Mechanical comparison of two knots and two crimp systems for securing nylon line used for extra-articular stabilization of the canine stifle.

Objective: To compare mechanical properties of knotted and crimped nylon loops.

Study Design: In vitro mechanical evaluation.

Sample Population: Loops of 27 kg-test nylon leader. Single strand-clamped square knot compared with 2 crimp systems. Two strand--self-locking knot compared with 2 crimped loops.

Methods: (a) Single pull to failure (n = 10) at 500 mm/min. Initial loop tension (N), peak load (N), peak elongation (mm), stiffness of the linear portion of the curve (N/mm), and failure mode were recorded. (b) Incremental cyclic loading to failure (n = 5)--each loop was cycled 5 times to 100 N at a loading rate of 200 mm/min. Cycling was repeated, with the load increased by 50 N after each set. Elongation (mm), tension remaining (N), and after permanent deformation was present, elongation at 10 N (mm) were measured.

Results: Initial tension and stiffness were greater for crimped loops when compared with knotted loops. There were no differences between crimped loops. The self-locking knot elongated more, and was less stiff, when compared with 2 crimped loops. With incremental loading, knotted loops elongated more than crimped loops. The tension remaining in the loop fell below 10 N more quickly for knotted loops compared with crimped loops.

Conclusion: Crimped loops are stiffer, and resist both static and cyclic load more effectively before becoming permanently elongated, when compared with knotted loops.

Clinical Relevance: Stifle stability will be maintained more effectively by crimped nylon loops when compared with knotted loops.