The effect of pulsed ultrasound on medial collateral ligament repair

Abstract

Objective To investigate the effect of pulsed ultrasound therapy (US) on medial collateral liga-ment healing in rats and it's mechanism. Methods Eighteen 3-month-old male Sprague-Dawley rats with transected medial collateral ligaments (MCLs) were studied. They were randomly divided into a control group, a 0.5 W/cm~2 group and a 1. 0 W/cm~2 group. The control group was not given any treatment. The 0. 5 W/cm~2 group and 1.0 W/cm~2 group were given 10 minutes of pulsed US (duty cycle: on/off = 3 ms/1 ms) daily for 8 days at either 0.5 or 1.0 W/cm~2 intensity. All the rats were sacrificed on the 9th day. After macroscopic examination, their MCLs were harvested and studied using haematoxylin-eosin staining, Van Gieson's staining and immunohistochemical tech-niques in order to detect transforming growth factor beta-1(TGF-β1) and any histological or histochemical changes.Results Macroscopically, the lacerated MCLs had healed with scar tissue formation. Scarring appeared to be greater in the 0.5 W/cm~2 and 1.0 W/cm~2 groups than in the control group. Inflamed cells appeared to be more numerous in the treated groups than in the controls. There were significant differences in collagen fiber extent among all three groups. In the 1.0 W/cm~2 group, the average level of TGF-β1 was significantly up-regulated, and TGF-β1 expres-sion was higher than in the other two groups. Conclusions Pulsed US can improve ligament healing in the short term, however whether long-term treatment with US can yield further improvement is unknown. Pulsed US can in-crease the level of TGF-β1, which will be higher with higher US dosage. Pulsed US may enhance injored ligament re-pair by up-regulating TGF-β1.Objective To investigate the effect of pulsed ultrasound therapy (US) on medial collateral liga-ment healing in rats and it's mechanism. Methods Eighteen 3-month-old male Sprague-Dawley rats with transected medial collateral ligaments (MCLs) were studied. They were randomly divided into a control group, a 0.5 W/cm~2 group and a 1. 0 W/cm~2 group. The control group was not given any treatment. The 0. 5 W/cm~2 group and 1.0 W/cm~2 group were given 10 minutes of pulsed US (duty cycle: on/off = 3 ms/1 ms) daily for 8 days at either 0.5 or 1.0 W/cm~2 intensity. All the rats were sacrificed on the 9th day. After macroscopic examination, their MCLs were harvested and studied using haematoxylin-eosin staining, Van Gieson's staining and immunohistochemical tech-niques in order to detect transforming growth factor beta-1(TGF-β1) and any histological or histochemical changes.Results Macroscopically, the lacerated MCLs had healed with scar tissue formation. Scarring appeared to be greater in the 0.5 W/cm~2 and 1.0 W/cm~2 groups than in the control group. Inflamed cells appeared to be more numerous in the treated groups than in the controls. There were significant differences in collagen fiber extent among all threegroups. In the 1.0 W/cm~2 group, the average level of TGF-β1 was significantly up-regulated, and TGF-β1 expres-sion was higher than in the other two groups. Conclusions Pulsed US can improve ligament healing in the short term, however whether long-term treatment with US can yield further improvement is unknown. Pulsed US can in-crease the level of TGF-β1, which will be higher with higher US dosage. Pulsed US may enhance injored ligament re-pair by up-regulating TGF-β1. Key words: Ultrasound therapy; Medial collateral ligament; TGF-β1; Tissue repair