The Journal of Bone and Joint Surgery, Vol 76, Issue 8 1193-1206, Copyright © 1994 by Journal of Bone and Joint Surgery, Inc
The potential role of the elastic fiber system in adolescent idiopathic scoliosis
N Hadley-Miller, B Mims and DM Milewicz
Department of Orthopedic Surgery, Baylor College of Medicine, Shriners Hospital for Crippled Children, Houston, Texas 77030.
To assess its possible role in the etiology of adolescent idiopathic
scoliosis, the elastic fiber system of the ligamentum flavum was examined
in twenty-three patients who had scoliosis and in five age-matched
individuals who did not. Elastic fibers are composed of two components: the
amorphous core of elastin and microfibrils, of which fibrillin is the
primary element. Fresh-frozen histological specimens of ligamentum flavum
removed at the time of an operation were examined by Verhoeff staining for
elastic fibers and by immunohistochemical staining with use of a monoclonal
antibody to fibrillin. Additionally, cultures of fibroblast cells from the
ligamentum flavum were used to study the biosynthesis and secretion of
fibrillin and its incorporation into the extracellular matrix in vitro. The
specimens from one patient did not provide sufficient material for the
histological studies; however, fibroblasts were harvested from this
specimen. In five (23 percent) of the remaining twenty-two specimens from
patients who had adolescent idiopathic scoliosis, Verhoeff staining of
elastic fibers showed a marked decrease in fiber density (the number of
fibers per unit area) and a non-uniform distribution of fibers throughout
the ligament. Eighteen specimens (82 percent) exhibited abnormalities on
immunohistochemical staining, including a marked disarrangement of the
fibers and a difference in the density of staining, when compared with the
control specimens from individuals who did not have adolescent idiopathic
scoliosis. Studies of the biosynthesis and secretion of fibrillin and its
incorporation into the extracellular matrix in vitro demonstrated that
fibroblasts from four (17 percent) of the twenty-three specimens produced
normal amounts of fibrillin and secreted it from the cell, but the
fibrillin failed to bind to other macromolecules, to form a sedimentable
complex, and to incorporate into the extracellular matrix. Collectively,
the results suggest the potential role of the elastic fiber system as a
component in the pathogenesis of adolescent idiopathic scoliosis in some
individuals.
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