Patients of more than 60 years of age and affected by chronic lower back pain were randomly assigned to two groups. Group A, consisting of 38 patients, was irradiated with a pulsed GaAs diode laser, 904nm, pulse width 200 nsec, pulse frequency 10,000 Hz, peak power of 20 W, average power 40 mW, spot size 150 cm2 in area, and an angle divergence of 6o. The laser was applied in the point technique with a dose of 4 J/cm2 per point in the area of pain. Group B, consisting of 33 patients, was treated with sham irradiation with a deactivated laser system. Neither the patient nor the operator knew to which group each patient was randomly assigned. The use of analgesic drugs and physical therapy was excluded in both groups. Ten daily consecutive sessions were carried out once per day. Pain was evaluated through an analogue and visual scale at the beginning and at the end of the treatment. Laser treatment was considered effective when pain relief was more than 60%. A follow-up was carried out over the following six months. The treatment was effective in 71% of patients in group A and 36.4% of group B (p < 0.007). The pain disappeared completely in 44.7% of group A and 15.2% of group B (p < 0.01). During the six month follow-up period, in those patients in whom the response to the treatment was effective, the pain recurred in 34.8% of group A and in 70% of group B. No cutaneous, ophthalmologic or systemic side effects were observed. These results suggest than irradiation with GaAs laser at the doses used and techniques applied in this study, relieves chronic low back pain in older patients in a statistically significant percentage of the patients but without causing. any adverse side effects.

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