The effect of immediate constrained digital motion on the strength of flexor tendon repairs in chickens.

Profundus tendon lacerations were repaired in the central toes of 216 chickens, and the digits were either immobilized in a cast or allowed immediate constrained motion in a tethering splint. The effect of digital motion on the early phases of tendon healing was investigated by comparing the rupture strengths of the two groups during the first 40 days after repair. The repairs in immobilized digits showed marked decreases in strength during the first 20 days, while the tendons in mobilized digits showed immediate and progressive gains in strength through the time intervals studied. By 5 days, the difference in strength between the two groups was significant (p less than 0.05), and the magnitude of this difference increased with time. The model developed in this study demonstrates that an initial loss of flexor tendon repair strength is not inevitable. Immediate constrained digital mobilization allows progressive tendon healing without an intervening phase of tendon softening.