Prediction of the natural frequencies of different degrees of degenerated human lumbar segments L2-L3 using dynamic finite element analysis. (September 2021) - Fan, Ruoxun
Highlights: l This study explored an approach for predicting the natural frequency of human lumbar spine. The simulative approach included many conveniences. In particular, the lumbar density could not be known during simulation and the effects of soft tissues in the lumbar spine on the natural frequency can be understood. l This approach could predict the natural frequency of lumbar spines for different populations on the premise of mastering lumbar CT images. Moreover, knowing the natural frequency could provide reference for designing external vibration source, which may be helpful in alleviating lumbar vibration injury. l Simulation results showed that the natural frequencies of the healthy and mildly degenerated L2–L3 spinal motion segments, moderately degenerated L2–L3 spinal motion segments, and seriously degenerated L2–L3 spinal motion segments were in the range of 5–7, 3–5, and 1–3 Hz. l The predicted results indicated that the natural frequencies of human L2–L3 spinal motion segments gradually decreased with the severity of degeneration. These phenomena may be related to changes in the lumbar structure and material due to degeneration. Abstract: Background and Objective: Chronic exposure to resonant environment may cause more serious injuries to human lumbar spine than other vibrations. On the condition that the natural frequency of human lumbar spine is known, excitation frequency from an external vibration source can be optimized to keep away from the natural frequency and thus avoid lumbar resonance. Therefore, this study aimed to present an approach to predict the natural frequency of the human lumbar spine. Methods: Four poroelastic finite element models of human L2–L3 spinal motion segments with different degrees of degeneration were established. Dynamic finite element analyses of these models during 1 h of vibration were then conducted. The mechanical parameters of these models under vibrations at different excitation frequencies were predicted. The excitation frequencies that resulted in the greatest changes in the lumbar mechanical parameters were identified as the natural frequencies of the established L2–L3 spinal motion segments. Results: Simulation results showed that the natural frequencies of the healthy and mildly degenerated L2–L3 spinal motion segments, moderately degenerated L2–L3 spinal motion segments, and seriously degenerated L2–L3 spinal motion segments were in the range of 5–7, 3–5, and 1–3 Hz, respectively. Conclusions: The predicted results indicated that the natural frequencies of the human L2–L3 spinal motion segments gradually decreased with the severity of degeneration. These phenomena may be related to changes in the lumbar structures and materials because of degeneration. This study provided a feasible method to predict the lumbar natural frequencies for different populations, which may be helpful in optimizing external vibration sources to avoid lumbar resonance.