Growth of severed flexor tendons in chickens.

To examine tendon growth in both the distal and proximal portions of severed tendons, we investigated the growth of severed flexor tendons within the fibro-osseous tunnel in young chickens. When the tendon was severed at the proximal site in the sole, dynamic tension applied by the muscle was lost. Growth in the distal tendon was retarded considerably, although passive tension initially was maintained through the residual vincula and later by adhesion to the chiasma of adjacent flexors. When the tendon was severed at the insertion, passive tension from the extensors was lost. Proximal tendon growth continued if active tension was maintained through the residual vincula. If not, the tendon was markedly shortened and degenerated. Maintaining normal tension may be the most important factor in longitudinal tendon growth.