Migration of tendinous insertions. I. Cause and mechanism.

The cause and mechanisms of the migration of tendons and ligaments were studied in young rabbits. Three techniques were used: (1) Marking of insertions, the neighbouring periosteum and the diaphysis with metallic markers. (2) Marking of insertion sites by tetracycline as an indicator of osteogenesis. (3) Histological examination. The insertions used in the study were of three different characters: (1) Insertions subject to muscular traction (patellar ligament, quadratus femoris muscle, tibialis anterior muscle). (2) The distal insertions of the medial collateral ligament of the knee, stretched by the activity of the proximal epiphyseal cartilage of the tibia. (3) The proximal and distal insertions of the anterior annular ligament of the tibia, inserted solely in bone and periosteum. The cause of migration is the growth of periosteum dragging the insertions during its stretching, caused itself by the activity of the epiphyseal plates. The local mechanism governing migration while ensuring a continuous connexion with the bone is not the same in all sites. It depends upon the character of the bony surface at the insertion and of the function of the insertion zone, which can be osteogenic, resorptive or both. A plexus of precollagenous fibres is present at all resorptive insertion sites, and at some of the osteogenic sites.