ABSTRACT
BACKGROUND:Patella-patellar tendon junction (PPTJ) injuries are a common disease in athletes and vulnerable to re-injury. Post-injury training is a double-edged sword. OBJECTIVE:To examine the effect of post-injury resting days on the quality of healing in PPTJ in view of histomorphology, expression levels of growth factor and collagen, and muscle tension. METHODS:Forty New Zealand white rabbits were randomly divided into control, and five post-injury training groups representing different time to restart training after acute injury:the rabbits restarted training at 24 (PIT24), 48 (PIT48), 72 (PIT72), 96 (PIT96) and 120 (PIT120) hours, respectively. All post-injury training groups received acupuncture at the PPTJ and then underwent 4-week low-intensity training. Afterwards, all rabbits were killed to take specimens for hematoxylin-eosin, safranin O and immuohistochemical staining. The muscle tension and hardness were detected using Myoton-3. The thickness of fibrous cartilage zones, cell density, as well as the expression levels of vascular endothelial growth factor and collagen were measured on Metamorph software. RESULTS AND CONCLUSION:Compared with the control group, in the PIT groups, the collagens arranged in disorder, and decreased cell density, increased mucopolysaccharide andrising tidephenomenon appeared. The fibrocartilage in the PIT24 and PIT120 groups was significantly thicker than that in the control group (P<0.05). The ratio of collagen type Ⅰ/Ⅲ was significantly decreased in the PIT24 and PIT48 groups compared with the control group (P<0.05), and the highest in the PIT72 group. The expression level of vascular endothelial growth factor in the PIT48, PIT72 and PIT96 groups was significantly higher than that in the control group (P<0.05). The muscle tension was negatively correlated with the collagen ratio (r=-0.538;P<0.01) and chondrocyte density (r=-0.570;P<0.01), while muscle hardness was positively correlated with the expression level of vascular endothelial growth factor (r=0.613;P<0.01). Our results suggest that different resting time makes significant differences in the PPTJ healing and the 72-hour resting is the best choice. Moreover, muscular properties are related to the cel density, collagen synthesis and growth factor expression, which can be used as a non-invasive indicator to guide post-injury training and prevent recurrence.
ABSTRACT
BACKGROUND: Although overuse-induced patella-patellar tendon junction injury is a common disease, its pathogenesis and healing mechanism remain unclear.OBJECTIVE: To establish an overuse-induced injury animal model by a repetitive traction at the patellar tendon insertion,and to explore its pathogenesis and healing mechanism based on histomorphology and growth factor expression levels.METHODS: Twenty-eight New Zealand rabbits were randomly divided into four groups: the rabbit left and right posterior limbs without any intervention as controls (n=4); cyclic loading training targeting the left posterior limb was done in model,healing and training groups (n=8 per group) for 4 weeks. Afterwards, the rabbits in the model group were killed immediately, rabbits in the healing group relaxed for another 4 weeks and then were killed, while rabbits in the training group were subjected to 4-week low-intensity training. The histological changes and growth factor expression levels during patella-patellar tendon junction injury and healing after load training were observed.RESULTS AND CONCLUSION: Compared with the control group, in the model group, the cells and collagenous fibers arranged in disorder, and the tidemark disappeared. The healing and training groups healed incompletely, but showed better histological changes than the model group. The thickness of fibrocartilage and basic fibroblast growth factor level in the control group were significantly lower than those in the other three groups (P < 0.05). The cell density and vascular endothelial growth factor level in the model group were significantly higher than those in the control and healing groups (P < 0.05). These results show that the animal model of overuse-induced patella-patellar tendon junction injury cannot return to normal after 4 weeks of rest, but the low-intensity training is conductive to healing quality.