Diagnostic ultrasound ( PDFDrive )

1936 PART V Pediatric Sonography
A
B
FIG. 55.12 Normal Neonatal Shoulder. (A) Illustration of anterior
and posterior axial planes of interrogation of the shoulder. (B) Anterior
axial image. Cartilaginous humeral head (H) anteriorly rests on glenoid
(G) posteriorly. Biceps tendon (arrowhead) can be seen in the bicipital
groove. M, Medial. (A reproduced with permission from Grissom LE,
Harcke HT. Infant shoulder sonography: technique, anatomy, and pathology.
Pediatr Radiol. 2001;31[12]:863-868. 85 )
of protrusion is measured between the scapular line and a line
connecting the osseous lip of the glenoid and the posterior margin
of the humeral head cartilage as the alpha angle, normally less
than 30 degrees. 89 he subluxated shoulder shows increased
protrusion, delection of the labrum, and deformity of the glenoid,
which becomes irregular and angled, and the dislocated shoulder
is not in contact with the glenoid surface. With internal rotation
the position may worsen, and with external rotation the shoulder
position may improve. his examination is technically challenging
because of patient movement and agitation, but with experience
it can be accomplished quickly and reproducibly. 87,90 One of the
diiculties is determining the correct plane and angulation of
interrogation. Repeat examination is recommended at 1, 3, 6,
and 12 months of age, during which time there can be increasing
displacement of the humeral head 90 (Fig. 55.13).
Inlammation
Infection
Ultrasound is increasingly used to evaluate pediatric patients
for infection of the sot tissues, 91 oten to supplement other
modalities. Cellulitis (infection of subcutaneous sot tissues) and
pyomyositis (infection of skeletal muscle) may be hematogenous
or may originate from a puncture wound. Sonographically, there
is heterogeneous sot tissue thickening and increased echogenicity
in the afected area, and there may be regional adenopathy. If
there is a puncture wound, foreign material or air may be present.
Comparison with the contralateral unafected side is helpful to
make the diagnosis. he inlammatory process can progress to
abscess formation or necrosis. Although inlammatory debris
within the abscess may be hypoechoic, it can also be isoechoic
or even hyperechoic and diicult to appreciate. 92 Color and power
Doppler may also assist in the diagnosis in that the rim of the
abscess will demonstrate increased low, and the debris within
the cavity should be avascular. 93 If the luid is mobile, motion
may cause color or power signal on Doppler sonography, but
spectral analysis will not reveal any true vascularity. Sonographic
guidance can be used to biopsy or drain an abscess. 94 A recent
hematoma, early myositis ossiicans, or a necrotic mass can have
a similar appearance to an abscess, and the best way to distinguish
infection from these entities is by clinical history and laboratory
tests. In myositis ossiicans and hematoma, ater calciication
has developed, the echo pattern changes, and being mistaken
for abscesses becomes unlikely.
Septic arthritis can be an isolated abnormality or can be
secondary to infection in the adjacent sot tissues or bone. Fluid
is visible in the joint, and debris may or may not be seen within
it. When joint luid is anechoic or hypoechoic, it may be diicult
to distinguish from the cartilage that caps the ends of the bones
forming the joint. In addition, if there is debris in the luid, it
may be diicult to detect the septic efusion, similar to the sot
tissue abscess (Fig. 55.14). Movement of the joint will show the
cartilage-luid interface clearly. Application of pressure to the
tissue around a joint will cause joint luid to shit, making
the luid easier to recognize. Pressure along the sides of the knee,
for example, can force luid into the suprapatellar bursa, thereby
conirming an efusion. Color or power Doppler sonography
may help because there is typically hyperemia in the capsule
with infection. 95 he absence of hyperemia does not exclude
septic arthritis. 56 As with hip efusions, sonography can be used
to aspirate from the joints. 96
Lyme disease, caused by the spirochete Borrelia burgdorferi
and spread by deer ticks, can result in arthritis. his usually
occurs in the subacute or chronic phase of the infection and is
characterized by relapsing efusions, particularly in the knee
joint. here may be synovial thickening, and cartilage loss is
seen late in the course. his can be confused with juvenile
rheumatoid arthritis, and the diagnosis should be considered in
patients with oligoarticular joint efusions. 97
Osteomyelitis typically occurs in the metaphyses of the
long bones. he earliest sonographic sign is deep sot tissue
swelling. Later signs are luid along the cortex of the bone or,
subperiosteally, luid in the adjacent joint (either sterile or septic),