This study, the first to evaluate the effects of nicotine on rotator cuff repair, found that when rats were exposed to nicotine following rotator cuff repair, inflammation persisted for a longer time in the shoulder joint. That's detrimental to healing. The researchers also noted that there was less cellular proliferation in the rats' surgically repaired shoulders and decreased collagen production, leading to inferior healing.
"When you have an injury and a repair, new cells come in and start to facilitate healing," Galatz says. "When the new cells arrive, they make proteins such as collagen to form the junction between tendon and bone. And in the rats exposed to nicotine, we saw lower cellular proliferation."
The rats also made less type-I collagen and had different biomechanical properties in their shoulders following rotator cuff repair. Measuring properties called maximum stress and maximum force, the researchers found that shoulder joints in the nicotine-exposed rats were weaker.
"Those changes were most apparent at earlier time points, and shoulder strength tended to equalize between the two groups about 8 weeks after surgery," Galatz says. "But certainly, the tissue was weaker early on and more vulnerable to re-injury."
Galatz and colleagues studied healing in the shoulders of 72 rats following rotator cuff surgery. The researchers implanted tiny, osmotic pumps under the skin of the rats, and those pumps delivered either nicotine or an inactive saline solution. Saline pumps were implanted to ensure that any changes observed between groups of rats resulted from nicotine exposure rather than from having a pump implanted beneath the skin. In the rats that got nicotine, the pumps maintained nicotine levels
Source:Washington University School of Medicine