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

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.

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.

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.

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.