Abstract
To determine the influence of low-level laser therapy on femoral growth plate in rats. Thirty male Wistar rats aged 40 days were divided into two groups, G1 and G2. In G1 the area of the distal growth plate of the right femur was irradiated at one point using GaAlAs laser 830 nm wavelength, output power of 40 mW, at an energy density of 10 J/cm(2). The irradiation was performed daily for a maximum of 21 days. The same procedure was done in G2, but the probe was turned off. Five animals in each group were euthanized on days 7, 14 and 21 and submitted to histomorphometric analysis. In both groups the growth plate was radiographically visible at all moments from both craniocaudal and mediolateral views. On the 21st day percentage of femoral longitudinal length was higher in G2 than G1 compared to basal value while hypertrophic zone chondrocyte numbers were higher in G1 than G2. Calcified cartilage zone was greater in G1 than in G2 at all evaluation moments. Angiogenesis was higher in G1 than in G2 at 14th and 21st days. The low-level laser therapy negatively influenced the distal femoral growth plate.
Highlights
Low-Level Laser Therapy (LLLT) has been evaluated experimentally by in vitro and in vivo studies as well as in clinical cases[1]
The area of the distal femoral growth plate was irradiated at one point, using a GaAlAs diode laser with 830 nm wavelength and output power of 40 mw, for 20 seconds, at an energy density of 10 J/cm[2]
The growth plate was radiographically visible at all moments in both groups from both craniocaudal and mediolateral views (Figure 4)
Summary
Low-Level Laser Therapy (LLLT) has been evaluated experimentally by in vitro and in vivo studies as well as in clinical cases[1]. The mechanism that leads to a positive effect of LLLT on the tissues is not completely understood and its therapeutic role remains controversial[1,2]. The conflicting results on the effects of laser stimulation on tissues reported in some studies may be related to the great variety of treatment protocols, animal models and cellular culture models used[1]. LLLT has been used with positive results in promoting or accelerating the healing of tendons, ligaments, nerves, wounds, ulcers and burns, in stimulating a better healing of bone defect or bone fracture, in relieving pain of lateral epicondylitis, and in a variety of oral and dental conditions2-,5, among others. In some cases the area to be irradiated is located next to a growth plate of a long bone in a young individual, and the risk of growth plate arrest inducing angular deformities and limb-length discrepancies by therapy stimulus should be considered[6]
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