Solubility of spinal ligament collagen in idiopathic and secondary scoliosis

Supraspinous and interspinous ligaments from patients with infantile and adolescent idiopathic scoliosis and from patients with secondary scoliosis were investigated for collagen content and cross-linking. No differences were demonstrated in the collagen content of ligaments from the idiopathic and secondary scoliosis groups. Collagen solubility studies were used to test for cross-linking defects. Similar amounts of neutral salt-soluble and acetic acid-soluble collagen were extracted from the ligaments of all diagnostic groups. Investigation of the normally insoluble collagen pool extracted from the ligaments of different diagnostic groups after "lyotropic relaxation" revealed no differences in the amount of collagen extracted or in its stability to alkaline denaturation. Control experiments using rat skin collagen showed that the lyotropic procedure solubilized undegraded alpha- and beta-polypeptide chains from the tissue. Reports from other laboratories have suggested the presence of a collagen defect in the skin of patients with adolescent idiopathic scoliosis. The results of the present investigation show that it is unlikely that a generalized defect of collagen cross-linking, or a specific defect of ligament collagen cross-linking, occurs in either infantile or adolescent idiopathic scoliosis.