Ultrastructural comparison of medial collateral ligament repair after single or multiple applications of GaAlAs laser in rats

Background and Objectives To examine single versus multiple applications of a gallium aluminum arsenide (GaAlAs) laser on the ultrastructural morphology of surgically injured medial collateral ligaments (MCLs) in rats. Study Design/Materials and Methods Sixteen rats were studied with 12 receiving right MCL transection and 4 receiving sham injury. Group 1 (n = 4) received one session of laser (31.6 J/cm 2 ) immediately after injury. Group 2 (n = 4) received 9 doses of transcutaneous laser (3.5 J/cm 2 ). The controls (Group 3, n = 4) received one session of placebo laser, while the sham Group 4 (n = 4) received no treatment. Ultrastructural analyses were done with electron microscopy at 3 weeks. Results The mass‐averaged diameters of collagen fibril in the core and periphery of MCLs treated with multiple laser were larger than the control and those with single laser treatment ( P  < 0.05). However, the sham injured group had larger fibrils than all other groups ( P  < 0.05). Conclusions The repairing MCLs had smaller collagen fibrils than the sham injured ligaments. Multiple laser treatments enhanced the collagen growth in the repairing MCLs at 3 weeks after injury, which are superior to a single treatment with similar dosage. Lasers Surg. Med. 35:317–323, 2004. © 2004 Wiley‐Liss, Inc.