Effects of the corticosteroids in the lesions by radiofrequency on rats' thigh in different age groups.

Background: The corticosteroids limit the late growth of the lesions by radiofrequency (RF) on the rats' infants' thighs, but the effects on the pubescent and adult rats are unknown.

Objective: Evaluate the effects of the corticosteroids in the healing of the lesions by RF on the rats' thighs muscles in different age groups.

Methods: Ablation was performed on the thigh muscle of 30 rats (1 lesion per animal): infants (30 days old, weight 73 g, n = 10), pubescents (60 days old, weight 230 g, n = 10) and 10 adults (90 days old, 310 g, n = 10), subdivided in control and treated groups, that received Hydrocortisone (10 mg/kg IM post-RF) and Betametasone (3.5 mg/kg IM, twice a week, for 29 days). The rats were sacrificed 60 days after the ablation for hystopathological and planimetric analysis with specified software (ImageJ).

Results: In the infant, pubescent and adult groups, the weight gain in the follow up did not differ between the control and the treated ones. In the control group, the lesions of the infants and pubescents were superior (p = 0.01) to the adults'. The treatment reduced the size of the lesion in the infants (5.58+0.61 mm² vs 4.02+0.23 mm(2); p < 0.01) and pubescents (5.20+0.47 mm(2) vs 4.16+0.48 mm(2); p < 0.01), but not in the adults (4.44+0.50 mm(2) vs 4.79+0.53 mm(2), p = NS). Infant and pubescent treated groups presented lower collagen deposition and less fibrotic bands invading the healthy tissue from the central fibrosis area, and forming lesions with remarkably more reduced dimensions than their controls. There were no differences in the adult groups.

Conclusion: The corticosteroids seem to reduce the late growth of lesion, in addition to attenuate the fibrotic proliferation in the infant and pubescent rats.