Biomechanical study of the Nice knot as an alternative fixation for anterior cruciate ligament reconstruction.

Abstract

Background: All-inside, one of the most popular techniques for anterior cruciate ligament reconstruction in which suspensory cortical devices for graft fixation are mandatory, has a technical concern during intra-articular passage of the fixation device. This can be overpass using a Nice knot tied over a button after the intra-articular passage of the graft avoiding, by this, any possible debris that can lock its progression and compromise final fixation. This study aimed to test the hypothesis that a Nice knot tied over a button has similar biomechanical performance to that of the currently available cortical fixation devices on the market and is suitable for anterior cruciate ligament graft fixation.

Methods: This controlled laboratory study was performed using two different validated cortical fixation devices for comparison: Endobutton, as a fixed loop, and Ultrabutton, as an adjustable loop. The devices were preconditioned; a cyclic loading of 50-250 N was applied for 1000 cycles and finally pulled to failure at 50 mm/min. Biomechanical properties of the devices were tested in terms of elongation, ultimate strength, and stiffness.

Results: The ultimate strength and displacement differences between the Nice knot and Endobutton were significant (p < 0.05). No significant differences in displacement and stiffness were found between the Nice knot and Ultrabutton; however, the ultimate failure load was significantly higher (p < 0.05) for Ultrabutton than for the Nice knot.

Conclusions: The performance of the Nice knot tied over a button exhibits similar displacement and stiffness characteristics to the Ultrabutton. However, its maximum ultimate strength (838 ± 28 N) is significantly lower than both tested devices. Despite this, it remains superior to the physiological forces experienced by patients during the initial phases of ACL rehabilitation.