Creep associated changes in intervertebral disc bulging obtained with a laser scanning device

Area of Science:

• Biomechanical Engineering
• Spinal Research
• Medical Imaging

Background:

• Traditional lumbar disc bulging assessment methods are limited, often involving physical contact, 2D analysis, and are time-consuming.
• Assessing 3D contours of biological tissues under load is complicated by tissue creep, altering shape over time.
• Understanding the impact of creep on intradiscal pressure and disc height is essential for accurate biomechanical analysis.

Purpose of the Study:

• To develop and validate a novel laser-based 3D contour scanner for assessing lumbar disc geometry.
• To investigate the influence of tissue creep on disc height, intradiscal pressure, and contour changes under static compression.
• To determine the optimal timeframe for contour assessment to minimize creep-related artifacts.

Main Methods:

• A custom 3D laser contour scanner was integrated into a spine tester.
• Seven human lumbar spinal segments underwent 15 minutes of 500 N static compression.
• Disc height, intradiscal pressure, and 3D disc contours were measured dynamically over time.

Main Results:

• Static compression reduced disc height by 1.14 mm, followed by creep behavior.
• Intradiscal pressure showed a slight but significant decrease from 0.49 to 0.48 MPa.
• Disc bulging was most pronounced anterolaterally and anteriorly, with creep increasing circumference, particularly posterolaterally.

Conclusions:

• Accurate biological tissue geometry should be captured within one minute to avoid superimposed creep effects.
• The developed 3D scanning method shows potential for evaluating disc injuries, degeneration, and treatment efficacy.
• Measuring disc contours under varying loads provides outer annular strain distribution, crucial for developing tissue-engineered implants.