
• V shaped growth plates are seen, because periosteal
ossification proceeds normally, there is relative widening
of the shafts.

10. • The ulna and tibia are often shorter than the radius and fibula.
• The tubular bones of the hands and feet are short and thick.
• The fingers are all the same length, with separation of middle
and ring fingers (Trident hand)
• Show prominent muscle insertions.

11. • Image shows femoral physes
with ‘inverted V’ (Chevron sign)
configuration of distal physes
which causes waddling gait.
• Genu varum: rhizomelic
shortening of both femurs with
metaphyseal flaring. The bones
are wide because of unaffected
appostional growth.

12. Thesplayedandcupped
metaphysesaswellasthe
shorteningoftheleg

13. Characteristictridenthand,
with separationofthe3rd
and4th digits(divergent
digits).Thefingersareall
thesameinlength.
Shortandthicktubular
bone.
Carpalandtarsalbonesare
littleaffected.

14. SPINE
• Posterior vertebral scalloping.
• Progressive decrease in interpedicular distance in lumbar
spine (L1 to L5).
• Gibbus: thoracolumbar kyphosis with bullet-
shaped/hypoplastic vertebra

15. • Short interapedicle distance causing canal stenosis.
• Laminar thickening.
• Widening of intervertebral discs.
• Increased angle between sacrum and lumbar spine.
• L5 is deeply set and excessive pelvic tilt causes
prominence of the buttocks and an illusion of lordosis.

16. • Note the posterior
scalloping of the
vertebral bodies.
• The pedicles are short
and thick and contribute
to the development of
lumbar spinal stenosis.

17. • Note the
increased disc
height and
bullet-nosed
vertebrae.

18. Thisisa19yroldpatientof achondroplasia.
Findingsnotedare:1.Shortpedicle.
2.Posteriorvertebralscalloping
3.Thoracolumbarkyphosis
4.Tombstoneiliacwings(squareshaped)

19. PELVIS & HIPS
• The entire pelvis is small.
• The ilia are shortened caudally and flattened. With small
sciatic notches.
• The acetabula are horizontally oriented (decreased
acetabular angle), and there is excessive thickening of
the Y cartilage/triradiate cartilage of acetabulum.

20. • The pelvis assumes a characteristic champagne glass
appearance (champagne glass type pelvic inlet).
• Small squared (tombstone) iliac wings.
• Short sacroiliac notches.

21. 1.Dysplasticorsquare
iliacbones
2.Narrowsacro-
sciaticnotches
3.Flatbilateral
acetabularroofs
4.Shortbothfemoral
necks
5.Champagneglass-
shapedpelviccavity

22. CHEST
•Anterior flaring
of ribs.
•Antero-posterior
narrowing of
ribs.
•Shortening of
ribs

23. PSEUDOACHONDROPLASIA
• Pseudoachondroplasia (PSACH) develop short-limbed
dwarfism with notable features of joint laxity, early onset
degenerative joint disease, metaphyseal and epiphyseal
maldevelopment, and vertebral malformations.
• It has autosomal dominant inheritance pattern.
• It presents between 2 and 4 years of age. It has a prevalence
of approximately 4 per million.

24. KEY PHYSICAL EXAMINATION
FEATURES ARE:
1. Normal facial appearance and intelligence.
2. The adult height ranges from 82 to 130 cm with a mean
height of approximately 118 cm.
3. There is marked shortening of the limbs with limited elbow
extension.

25. 4. Patients are also noted to have deformities secondary
to osteoarthritis and joint laxity, including cervical spine
instability, genu valgum, genu varum, and genu
recurvatum.
5. Deformities of the back may include scoliosis, lumbar
lordosis, and thoracolumbar kyphosis.
6. Of importance, disturbance of gait (waddling gait) or a
deformity of the legs at approximately 2 years of age.

26. KEY RADIOLOGICAL FEATURES ARE:
• A normal skull and variable vertebral findings.
• There may be a persistent oval shape to the vertebral bodies during
childhood. Characteristic ‘central anterior tongues’ are seen.
• Anterior "beaking," platyspondyly, triangular outline, odontoid
dysplasia, and disc space widening may also be present.
• The long bones are shortened, have flared metaphyses, and have
small epiphyses that appear flared and irregular. These
manifestations are most notable in the hands and feet, but may also
be seen proximally.

27. • The development of the epiphyses is also delayed.
• The acetabulum is usually poorly formed and reveals a
widened triradiate cartilage.
• One finding very characteristic is the medial beaking seen in
the medial portions of the proximal femoral neck.
• The hands and wrists show delayed maturation, and there is
shortening and widening of the phalanges, metacarpals, and
metatarsals.

28. Xray PBHreveals:
Squareiliawithshort
pubisandischia.
Dysplasticacetabuli.
Characteristicmedial
beakoffemur
bilaterally

29. • X ray Tibia-fibula
with ankle
reveals:
• Short bones.
• Marked flared
epiphysis.
• Irregular and
deformed
epiphysis

30. • X ray spine reveals:
• Tongue-like
projections of the
vertebral bodies, also
called central beaking
• Superior and inferior
defects.
• Platyspondyly is seen
throughout the spine.

31. • X ray hands reveals:
• The phalanges are stubby
and the epiphyses angular
and irregular.
• The metacarpals short.
• The carpal bone epiphyses
appear late (delayed) and
irregular
• In both the hands-the
radius and ulna are flared
at the metaphyses.

32. • Exaggerated Kypho-
scoliosis is noted in a
patient of
pseudoachondroplasia

33. • Normal skull of
pseudoachondroplasia
patient.
• No skull bossing,
depressed nose or small
skull base noted.

34. HYPOCONDROPLASIA
• It is condrodystrophy with autosomal dominant
inheritance, is a form of short stature.
• FGFR3 gene mutation is known to be associated
with it.
• In it skull in never involved. Always appears
normal.

35. Physical Features:
• Short stature.
• Shortening of proximal (rhizomela) or middle
(mesomelia) segment of the extremities.
• Broad, short hands and feet (brachydactyly).
• The abdomen and buttocks are prominent.
• Bow legs (genu varus).
• Mild to moderate intellectual disability.
• Scoliosis.

36. Radiological fetaures:
• Shortening of long bones with metaphyseal
flaring.
• Narrowing of interpedicular distance from L1 to
L5 with short pedicles.
• Brachydactyly.
• Short and broad femoral neck.
• Distal fibula overgrows as compared to distal
tibia.
• Small iliac bones.

37. • Short and broad
femoral neck is seen
here.

38. • Narrowing of
interpedicular
distance from L1 to
L5, which leads to
canal stenosis

39. THANKYOU