NEW YORK, Oct 26: Smokers may have a tougher time recovering from tendon injuries, such as rotator cuff tears and Achilles tendon ruptures, a new study in rats suggests.
Based on the observed effects of nicotine on tendon healing in rats, the study's authors recommend that people who are about to undergo rotator cuff repair should avoid tobacco products entirely.
While cigarette smoking is known to hamper the healing of bones and skin, the current investigation is the first to show it can slow tendon healing as well, Dr Leesa Galatz of the Washington University School of Medicine in St Louis, Missouri, told Reuters Health in an interview.
Galatz and her team tested nicotine's effects on the outcome of rotator cuff repair surgery in 72 rats. Half of the animals were given nicotine via an implanted pump that maintained a nicotine concentration in the bloodstream equivalent to that in a human who smokes 20 to 30 cigarettes a day. The rest of the rats received saline solution, an inactive water and salt solution.
Inflammation lasted longer in the rats given nicotine, while the rats on saline showed higher levels of type-1 collagen, indicating faster healing. Cell growth and density was greater in the saline-solution rats at day 10 and day 28 of the experiment, but were similar in the two groups by day 56.
The repaired joint was weaker in the rats on nicotine when checked at day 10 and day 28, but was actually stronger in these rats at day 56. This may have been due to the accumulation of the end products of advanced glycation, which is known to be increased in smokers, Galatz and her team note, and may make collagen more brittle and less elastic.
Nicotine ''has the greatest effect at the early time points,'' Galatz said. ''There's probably a period of vulnerability where that smoking has the greatest effect.'' She added that cigarette smoking contains many other potentially harmful substances beside nicotine, such as carbon monoxide and tar, which could also impair healing. ''If anything,'' she said, ''we may have underestimated the effect that smoking has.''