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Fig. 13.15. (a). A skyline
(a)
view of the patella. Note
Patella
how the lateral femoral
condyle projects more
anteriorly, tending
to prevent lateral
Lateral Medial
femoral femoral patellar dislocation;
Medial collateral Medial
condyle condyle Lateral Fibular collateral
(b) intercondylar view of ligament meniscus meniscus ligament
the knee.
(c)

Patellar tendon
Medial retinaculum Patella

(b)
Patella


Lateral
Medial
femoral
femoral
condyle
condyle
grooved by
popliteus
tendon


Medial Lateral
tibial tibial
condyle condyle

Medial and lateral Semi-membranosus Posterior
Head of head of tendon cruciate
fibula gastrocnemius ligament


Fig. 13.16. PD MRI of the knee (a) sagittal; (b) coronal; (c) axial.




Ossi¬cation is shown in Fig. 13.18.
Ultrasound scanning may be used to assess the patellar tendon, the
collateral ligaments and meniscal and popliteal cysts.
The tibio¬bular joints
The superior tibio¬bular joint is a plane synovial joint between the
The lower leg
head of the ¬bula and the articular surface under the lateral tibial
The tibia and ¬bula (Fig. 13.17) condyle.
The inferior tibio¬bular joint is a ¬brous joint (syndesmosis)
These are joined by a tough ¬brous interosseous membrane. They
between the lower end of the ¬bula and the ¬bular notch of the tibia.
give rise to the attachments of many of the muscles of the lower leg.

136
The lower limb a. newman sanders


Fig. 13.17. The tibia and
(a) (b)
Tubercles of Groove for ¬bula; (a) anterior,
intercondylar tendon
(b) posterior.
eminence of popliteus
Lateral condyle Lateral condyle
Medial condyle
of tibia of tibia
of tibia
Apex
Apex of head
of fibula
Head of fibula
Tuberosity
of tibia
Head of Soleal line
fibula
Nutrient
Anterior border
foramen
Interosseous
Interosseous
border
border
Medial crest
Medial crest
Anterior Vertical line
border
Anterior surface
Medial border
Medial surface
Medial part of
Posterior Interosseous
posterior surface
border border
Lateral surface




Groove for tibialis
Triangular
posterior tendon
subcutaneous Groove for
area peroneal
Medial Medial malleolus
tendons
malleolus
Lateral
Lateral
malleolus
malleolus




Tibialis Tibialis Posterior tibial
anterior posterior vessels
Flexor
Extensor
digitorum
digitorum
longus
longus


16th“18th Soleus
year
I2th year
Ist year
Anterior
Medial
tibial
head of
vessels
gastrocnemius




Peroneus
longus
Fig. 13.18. Ossi¬cation of the tibia and ¬bula. The distal and proximal epiphyses and brevis
tendons
fuse with the shaft at 16“18 years.

Lateral
Flexor hallucis head of
It is reinforced by the interosseous ligament of the joint and the ante- longus gastrocnemius
rior and posterior inferior tibio¬bular ligaments. Movements at both
joints are extremely limited.
Fig. 13.19. T1W axial MRI of the mid-calf.

The muscles of the lower leg (Figs. 13.19, 13.20)
Anterior compartment
Tibialis anterior takes origin from the upper part of the anterior tendons, which pass under the extensor retinaculum and insert
surface of the tibia and adjacent interosseous membrane and forms via a dorsal expansion onto the dorsum of the middle and distal
a tendon which descends anterior to the ankle joint deep to the phalanges of the lateral four toes. Peroneus tertius arises from the
extensor retinaculum to attach to the medial cuneiform and the base anterior surface of the ¬bula and inserts into the shaft of the ¬fth
of the ¬rst metatarsal. metatarsal.
Extensor hallucis longus (EHL) arises from the anterior surface of
The lateral (peroneal) compartment
the ¬bula. Its tendon passes under the extensor retinaculum and
inserts on to the dorsum of the base of the distal phalanx of the These muscles arise from the lateral surface of the ¬bula. Distally,
hallux. the tendon of peroneus longus passes behind the lateral malleolus
Extensor digitorum longus arises above and lateral to EHL from beneath the peroneal retinaculum, passes forwards lateral to the
the anterior surface of the ¬bula. Distally, it divides into four calcaneus and into a groove in the inferior surface of the cuboid

137
The lower limb a. newman sanders


(a) of FHL (at the so-called Knot of Henry), and giving four slips to the
Tibialis anterior tendon
distal phalanges of the lateral four toes.
Tibialis posterior tendon
Tibialis posterior arises from the interosseous membrane and
the adjacent posterior aspects of the tibia and ¬bula. Its tendon
Flexor digitorum longus shares a groove under the medial malleolus with that of FDL and
tendon
attaches to the tuberosity of the navicular, giving slips to the
Posterior tibial nerve and other cuneiforms and the bases of the second, third, and fourth
vessels
metatarsals.

The ankle joint
Flexor hallucis longus
tendon
The ankle joint (Fig. 13.20), is a synovial hinge joint between the dome
of the talus and the concavity formed by the medial and lateral malle-
Achilles tendon oli and the inferior articular surface (plafond) of the tibia. The ¬brous
Peroneus longus
capsule is attached around the articular margins except anteriorly,
and brevis tendons
where its attachment extends down the anterior surface of the neck of
the talus. The synovial membrane lines the ¬brous capsule.
The ankle joint is strengthened medially by the deltoid or medial
(b)
collateral ligament, which has three components attached above
Flexor hallucis
to the medial malleolus and below to the tuberosity of the navicular
Dome of talus longus tendon Lateral malleolus
(tibionavicular), the sustentaculum tali of the calcaneum (tibiocal-
caneal), and the medial side of the talus and its medial tubercle
(posterior tibiotalar). The lateral ligament complex is made up of the
anterior talo¬bular ligament, joining the lateral malleolus to the neck
of the talus, the calcaneo¬bular ligament, joining the lateral malleolus
to the tubercle on the lateral side of the calcaneum (which is crossed
by the tendons of peroneus longis and brevis), and the posterior
talo¬bular ligament, which passes backwards from the lateral malleo-
lus to the posterior process of the talus.
The movements of the joint are dorsi¬‚exion, produced by tibialis
anterior, extensor digitorum longus, extensor hallucis longus, and per-
Talonavicular joint Middle facet of Peroneus brevis and longus tendons
subtalar joint
oneus tertius, and plantar¬‚exion produced in the main by gastrocne-
mius and soleus but assisted by the three other muscles of the
posterior compartment of the leg.
Fig. 13.20. PD MRI of the ankle. (a) axial; (b) sagittal.

