Ex Vivo Mechanical Evaluation of a Sternal ZipFix(®) Implant for Prosthetic Laryngoplasty in Horses.
Authors: Markwell Harry J, Mueller P O Eric
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: ZipFix Sternal Implant for Equine Laryngoplasty Prosthetic laryngoplasty remains a cornerstone treatment for recurrent laryngeal neuropathy in horses, yet the ideal implant material continues to evolve. Markwell and Mueller conducted an ex vivo biomechanical comparison of the ZipFix sternal implant against traditional USP 5 braided polyester (TiCron) suture in equine arytenoid and cricoid cartilages, subjecting 54 cartilage samples to both single load-to-failure testing and cyclic loading protocols with 1,000 cycles prior to failure testing. Whilst the ZipFix implant demonstrated substantially superior mechanical properties in successful samples—arytenoid cartilages fixed with ZipFix sustained failure loads of 359 N compared to 159 N for TiCron, with stiffness values nearly 2.4 times greater—a critical finding emerged: 11% of arytenoid cartilages fractured during implant placement itself, before any mechanical testing occurred. Following cyclic loading, the mechanical advantage persisted (295 N failure load versus 128 N for TiCron), yet this iatrogenic failure rate during insertion presents a substantial clinical barrier. For equine veterinarians and surgical teams considering prosthetic laryngoplasty options, these results suggest the sternal ZipFix implant's brittleness during placement outweighs its superior load-bearing capacity, indicating that traditional suture fixation techniques remain safer for routine clinical application despite their lower mechanical strength.
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Practical Takeaways
- •ZipFix implants show biomechanical advantages over traditional suture but carry unacceptable risk of iatrogenic cartilage damage during placement—clinicians should not use this implant for equine laryngoplasty
- •Traditional TiCron suture remains safer for prosthetic laryngoplasty despite lower load-bearing capacity, as it does not fracture cartilage during implant insertion
- •Further implant design modifications are needed before ZipFix or similar devices can be safely used in equine laryngeal surgery
Key Findings
- •ZipFix implant showed significantly higher failure loads (359 N) compared to TiCron suture (159 N) in arytenoid cartilage under single load testing
- •ZipFix implant demonstrated greater stiffness in both arytenoid (31.32 N/mm vs 13.18 N/mm) and cricoid cartilages (20.83 N/mm vs 13.6 N/mm) compared to TiCron
- •ZipFix implant caused cartilage fractures in 4 of 36 arytenoid cartilages during implant placement, indicating potential iatrogenic damage during clinical application
- •Despite superior biomechanical properties, authors concluded ZipFix is unsuitable for clinical use due to high rate of cartilage failure during placement