The objective of our research is to elucidate the pathogenesis of soft-tissue contracture. Here we present a comparison of collagens isolated from deltoid ligament of 23 clubfeet classified according to the Dimeglio-classification and of 14 matched controls of normal feet.

Collagens were isolated by acetic acid extraction and by limited pepsin-solubilisation and analysed by SDS-PAGE. Ligaments and solubilised collagens were analysed for their extent of hydroxylation of prolyl- and lysyl-residues, their content of galactosyl-hydroxylysine and glucosyl-galacto-syl-hydroxylysine and their content of lysyl-oxidase dependent cross-links histidinohydroxylysino-norleucine (HHL), hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP). Analysis were carried out using an amino acid analyser (Bio-chrom 20, Amersham Pharmacia Biotech) and a reverse-phase HPLC system (Gynkothek).

Percentage of collagen of total protein decreases in club-foot as compared to controls. SDS-PAGE of solubilised collagens shows a high content of type I, less of type III and small amounts of type V collagen in both groups. The extent of hydroxylation of proline appears to be very similar, whereas the degree of hydroxylation of lysine follows the Dimeglio-classification. In addition, glycosylation of hydroxylysine increases parallelly to the classification. However, the increase is found solely in the amount of disac-charides. Total content of HHL, the most important collagen cross-link in soft tissues, was increased significantly in club-feet as compared to controls. HP, the hard tissue specific collagen cross-link was increased slightly in clubfeet. Levels of LP were too low to detect differences precisely.

The data presented show distinct differences in the post-translational modifications of collagen (hydroxylation of lysyl-residues, glycosylation and lysyl-oxidase dependent cross-links) isolated from congenital idiopathic clubfeet and from controls.