Quasi-static and cyclic compressive loading studies of the intervertebral disc with combined flexion and torsion

bovine caudal motion segments were used to investigate the loss of load-bearing ability of the intervertebral disc (ivd) under both quasi-static and cyclic compressive loading combined with torsion and flexion. while the response of the disc to both compressive hyper-flexion and hyper-torsion has been previously investigated much less is known about their individual and combined influence on compressive failure. eighty motion segments dissected from 41 bovine tails were subjected to quasi-static and cyclic compression with added components of flexion and torsion. the four different combinations of flexion and torsion were 0o torsion/0o flexion, 10o torsion/15o flexion, 10o torsion/0o flexion and 0o torsion/15o flexion. quasi-static compression failed to show any significant difference among the different combinations of torsion and flexion for failure stress, failure strain and compressive tangent modulus. cyclic compression indicated a significant influence of torsion in reducing the disc's load-bearing ability. cyclic loading provides a more sensitive tool for the assessment of potentially damaging mechanical parameters for the ivd.