The effect of low level laser therapy on tendon healing in male rats


The study was focused to evaluate the efficacy of low level laser therapy on healing of injured Achilles tendon in rats. Ninety adult male Wistar rats weighing 240±20gm, 10-12 wks. old were used. Animals were divided into three main equal groups; control and two laser treatment groups. Each main group was divided into two equal subgroups; 1-Crushing tendon group, 2-Tendon cutting and anastomosis. Percutaneous crushing of Achilles tendon 1 cm above the hock joint was performed by using artery forceps in 45 rats (15 control, 15 for 4J/cm2, and 15 for 8J/cm2). Completely transverse sever (by scalpel) of Achilles tendon 1 cm above the hock joint was performed in another 45 rats. The cutting tendon was suturing by (modified Kessler technique) using 0/5 silk suture material, and the skin was closed by 0/4 silk simple interrupted suture. GaAlAs diode laser with a wave length of (660 nm) were used for the laser treatment which started immediately after suturing or crushing of tendon, and daily repeated (once a day) for 14 consecutive days. Two doses 4J/cm² and 8J/cm² were used (30 rats for each dose). Control group 30 rats were left without treatment. Specimens of healed tendons (1 cm in length) were taken after (14, 21, and 28) days post injury for histopathological examination by light microscopy after processing and staining with H&E stain to evaluate the healing process. The histopathological findings suggest the favorable qualitative pattern of the newly synthesized collagen, significant number of tenocyte, absence of inflammatory cells and stimulate synthesis of angiogenesis of the regenerating tendons. However, energy density of 8J/cm2 was more effective to healing process than 4J/cm2, by presence of more collagen deposition, significant number of tenocyte, less inflammatory cells and more capillaries were seen. In conclusion, the laser wave length 660 nm in the two doses used in this study was promote healing process in injured Achilles tendon, further the energy density of 8J/cm2 was seen the better in stimulation and maturation of injured Achilles tendon compare with 4J/cm2 dose.