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Influence of Complex Loading Conditions on Intervertebral Disc Failure.
Nikolaus Berger-Roscher1, Gloria Casaroli2, Volker Rasche3,4
1Institute of Orthopedic Research and Biomechanics, Trauma Research Center Ulm (ZTF), Ulm University, Ulm, Germany.
Spine
|May 18, 2016
Summary
Complex loading can cause endplate junction failures in ovine lumbar discs, with combined flexion, bending, rotation, and compression posing the highest risk. Herniation requires additional endplate failure, likely from compression.
Area of Science:
- Biomechanical engineering
- Spinal research
- Imaging techniques
Background:
- Intervertebral disc failure mechanisms under various conditions are not fully understood.
- The impact of different loading directions on failure modes under complex loading has not been systematically studied.
Purpose of the Study:
- To investigate how diverse loading combinations influence the mechanism and extent of intervertebral disc failure.
- To analyze ovine lumbar disc failure under simulated complex physiological loading.
Main Methods:
- Utilized a dynamic 6-degree-of-freedom (6-DOF) simulator to apply complex loading to 30 ovine lumbar spinal segments.
- Tested five loading combinations including flexion, lateral bending, axial rotation, and axial compression for 1000 cycles at 2 Hz.
- Conducted high-resolution imaging using 11.7 T MRI and micro-computed tomography to assess disc failure.
Main Results:
- Identified 13 large endplate junction failures (EPJFs), with 10 occurring caudally, and all but one maintaining an intact cartilaginous endplate.
- Observed four failures solely affecting the outer posterior annulus; no disc herniations were recorded.
- Measured maximum median moments of 52.5 N·m in flexion, 16.5 N·m in lateral bending, and 14.0 N·m in axial rotation.
Conclusions:
- Complex loading protocols can induce endplate junction failures (76%) and annulus failures (24%) in vitro.
- The combination of flexion, lateral bending, axial rotation, and axial compression presents the highest risk for caudal EPJF.
- Flexion and lateral bending have a greater influence on failure risk than axial compression and rotation; herniation likely requires additional endplate failure.
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