This study was undertaken to evaluate the individual effects of motion
and tension on the healing response of injured flexor profundus tendo
ns in chickens. Partial midsection transverse lacerations of the profu
ndus tendons were produced in 53 chickens. Postoperatively, they were
assigned randomly to four management groups: both motion and tension;
only motion, no tension; no motion, only tension; no motion and no ten
sion. Biomechanical results at 4 weeks showed that breaking strength s
ignificantly increased with both motion and tension, significantly dec
reased with neither, and was intermediate with only motion or only ten
sion. Histologic evaluation generally showed the greatest cellular act
ivity with both motion and tension, the least with neither, and an int
ermediate response with one or the other alone. Collagen fiber stainin
g was increased primarily in the tension groups. The finding that both
motion and tension enhance the tendon's response to injury encourages
the development of active mobilization protocols following tendon rep
air.