The foot
The tarsus consists of seven bones arranged in three rows as demon-
before inserting on the base of the ¬rst metatarsal and the adjacent
strated in Fig. 13.21.
medial cuneiform.
The tendon of peroneus brevis descends anteriorly to that of per-
The talus
oneus longus to insert on the base of the ¬fth metatarsal.
This bone, which bears no muscle attachments, is made up of a body,
neck, and head (Fig. 13.22).
The posterior compartment.
Gastrocnemius, the most super¬cial of the muscles of the calf, arises
The calcaneum
by two heads from the posterior surfaces of the medial and lateral
This, the largest of the tarsal bones, is irregularly cuboidal in shape
femoral condyles. A sesamoid bone, the fabella, is frequently found in
with its long axis directed forwards upwards and slightly laterally
the lateral head of gastrocnemius.
(Fig. 13.23).
Soleus arises from the upper posterior surface of the ¬bula and
from the posterior surface of the tibia. The tendons of gastrocnemius
The navicular
and soleus unite to form the Achilles™ (or calcaneal) tendon, the thick-
The proximal surface articulates with the talus. The distal surface is
est and strongest tendon in the body.
divided into three facets for articulation with the three cuneiform
Flexor hallucis longus (FHL) takes origin from the posterior
bones. The lateral surface may have an articular surface for the
surface of the ¬bula. Its tendon descends behind the lower tibia and
cuboid. The medial surface bears a tuberosity, which is the principal
talus and under the sustentaculum tali, passing forward into the
insertion of the tibialis posterior tendon.
¬brous sheath of the hallux and attaches to the base of its distal
phalanx.
The cuneiform bones
Flexor digitorum longus (FDL) arises from the posterior aspect of the
These are bones lying between the navicular and the bases of the ¬rst
tibia. Its tendon descends behind the medial malleolus and then
three metatarsals. The medial cuneiform is the largest of the three
passes under the sustentaculum tali into the foot, crossing the tendon


138
The lower limb a. newman sanders


(a) Fig. 13.21. (a) Oblique,
(b)
and (b) dorsiplantar
radiograph of the foot.
Distal
Phalanges

Proximal
phalanx
of hallux
Distal
Sesamoid
Middle
bones in
tendon of
Proximal
flexor
hallucis
brevis 1st-5th
1st
metatarsals
2nd
Medial
Medial
3rd
cuneiform Middle
4th
Middle
Lateral
cuneiform
5th
Cuneiform
Lateral
cuneiform Metatarsal Navicular
Cuboid
Navicular
Cuboid
Talus
Talus

Calcaneum
Medial
malleolus
Lateral
malleolus




(b)
(a)

Head
For anterior
Neck
ligament of For navicular bone
Anterior calcanean
ankle joint articular surface


For plantar calcaneo-
Trochlear
navicular ligament
surface

Middle calcanean
Facet for lateral articular surface
malleolus Sulcus tali
Posterior
calcanean articular
Facet for inferior
surface
transverse ligament


Lateral tubercle Medial tubercle

Groove for flexor Groove for flexor
hallucis longus hallucis longus muscle
(d)
(c)

For medial malleolus Trochlear surface
Trochlear surface
Neck For lateral malleolus
for tibia
Neck

Posterior

Lateral
For
tubercle
navicular
bone
Groove for For Posterior
flexor For deltoid navicular calcaneal
hallucis For plantar
Medial ligament bone facet on plantar
Fig. 13.22. The talus: (a)
longus calcaneonavicular
tubercle
surface
Sulcus tali Lateral
ligament
dorsal (superior), (b)
process
plantar (inferior), (c)
medial, (d) lateral.



139
The lower limb a. newman sanders


(a) (b)
Anterior articular
surface for talus Middle articular Middle articular
surface for talus surface for talus Sulcus calcanei

Posterior articular
surface for talus
Anterior articular
surface for talus



Peroneal
tubercle Sulcus tali

Sulcus calcanei

Posterior articular
surface for talus
Peroneal
tubercle
For calcaneo- Lateral process of
fibular ligament calcaneal tuberosity

Posterior surface
(d)
(c)

For cuboid bone

Sustentaculum tali
Anterior Middle articular
tubercle surface for talus
Posterior articular
surface for talus
Anterior articular
surface for talus


Sustentaculum
tali
Groove for flexor
hallucis longus
Posterior
surface
Medial process For cuboid bone


Anterior tubercle
Fig. 13.23. The
Tuber calcanei
Medial process of
Lateral process calcaneum: (a) dorsal,
calcaneal tuberosity
(b) lateral, (c) plantar,
(d) medial.




