The healing of flexor tendons in chickens

The healing of flexor tendons was studied in chickens using transmission electron microscopy. After resecting the flexor sheath between the proximal and distal pulleys in zone II, the profundus tendon was severed and sutured. Intermittent passive motion was carried out 35 times daily immediately afterwards. The chickens were sacrificed at 3, 6 and 9 weeks. In vivo healing was shown to be much more rapid than in in vitro studies. There was marked proliferation of endoplasmic reticulum and phagocytosis at 3 weeks, collagen synthesis at 6 weeks and remodelling at 9 weeks. Healing was by a combination of extrinsic and intrinsic mechanisms.