Classification of proximal femoral focal deficiency (PFFD) can be complicated and a number of classifications have been proposed. For a discussion of the condition, refer to the article proximal femoral focal deficiency.
One of the simplest and most widely used is that proposed by Aitken 1 which is based on the anatomic relationship between the acetabulum and the proximal end of the femur and designates four classes:
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class A
the femoral head is present and attached to the shaft by the femoral neck (least severe type)
the femur is shortened (as in all types), and a coxa vara deformity is present
a cartilaginous neck is not seen on early radiographs but later ossifies
occasionally, the cartilaginous connection between the neck and the shaft forms a subtrochanteric pseudarthrosis
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class B
the acetabulum is “adequate” or moderately dysplastic and contains the femoral head
at maturity, no osseous connection is seen between the femoral head and the shaft
the femoral segment is short and usually has a bulbous bony tuft
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class C
the acetabulum is severely dysplastic
the femoral head is absent or is very small and not attached to the femoral shaft
the shortened femoral segment has a tapered proximal end
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class D
absence of the acetabulum and proximal femur (most severe type)
no proximal tuft is present
Amstutz 2 further subdivided Aitken’s classification into five types. He divided class A into types 1 and 2. Type 1 is reserved for the milder form with simple femoral shortening and coxa vara. In type 2, a subtrochanteric pseudarthrosis is present. The remaining types correspond to those of Aitken’s classification.
Several other classifications were proposed, but Aitken’s and Amstutz’s classifications are the most widely used.
Since the management of type 1 varies from that of type 2, a distinction between them is necessary.
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