The Animal Experimental Study On Low Intensity Pulsed Ultrasound For Early Restoration Of Bone-Tendon Junction

Objective To explore the effects of low-intensity pulsed ultrasound (LIPUS) on bone-tendon junction in a Patella-Patellar Tendon Complex (PPTC) and early mobilization via surface functional electronic stimulation (FES) to establish an active postoperative rehabilitation program.Methods Animal model of partial patellectomy in 72 mature female New Zealand white rabbits (18-weeks-old) were established and randomly classified into 3 groups. The LIPUS and LIPUS+FES group was given low-intensity ultrasound exposure daily, At postoperative 5th week quadriceps muscles of the operated hindlimb will be stimulated via an FES, while the control group had sham exposure, quadriceps muscle-patella-patellar tendon (QMPPT) was harvest at 6, 12, 18weeks after operation for gross .. histological observation (standard H&E stain, matrix proteoglycan and matrix collagen) and tensile strength of QMPPT complex examinations.Results The histological examination revealed that all of the groups wererestoration with healing over time. In the control group, the scar tissue progressively formed and remodeled between the tendon and bony cut ends. At 6 weeks, the outgrowth of new trabecular bone towards the tendon could be clearly observed in LIPUS and LIPUS+FES group. The characterizations of the microscopic appearance were hypercellular and increased synthesis of extracellular matrix in LIPUS group, especially in the earlier period, more regularity of the alignment of the cell and collagen fiber in LIPUS+FES group was found. The junction healing both of LIPUS and LIPUS+FES groups were better than control group. Mechanical testing result proved it too. But no a typical intermitted fibrocartilage between bone-tendon interface was seen in all of groups. The gross and histological observations showed that the tissue healing of ultrasound group was quicker than those of the control group.Conclusion low-intensity ultrasound could accelerate early healing of bone-tendon junction, on this base, early active rehabilitation by inducing tensile mechanical loading via FES on quadriceps muscles could affiliate bone-tendon junction remodel.