Fibronectin in healing flexor tendons subjected to immobilization or early controlled passive motion.

The medial and lateral forepaw flexor tendons of 20-adult mongrel dogs (n = 40) were transected and repaired with a modified Kessler suture. Post-operatively the dogs were subjected either to immobilization or early controlled passive digital motion. Sacrifices were at 3, 7, 10 and 17 days. The tendons of the contralateral limbs were left intact and used as controls. Urea-heparin-extracted fibronectin was quantitated by competitive ELISA in the tendons and sheaths at the four post-injury/repair time periods. In both groups (controlled passive motion and immobilization), fibronectin concentrations were higher in the injured tissues than in control tissues. However, peak fibronectin concentration (7-days post-injury/repair) was approximately twice as high in the controlled passive motion tissues as in the immobilized tissues. It was concluded, therefore, that, relative to early controlled passive motion, early immobilization depresses the accumulation of tissue fibronectin during the early stages of healing following injury.