Can cervical disc herniations be provoked in vitro?

Area of Science:

• Biomechanical Engineering
• Orthopedic Surgery
• Spinal Research

Background:

• Neck pain is a leading cause of disability, often linked to cervical disc herniation.
• Understanding the mechanisms and risk factors of cervical disc herniation is crucial for preventing disability.

Purpose of the Study:

• To simulate cervical disc herniation under complex mechanical loading.
• To identify failure mechanisms and risk factors associated with daily activities.

Main Methods:

• Developed a novel dynamic disc loading machine to simulate complex neck motions.
• Tested human cervical motion segments (C4-C5, C6-C7) with varying degeneration grades.
• Applied dynamic loading protocols to intact discs, after partial PLL incision, and after complete PLL transection.

Main Results:

• No herniations occurred in intact discs under dynamic loading.
• Herniations (protrusion and extrusion) were observed only after artificial injury to the posterior longitudinal ligament (PLL).
• Younger donors with less degenerated discs were more susceptible when the PLL was compromised.

Conclusions:

• Intact cervical discs are unlikely to herniate from daily activities, even with long-term complex loading.
• The posterior longitudinal ligament (PLL) plays a significant protective role against cervical disc herniation.
• Younger individuals with less disc degeneration may have a higher risk if the PLL is compromised.