Low-intensity pulsed ultrasound accelerates bone-tendon junction healing: a partial patellectomy model in rabbits.
BACKGROUND
Low-intensity pulsed ultrasound has been demonstrated to be beneficial for accelerating fracture healing, delayed union, nonunion, and soft tissue repair.


OBJECTIVE
Low-intensity pulsed ultrasound accelerates healing of bone-to-tendon junction repair by promoting osteogenesis and tissue remodeling at the healing junction.


METHODS
Controlled laboratory study.


METHODS
Standard 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.


RESULTS
Radiographic 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).


CONCLUSIONS
Low-intensity pulsed ultrasound was able to accelerate bone-to-tendon junction repair.


CONCLUSIONS
These results may help establish treatment efficacy for accelerating bone-to-tendon junction repair and facilitating earlier rehabilitation.
Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
Hongbin
H
Lu
Ling
L
Qin
Pikkwan
P
Fok
Winghoi
W
Cheung
Kwongman
K
Lee
Xia
X
Guo
Wannar
W
Wong
Kwoksui
K
Leung
D000704:Analysis of Variance; D000818:Animals; D016723:Bone Remodeling; D050376:Bone-Patellar Tendon-Bone Grafting; D004195:Disease Models, Animal; D005260:Female; D051445:Fibrocartilage / Q000601:surgery; D017102:Fracture Healing; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy; D007719:Knee Joint / Q000601:surgery; D008856:Microscopy, Fluorescence; D010012:Osteogenesis; D010329:Patella / Q000000981:diagnostic imaging / Q000293:injuries / Q000503:physiopathology / Q000601:surgery*; D017847:Patellar Ligament / Q000000981:diagnostic imaging / Q000293:injuries / Q000503:physiopathology / Q000601:surgery*; D011817:Rabbits; D011859:Radiography; D013314:Stress, Mechanical; D013708:Tendon Injuries / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy; D014464:Ultrasonic Therapy