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

Abstract

OBJECTIVE: To evaluate the properties of a ZipFix(&#xae;) (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(&#xae;) implant or a single strand of USP 5 braided polyester (TiCron&#x2122;), 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&#x2009;&#xb1;&#x2009;57.98 N) than arytenoid-Ticron (159.11&#x2009;&#xb1;&#x2009;22.98 N; n=12; P<.001). Arytenoid-ZipFix stiffness (31.32&#x2009;&#xb1;&#x2009;4.26 N/mm) was significantly greater than arytenoid-Ticron (13.18&#x2009;&#xb1;&#x2009;2.60 N/mm; P<.001). Cricoid-ZipFix stiffness (20.83&#x2009;&#xb1;&#x2009;3.37 N/mm) was significantly greater than cricoid-Ticron (13.6&#x2009;&#xb1;&#x2009;3.82 N/mm; n=6; P=.006). Under cyclic load, arytenoid-ZipFix distraction (2.53&#x2009;&#xb1;&#x2009;0.63 mm; n=5) was significantly less than arytenoid-Ticron (5.06&#x2009;&#xb1;&#x2009;1.37 mm; n=6, P=.006). After cyclic load, arytenoid-ZipFix failure load (295.16&#x2009;&#xb1;&#x2009;54.95 N) was significantly greater than arytenoid-Ticron (127.69&#x2009;&#xb1;&#x2009;32.67 N; P=.002). Arytenoid-ZipFix stiffness (35.59&#x2009;&#xb1;&#x2009;1.58 N/mm) was significantly greater than arytenoid-Ticron (24.10&#x2009;&#xb1;&#x2009;6.85 N/mm; P=.019). CONCLUSION: In arytenoid cartilages, the sternal ZipFix(&#xae;) implant was significantly stronger and stiffer compared to a single strand of Ticron. During placement of the ZipFix(&#xae;) implant, frequent arytenoid cartilage failure occurred before testing, suggesting the implant is not suitable for clinical application.