The pineal hormone melatonin was recently shown to have a free radical scavenging ability which reduces lipid peroxidation and has also been shown to scavenge the hydroxyl radical and other reactive oxygen species. Melatonin stimulates several antioxidative enzymes, which increases its efficiency as an antioxidant. Also, melatonin stimulates osteoblast differentiation and mineralization of matrix and it may regulate osteoclastic activity via superoxide dismutase in vitro. Therefore, the effect of melatonin in fracture healing depends in part on the free radical scavenging and osteoblastic-osteoclastic regulatory properties of melatonin.

In this study the effect of melatonin (MEL) on fracture healing in rat tibia model was studied by using biochemical, radiological and histopathologic methods.

Male Sprague-Dawley rats (n=80) were randomized into control and melatonin groups with 8 rats per group according to the day of sacrifice (Days 1, 3, 7, 14, 28). Group B (melatonin group) received 30 mg/kg melatonin intraperitoneally (i.p.) for the duration of the experiment.

Malondialdehyde (MDA) levels in MEL group decreased at days 3, 7, 14, and 28 compared to control values (p< 0.05). Superoxide dismutase (SOD) activity in MEL group decreased at days 3, 7, and 14, and returned to the first day value after 28 days. Myeloperoxidase (MPO) values in MEL group decreased at days 1, 3, and 7 (p< 0.001). Both radiologically and histopathologically fracture healing was significantly more advanced in the MEL group (p< 0.05, p< 0.05 respectively).

We conclude that exogenously administering a pharmacological dose of melatonin has a positive effect on fracture healing and may be beneficial as a supportive agent in fracture cases.