A disc herniation that does not penetrate the PLL is called what?

A disc herniation that does not penetrate the PLL is called what?

• A. Subligamentous extrusion
• B. Transligamentous extrusion
• C. Extrusion
• D. Sequestration

Answer: (A)

Understanding how disc herniations relate to the posterior longitudinal ligament (PLL) clarifies this. When a herniated disc material breaks through the outer ring (annulus fibrosus) but the PLL remains intact over it, the fragment is described as a subligamentous extrusion. The key point is that the PLL has not been penetrated. If the PLL were breached and the material passed through it into the epidural space, it would be a transligamentous extrusion. If the fragment fully separates from the disc and becomes free in the canal, that’s sequestration. So, a disc herniation that does not penetrate the PLL is a subligamentous extrusion.

Understanding how disc herniations relate to the posterior longitudinal ligament (PLL) clarifies this. When a herniated disc material breaks through the outer ring (annulus fibrosus) but the PLL remains intact over it, the fragment is described as a subligamentous extrusion. The key point is that the PLL has not been penetrated. If the PLL were breached and the material passed through it into the epidural space, it would be a transligamentous extrusion. If the fragment fully separates from the disc and becomes free in the canal, that’s sequestration. So, a disc herniation that does not penetrate the PLL is a subligamentous extrusion.