Proximal femoral focal deficiency. Evidence for a defect in proliferation and maturation of chondrocytes
Boden, S.D.; Fallon, M.D.; Davidson, R.; Mennuti, M.T.; Kaplan, F.S.
Journal of Bone and Joint Surgery. American Volume 71(8): 1119-1129
1989
ISSN/ISBN: 0021-9355 PMID: 2777837 Document Number: 336228
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 markeldy 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. CLINICAL RELEVANCE: This investigation of proximal femoral focal deficiency provided a unique insight into a rare growth disorder during its prenatal stages and resulted in observations that may challenge the prevailing theories of its etiology. In the fetus that was studied, the disorder did not appear to result from a morphological defect in the cartilaginous analage or from a primary vascular defect. The defect was characterized by altered proliferation and maturation of chondrocytes. This was manifested by histological changes in every zone of the growth plate, including a lack of normal preparation of matrix by the hypertrophic cells. Consequently, the timing and occurrence of mineralization of the matrix, vascular invasion, and endochrondral growth in the proximal part of the involved femur was markedly disturbed.