How do compression and flexion-compression injuries destabilize the spine? A novel in vitro protocol for analyzing three-dimensional biomechanical instability
IntroductionUnstable traumatic spinal injuries require surgical stabilization. However, biomechanical instability of specific spinal injuries has been little investigated, although restoring stability represents a primary goal of surgical treatment. This study aimed (1) to develop an in vitro protoc...
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Frontiers Media S.A.
2025-05-01
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fbioe.2025.1576720/full |
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| author | Ann-Kathrin Greiner-Perth Hans-Joachim Wilke Christian Liebsch |
| author_facet | Ann-Kathrin Greiner-Perth Hans-Joachim Wilke Christian Liebsch |
| author_sort | Ann-Kathrin Greiner-Perth |
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| description | IntroductionUnstable traumatic spinal injuries require surgical stabilization. However, biomechanical instability of specific spinal injuries has been little investigated, although restoring stability represents a primary goal of surgical treatment. This study aimed (1) to develop an in vitro protocol to generate standardized spinal compression injuries, (2) to establish a three-dimensional flexibility analysis to identify relevant biomechanical instability parameters, and (3) to examine effects of person-specific factors on vertebral fragility.MethodsMechanical fracture simulation was performed on twelve fresh-frozen human spine specimens (T9-11; 4 f/8 m; 40–60 years) using a material testing machine. Pure compression trauma (n = 6) was simulated by applying displacement-controlled axial compression at 300 mm/s until 20% compression of the T10 vertebral body height. Flexion-compression trauma (n = 6) was achieved by additional flexural loading of 10 Nm. Pre- and post-traumatic pure moment testing with 5 Nm was performed in flexion/extension, lateral bending, and axial rotation using optical motion tracking to determine range of motion (ROM), neutral zone (NZ), coupled rotations, and coupled translations. Translations under shear loading of 100 N and axial deformation under 400 N compression were analyzed.ResultsAll specimens exhibited AOSpine A1 injuries occurring at a median fracture load of 5.0 kN (2.4–9.2 kN). Pure compression generated isolated medial endplate fractures (n = 5), while flexion-compression primarily provoked combined endplate and ventral compression injuries (n = 3). Significant (p < 0.05) increases were detected for all parameters except for coupled rotations and posterior (compression) and left shear translation (flexion-compression). Highest instability increases were determined for axial deformability (compression: +136% / flexion-compression: +200%) and NZ (flexion/extension: +177% / 188%; lateral bending: +174% / +126%). Mild to moderate disc degeneration and age did not correlate with fracture loads (p > 0.05). In compression trauma, cortical bone mineral density (BMD) of T10 had no effect on fracture loads (p > 0.05), whereas in flexion-compression trauma, a significant (p < 0.05) linear correlation was found (Spearman’s rs = 0.83).DiscussionRelevant instability parameters of minor compression and flexion-compression injuries include axial deformability, NZ, ROM, and coupled translations. Cortical BMD of the target vertebra solely affects fracture generation in flexion-compression trauma. Consequently, risk factors for fracture development may vary between trauma mechanisms. |
| format | Article |
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| publishDate | 2025-05-01 |
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| spelling | doaj-art-b9c52b37b20c4886b8f5605d9cfae4782025-08-20T03:07:55ZengFrontiers Media S.A.Frontiers in Bioengineering and Biotechnology2296-41852025-05-011310.3389/fbioe.2025.15767201576720How do compression and flexion-compression injuries destabilize the spine? A novel in vitro protocol for analyzing three-dimensional biomechanical instabilityAnn-Kathrin Greiner-PerthHans-Joachim WilkeChristian LiebschIntroductionUnstable traumatic spinal injuries require surgical stabilization. However, biomechanical instability of specific spinal injuries has been little investigated, although restoring stability represents a primary goal of surgical treatment. This study aimed (1) to develop an in vitro protocol to generate standardized spinal compression injuries, (2) to establish a three-dimensional flexibility analysis to identify relevant biomechanical instability parameters, and (3) to examine effects of person-specific factors on vertebral fragility.MethodsMechanical fracture simulation was performed on twelve fresh-frozen human spine specimens (T9-11; 4 f/8 m; 40–60 years) using a material testing machine. Pure compression trauma (n = 6) was simulated by applying displacement-controlled axial compression at 300 mm/s until 20% compression of the T10 vertebral body height. Flexion-compression trauma (n = 6) was achieved by additional flexural loading of 10 Nm. Pre- and post-traumatic pure moment testing with 5 Nm was performed in flexion/extension, lateral bending, and axial rotation using optical motion tracking to determine range of motion (ROM), neutral zone (NZ), coupled rotations, and coupled translations. Translations under shear loading of 100 N and axial deformation under 400 N compression were analyzed.ResultsAll specimens exhibited AOSpine A1 injuries occurring at a median fracture load of 5.0 kN (2.4–9.2 kN). Pure compression generated isolated medial endplate fractures (n = 5), while flexion-compression primarily provoked combined endplate and ventral compression injuries (n = 3). Significant (p < 0.05) increases were detected for all parameters except for coupled rotations and posterior (compression) and left shear translation (flexion-compression). Highest instability increases were determined for axial deformability (compression: +136% / flexion-compression: +200%) and NZ (flexion/extension: +177% / 188%; lateral bending: +174% / +126%). Mild to moderate disc degeneration and age did not correlate with fracture loads (p > 0.05). In compression trauma, cortical bone mineral density (BMD) of T10 had no effect on fracture loads (p > 0.05), whereas in flexion-compression trauma, a significant (p < 0.05) linear correlation was found (Spearman’s rs = 0.83).DiscussionRelevant instability parameters of minor compression and flexion-compression injuries include axial deformability, NZ, ROM, and coupled translations. Cortical BMD of the target vertebra solely affects fracture generation in flexion-compression trauma. Consequently, risk factors for fracture development may vary between trauma mechanisms.https://www.frontiersin.org/articles/10.3389/fbioe.2025.1576720/fulltraumainjurythoracic spinecompressionflexion-compressionvertebral fracture |
| spellingShingle | Ann-Kathrin Greiner-Perth Hans-Joachim Wilke Christian Liebsch How do compression and flexion-compression injuries destabilize the spine? A novel in vitro protocol for analyzing three-dimensional biomechanical instability Frontiers in Bioengineering and Biotechnology trauma injury thoracic spine compression flexion-compression vertebral fracture |
| title | How do compression and flexion-compression injuries destabilize the spine? A novel in vitro protocol for analyzing three-dimensional biomechanical instability |
| title_full | How do compression and flexion-compression injuries destabilize the spine? A novel in vitro protocol for analyzing three-dimensional biomechanical instability |
| title_fullStr | How do compression and flexion-compression injuries destabilize the spine? A novel in vitro protocol for analyzing three-dimensional biomechanical instability |
| title_full_unstemmed | How do compression and flexion-compression injuries destabilize the spine? A novel in vitro protocol for analyzing three-dimensional biomechanical instability |
| title_short | How do compression and flexion-compression injuries destabilize the spine? A novel in vitro protocol for analyzing three-dimensional biomechanical instability |
| title_sort | how do compression and flexion compression injuries destabilize the spine a novel in vitro protocol for analyzing three dimensional biomechanical instability |
| topic | trauma injury thoracic spine compression flexion-compression vertebral fracture |
| url | https://www.frontiersin.org/articles/10.3389/fbioe.2025.1576720/full |
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