The phalanges
and articulates with the base of the ¬rst metatarsal. It is wedge-
shaped, which helps to maintain the transverse arch of the foot. As in the hand, there are two phalanges in the ¬rst digit (hallux)
and three in the others. A minor degree of valgus in the great toe is
The cuboid often seen. In infants, the hallux is often adducted (metatarsus
The most lateral of the distal row of the tarsus articulates proximally adductus) but this is physiological and usually corrects with weight
with the distal calcaneum and distally with the bases of the fourth bearing.
and ¬fth metatarsals. The medial surface articulates with the lateral
The subtalar joint
cuneiform and sometimes with the lateral surface of the navicular.
The lateral and plantar surfaces are grooved by the tendon of per- This is functionally a single unit composed of two articulations
oneus longus. between the talus and the calcaneum (Fig. 13.24). The posterior talocal-
caneal joint is the articulation between the posterior of the three
The metatarsal bones facets on the inferior surface of the talus and the corresponding facet
The ¬ve metatarsal bones each possess a proximal base, a shaft, and a on the upper surface of the calcaneum posterior to the sinus tarsi.
distal head. The bases articulate with the distal row of the tarsus and It is reinforced by medial and lateral talocalcaneal ligaments and
with each other. The heads articulate with the proximal phalanx of by the interosseous talocalcaneal ligament, which joins the sulcus
the corresponding digit. The ¬rst metatarsal is the shortest and thick- tali to the sulcus calcanei, ¬lling in the sinus tarsi. The talocalcaneon-
est. Its head bears two articular facets on its plantar surface for articu- avicular joint is the articulation between the head of the talus and
lation with the two sesamoid bones, which are always found in the the concave posterior surface of the navicular anteriorly and the ante-
tendon of ¬‚exor hallucis brevis. The second metatarsal is the longest. rior two facets on the upper surface of the calcaneum together with
The base of the ¬fth metatarsal bears a tuberosity on its lateral aspect the plantar calcaneonavicular (spring) ligament. This ligament con-
to which is attached the tendon of peroneus brevis and part of the nects the anterior margin of the sustentaculum tali with the plantar
plantar aponeurosis. suface of the navicular bone.

140
The lower limb a. newman sanders


Fig. 13.25.
(a)
Tibiotalar component
(a) Anteroposterior (AP)
Tibiotalar joint of deltoid ligament Achilles tendon
and (b) lateral
radiographs of the
ankle.




Medial
Calcaneus
Interosseous talocalcaneal Posterior facet subtalar joint
malleolus
ligament Inferior
tibiofibular
joint
Fig. 13.24. T1W MR arthrogram of the subtalar joint.



Inversion of the forefoot, which is also associated with plantar
¬‚exion, is produced by tibialis anterior and posterior and is limited
by tension in the peronei and the lateral components of the
interosseous talocalcaneal ligament. Eversion, which is associated
Dome of
with dorsi¬‚exion, is produced by peroneus longus and brevis and Lateral talus
malleolus
limited by tibialis anterior and posterior and by the medial collateral
(deltoid) ligament.
The remainder of the joints of the foot are of less clinical interest
and will not be described.


Imaging of the foot and ankle
Plain radiography permits assessments of the bony structures and
may detect soft tissue swelling. If stress views are used, it can give
indirect information about ligamentous disruption. The ankle
(b)
joint is routinely imaged using anteroposterior and lateral radi-
ographs (Fig. 13.25). The normal joint space is 3 mm. The foot is
normally radiographed in dorsiplantar and oblique projections
(Fig. 13.21). On the dorsiplantar view, the midline of the foot,
which passes through the centre of the calcaneum and the head of
the third metatarsal, should make an angle of 15° with the long axis
of the talus.
The subtalar joint may be imaged with a series of oblique radi-
ographs with the foot internally rotated. Optimal imaging is more Fibula
normally obtained using MRI or CT.
US scanning may be used to assess the Achilles™ tendon and other
tendons of the foot and ankle. US is also employed in the evaluation
of the plantar fascia and soft tissue masses in the foot.
Dome of
Tibia
MRI in various planes, depending on the precise part of the ankle or talus
foot, can be performed to demonstrate the tendons and ligaments as Medial
well as cartilage and bone marrow (Figs. 13.20, 13.24). malleolus

Head of Lateral malleolus
talus
Vascular supply of the lower limb
Navicular Calcaneum
Arterial supply
The aorta divides into the two common iliac arteries at the level
of the fourth lumbar vertebra. The internal iliac artery and its
branches are discussed in the chapter on the Pelvis. Some of the
branches of the internal iliac artery are involved in the supply of
Medial
the hip and muscles of the pelvic girdle. The blood supply to the cuneiform
Cuboid
leg is mainly from the external iliac artery and its tributaries
Base of 5th metatarsal Sustentaculum tali
(Fig. 13.26).

141
The lower limb a. newman sanders


(a) (b)


Superior gluteal Lumbar
Aorta
artery arteries
Inferior gluteal
artery
Inferior
Medial circumflex Lateral circumflex mesenteric
femoral artery femoral artery artery
Common iliac artery
(transverse branch)
Profunda femoris
artery
Median sacral artery
Perforating
Femoral artery Internal iliac artery
Arteries


Superior gluteal
Hiatus in
artery
adductor magnus Superior lateral
genicualr artery
Superior medial
Lateral sacral
Popliteal artery
genicular artery Deep artery
circumflex
Inferior lateral
Inferior gluteal
iliac artery
genicular artery
Inferior medial artery
genicular artery
Anterior tibial
artery
Catheter
Lateral
Common
circumflex
femoral
femoral
Posterior tibial Fibular (peroneal) artery
artery
artery artery
Medial
circumflex
Profunda
Perforating
femoral
femoris
branch
artery artery
Lateral plantar Superficial
artery femoral
Medial plantar artery
Plantar arch
artery
Plantar metatarsal
Deep branch of artery
dorsalis pedis artery (d)
Plantar digital
Anterior
Tibia
arteries
tibial artery
Tibio-
peroneal
trunk

(c) Common Peroneal
femoral artery Anterior
artery tibial artery

Lateral
circumflex Posterior
femoral Medial circumflex tibial
artery femoral artery artery
Profunda
Profunda
femoral
femoris
artery
artery


Perforating Superficial Superior Perforating
Fibula
artery femoral femoral arteries
artery artery

Muscular
branch of
posterior
tibial artery




Femur
Peroneal
Superior
artery
genicular
artery




Posterior Anterior
tibial tibial artery
artery
Fig. 13.26. (a)“(d). The
lower limb arteries and
arteriography.


