Biomechanical in Vitro and Finite Element Study On Different Sagittal Alignment Postures of the Lumbar Spine During Multiaxial Daily Motion

Abstract

Lumbar Lordotic correction (LLC), the gold standard treatment for Sagittal Spinal malalignment (SMA), and its effect on sagittal balance have been critically discussed in recent studies. This paper assesses the biomechanical response of the spinal components to LLC as an additional factor for the evaluation of LLC. Human lumbar spines (L2L5) were loaded with combined bending moments in Flexion (Flex)/Extension (Ex) or Lateral Bending (LatBend) and Axial Rotation (AxRot) in a physiological environment. We examined the dependency of AxRot range of motion (RoM) on the applied bending moment. The results were used to validate a Finite Element (FE) model of the lumbar spine. With this model, the biomechanical response of the intervertebral discs (IVD) and facet joints under daily motion was studied for different sagittal spinal alignment (SA) postures, simulated by a motion in Flex/Ex direction. Applied bending moments decreased AxRot RoM significantly (all P<0.001). A stronger decline of AxRot RoM for Ex than for Flex direction was observed (all P<0.0001). Our simulated results largely agreed with the experimental data (all R2>0.79). During daily motion, the IVD was loaded higher with increasing lumbar lordosis (LL) for all evaluated values at L2L3 and L3L4 and posterior Annulus Stress (AS) at L4L5 (all P<0.0476). The results of this study indicate that LLC with large extensions of LL may not always be advantageous regarding the biomechanical loading of the IVD. This finding may be used to improve the planning process of LLC treatments.

Prediction of Temperature and Loading History Dependent Lumbar Spine Biomechanics Under Cyclic Loading Using Recurrent Neural Networks

“…The specimens were tested under pure moment loading in all three directions under physiological environment using previously reported methods. 3 , 4 , 31 The use of an electromagnetic tracking sensor (Aurora V2, Northern Digital Inc., Canada) connected firmly to the top of the embedding enabled the measurement of the motion of the upper vertebrae without visual sight. The specimens were tested in a humidified chamber, which was kept at C for the specimens tested at BT.…”

In vitro study design derived from an in vivo lifting task

“…The Institute of General Mechanics of RWTH Aachen University has developed a test rig that allows loading spinal tissue under physiological conditions [20,26]. The latest extension of the test rig has been described and illustrated in [19], and it includes the addition of an axial compression cylinder including a follower load principle system (FLPS) that permits specimen preconditioning and cyclic and static loading on the same test rig in a liquid environment at body temperature.…”

Extension of an In Vitro Spine Test Rig to Track Load‐dependent Biomechanics of the Lumbar Spine under Physiological Conditions

“…In the initial setup [12,13], spinal segments could be loaded in order to apply flexion/extension, lateral bending, and axial rotation moments. Beckmann et al [13] and Wilmanns et al [15] conducted preconditioning by applying a static axial compression force of 500 N for 15 minutes to the specimen exposed to air to establish a physiological hydration equilibrium using another test rig.…”

“…Beckmann et al [12,13] and Wilmanns et al [15] presented an experimental test rig to track vertebral motions under physiological conditions. To apply pure moment loading in flexion/extension and lateral bending direction, a universal joint was directly attached to the cranial mounting pot.…”

“…According to Holsgrove et al [5], it is crucial that test methods replicate all aspects of the in vivo environment to maximize transferability to the clinical setting. This setup has been extended, based on new insights and challenges within various projects [14,15]. The latest enhancements are made to better approximate in vivo conditions.…”