Comparison of single and multiple applications of GaAlAs laser on rat medial collateral ligament repair

Background and Objectives 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. Study Design/Materials and 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/cm2) 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/cm2). 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. Lasers Surg. Med. 34:285–289, 2004. © 2004 Wiley‐Liss, Inc.