142
The lower limb a. newman sanders


The external iliac artery becomes the common femoral artery at the medial malleolus deep to the ¬‚exor retinaculum where it is easily pal-
level of the inguinal ligament. Just before this, it gives off the inferior pable. It divides within the plantar aspect of the foot into medial and
epigastric artery and the deep circum¬‚ex iliac artery. lateral plantar arteries. The peroneal artey arises from the posterior
The common femoral artery gives off four super¬cial branches tibial artery at the upper end of the ¬bula and descends towards the
immediately below the inguinal ligament; the super¬cial epigastric lateral aspect of the ankle. The anterior tibial artery pierces the
artery, the super¬cial circum¬‚ex iliac artery, the super¬cial external interosseous membrane and passes forward into the upper part of the
pudendal artery, and the deep external pudendal artery. As it passes anterior compartment of the leg descending on the interosseous
into the subsartorial canal, it gives off the profunda femoris artery and membrane crossing the anterior aspect of the ankle joint between
continues as the super¬cial femoral artery. The profunda femoris has the tendons of tibialis anterior and extensor hallucis longus. It contin-
six branches: the medial femoral circum¬‚ex artery which contributes ues into the foot as the dorsalis pedis artery.
to the supply of the hip joint, the lateral femoral circum¬‚ex artery,
Venous drainage
and four perforating arteries, which supply the muscles of the thigh.
The supply of the femoral head is of importance because of its rele- The deep veins of the leg correspond closely to the arterial supply
vance to the management of femoral neck fractures. with paired veins accompanying the major arterial branches. The
As the super¬cial femoral artery passes through the adductor super¬cial veins communicate with the deep veins via perforating
hiatus, it gives off a descending genicular branch and enters the veins which possess valves to promote drainage of super¬cial veins
popliteal fossa as the popliteal artery. This gives off seven branches to into the deep veins. The super¬cial veins also drain via the short
the knee joint and adjacent muscles as it descends behind the knee (small) saphenous vein, which drains the lateral side of the dorsal
deep to the popliteal vein before dividing into the anterior and poste- venous arch and drains into the popliteal vein. The long (great) saphe-
rior tibial arteries. The posterior tibial artery descends between tibialis nous vein starts at the medial side of the foot, passes anterior to the
posterior and soleus muscles emerging on the medial side of the ankle medial malleolus, and passes up the medial side of the leg draining
joint posterior to the ¬‚exor digitorum longus tendon behind the into the common femoral vein in the groin (Fig. 13.27).



(a) (b)

Inferior vena cava




Common
ilac vein

Right femoral

Right long
saphenous



Right popliteal
Right short
External
saphenous
iliac vein


Right
anterior
tibial

Right
Common
peroneal
femoral vein
Right long
saphenous
Right
posterior
tibial




Right medial
plantar

Right lateral
plantar

Right plantar
arch


Fig. 13.27. (a)“(e) The lower limb veins, diagram and venography. (f) Ultrasound scans of the femoral artery, B mode ultrasound and Doppler.


143
The lower limb a. newman sanders


Fig. 13.27. Continued
(c) (d)




Superficial
femoral vein




External
iliac vein




Venous valve



Common
femoral
vein


Sapheno-
Femur
femoral
junction



Femur Superficial
femoral
vein




(e)
Popliteal vein




Patella
(f)
Femur
Common femoral artery
Popliteal
vein Superficial femoral artery




Profunda femoris artery
Anterior
tibial
veins

Venous
valves


Nerve supply of the lower limb
The nerve supply of the lower limb is derived form the branches of
the lumbosacral plexus. The sciatic nerve is formed in the pelvis from
the L4,5 and S1 and S2 roots and passes out of the sciatic notch below
piriformis deep to the glutei into the posterior thigh. It passes within
the hamstring compartment supplying those muscles accompanied by
Perforating
its own blood supply derived from the inferior gluteal artery. At the
veins

upper end of the popliteal fossa, it divides into the common peroneal
nerve and the tibial nerve. The tibial nerve gives off some muscular
branches and the sural nerve. It then descends in the posterior com-
partment of the leg accompanying the posterior tibial artery as it
passes behind the medial malleolus deep to the ¬‚exor retinaculum. It

144
The lower limb a. newman sanders


divides into medial and lateral plantar branches. The common per- together with the contribution from the common peroneal nerve
oneal nerve passes laterally, winding round the neck of the ¬bula accompanies the short saphenous vein to supply the lateral aspect of
where it is susceptible to compression injury. It gives off two the foot.
branches: a communicating branch to the sural nerve and the lateral The femoral nerve is derived from the L2,3 and 4 roots of the
cutaneous nerve of the calf and then pierces the peroneus longus lumbar plexus and is formed in the psoas muscle descending deep to
muscle and divides into deep and super¬cial peroneal branches. The the inguinal ligament lateral to the femoral vessels. It supplies the
super¬cial peroneal nerve supplies the muscles of the peroneal com- muscles of the anterior compartment and terminates in the saphe-
partment and the skin of the anterior calf and dorsum of the foot. The nous nerve, which supplies the skin on the anteromedial aspect of the
deep peroneal nerve supplies the muscles of the anterior compart- knee lower leg and foot.
ment and the cleft between the ¬rst and second toes. The sural nerve




