Evaluation of passive and active rehabilitation and of tendon repair for partial tendon lacerations after three weeks of healing in canines

Background. Both passive and active rehabilitation have been shown to be superior to immobilization following partial tendon laceration, but few studies have directly compared these two rehabilitation protocols. In addition, controversy still remains over whether a partial tendon laceration should be repaired. Methods. We evaluated gap formation, adhesions, gliding function and structural properties of repaired and unrepaired tendons following 3 weeks of unrestricted active rehabilitation versus passive mobilization for partial laceration of canine flexor digitorum profundus tendons. An ex vivo radiographic method was used to measure tendon excursion and rotation at each finger joint. The tendon was examined for adhesions, and gapping was measured with calipers. The tendons were tensile tested to failure. Findings. We found no significant differences in tendon excursion, total joint rotation, or adhesions between any groups. Gap size was higher with active mobilization. We found no effect of rehabilitation protocol on the strength or stiffness of healing tendons at 3 weeks. Tendon repair did not affect tendon strength, but did produce higher stiffness in healing tendons at 3 weeks. Interpretation. The results indicate that active rehabilitation appears safe for partial lacerations less than 60 percent. Though repair appears to weaken the tendon in the early stages of healing, it may provide some biomechanical benefit by the middle stages of healing.