Cigarette US researchers have found that smoking slows down fracture and ligament repair, by following injuries in mice. The researchers at the Washington University School of Medicine examined the effects of smoking on fractures and ligament healing in mice, and found that healing of both types of injury was delayed.

Earlier studies have shown that the numerous toxins contained in cigarette smoke can undermine fracture and ligament repair following injury. In addition, smokers have higher rates of hip fracture, fracture healing problems and bone infections, and smoking has been shown to impair soft tissue wound healing.

In the first study, researchers found that mice exposed to smoke had delayed fracture healing especially during the early stages of the healing process. Specifically, they were able to show that there was a delay in the development of mature cartilage cells in the mice exposed to cigarette
smoke. This was the first study to analyze the molecular and cellular mechanisms of fracture healing in mice exposed to smoke.

“Clinically, if specific events can be identified, smoking cessation in humans, even temporarily, may improve or speed the healing process after injury and decrease the significant morbidity associated with cigarette smoking during fracture healing.”

In the second study, the researchers examined the effects of smoking on medial collateral ligament (MCL) injury. They performed MCL surgery on mice, and found that normal wound healing was partially inhibited in mice exposed to cigarette smoke. Based on their findings, the authors
suggest that this delay is due to a difference in the recruitment of cells to the site of injury.

In addition, the study found that mice exposed to smoke had impaired or delayed extracellular matrix development, shown by lower collagen type I gene expression, one week after injury. This may lead to a delay in restoring biomechanical stability of the healing MCL.

“Ultimately, a better understanding of the cellular and molecular mechanisms involved in the MCL healing process will allow physicians to improve or speed the healing process, as well as potentially overcome the deleterious effects of smoking on ligament healing,” the authors concluded.