145
Section 6 Developmental anatomy

Chapter 14 Obstetric imaging


IAN SUCHET
and R U T H W I L L I A M S O N




Ultrasound forms the mainstay of obstetric imaging. It may be used
throughout gestation allowing high resolution real time imaging to be
performed in any plane. MRI is occasionally used in second and third
trimester imaging for evaluation of speci¬c abnormalities or in plan-
ning delivery. (Table 14.1).
Until 7 weeks™ gestational age (GA), the fetus is only detectable by
transvaginal scanning. Subsequently transabdominal scanning is used
with transvaginal scanning, until 11 weeks™ GA, crown rump length
being the most accurate predictor of fetal age (Fig. 14.1)
During early development, the yolk sac may be visualized soon after
5 weeks GA with a discernable embryo detected as asymmetrical
thickening of the yolk sac from 6 weeks™ GA. By 7 weeks fetal cardiac
pulsation is seen, with head, body, and limb buds being visible from
8 weeks (Fig. 14.2)




ta b l e 1 4 . 1 . Indications for obstetric ultrasound

First trimester Second trimester Third trimester Fig. 14.1. Transvaginal scan at 5 weeks. Transvaginal scan performed at 5 weeks
Reserved for high- GA, demonstrating an echogenic rim of tissue around the gestational sac
risk pregnancies comprising decidua basalis (villi on the myometrial or burrowing side of the
conceptus) and the decidua capsularis or parietalis (villi covering the rest of the
Identi¬cation of viable Con¬rmation of Serial scans to assess
developing embryo). The interface between the decidua capsularis and bright
intrauterine pregnancy gestational age growth
well-vascularized endometrium is called the double decidual reaction and is
Documentation of fetal Screening for Biophysical pro¬le represented by two concentric rings or crescents around the gestational sac.
number and gestational fetal structural incorporating amniotic This implies that this is a true gestational sac associated with an intrauterine
age abnormalities ¬‚uid volume, fetal pregnancy.
movement, and reactivity
Placental position Fetal lie Doppler studies of uterine
From this point, rapid development occurs with formation of limb
and umbilical arteries to
buds, the early brain structures, and the gut which is extra-abdominal
indicate increased fetal
risk between weeks 8 and 13.
Once the viability of an early pregnancy is established, medical
Screening for gross Placental position Fetal lie
fetal abnormality/ imaging is in the ¬rst trimester used primarily for providing an accu-
chromosome rate estimation of gestational age. This is usually done at the time of
abnormality
patients booking for obstetric services.
Fetal weight/ Placental position Scanning of the width of the sonolucent nuchal fold is performed
amniotic ¬‚uid index
from 10“14 weeks as a screening test for chromosomal abnormality
(Fig. 14.3).

Applied Radiological Anatomy for Medical Students. Paul Butler, Adam Mitchell, and Harold Ellis (eds.) Published by Cambridge University Press. © P. Butler,
A. Mitchell, and H. Ellis 2007.

146
ian suchet and ruth williamson
Obstetric imaging




Fig. 14.2. Transvaginal scan at 6 weeks of gestation. By 6 weeks of gestation, the
crown rump length of the embryo reaches 5 mm and the embryo can be seen
as a separate structure from the yolk sac and cardiac pulsations should be
visible. The mean gestational sac size reaches 18“20 mm.




Fig. 14.4. Biparietal diameter/head circumference. Axial plane through the fetal
head at a level which includes the midline echo with the cavum septum
pellucidum anteriorly and the thalami more posteriorly. The skull has an ovoid
shape, the Biparietal diameter (BPD) being 80“90% of the occipitofrontal
diameter (OFD). The head circumference (HC) measurements are obtained
at the same level but involve the circumference of the cranium rather than the
diameter. The head circumference is measured from outer surface of the skull
table in the near ¬eld to the inner margin of the skull table in the far ¬eld (outer
Fig. 14.3. Nuchal translucency scan. Nuchal translucency measurement. The
to inner).
risk of chromosomal abnormality is calculated using software incorporating
maternal age, fetal gestation and, in some centers, results from serum
screening.


be measured on a single image, and it may vary considerably, depen-
dent on fetal ¬‚exion or extension.
Determination of gestational age
During the ¬rst trimester gestational age is determined by published
The 20-week (Level 2) scan
tables of the mean gestational sac diameter or by the crown rump
length (CRL) of the embryo, when it measures between 6 and 75 mm.
This is performed as a routine anomaly screening examination in
During the second and third trimester, gestational age is deter-
most centers and includes the following information:
mined by measuring known body parts. Although tables have been
published for a large number of body parts, the head circumference • number of fetuses
(HC), biparietal diameter (BPD) (Fig. 14.4), abdominal circumference • presentation
(AC) (Fig. 14.5), and femur length (FL) (Fig. 14.6) are measured routinely. • placental position and appearance of umbilical cord
The crown rump length is no longer useful as the fetus is too large to • amount of amniotic ¬‚uid.

147
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Obstetric imaging




Fig. 14.6. Femur length. The length is measured from blunt end to blunt end
Fig. 14.5. Abdominal circumference. Transverse image of fetal abdomen at a level
parallel to the shaft. After 32“34 menstrual weeks, the distal femoral epiphysis
which demonstrates the umbilical portion of left portal vein within liver, as it
should be visualized but not included in the measurement.
meets the “pars transversa” (horizontal portion of left portal vein) and the ¬‚uid-
¬lled fetal stomach on the left. This is the best parameter for assessing both
fetal size and growth as the measurement is obtained at the level of the fetal
liver, which is large in utero and constitutes 4% of total fetal weight, and which
increases in size throughout the gestation.
(Fig. 14.9). The spine is examined throughout its length both in sagittal
and axial section to look for evidence of spina bi¬da (Fig. 14.10).
Measurements of fetal size are plotted on normograms. These may
include any of BPD, head circumference, abdominal circumference
Heart and thorax
and femur length.
The cardiac chambers are assessed by the four-chamber view
Fetal anatomy is examined with documentation of normal head,
(Fig. 14.11). The heart occupies about one-third of the chest cavity and
brain, neck, spine, face, thorax, heart, abdominal wall, GIT urinary
is situated with the apex pointing towards the left side. The left
tract, and extremities. Some centers will indicate the sex of the fetus.
atrium is the chamber that is most posterior (just anterior to the
This is done more routinely in multiple pregnancies.
spine). The left ventricle lies posterolaterally and the right ventricle
anteromedially. The foramen ovale and its ¬‚ap are situated in the left
Head and spine
atrium. The atrioventricular valves are evident separating the atria
from their respective ventricles with the tricuspid valve situated
Most of the intracranial structures are visualized by 20 weeks (Fig. 14.7).
slightly more inferior. The interventricular septum is a thick band of
Normal development of the facial structures (Fig. 14.8) is assessed along
muscle separating the left from right ventricles. A band of tissue, the
with a coronal view of the lips and hard palate to look for midline clefts

148
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Obstetric imaging




Fig. 14.7. Fetal brain. Typical appearances of brain at 20 weeks of gestation.




moderator band, is usually evident in the right ventricle. The aortic
and pulmonary out¬‚ow tracts require special views for visualization.
The myocardium and pericardium are usually inseparable unless a
small amount of pericardial ¬‚uid is present.

