Ex Vivo Mechanical Evaluation of a Sternal ZipFix® Implant for Prosthetic Laryngoplasty in Horses

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Objective:To evaluate the properties of a ZipFix® (ZipFix) implant in equine laryngeal cartilages.Study Design:Ex vivo biomechanical study.Sample Population:Equine arytenoid (n=36) and cricoid cartilages (n=18).Methods:Suture bites were placed in arytenoid or cricoid cartilages using a ZipFix® implant or a single strand of USP 5 braided polyester (TiCron™), and arytenoid and cricoid cartilages were separately subjected to single load to failure (25 N preload) or cyclic loading for 1,000 cycles, followed by single load to failure. Load, distraction, and stiffness were recorded.Results:Four arytenoid-ZipFix cartilages fractured on implant placement. Under single load, arytenoid-ZipFix (n=9) failed at a greater mean load (359.01 ± 57.98 N) than arytenoid-Ticron (159.11 ± 22.98 N; n=12; P<.001). Arytenoid-ZipFix stiffness (31.32 ± 4.26 N/mm) was significantly greater than arytenoid-Ticron (13.18 ± 2.60 N/mm; P<.001). Cricoid-ZipFix stiffness (20.83 ± 3.37 N/mm) was significantly greater than cricoid-Ticron (13.6 ± 3.82 N/mm; n=6; P=.006). Under cyclic load, arytenoid-ZipFix distraction (2.53 ± 0.63 mm; n=5) was significantly less than arytenoid-Ticron (5.06 ± 1.37 mm; n=6, P=.006). After cyclic load, arytenoid-ZipFix failure load (295.16 ± 54.95 N) was significantly greater than arytenoid-Ticron (127.69 ± 32.67 N; P=.002). Arytenoid-ZipFix stiffness (35.59 ± 1.58 N/mm) was significantly greater than arytenoid-Ticron (24.10 ± 6.85 N/mm; P=.019).Conclusion:In arytenoid cartilages, the sternal ZipFix® implant was significantly stronger and stiffer compared to a single strand of Ticron. During placement of the ZipFix® implant, frequent arytenoid cartilage failure occurred before testing, suggesting the implant is not suitable for clinical application.

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