Flexor tendon growth in chickens.

We investigated the longitudinal growth of the flexor tendon in detail by marking tendons along their lengths in young chickens, using a microsurgical technique, and observing the separation of the marks at various times during tendon growth to establish normative standardized data on the longitudinal growth of flexor tendons. The interstitium throughout the entire tendon was found to increase in length, although the growth at the insertion zone was less marked than that in other areas. To determine the relationship between the growth of the tendon and the growth of the underlying bone, the lengths of the phalanges and metatarsus were measured. The distance from the insertion to the bifurcation of the tendon and the distance from the bifurcation to the most distal point of the musculotendinous junction also were measured. The findings suggest that the growth of tendon is proportionate to the growth of underlying bone. Tendon growth at the musculotendinous junction was studied in further detail, and no significant difference was found between growth at the most proximal zone of the tendon and growth at the zone within the musculotendinous junction.