1. Further views of the heart are obtained to demonstrate the
pulmonary and aortic out¬‚ow tracts. Two separate vessels are
present. They pulmonary artery is slightly larger than the
ascending aorta
Fig. 14.8. Face. The sagittal plane demonstrates the fetal pro¬le and is good for
2. The aorta arises from the posterior aspect of the left ventricle, and
assessing the relationship between the forehead, nasal bridge, lips, and
sweeps to the right and cranially before turning posteriorly.
mandible.
3. The pulmonary artery arises from the anterior aspect of the right
ventricle and courses posteriorly toward the descending aorta and
fetal spine.
Abdomen
4. The aorta and pulmonary artery cross over each other as they exit
The fetal liver occupies most of the upper abdominal cavity. The
their respective ventricles of the heart.
left lobe is larger than the right lobe and has a uniform low
5. The aorta and ductus arteriosus (continuation of the pulmonary
re¬‚ectivity.
artery) join just in front and to the left of the fetal spine.

149
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Obstetric imaging




Fig. 14.10. Spine imaged in sagittal and axial plane. In the sagittal plane the spine
appears as two parallel lines corresponding to the vertebral lamina and bodies.
Fig. 14.9. Face: fetal upper lips and nose (coronal view). This view is used to
These converge at the sacrum. S4 is the most caudal ossi¬cation center
screen for cleft lip and palate.
sonographically visible in the second trimester, while S5 is most caudal in the
third trimester. Demonstration of the cord and dura may be possible in this plane.

The umbilical vein enters the liver anteriorly and runs a 45 degree
oblique course cephalad to join the posterior portal veins and enter
advancing gestation. The outline of the kidney becomes increasingly
the inferior vena cava via the ductus venosus.
lobulated with advancing gestation (fetal lobulation). The ureters are
The gall bladder is an anechoic pear-shaped echo-free structure at
not visualized unless they are obstructed. The urinary bladder should
the right inferior border of the liver (see images of abdominal circum-
always be visualized as a round ¬‚uid-¬lled collection, while the urethra
ference).
may only be evident during fetal micturition (Fig. 14.13).
The spleen is situated posteriorly in the left upper quadrant of the
The fetal suprarenal glands are usually observed in a transverse or
abdomen. It has a uniform re¬‚ectivity, similar to liver (Fig. 14.12).
sagittal plane just above the kidneys. They are usually evident by the
The fetal stomach should always be visualized as a ¬‚uid-¬lled struc-
20th week of pregnancy and contain a dense re¬‚ective central region
ture by 14“16 weeks; however, the small intestines and colon are not
(adrenal medulla) surrounded by a less dense peripheral portion
usually evident until the third trimester.
(adrenal cortex). The suprarenal glands are large in utero.
The kidneys are visualized on either side of the lumbar spine on
transverse views. They have a homogeneous appearance and are con-
stantly visualized from weeks 15“16 and onwards. The renal pelvis is an
Umbilical cord and placenta
echo-free space in the central portion of the kidney, with the medullary
The umbilical cord contains a single umbilical vein and two umbilical
pyramids arranged as an echo-poor rosette around the pelvis. The renal
arteries. In cross-section the appearance is that of “Mickey-mouse.”
capsule becomes visible at about 20 weeks as a dense thin re¬‚ective
The larger vein transports oxygenated blood from the placenta to the
line. This line becomes brighter as perinephric fat is deposited with

150
ian suchet and ruth williamson
Obstetric imaging




Fig. 14.13. Fetal kidneys. Axial section through fetal kidneys showing their
posterior location on either side of the fetal spine.




Fig. 14.11. Four-chamber view of heart. The following are demonstrated: two atrial
chambers of equal size (LA is posterior, closer to the fetal spine); two ventricular
chambers of equal thickness, RV camber is slightly larger than the left (more
Fig. 14.14. Umbilical cord. This demonstrates the “Mickey Mouse” cross-section
obvious in third trimester); mitral and tricuspid valves, intraventricular and intra
formed by the smaller paired umbilical arteries alongside the larger umbilical
atrial septa, the latter containing the foramen ovale with its ¬‚ap.
vein.




Fig. 14.15. Typical appearance of the placenta showing insertion of umbilical
Fig. 14.12. Fetal liver and spleen. Axial section demonstrating homogeneous cord. The chorionic plate and placental villi comprise the fetal portion of the
re¬‚ectivity of liver and spleen, which together occupy much of the abdomen. placenta, whilst the basal plate is the much smaller maternal component.


151
ian suchet and ruth williamson
Obstetric imaging


fetus, while the paired arteries transport deoxygenated blood from the placenta is homogeneous and smooth and becomes more dense and
fetus to the placenta. The cord usually inserts centrally into the pla- calci¬ed in the third trimester. It may implant in the uterine fundus,
centa and into the fetus at the umbilicus. A collagenous material anterior or posterior uterine walls, laterally or occasionally over the
called Wharton™s jelly supports the spiraling umbilical arteries and cervix (placenta previa). The thickness of the placenta varies with
umbilical vein (Fig. 14.14). gestational age from about 15 mm to almost 50 mm at term
The placenta plays a major role in exchange of oxygen and nutri- (Fig. 14.15).
ents between maternal and fetal circulations. The echo texture of the




152
Section 6 Developmental anatomy

Chapter 15 Pediatric imaging


RUTH WILLIAMSON




Introduction
Imaging children often uses different techniques from adults. The
increased risk of malignancy from irradiating children compared with
adults means that the use of ionizing radiation is limited wherever
possible. The inability of children to keep still makes techniques such
as CT, MRI or nuclear medicine problematic, often requiring the addi-
tional use of sedation or anesthesia. However, the small size and lack
of bony ossi¬cation in younger children mean that ultrasound can be
used to greater extent than in adults. Knowledge of pediatric anatomy
and pathology requires a thorough understanding of the way in which
different anatomical structures mature and a working knowledge of
the commonly occurring anatomical variants.


