Proximal femoral focal deficiency is a rare congenital malformation,
characterized by a failure of normal development of the proximal part of
the femur. To our knowledge, there have been no reports on the histology of
fetal growth plates that are affected by this disorder. To characterize
this focal developmental anomaly further, we studied the histopathology of
the growth plates and epiphyses from a twenty-one-week fetus with
unilateral proximal femoral focal deficiency. Although the shape of the
cartilaginous anlage of the fetus appeared normal, the growth plate of the
proximal part of the involved femur was markedly abnormal. The major
findings were: (1) striking failure of the proximal growth plate to migrate
proximally, away from the central part of the diaphysis, and failure of
formation of a normal growth plate; (2) failure of organization of
proliferative and hypertrophic chondrocytes into longitudinal columns; (3)
truncation of an immature hypertrophic zone that had abnormal septal
architecture; and (4) disorganized vascular invasion with a honeycomb
rather than a columnar pattern of primary trabeculae. In contrast, the
histological characteristics of the growth plates from the distal part of
the femur and from all other long bones were normal.