| Bone-tendon(B-T) junction injury is common and its repair is difficult because of poor regeneration capacity of its interface fibrocartilage. Extracorporeal shock wave treatment(ESWT) was proven to be able to treat the chronic injuries of soft tissues and delayed fracture healing or non-union fracture.No study was conducted to show if ESWT could be indicated for treatment of delayed healing(DH) at bone-tendon junction. This experiment was designed to establish a B-T interface delayed healing animal model and to study the treatment efficiency of ESWT on this model. The research would provide a DH model on B-T junction for the further study in this area and revealed the effect mechanism of ESWT.Hope the result of this research will be utilized in the clinic to improve the treatment for patients.Methods:A standard partial patellectomy was used for establishing the delayed B-T repair by shielding the B-T surgical repair for 4 weeks once ESWT at week 6 on the healing interface of patella in 47 female mature rabbits. Evaluations were performed at week 8 and 12 after surgery radiographically,densotometrically,biomechanically,and histologically.Results:Establishment of B-T junction delayed healing animal model:Radiological measurements showed significant delayed osteogenesis at B-T healing junction in the delayed healing groups.Bone mineral density(BMD) of new bone was 56.0%lower in the delayed healing group at week 8,but this difference diminished at week 12.The healing quality of B-T healing was significantly poor in the delayed healing group,as shown with 22.9%and 24.2%lower failure load than that of control group at week 8 and week12, respectively.The repair quality was explained by histological findings that the healing process of B-T junction was found slower in both early repair and later remodeling stage,typically with a limited regeneration of the B-T junctional fibrocartilage zone in the delayed healing group, with a thickness of the regenerated fibrocartilage zone only 39.7%and 57.8%of the control group at week 8 and week 12,respectively.The failure load of DH group was only 39.7%and 57.8%of CON group.Treatment efficiency of ESWT on the B-T junction delayed healing model: Radiographic measurements showed 293.37%and 185.77%more newly formed bone at the patella-patellar tendon(PPT) healing junction in the ESWT group compared with the DH group at week 8 and week 12 after partial patellectomy.Significant differences in bone mineral density and content(BMD and BMC) were only found at week 12 between the ESWT and DH groups.Histologically,the ESWT group showed advanced remodeling in terms of better alignment of collagen fibers,thicker and mature regenerated fibrocartilage zone at both weeks 8 and 12 as compared with DH group,correspondingly.Tensile testing showed 167.66%and 145.14% higher tensile load and strength in the ESWT group than DH group, respectively at week 8 and week 12.Conclusions:This study demonstrated for the first time a delayed B-T healing experimental model characterized with delay in osteogensis,regeneration of fibrocartilage zone and tensile load.ESWT was able to treat delayed healing at bone-to-tendon junction by promoting osteogenesis,regeneration of fibrocartilage zone and tissue remodeling at PPT healing complex in rabbits. |
