Viscoelastic properties of a spinal posterior dynamic stabilisation device

Area of Science:

• Biomaterials Science
• Orthopedic Biomechanics

Background:

• Spinal posterior dynamic stabilization devices are used to manage spinal instability.
• Understanding the viscoelastic properties of these devices is crucial for predicting their in vivo performance and interaction with spinal structures.

Purpose of the Study:

• To quantify the frequency-dependent viscoelastic properties of two types of spinal posterior dynamic stabilization devices (BDyn 1 level and BDyn 2 level) and their elastomeric components.
• To determine the relationship between viscoelastic properties and frequency.
• To compare the viscoelastic properties of the devices with their individual components.

Main Methods:

• Dynamic Mechanical Analysis (DMA) was used to measure the storage and loss stiffness of the devices and their components (polycarbonate urethane and silicone).
• Measurements were conducted in air at 37°C over a frequency range of 0.01-30Hz.
• The study analyzed six units of each device type.

Main Results:

• Both BDyn devices and their elastomeric components demonstrated viscoelastic behavior across the entire tested frequency range.
• A logarithmic relationship was observed between storage and loss stiffness and frequency for all tested components and devices.
• Storage stiffness ranged from 95.56-119.29 N/mm for BDyn 1 and 39.41-42.82 N/mm for BDyn 2. Loss stiffness ranged from 10.72-23.42 N/mm for BDyn 1 and 4.26-9.57 N/mm for BDyn 2.
• No resonant frequencies were detected for the devices or components.

Conclusions:

• The viscoelastic properties of the BDyn 1 level device are influenced by its polycarbonate urethane and silicone components within the physiological frequency range.
• The quantified viscoelastic properties provide a basis for comparison with other spinal devices and native spinal tissues.
• These findings contribute to a better understanding of the mechanical behavior of dynamic spinal stabilization systems.