The authors have studied the effects of the Holmium: Yttrium Aluminum Grenade (Ho:YAG) laser on tendon sizes (proximal and distal length and width) and on the cellularity and arrangement of collagen fibers in 20 Wistar variety, male, white, adult rats (Rattus Novergicus). The animals have been divided in two groups, according to the follow-up time (12 and 24 weeks) and pursuant to the for form of laser application (continuous or two-point). A Holmium laser (pulsed, solid state, 2.1 micron waves, 40 watts, OmniTip 30º tip) apparatus was used. After the animals were sacrificed, the proximal and distal length and width of the operated size of such rats were compared to those of the non-operated size be means of non-parametric testing (considering p=0,05). The length in the operated size was significantly bigger for both follow-up groups, when compared to the length of the non-operated size, however there was no significant difference in such measures in function of the type of laser application. In the same manner, the width, both in the proximal and distal regions, was significantly bigger in the operated size in both follow-up groups, without showing any significant difference whatsoever in function of the type of application. When the measures in both follow-up groups were compared, distal length and width showed a trend to become bigger after 24 weeks, while width in the proximal region was significantly bigger in this group. As for the subjective microscopic evaluation, both in longitudinal and cross sections, it was possible to observe and increase in the number of fibroblasts, mainly in the 12-week group. The average fibroblast concentration in the tendon with 24-week follow-up was group deemed to be intermediate between the 12-week group and non-operated tendon. The conjunctive tissue was exuberant in the region amidst the fasciculi for the 12-week group, with evident vascular neoformation. In the 24-week group, collagen fibers were regularly arranged, parallel to the tendon axle.
Laser; Collagen; Tendon; Wound healing