Neuroanatomy
Day-to-day neuroimaging of infants is often carried out using ultra-
sound, as the anterior fontanelle, which remains open until approxi-
mately 15 months of age, allows an acoustic window through which
Corpus callosum
much of the brain may be visualized. Conventional imaging uses a
fan-like array of coronal and sagittal sections acquired with a small
Third ventricle Lateral ventricle
footprint 5“7 MHz ultrasound probe. Like most ¬‚uids, the CSF appears
anechoic making the ventricles easy to visualize. Sylvian fissure
The most anterior section demonstrates the frontal lobes and
frontal horns of the lateral ventricles. The next plane is taken through Temporal lobe
the Y-shaped foramen of Monro, which connects the two lateral ven-
tricles with the third ventricle. At this level, the following may be Skull vault
identi¬ed: the corpus callosum above and between the slit-like lateral
venticles, the cavum septum pellucidum, a CSF ¬lled space in the
central septum pellucidum, which may persist into adulthood, the
middle cerebral arteries, and the caudothalamic groove. The latter is
an important landmark in neonates as this is the location of the resid-
ual embryonic germinal matrix, which is often the primary site of the Fig. 15.1. Neonatal cranial ultrasound. Coronal section through the foramen of
hemorrhage, which occurs in premature neonates in response to a Monro.
variety of insults. More laterally, the sylvian ¬ssure and temporal
lobes may be seen (Fig. 15.1).




Applied Radiological Anatomy for Medical Students. Paul Butler, Adam Mitchell, and Harold Ellis (eds.) Published by Cambridge University Press. © P. Butler,
A. Mitchell, and H. Ellis 2007.

153
Pediatric imaging ruth williamson


As myelination proceeds, in an orderly manner from central to periph-
Posterior to this, a section is taken through the thalami to include
eral and from dorsal to ventral, these changes can be tracked by MRI
the posterior part of the third ventricle in line with the aqueduct of
as the myelinated nerves have a different signal pattern. At birth, only
Sylvius as it communicates infero-posteriorly with the fourth ventricle.
the medulla, dorsal midbrain, inferior and posterior cerebellar pedun-
This also demonstrates the tentorium and cerebellum and the star-
cles, posterior limb of the internal capsule, and ventro-lateral thala-
shaped quadrigeminal plate cistern. More posterior sections demon-
mus are myelinated.
strate the parietal and occipital lobes and the posterior horns of the
By 3 months, when an infant is able to make more purposeful
lateral ventricles, which contain highly re¬‚ective choroid plexus. The
choroid plexus is distinguished from intraventricular hemorrhage by movements, the cerebellum is fully myelinated, by 8 months the brain
begins to take on a more adult appearance, although myelination of
the fact that there is echo-free CSF around its postero-lateral borders.
the frontal and temporal lobes does not occur until approximately 18
Sagittal and parasagittal sections are also obtained. The midline
months of age. At this point the brain is essentially adult in appear-
section demonstrates the third and fourth ventricles, the brainstem,
ance. Further development is still occurring and from 15 to 30 years
which has lower re¬‚ectivity than the remainder of the brain, and the
myelination of the association tracts of the peritrigonal white matter
cerebellum, which has slightly higher re¬‚ectivity. Above the third
becomes apparent. More recently, MR spectroscopy has allowed
ventricle, the corpus callosum is seen (Fig. 15.2). Parasagittal sections
demonstration of metabolic and biochemical changes within the
on either side through the bodies of the lateral ventricles demonstrate
maturing brain, particularly during the ¬rst 5 years of life.
the caudate heads and the caudothalamic groves anterior to which
is the germinal matrix. The most lateral sections are used to visualize
the temporal and occipital cerebral cortex. Finally, an assessment
Spinal anatomy
of the amount of CSF super¬cial to the brain is made, as otherwise
subdural effusions, collections, or hemorrhage will be missed. In the early neonatal period, ultrasound may be used for evaluation
MRI in the pediatric population is used for the assessment of of gross spinal abnormalities. The posterior elements of the vertebral
acquired or inherited myelination abnormalities, for tumor evalua- bodies are not ossi¬ed, allowing the through transmission of ultra-
tion, and for the investigation of epilepsy. The MRI appearances of sound. The cord and nerve roots can be identi¬ed within the thecal
the neonatal brain differ signi¬cantly from that of the adult. sac (Fig. 15.3). In the newborn the cord terminates at approximately
L2“3 but, with growth of the vertebrae exceeding that of the cord, the
normal termination of the cord is at L1“2. This is relevant when decid-
ing where to perform lumbar puncture, for example. Plain radiology is
used in trauma. The cervical spine in children ¬‚exes around a fulcrum
at approximately C3 compared with C5“6 in adults. A plain ¬lm taken
with a degree of ¬‚exion can give the impression of anterior spinal sub-
luxation. Expert evaluation is essential to con¬rm or exclude serious
spinal injury.
Despite the use of US, MRI still forms the main technique for
detailed spinal imaging in children, with unco-operative subjects
being imaged under sedation or anesthesia.
Plain radiology of the spine is used in the assessment and manage-
ment of scoliosis, which may be due to underlying vertebral body
abnormalities or may be idiopathic. In all cases the X-ray image should
include the iliac crests, as these provide an indicator of skeletal matu-
ration and hence may predict whether a scoliosis is likely to progress.


