The early stages of flexor tendon healing: a morphologic study of the first fourteen days.

Healing canine flexor tendons treated with protected early motion were studied by light and transmission electron microscopy in the early stages after repair. Two micrometer sections were made across the repair sites. The repair site configuration varied with the extent of gaps that formed between the tendon ends. Each tendon had areas where the tendon stumps were well coapted, and other areas had defects of up to 3 mm. Some areas had gaps healed by way of a marked cellular response from the epitenon, whereas more closely coapted areas had a greater initial endotenon response. The repair site was revascularized by day 7 in regions with close tendon stump approximation and by 10 to 14 days in regions with larger gaps between the tendon ends.