title: Low-intensity pulsed ultrasound accelerates healing in rat calcaneus tendon injuries.
abstract: METHODS
  Controlled laboratory study.
  
  
  OBJECTIVE
  To evaluate the effect of low-intensity therapeutic ultrasound on the murine calcaneus tendon healing process.
  
  
  BACKGROUND
  Therapeutic ultrasound promotes formation and maturation of scar tissue.
  
  
  METHODS
  Calcaneus tendon tenotomy and tenorrhaphy was performed on 28 Wistar rats. After the procedure, the animals were randomly divided into 2 groups. The animals in the experimental group received a 5-minute ultrasound application, once a day, at a frequency of 1 MHz, a spatial average temporal average intensity of 0.1 W/cm2, and a spatial average intensity of 0.52 W/cm2 at a 16-Hz frequency pulse mode (duty cycle, 20%). Data for the injured side were normalized in relation to the data from the contralateral healthy calcaneus tendon (relative values). The animals in the control group received sham treatment. After a 28-day treatment period, the animals were sacrificed and their tendons surgically removed and subjected to mechanical stress testing. The parameters analyzed were cross-sectional area (mm2), ultimate load (N), tensile strength (MPa), and energy absorption (mJ).
  
  
  RESULTS
  A significant difference between groups was found for the relative values of ultimate load and tensile strength. The mean ± SD ultimate load of the control group was -3.5% ± 32.2% compared to 33.3% ± 26.8% for the experimental group (P = .005). The mean tensile strength of the control group was -47.7% ± 19.5% compared to -28.1% ± 24.1% for the experimental group (P = .019). No significant difference was found in cross-sectional area and energy absorption.
  
  
  CONCLUSIONS
  Low-intensity pulsed ultrasound produced by a conventional therapeutic ultrasound unit can positively influence the calcaneus tendon healing process in rats.
authors.affiliation: University of Sao Paulo, School of Medicine, Department of Orthopaedic Surgery, Sao Paulo, SP, Brazil.
authors.forename: Sérgio Luiz
authors.initials: SL
authors.lastname: Jeremias Júnior
authors.forename: Gilberto Luis
authors.initials: GL
authors.lastname: Camanho
authors.forename: Ana Cristina Ferreira
authors.initials: AC
authors.lastname: Bassit
authors.forename: Andrea
authors.initials: A
authors.lastname: Forgas
authors.forename: Sheila J M
authors.initials: SJ
authors.lastname: Ingham
authors.forename: Rene Jorge
authors.initials: RJ
authors.lastname: Abdalla
mesh_terms: D000125:Achilles Tendon / Q000293:injuries; D000818:Animals; D002111:Calcaneus / Q000293:injuries; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013708:Tendon Injuries / Q000628:therapy*; D013718:Tensile Strength; D014464:Ultrasonic Therapy / Q000379:methods*; D014945:Wound Healing