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

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).