In vitro mechanical testing of braided polyurethane elastic fiber and braided polyester for equine laryngoplasty.

OBJECTIVES: In vitro comparison of the mechanical properties of braided polyurethane elastomer (Lycra®) and braided polyester (Ethibond™) (1) when inserted into the muscular process of the arytenoid cartilage and (2) as suture loops.

STUDY DESIGN: Experimental.

ANIMALS: Equine cadaver larynges (n = 15).

METHODS: The muscular processes (n = 30) of the arytenoid cartilages were dissected from each larynx and embedded in a resin base. Lycra® and Ethibond™ prostheses were randomly allocated to the left or right muscular process and each underwent cyclic fatigue (25-50 N) followed by load-to-failure testing. Isolated suture loops of Lycra® (n = 25) and Ethibond™ (n = 25) also underwent the same cyclic fatigue followed by load-to-failure testing (n = 20) or a creep testing protocol (25 N for 10 min; n = 5).

RESULTS: Lycra® prostheses pulled through the cartilage in a significantly greater proportion of cyclic tests (P = .015) and at lower mean (±SD) loads, (95.9 ± 23.4 N) during load-to-failure testing than Ethibond™ prostheses (155.2 ± 24.4 N; P = .0041). Lycra® had a significantly greater displacement with and without a cartilage interface when compared to Ethibond™ (P < .001, P < .002). The Lycra® isolated suture loops failed at significantly greater loads (233.0 ± 38.7 N) during load-to-failure testing than Ethibond™ loops (201.6 ± 47.4 N; P = .042).

CONCLUSIONS: Lycra® prostheses embedded in laryngeal cartilage pulled through the cartilage at lower loads than Ethibond™ prostheses. Lycra® suture loops were stronger than Ethibond™ suture loops. Lycra® had greater displacement than Ethibond™ in all tests as suture loops or when embedded in cartilage.