The Effect of Ethanol on Rotator Cuff Repairs in a Rodent Model.

Background: Alcohol consumption is a significant risk factor for both the occurrence and severity of rotator cuff tears. However, there is limited supporting evidence to suggest alcohol use is associated with suboptimal outcomes following operative repair of rotator cuff tears. Rat shoulders have been demonstrated as consistent and reliable models for studying rotator cuff disease.

Hypothesis/purpose: Perioperative alcohol exposure will negatively impact biomechanical and histologic properties of surgically repaired rotator cuffs in rats.

Methods: Rats were randomized to receive a 20% ethanol or isocaloric control solution as their primary source of drinking water. A tenotomy of the supraspinatus tendon from bone was performed surgically and then immediately repaired with a transosseous technique. Following surgery, rats were continued on the same exposure solution until animals were humanely euthanized at 7, 14, or 21 days postoperatively. The surgically-repaired shoulders underwent biomechanical testing to assess load to failure and failure strain. Histological evaluation of tendon-to-bone healing was performed by a blinded pathologist using a qualitative grading system. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) on total RNA from tendon-to-bone interface tissue was performed to quantify the mRNA expression of Type I & III collagen, and transforming growth factor-beta 1 (TGF-B1) & 3 (TGF-B3) at the repair site.

Results: Biomechanical testing showed that repaired shoulder constructs in rats exposed to ethanol had significantly lower load to failure at 7 days postop relative to repairs in rats exposed to a control solution. No other biomechanical parameters or time points reached statistical significance. TGF-B3 mRNA expression was found in significantly higher quantities at the repair sites of rats exposed to ethanol at 7 days postop relative to control rat repair sites. No other time points or factors reached statistical significance. No significant differences were identified amongst time points or groups at the healing tendon-to-bone interface.

Conclusion: Alcohol exposure significantly decreases biomechanical load to failure of rotator cuff repairs in the early postoperative period in rat models. In the later postoperative period, alcohol exposure was not associated with a decrease in biomechanical load to failure compared to controls. Additionally, rats exposed to ethanol have significantly higher TGF-B3 expression at repair sites on postoperative day 7. This data suggests that ethanol consumption does deleteriously affect rotator cuff and bone healing. Future study is needed to validate the clinical significance of these findings in humans.