![]() The cartilaginous femoral head is recognized as a hypoechoic rounded structure with specular internal echoes that allow transmission of the sound wave to the acetabulum and the triradiate cartilage. More complex systems are also available (Fig. However, prediction of the final relationships is not always possible. These systems predict femoral head development and its relation to the acetabulum and femoral neck. The Amstutz system further divides Aitken A into types 1 and 2, based on characteristics of the femoral neck (cartilaginous in type 1 pseudarthrosis in type 2) Aitken B through D are termed Amstutz 3–5. Both the femoral head and the acetabulum are absent in class D, and the femoral segment is even shorter and more deformed, often pointed proximally. A short femur tapers proximally and has a small proximal tuft. Class C is defined by complete absence of ossification of a femoral head. The acetabulum is either adequate or moderately dysplastic. In class B, the femoral head is also present, but there is no bony connection between it and the femoral shaft at maturity there may be no cartilaginous connection either. A bony connection eventually forms between the proximal femur and the shaft, but often with a pseudarthrosis. In class A, the femoral head is well formed and attached to a short but otherwise well-formed femur the acetabulum is normal. 11.13) (Table 11.1) divides PFFD into four classes. Of the many classification systems available, the Aitken and the Amstutz are often employed. While PFFD may be difficult to classify at an early stage, doing so improves prognosis by helping to direct appropriate therapy. Clinical correlation is extremely important, as young athletes often experience muscle strain in this region, and this may not necessarily correlate with radiographic asymmetry (see Chap. Magnetic resonance imaging (MRI) can be misleading, as increased asymmetric signal makes distinguishing between normal variation and pathology difficult. This asymmetry is well defined, does not extend into adjacent bone, and is never more active than that adjacent to the triradiate cartilage (Fig. In almost one half of patients, scintigraphy reveals bilateral but unequal uptake in this area. Unilateral synchondrosis expansion can be found in 57 % of children at age 7. Occasionally, there is cyclic swelling, bone union, reopening, swelling, and repeat closure, sometimes associated with pain. The lucent cartilaginous component often enlarges before closure and may appear swollen or bubbly for up to 3 years (Fig. The timing of closure of the ischiopubic synchondrosis is extremely variable, closing as early as 3 years of age, but incomplete in 18 % of children at age 12.
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