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Avoiding Ring Avulsion Injuries with Silicone Rings: a Biomechanical Study
Callie A Jewett, M.D.1, Mihir J. Desai, MD2 and Sasidhar A Uppuganti, MS1, (1)Vanderbilt University, Nashville, TN, (2)Vanderbilt Orthopaedics, Nashville, TN

Purpose: Finger avulsion and amputation injuries account for 4.9% of all upper extremity injuries requiring evaluation in an emergency room in the United States. Ring avulsion injuries are oftentimes devastating injuries that require microvascular reconstruction or possibly completion amputation. The outcomes of reconstruction following ring avulsion injuries are modest and amputation is a less than ideal outcome. As the public awareness of these injuries rises, there is a growing market for silicone rings with limited data on their ability to avoid these injuries.



Hypothesis: Silicone rings have a lower ultimate force to failure than metal rings and thus less soft-tissue injury following ring avulsion injury.



Methods: Four cadaver forearms were fixed to a custom fixture to allow for ring avulsion simulations. Silicone or metal rings of varying sizes (#4-11) were randomly assigned to one of five fingers on either the left or right hand of each donor; the contralateral corresponding finger was tested using a ring of the same size in the other material. A preload of 2N was applied to each ring and ultimate failure force was determined by applying an upward force at a loading rate of 500 mm/sec until failure. Additionally, a fifth cadaver forearm was used to determine the ultimate failure force of silicone rings in a clenched fist position.



Results: The average ultimate force to failure for silicone rings of all sizes was 53.0N, compared to 495.2N for metal rings of all sizes (p<.01). The average ultimate force to failure of silicone rings in the clenched fist position was 99.9N, which was significant for silicone rings sized 8, 10, and 11 (p<.05). There were no devolving injuries in the silicone ring avulsion group.



Conclusion: Ring avulsions are devastating injuries and the functional outcomes after microvascular reconstruction, completion amputation or ray resection remain suboptimal. Silicone rings provide protection against ring avulsions as they have a significantly lower force to failure than metal rings. The use of silicone rings can be encouraged in professions where ring avulsion injuries are more likely, such as healthcare professionals and heavy laborers.
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