Mechanical Comparison of Loop and Crimp Configurations for Extracapsular Stabilization of the Cranial Cruciate Ligament-Deficient Stifle

Abstract

Objective: To biomechanically compare different loop and crimp configurations used for extracapsular suture stabilization of the CCL-deficient stifle. Study Design: In vitro study. Sample Population: Crimped loop constructs of 100lb Ande type nylon leader line in 7 different configurations comprising single and double loops, single and double crimps, and the interlocking loop configuration. Methods: Constructs premade on external skeletal fixator bars 60mm apart and tested in tension with a custom-made split circular arm mounted on a table-top materials testing machine. Data were derived from force/displacement plots. In "load to failure" test (10/group) constructs were loaded to failure with distraction rates of 10mm/min; ultimate load, tension at 2mm elongation and failure were recorded. In "staircase" test (5/group) constructs cycled at 100N/s from 75N with incremental increases of 50N/cycle; ultimate load, maximum tension before elongation at rest over 2mm and failure were recorded. In "cycling and jumping" test (10/group) 3 of 7 constructs cycled at 100N/s 100 times from 50 to 100N, then 5 times from 50 to 600N; failure and elongation at cycles 1, 50 and 100 and at jumps 1 to 5 recorded. Results: Double-loop double-crimp configurations were statistically superior to all other configurations in ultimate load, and to single-loop and interlocking loop configurations in elongation in "load to failure" and "staircase" tests. In "cycling and jumping" test the interlocking loop configuration specimens elongated significantly more than the others and only in the double-loop double-crimp group did all constructs complete the test. Conclusions: Double-loop double-crimp configurations are mechanically superior to other previously described configurations.