• Hongbin Lu, Ling Qin, Pikkwan Fok, Winghoi Cheung, Kwongman Lee, Xia Guo, Wannar Wong, and Kwoksui Leung.
• Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
• Am J Sports Med. 2006 Aug 1; 34 (8): 1287-96.

BackgroundLow-intensity pulsed ultrasound has been demonstrated to be beneficial for accelerating fracture healing, delayed union, nonunion, and soft tissue repair.HypothesisLow-intensity pulsed ultrasound accelerates healing of bone-to-tendon junction repair by promoting osteogenesis and tissue remodeling at the healing junction.Study DesignControlled laboratory study.MethodsStandard partial patellectomy was conducted in forty-eight 18-week-old rabbits divided into an ultrasound treatment and control group. Daily ultrasound was delivered 3 days after surgery onto the patellar tendon-patella healing junction and continuously up to weeks 2, 4, 8, and 16 postoperatively, when the patella-patellar tendon complexes were harvested for radiographic, histologic, and biomechanical evaluations.ResultsRadiographic measurements showed significantly more newly formed bone at the patellar tendon-patella healing junction in the ultrasound group compared with the controls at week 8 (4.91 +/- 2.74 mm(2) vs 2.50 +/- 1.83 mm(2), P < .05) and week 16 (7.22 +/- 2.34 mm(2) vs 4.61 +/- 2.22 mm(2), P < .05) after partial patellectomy. Histologically, the ultrasound group at weeks 8 and 16 showed improved tissue integration, characterized by trabecular bone expansion from the remaining patella and regeneration of fibrocartilage layer at the patellar tendon-patella healing junction. Fluorescence microscopy revealed earlier bone formation in the ultrasound group when compared with the controls at week 8 (1.78 +/- 0.32 vs 1.23 +/- 0.43, P < .01) and week 16 (2.10 +/- 0.67 vs 1.29 +/- 0.35, P < .01). Mechanical testing showed significantly higher failure load and ultimate strength in the ultrasound group (300.2 +/- 61.7 N and 7.10 +/- 1.29 MPa, respectively) as compared with controls (222.3 +/- 65.1 N and 5.26 +/- 1.36 MPa, respectively) at week 16 (P < .05 for both).ConclusionLow-intensity pulsed ultrasound was able to accelerate bone-to-tendon junction repair.Clinical RelevanceThese results may help establish treatment efficacy for accelerating bone-to-tendon junction repair and facilitating earlier rehabilitation.

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