EFFECT OF TWO DIFFERENT PERIODS OF EARLY PULSED ULTRASONIC APPLICATION ON THE TENSILE STRENGTH OF RUPTURED ACHILLES TENDONS IN RATS.

摘要

The study was done to compare the effects of two different pulsed ultrasound regimens on the tensile strength of experimentally tenotomized rat Achilles tendons. Thirty three female Wistar rats aged between 12 and 14 weeks and weighing between 225 and 250 grams were randomly assigned to three groups of 11. Each rat underwent tenotomy of the right Achilles tendon after which the tendon ends were approximated with a single suture and the operated leg immobilized in a splint. Rats in Group 1 received pulsed ultrasound (0.5 watt/cm('2)) to their tenotomized tendon for 5 minutes once daily from the second to the fourth post-operative day. Rats in Group 2 received the same treatment but from day five to day seven post-operatively. Rats in Group 3 received no ultrasound and served as control. The rats were sacrificed on the eighth post-operative day and the healing tendons subjected to mechanical testing with a strain gauge and recorded on a storage oscilloscope.;The study shows that the effect which pulsed ultrasound has on the tensile strength of ruptured rat Achilles tendons depends on when in the healing period the treatment is applied. When treated from the second to the fourth post-operative day and tested for tensile strength on the eighth day, sonicated tendons were found to have higher tensile strength than tendons treated from day five to seven and nontreated control. Tendons treated from the fifth to the seventh post-operative day also had higher tensile strength than the nontreated controls.;Analysis of covariance of group mean tensile strength with final body weight as a covariate showed the mean tensile strength of Group 1 tendons to be significantly higher than those of Groups 2 (p < .001) and 3 (p < .001). The mean tensile strength of Group 2 tendons was significantly higher than that of Group 3 (p < .01). There were significant correlations between the tensile strength of healing tendons and final body weight of rats in Groups 2 (r = .78, p (GREATERTHEQ) .008) with 3 (r = .78, p (GREATERTHEQ) .008) but not in Group 1 (r = .58, p (GREATERTHEQ) .10). Weaker fibrous adhesions were noted between the ruptured Achilles tendons and the overlying skin in Groups 1 and 2 relative to Group 3 rats.