BIOMECHANICAL RESPONSE OF LUMBAR INTERVERTEBRAL DISCS TO CYCLIC COMPRESSIVE LOADING AT DIFFERENT RATES: AN EXPERIMENTAL ANIMAL MODEL AND FINITE ELEMENT ANALYSIS STUDY

Understanding the dynamic response of the intervertebral disc (IVD) is crucial for developing synthetic and engineered tissues to treat disc degeneration or injury. However, limited studies have investigated the effects of loading mode and rate on the IVD’s global mechanical response. This study explores the time-dependent behavior of the IVD, focusing on the viscoelastic properties of the annulus fibrosus (AF) and nucleus pulposus (NP). By examining how various periodic loading rates influence the disc’s biomechanical behavior in both in vitro and in silico environments, this research aims to enhance our understanding of the IVD’s dynamic performance under cyclic loading conditions. In vitro experiments were conducted on 16 sheep lumbar motion segments subjected to cyclic loading for 60[Formula: see text]min at frequencies of 0.25, 0.5, 1, and 2.5[Formula: see text]Hz and pressures ranging from 0.1 to 0.8[Formula: see text]MPa. The findings revealed that increasing loading frequencies led to higher dynamic stiffness and reduced disc height and area displacement. Finite element analysis (FEA) demonstrated strong agreement between numerical models and experimental results, validating the assumed biomechanical properties under periodic loads. This study found that dynamic stiffness increases at higher frequencies due to interactions between the solid matrix and fluid flow within the disc. The insights gained from this work provide valuable information about the behavior of IVDs under dynamic loading, with potential implications for improving clinical treatments and advancing research in spinal biomechanics.