The effect of ethanol intake on tendon healing: a histological and biomechanical study in a rat model

Ethanol has a suppressive effect on inflammation and the immune system, but the effect of ethanol on tendon healing in vivo has not been studied. The purpose of this study was to investigate the histological and biomechanical effects of ethanol intake on tendon healing in a rat tendon injury model.

Forty-seven rats were randomly assigned to either ethanol or control groups. Progressively increasing concentrations of ethanol combined with glucose were administered to these rats in their drinking water. After 1 week, the Achilles tendon of each rat was injured proximal to its insertion on the calcaneus. All rats were euthanized at 4 weeks. The tendons were evaluated both histologically and biomechanically. The histologic examination of these tendons was done using a semi-quantitative 4-point scale to rate cell morphology, the degree of ground substance staining, collagen organization, and vascular changes. Load to failure (N) strength was obtained with biomechanical testing.

Tendon failure loads were lower in the ethanol group (31.6 +/- 8.8 N) than in the control group (39.7 +/- 8.2 N) (P = 0.04). Histologic tenocyte scores were higher in the ethanol group (1.90 +/- 0.73) than the control group (0.9 +/- 0.73) (P = 0.01).

Ethanol ingestion resulted in abnormal tenocyte morphology, disorganized collagen bundles with a tendency toward increased tenocyte number, and neovascularization 3 weeks after the tendon injury indicating delayed and abnormal healing. The healing tendons in the alcohol treated group failed at statistically lower loads than the control group.