Which part of the cervical intervertebral discs is considered the weakest?

• A. Anterior annulus fibrosis
• B. Posterior annulus fibrosis
• C. Nucleus pulposus
• D. Cortical bone

Answer: (B)

The posterior annulus fibrosis is considered the weakest part of the cervical intervertebral discs due to its structural characteristics and the biomechanical stresses it encounters. The annulus fibrosus is composed of fibrocartilaginous rings that encase the nucleus pulposus. These rings are arranged in a lamellar pattern, which provides tensile strength; however, the posterior portion does not have as robust a structure or as many fiber layers as the anterior part. This makes it more susceptible to strains and tears, particularly under movements that may flex or extend the cervical spine.

Additionally, the posterior annulus fibrosis has less support from surrounding structures compared to the anterior region, making it more vulnerable to injury. Conditions such as disc herniation commonly occur posterolaterally, often affecting the integrity of the posterior annulus and leading to potential nerve root compression. Understanding the weaknesses of the posterior annulus is critical for assessing cervical disc pathology and guiding treatment strategies.

The nucleus pulposus is not structurally weak, as it is a gel-like substance that can withstand compression forces, while cortical bone is the dense outer layer of vertebrae and is quite strong. The anterior annulus fibrosis, with its thicker composition, is designed to handle greater tensile loads