Effects of increased in vivo excursion on digital range of motion and tendon strength following flexor tendon repair

Postoperative rehabilitation is an important factor in determining function al outcome following intrasynovial flexor tendon repair. We hypothesized th at a rt habilitation protocol that produced increased in vivo excursion wou ld lead to increased digital range of motion and tendon strength and decrea sed adhesion formation in a canine model. Ninety-six flexor digitorum profu ndus tendons from 48 dogs were cut transversely and repaired by a multistra nd suture technique. Postoperative rehabilitation was performed daily with a low excursion-low force (1.7-mm average excursion; < 10 N force) or a hig h excursion-low force (3.6 mm excursion, < 10 N force) protocol. After deat h of the dogs at 10, 21, or 42 days, specimens were evaluated for digital r ange of motion, tensile mechanical properties, elongation of the repair sit e, and adhesion formation. Our data indicate that the range of motion of di gits whose tendons were at low or high excursion was similar to that of con trols. Increased in vivo tendon excursion due to synergistic wrist motion d id not significantly affect ex vivo flexion of the distal and proximal inte rphalangeal joints or tendon displacement (p > 0.05). Similarly, tensile pr operties (ultimate load. repair site rigidity, and repair site strain at 20 N and at failure) and length of the Sap at the repair site were not signif icantly affected by increased excursion (p > 0.05). Severity of adhesion fo rmation was reduced slightly by increased excursion (p = 0.04). Our finding s indicate that 1.7 mm of tendon excursion is sufficient to prevent adhesio n formation following sharp transection of the canine flexor tendon and tha t additional excursion provides little added benefit.