title: Comparison of single and multiple applications of GaAlAs laser on rat medial collateral ligament repair.
abstract: OBJECTIVE
  To examine single versus multiple applications of the gallium aluminum arsenide (GaAlAs) laser on the healing of surgically injured medial collateral ligaments (MCLs) in rats.
  
  
  METHODS
  Sixteen rats were studied, with 12 receiving surgical transection to their right MCL and 4 receiving a sham injury. Group 1 (n = 4) received a single dose of GaAlAs laser therapy (wavelength 660 nm, average power 8.8 mW, pulse 10 kHz, dosage 31.6 J/cm(2)) directly to their MCL during surgery. Group 2 (n = 4) received 9 doses of GaAlAs laser therapy applied transcutaneously on alternate days (wavelength 660 nm, average power 8.8 mW, pulse 10 kHz, dosage 3.5 J/cm(2)). The controls (Group 3, n = 4) received one session of placebo laser at the time of surgery, with the laser equipment shut down, while the sham injured Group 4 (n = 4) received no treatment. Biomechanical tests for structural stiffness, ultimate tensile strength (UTS), and load-relaxation were done at 3 weeks after injury. The stiffness and UTS data were normalized by expressing as a percentage of the left side of each animal before statistical analysis.
  
  
  RESULTS
  The load-relaxation data did not show any differences between the groups (P = 0.18). The normalized stiffness levels of Groups 2 (81.08+/-11.28%) and 4 (92.66+/-13.19%) were significantly higher (P = 0.025) than that of the control Group 3 (58.99+/-15.91%). The normalized UTS of Groups 2 (81.38+/-5.68%) and 4 (90.18+/-8.82%) were also significantly higher (P = 0.012) than that of the control (64.49+/-9.26%). Although, Group 1 had higher mean stiffness and UTS values than the control, no statistically significant difference was found between these two groups.
  
  
  CONCLUSIONS
  Multiple laser therapy improves the normalized strength and stiffness of repairing rat MCLs at 3 weeks after injury. The multiple treatments seem to be superior to a single treatment when the cumulative dosages are comparable between the two modes of application.
authors.affiliation: Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. rsgng@polyu.edu.hk
authors.forename: Gabriel Y F
authors.initials: GY
authors.lastname: Ng
authors.forename: Dicky T C
authors.initials: DT
authors.lastname: Fung
authors.forename: Mason C P
authors.initials: MC
authors.lastname: Leung
authors.forename: Xia
authors.initials: X
authors.lastname: Guo
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D028022:Low-Level Light Therapy; D008297:Male; D017888:Medial Collateral Ligament, Knee / Q000293:injuries* / Q000503:physiopathology / Q000528:radiation effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014945:Wound Healing / Q000528:radiation effects