Nerve roots
leaving cord



Cord with
Cord
central
termination
echogenic
white line

CC

CSP




*
Cl P
C
M
Fourth ventricle
Shadows from calcified
spinous processes

Fig. 15.2. Neonatal cranial ultrasound. Midline sagittal section showing third and
fourth ventricles, cerebellum and brainstem. Fig. 15.3. Midline sagittal ultrasound of neonatal lumbar spine.


154
Pediatric imaging ruth williamson


Thoracic anatomy
Within the ¬rst few seconds after birth, a complete change in the cir-
culatory system occurs. The foramen ovale which, during fetal devel-
opment allowed the shunting of enriched placental blood into the
Umbilical venous line
systemic circulation, closes. As the newborn infant takes its ¬rst
breaths, the vascular resistance of the lungs reduces. The connection Umbilical artery line
between pulmonary trunk and aorta, the ductus arteriosus, also closes
establishing the normal adult type circulation. In premature infants
there may be failure of closure of the ductus, causing left to right
shunting of oxygnated blood. In some cardiac defects, e.g. tetralogy of
Fallot and tricuspid atresia, medical intervention is used to maintain
the patency of the ductus until surgical correction can be achieved.
Although some cardiac abnormalities have typical chest radiographic
appearances, echocardiography or MRI are now the investigations of
Endotracheal tube
choice for their assessment.
The umbilical arteries and veins close following clamping of the
cord. They may however be used for central venous access in the ¬rst
Right Left
24“48 hours of life. A knowledge of their normal anatomy is essential
to the evaluation of correct catheter position. Blood from the umbili-
cal vein passes into the left portal vein then through the ductus
venosus into the inferior vena cava and right atrium. An umbilical
vein catheter should follow a course curving slightly to the right with
its tip just in the IVC. Umbilical arteries join the systemic circulation
via the internal iliac arteries. Arterial catheters, to allow blood sam- Umbilical
venous line
pling and pressure measurement, should be placed with the tip avoid- Umbilical
artery line
ing the major abdominal vessels. On plain X-ray, the catheter is seen
to dip into the pelvis as it joins the iliac vessels before resuming its
cranial direction within the aorta. The tip should either be below L3“4
or above T12 (Fig. 15.4).
There are several important considerations when reviewing chest
radiographs in children, particularly infants. Whilst adult ¬lms are
usually taken erect in the postero-anterior projection with the anterior
chest wall adjacent to the ¬lm, this is not usually the case in infants,
who are usually imaged supine with the ¬lm behind them. As a result
the anterior structures of the chest (heart and thymus) are relatively
magni¬ed. This magni¬cation is further increased by the fact that
infants have a much rounder cross-section than adults. Whereas in the
adult the cardiac silhouette should be no more than 50% of the width of
the ribs, in infants up to 65% may be within normal limits. The thymus
Fig. 15.4. Radiograph of neonatal chest and abdomen showing correct
comprises right and left lobes and is situated in the anterior medi-
positioning of umbilical arterial and venous llines.
astinum. It is usually visualized on neonatal ¬lms. It is a fatty structure
and therefore has low radiodensity. This means that pulmonary blood
vessels can usually be seen through it. The shape is characteristically
Gastrointestinal and hepatobiliary anatomy
sail-like, with a concave inferior border, although it may change sub-
Radiological imaging of the pediatric gastrointestinal tract is predomi-
stantially with changes in position of the infant (Fig. 15.5).
nantly with plain ¬lms and single contrast barium examinations.
Assessment of the pulmonary vascular pattern is often dif¬cult as
Ultrasound has a few speci¬c applications, e.g., demonstration of the
patient movement or an expiratory ¬lm may mimic increased pul-
mass of hypertrophic pyloric stenosis and in identifying the ¬xed
monary vascularity. A good inspiration allows visualization of the sixth
in¬‚amed appendix. It is, however, the imaging modality of choice in
rib anteriorly and the eighth rib posteriorly. Movement artifact is best
investigation of the solid organs of the abdomen and the biliary tree.
appreciated by looking at the diaphragms, as the rapid pulse in babies
Radionuclide radiology can also give important functional informa-
means that there is usually blurrring of the cardiac outline. In the ¬rst
tion regarding the GI and hepatobiliary systems.
few hours of life, amniotic ¬‚uid is gradually absorbed from the lungs,
Plain ¬lms of the abdomen are often the ¬rst investigation in
but chest ¬lms taken during this time may show persistent ground glass
infants with acute abdominal symptoms. They are performed in the
opacitly of the lungs or small pleural effusions. In some term infants,
supine position. Compared with the adult liver, the infant liver has a
this ¬‚uid is slow to clear giving rise to transient tachypnea of the
larger silhouette. The bowel ¬lls with air during the ¬rst 24 hours of
newborn. Radiologically this is indistinghishable from surfactant
life. When there are numerous gas-¬lled loops, it is impossible to dis-
de¬ciency disease, although the gestational age of the child and its rapid
tinguish reliably large from small bowel. The presence of only two air
spontaneous resolution are usually enough to make a ¬rm diagnosis.

155
Pediatric imaging ruth williamson


bowel obsturction, e.g. Hirschsprung™s disease, meconium ileus. There
is also growing use of contrast studies for examination of the bowel
prior to reanastomosis in babies who have had surgery with enteros-
tomy for necrotizing enterocolitis. In all cases, single contrast studies
are performed either with barium or water-soluble contrast agents.
The latter may have signi¬cantly higher osmolality than plasma and
may be responsible for large ¬‚uid shifts. The normal colon is relatively
smooth and forms a relatively square outline around the periphery of
the abdomen. Contrast agents will usually re¬‚ux through the ileocecal
valve into small bowel.
The solid organs of the abdomen are examined readily with ultra-
sound. Although CT may be used in tumor staging, it is a specialist
technique as intra-abdominal contrast is poor owing to the relative
lack of intra-abdominal fat.

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