The use of 808-nm light therapy to treat experimental chronic osteomyelitis induced in rats by methicillin-resistant Staphylococcus aureus.

ABSTRACT

BACKGROUND DATA In vivo and in vitro studies have reported that laser energy in differing wavelengths and irradiation regimes has a potential bactericidal effect on Staphylococcus aureus. OBJECTIVE: The purpose of this study was to investigate whether a light wavelength of 808 nm in varying doses has an effect on chronic osteomyelitis induced experimentally in the rat tibia. METHODS: Intramedullary cavities were surgically created in the left tibias of 39 adult Wistar albino rats. Five randomly selected subjects were injected with a sterile saline solution, and methicillin-resistant S. aureus (MRSA) was used to induce osteomyelitis in the remaining rats. After 3 weeks, rats with evidence of osteomyelitis were treated with debridement alone (n = 7), with debridement plus laser irradiation to induce photoeradication (n = 21), or were not treated at all [negative control, (n = 6)]. Active irradiation was performed using an 808 nm, 100 mW continuous-wave diode laser with a beam spot size of 0.7854 cm(2) (irradiance = 127.3 mW/cm(2)). Laser treatment commenced immediately after debridement surgery and was applied daily for 5 consecutive days. Irradiation lasted 60 secs (6 J at 7.64 J/cm(2) n = 7), 120 secs (12 J at 15.29 J/cm(2) n = 7), or 180 secs (18 J at 22.93 J/cm(2) n = 7). Rats in the sham and negative control groups were killed 21 days post-induction surgery, and those in the treatment groups were killed after 42 days. Following killing, tibias were removed and analyzed histopathologically, radiographically, and microbiologically. RESULTS: Histopathological analysis showed that infection levels had decreased by 37%, 67%, 81%, and 93% in the groups treated by debridement or by debridement plus 7.64, 15.29, and 22.93 J/cm(2) light therapy, respectively, compared to the negative control group. Osteomyelitis-induced rats had the highest bacteria count (5 × 10(5)). Bacterial counts fell to 1.6 × 10(4), 4.3 × 10(2), 5.5 × 10(1), and 3.3 × 10(0) in groups treated by debridement or by debridement plus 7.64, 15.29, and 22.93 J/cm(2) light therapy, respectively, compared to the negative control group. CONCLUSIONS: Within the limitations of this study, laser phototherapy with the appropriate irradiation parameters appears to be a promising adjunct and/or alternative technique to pharmacological agents in the treatment of osteomyelitis. The 808 nm 100 mW (127.3 mW/cm(2)) laser device used in this study achieved a maximum effect with an irradiation time of 180 secs, delivering 18 J at an energy density of 22.93 J/cm(2).