Diagnostic ultrasound ( PDFDrive )

CHAPTER 55 The Pediatric Hip and Other Musculoskeletal Ultrasound Applications 1933
A
B
FIG. 55.7 Normal Foot Compared With Congenital Vertical Talus. (A) Sagittal view of the dorsum of the normal foot. The tibia (T) is visible
proximally, and the talus (t), navicular (n), and cuneiform (c) in a line distally. (B) Congenital vertical talus. Sagittal view of the dorsum of the foot.
The navicular (n) is displaced dorsally and superiorly overlying the head of the talus (t). The cuneiform (c) and metatarsal (m) distally are aligned
with the navicular. The tibia (T) is visible superiorly.
bone with respect to the plantarlexed (vertical) talus, and it is
not reducible. Oblique talus is similar in that the talus is more
vertical than normal, and there is dorsal displacement of the
navicular in dorsilexion, reducible in plantarlexion. In the infant
with unossiied navicular and small talus, it can be diicult to
determine the alignment of the joint radiographically, but with
ultrasound the joint is easily seen when scanning in the sagittal
plane dorsally. Normally, the navicular is located at the head of
the talus in a straight line with the irst metatarsal. In congenital
vertical talus and oblique talus at rest, the navicular is dorsally
displaced, projecting anterior to the head of the talus. With plantar
lexion, the alignment will not change in vertical talus but corrects
with oblique talus. 71 Some investigators use serial manipulation
to correct vertical talus, 72 and ultrasound can be used to conirm
improving alignment in these patients (Fig. 55.7). Other foot
deformities that can be evaluated sonographically include skewfoot
and metatarsus adductus. 66
Congenital Limb Deformities
Proximal Focal Femoral Deiciency
Proximal focal femoral deiciency (PFFD) is a rare congenital
anomaly with variable hypoplasia or absence of the proximal
femur, usually unilateral and most oten isolated. Prenatal
diagnosis focuses on the diagnosis of a short femur based on
routine femur measurements. If both femurs are short, it suggests
skeletal dysplasia. Ater birth, ultrasound can be used to determine
the subtype of PFFD, and thus the treatment, based on what
cartilaginous components are present before they are ossiied.
Scanning includes the standard views of the hip with additional
longitudinal and transverse views of the proximal femur. If there
is a cartilaginous femoral head, it is essential to determine if it
is connected to the proximal femur (Fig. 55.8). his is a diicult
examination because of lexion contractures, the small size of
the structures, and patient movement, but it can be helpful until
the patient can undergo deinitive MRI. 73-75
Tibial Hemimelia
Tibial hemimelia is a rare defect in which there is hypoplasia
or aplasia of the tibia, oten associated with other congenital
anomalies. As in PFFD, evaluation of cartilaginous and sot tissue
components is important in the determination of surgical treatment
and prognosis, and sonography can be used for this before
ossiication, scanning anteriorly in longitudinal and transverse
planes with lexion and extension of the knee. he osseous defect
in the tibia may be proximal or distal, and there may be a
substantial cartilaginous component that can be seen sonographically.
76,77 he presence and function of the quadriceps tendon
and the extensor mechanism are key; when the mechanism is
intact, the cartilaginous patella will be visible overlying the
intercondylar notch of the distal femur, and the patellar tendon
will extend from the lower pole of the patella to the proximal
tibia. he presence of an intact quadriceps mechanism allows
reconstructive surgery and preservation of the knee joint, oten
with below-knee amputation and use of a prosthesis. he absence
of the quadriceps mechanism may lead to disarticulation of the
knee and use of a prosthesis without the beneit of knee
extension. 76,78
Congenital Nonhip Dislocations
Elbow and Knee Dislocations
Elbow and knee dislocations are rare, usually occurring secondary
to malposition in utero and various syndromes, especially
arthrogryposis and Larsen syndrome. Radial head dislocation
can also be isolated. Diagnosis of knee dislocation can be
problematic radiographically because of the large amount of
cartilage making up the joints, and ultrasound is an easy way to
diagnose displacement or dislocation, scanning anteriorly in
longitudinal and transverse planes (Fig. 55.9). Circumferential
scanning may be helpful when the orientation of the joint is
uncertain. Comparison views of the contralateral side can be
used for conirmation, but dislocation is oten bilateral. Dynamic