Smokers suffer impaired bone healing.

Cigarette smoking has been linked with a laundry list of ills, including heart disease and a variety of cancers. During the last 20 years, a number of research groups have demonstrated that smoking harms the body's ability to heal skin wounds. Now, for the first time, scientists have documented slower bone healing among smokers.

From November 1988 to August 1990, orthopedic surgeon George Cierny III of Emory University in Atlanta and his co-workers studied 29 men and women who suffered from osteomyelitis, a bacterial infection of the bone and bone marrow that can develop after a wound or fracture.

At the study's start, the researchers obtained a detailed smoking history from each participant and tested urine and blood samples for telltale markers of a smoking habit, such as cotinine, a metabolite of nicotine. Many of the recruits denied a smoking habit until their test results came back. The researchers identified nine nonsmokers, nine ex-smokers and 11 people who continued to smoke during the study.

All 29 patients underwent an operation in which surgeons cut through the skin and tissue and remove the infected segment of the tibia (shinbone). This procedure left each patient's tibia with a gap ranging from 4 to 10 centimeters in length. The surgeons then closed the incision and attached an external, circular device to the leg. This device, known as an Ilizarov apparatus, has wires that fasten to each end of the tibia, creating tension. Over time, the tension spurs one end of the tibia to regenerate, so that the bone ultimately heals.

Using X-rays to monitor bone growth, Cierny's group discovered that non-smokers formed new bone within two months of the operation, whereas smokers showed minimal bone growth at the two-month point. Cierny presented the new findings at the annual meeting of the American Academy of Orthopaedic Surgeons, held last week in Washington, D.C.

The time from the operation until the recruits could resume normal activities ranged from eight to 18 months. When the researchers looked closely at the data, they found that smokers spent more time recuperating. On average, smokers took 2.98 months of manufacture 1 cm of new bone, while non-smokers took 2.32 months. For non-smokers with a 5-cm bone gap, that translates to a 10-month recuperation period, Cierny notes. For smokers, the same 5-cm gap would take 15 months to close.

"So you essentially had another half-year of disability if you were smoking during treatment," Cierry told Science News.

Although ex-smokers also showed impaired bone regeneration, kicking the habit paid off: Ex-smokers took about 2.72 months to grow 1 cm of bone. Osteomyelitis patients who quit smoking before undergoing surgery can expect to recover much faster than if they continued to puff away, Cierny says.

Cigarette smoke contains thousands of harmful substances, but Cierny believes nicotine plays a key role in this drama of poor bone healing. Thomas K. Hunt of the University of California, San Francisco, agrees. In recent years, Hunt has found evidence that cigarette smoke can reduce the amount of oxygen reaching body tissue, probably through the activity of nicotine. The lack of oxygen impairs the body's ability to make collagen, a protein used to form new bone, he says.

Cierny's study demonstrates impaired bone regeneration among smokers who undergo surgery for osteomyelitis. But what about smokers who have simply broken an arm, finger or leg? Cierny believes they, too, would experience delayed healing. However, additional research must verify that suspicion, he adds.