Background: After flexor tendon repair, the strength of the repair
and the resistance to digital motion are important considerations in deciding
when to initiate postoperative rehabilitation. Our objective was to assess
these factors in a short-term in vivo canine model of flexor tendon
Methods: Forty-eight dogs were randomly allocated to four groups
based on the duration of postoperative follow-up (one, three, five, or seven
days). In each group, two flexor digitorum profundus tendons of one forepaw
were exposed. One tendon (the repair tendon) was sharply transected and
repaired with a modified Kessler suture, and the other one (the sham tendon)
was simply exposed without laceration. The involved paw was immobilized until
the animal was killed on the designated day. Three tendons from each dog,
including the repair tendon, the sham tendon, and a control tendon from a
corresponding normal digit on the contralateral side, were tested.
Results: The mean peak total digital resistance force in the repair
group was lowest at five days (p < 0.01 compared with seven days; p >
0.05 compared with one and three days). The mean peak force needed to overcome
the internal gliding resistance between the repaired tendon and sheath was
significantly higher than that in both the sham and control groups at all
time-points (p < 0.001); however, this value was also smallest at five
days. There was no significant difference in suture strength at any time-point
(p > 0.05).
Conclusions: When we evaluated tendon-gliding and suture strength
after flexor tendon repair, the least favorable ratio of repair strength to
force needed to overcome the resistance to digital motion was noted on Day 7,
whereas the best combination of tendon strength and low peak resistance force
was noted on Day 5.
Clinical Relevance: The results of the present study suggest that
postoperative Day 5 may be the best time to begin rehabilitation, with either
active or passive therapies, as the amount of tendon force necessary to
initiate tendon motion is least at this time.