Effect of shock-wave therapy on patellar tendinopathy in a rabbit model

This study investigated the effect of shock-wave therapy (SWT) on collagenase induced tendinopathy in the rabbit patellar tendon. Eighteen rabbits were treated by ultrasonography-guided injection of 0.025 ml collagenase into the patellar tendon in both knees. After tendinopathy was confirmed at 3 weeks post-treatment by the histological examination, SWT was initiated to the right patellar tendon involving 1500 cycles at 0.29 mJ/mm² in two separated weekly courses from 4 weeks post-treatment. The rabbits were randomly divided into two groups, which were sacrificed at the 4th and 16th week after SWT, respectively. The histological examination, the mechanical and biochemical tests then were performed. The ultimate tensile load in the SWT tendon increased 7.03% at 4 week and 10.34% at 16 week after treatment as compared to the sham group. Hydroxyproline concentrations increased in the SWT tendons over both the 4 and 16 weeks after treatment. Moreover, the pyridinoline concentration increased at the 4th week but decreased at 16th week as compared to the sham group. The histological examination demonstrated increased blast-like tenocyte at the 4th week, while more mature tenocyte with neovasculization at the 16th week. The result obtained here validates the effectiveness of the SWT in the established tendinopathy. SWT may increase collagen synthesis and collagen crosslink formation during early healing process.