Effect of near-infrared light on in vitro cellular ATP production of osteoblasts and fibroblasts and on fracture healing with intramedullary fixation.

Abstract

Evaluate the effect of near-infrared light (NIR) on immediate production of ATP by osteoblasts and fibroblasts in vitro, and the healing process of rat femur fractures with intramedullary fixation. NIR is one potential treatment option for complications of fracture healing, which has shown to stimulate cellular proliferation and to enhance the healing process. Cell culture - MC3T3-E1 and 3T3-A31 cells were subjected to NIR at 660nm, 830nm, or both combined. ATP was assayed at 5, 10, 20, and 45min after exposure. Animal study - 18 rats had surgery with retrograde intramedullary pins inserted into their femurs, which then underwent closed, transverse femur fracture. Rats were randomly divided into 3 study groups of 6 each: nonirradiated controls, 660nm, and 830nm NIR. Healing process was assessed by a blinded radiologist, assigning a healing score of 1-6 for radiographs taken on days 0, 7, 14, and 21. Cell culture - All groups gave significant increase in ATP within 5-10min, with decay to baseline by 45min. 660nm NIR was significantly more effective than 830nm with fibroblasts or either wavelength with osteoblasts. Animal study - A significant increase in the fracture healing grade in the 660nm group at day 14, but with no differences at day 21. The study demonstrated an immediate increase in ATP production in vitro and an initial acceleration of callus formation in the fracture healing process, in the presence of NIR.