Effects of different size of disc needle injury on the biomechanical properties of the lumbar disc

Author: Zijie Wang

Wang, Zijie, 2020 Effects of different size of disc needle injury on the biomechanical properties of the lumbar disc, Flinders University, College of Science and Engineering

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Lower back pain is one of the most commonly seen back issues in Australia, disc problems such as disc herniation or disc degeneration can lead to back pain. To find out which one or more damaged discs are causing the pain, discography is needed and served as a surgical diagnostic tool which has been used for the last few decades. Discography includes contrast agent insertion through needle injection as part of the clinical procedure, and it is suggested that acceleration of disc degeneration may occur even with very small needle in modern discography. A two needle system is applied in discography to reduce the chance of discitis, 18G or 20G, 3.5 inch introducers and 22G or 25G, 6 inch inner needle are recommended for discography in different region of spine.


The primary aim of this thesis was to assess the effects of different sizes of needle injury on the biomechanical properties of sheep lumbar FSUs. The properties evaluated include the stiffness and energy absorption by 6 Degree of freedom (6DOF) tests before and after 25G and 30G needle injury.


Healthy sheep lumbar functional spine units (FSUs) in from lumbar region with posterior elements removed (n = 12), L4-5 (n = 3) and L2-3 (n = 9) of similar disc diameter and height were randomly divided into 2 groups: (1) 25G group (n = 6) and (2) 30G group (n = 6). The needle was inserted into the discs through the posterolateral pathway. 6DOF tests were carried out before and after needle injury. The 6DOF biomechanical properties of each group were calculated and analysed using MATLAB in terms of stiffness and energy absorption. Statistical analysis in terms of paired t-test was conducted to investigate if there is significant difference between before and after needle injury.



No significant difference was found in stiffness due to the needle injury apart from the anterior-posterior shear stiffness in 25G group (p = 0.048) where the stiffness significantly decreases after induced needle injury. No significant difference was obtained in terms of energy absorption.


These findings suggest that relatively small needle injury does not induce significant changes in the discs in terms of 6DOF biomechanical properties.

Keywords: Biomechanical properties, intervertebral disc, needle injury, Sheep lumbar spine

Subject: Engineering thesis

Thesis type: Masters
Completed: 2020
School: College of Science and Engineering
Supervisor: Associate Professor John Costi