Abstract
3D printed clamps provide multiple advantages compared to potting for the fixation of spinal specimens and in a recent study, superior fixation stability was reported. The aim of this study was to evaluate the fixation efficacy of 3D printed vertebra clamps during routine application and to present and evaluate a novel clamp for sacrum fixation. Further, public access to the template files is provided. 98 human single-level cadaveric specimens were biomechanically tested in flexion–extension (FE), lateral bending (LB), axial rotation (AR), anteroposterior shear (AS), lateral shear (LS) and axial compression-decompression (AC). Loading amplitudes were +/-7.5 Nm for FE, LB and AR, +/- 150 N for AS and LS and + 400/-100 N for AC. The novel sacrum clamp was used in 8 specimens. The median relative motion between clamps and specimens was 0.6° in FE, 0.7° in LB, 0.3° in AR, 0.5 mm in AS, 0.5 mm in LS and 0.1 mm in AC. With sacrum clamps, the median relative motion was 0.3° in FE, 0.1° in LB, 0.08° in AR, 0.8 mm in AS, 0.7 mm in LS and 0.2 mm in AC. The vertebra clamps used during routine testing provided better stability compared to the values in the literature in all six loading directions (p < 0.05). The sacrum clamp showed superior anchoring stability in three loading directions compared to the caudal vertebra clamps (p < 0.05), while inferior stability was measured in AS (p < 0.001). We conclude that 3D printed vertebra clamps and 3D printed sacrum clamps represent reliable methods for specimen fixation during routine biomechanical testing.
Highlights
Biomechanical experiments on spinal segments are an indispensable method to analyze the mechanical characteristics of the spine, to eval uate spinal implants and to validate numerical models
Accurate and reliable specimen fixation is a relevant factor for biomechanical experiments. 3D printed clamps were proposed as an alternative to potting as they provide the ability to accurately plan specimen orientation, can be adapted to provide simple access to anatomical structures, do not cause specimen heating or require screw insertion and provide the possibility of non-destructive removal (Cornaz et al, 2020a)
The data on relative motion at the specimen-clamp interface served as benchmark for this study to test the performance of routine application of the 3D printed vertebra clamps
Summary
Biomechanical experiments on spinal segments are an indispensable method to analyze the mechanical characteristics of the spine, to eval uate spinal implants and to validate numerical models. 3D-printed clamps have been proposed as an alternative to traditional potting techniques for the fixation of thoracic and lumbar spinal segments (Cornaz et al, 2020a). The stability of 3D printed vertebra clamps during high vol ume routine testing remains unknown and further application of this concept for the fixation of sacral bone for biomechanical testing of the lumbosacral transition has not yet been described. The aim of this study was to verify the effectiveness of the 3D printed vertebra clamps during routine application and to test the stability of the novel 3D printed sacrum clamp. Novelties of this study are the infor mation on fixation rigidity in large volume routine biomechanical testing, the description and evaluation of the novel sacrum clamp and public access to the template files of the different clamp designs (sup plementary data)
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