Data Sheet 1_An inter-laboratory study of the multi-dimensional behaviors of analogue lumbar spine surrogates: towards standardization in spine testing.pdf

IntroductionExperimental reproduction of lumbar spinal loading throughout activities of daily living is challenging and has historically relied on simplifications to the applied loading to pure moment testing along primary orthogonal anatomical planes. The primary objective of this study was to evaluate the reproducibility and crossplatform translation of multi-dimensional spinal loading protocols between two distinct biomechanical testing systems.
MethodsLumbar spinal surrogate models are used as repeatable, transportable, and inexpensive specimens to serve as standardized test articles for inter-laboratory comparison. Combined displacement-controlled Flexion-Extension (FE) and Lateral Bending (LB) trajectories and combined Axial Loading and Axial Rotation (AR) trajectories were applied to the specimens on a six-axis robotic arm and a two-axis linear-torsion testing system with custom jig. Both protocols were able to be decomposed and translated between the two testing systems, lending credibility to this method as a standardizable, reproducible process among biomechanics laboratories.
ResultsThe results demonstrated strong agreement in combined FE-LB range of motion (ROM) and load across the two laboratory setups, with inter-laboratory ROM differences of 0.53°–0.55° (8%–10%) and peak load differences of 0.92–1.64 Nm (10%–18%) for the 3D printed surrogates. Combined AR and axial loading yielded similar behavior, with ROM differences of 0.80°–0.85° (3%–4%) and peak load differences of 0.21–0.89 Nm (1%–5%) between laboratories (all p > 0.05). Furthermore, both laboratories were able to utilize adopted methods to highlight specimen asymmetries and biomechanical responses that would be otherwise overlooked by traditional pure moment testing.
DiscussionThis work lays a foundation for future multidimensional testing for capturing complex biomechanical behavior of the spine.