Nicotine Exposure Via Electronic Cigarettes Significantly Impedes Biomechanical Healing Properties of Tendon Healing in a Rat Model

Purpose: To evaluate the biomechanical and histologic effects on Achilles tendon repair of inhaled combusted tobacco versus nicotine exposure via electronic cigarette versus a control group in a small-animal model (Sprague-Dawley rat). Methods: Fifty-four Sprague-Dawley rats were randomized into 3 groups: combusted tobacco, e-cigarettes, or control. Experimental rats were exposed to research cigarettes or e-cigarette vapor in a smoking chamber for 4 weeks. Surgical transection and repair of the Achilles tendon were then completed, followed by 2 additional weeks of exposure. Achilles tendons were harvested, and biomechanical tensile testing was performed. Histologic evaluation was completed, including hematoxylin-eosin staining, trichrome staining, and immunohistochemistry analysis for type I and type III collagen. Results: The control group showed the highest mean tensile load to failure, at 41.0 ± 10.4 N (range, 18.3-55.1 N); the cigarette cohort had the second highest mean, at 37.3 ± 11.1 N (range, 14.0-54.7 N); and finally, the vaping group had the lowest mean, at 32.3 ± 8.4 N (range, 17.8-45.1 N). One-way analysis of variance showed a significant difference in load to failure when comparing the control group with the e-cigarette group (P = .026). No statistical difference was detected between the control group and cigarette group (P = .35) or between the e-cigarette group and cigarette group (P = .23). Stiffness and qualitative histologic analysis showed no difference among groups. Conclusions: This investigation shows that in a rat model, nicotine exposure via e-cigarette significantly impedes the biomechanical healing properties of Achilles tendon surgical repair. Clinical Relevance: The results indicate that although e-cigarettes are often used as a perceived “safer” alternative to smoking, their use may have a detrimental effect on tendon load to failure.