Quantifying the Impact of Spinal Fusion Systems by Multibody Simulation

Area of Science:

• Biomechanics
• Spinal Surgery
• Medical Device Engineering

Background:

• Spinal fusion is increasingly performed worldwide, driven by surgical advancements and improved implants.
• There is ongoing debate regarding whether spinal fusion causes degeneration in adjacent spinal segments.
• Understanding the biomechanical consequences of spinal fusion is crucial for patient outcomes.

Purpose of the Study:

• To investigate the biomechanical effects of mono-segmental and multi-segmental spinal fusion on spinal structures using MultiBody Simulation (MBS).
• To analyze the influence of implant size on spinal structure loading within detailed human MBS models.
• To assess the impact of spinal fusion on adjacent functional spinal units (FSU), particularly intervertebral discs (IVD) and facet joints.

Main Methods:

• Utilized MultiBody Simulation (MBS) with detailed human spinal models to analyze biomechanical impacts.
• Simulated both mono-segmental and multi-segmental spinal fusion procedures.
• Investigated the effect of varying implant sizes on the loading of spinal structures, focusing on the lumbar spine.

Main Results:

• Mono-segmental and multi-segmental fusion did not significantly increase the load on adjacent intervertebral discs (IVD) in the specific models analyzed.
• Load redistribution occurred, leading to increased stress on the posterior facet joints in the upper lumbar spine.
• Implant sizes not matching the original intervertebral disc (IVD) space resulted in a substantial increase in IVD loads.

Conclusions:

• Spinal fusion can alter load distribution, potentially increasing stress on facet joints rather than adjacent discs.
• Careful selection of implant size is critical to avoid excessive loading on intervertebral discs (IVD).
• These findings offer insights for improving surgical techniques and implant selection to minimize adverse effects and enhance surgical outcomes.