Final answer:
Degenerative disc disorder (DDD) involves the dehydration and thinning of the nucleus pulposus beginning around the age of 30, leading to reduced disc flexibility and shock absorption. By ages 40-60, tension and tears in the anulus fibrosus increase, leading to further degeneration. In advanced stages, the weakened anulus fibrosus may result in disc herniation and potential nerve compression.
Step-by-step explanation:
The pathogenesis of degenerative disc disorder (DDD) is characterized by several significant changes that happen in the intervertebral discs with age:
- At around 30 years old, there is a decrease in the water content of the nucleus pulposus, which leads to thinner, less flexible discs, impacting the disc's ability to bear weight and absorb shocks from movement.
- By the age of 40, the nucleus becomes dehydrated and the anulus fibrosus may begin to suffer from tension, potentially leading to various types of tears.
- Between 40 and 60 years old, the annular tension and existing tears can increase, compromising the strength and integrity of the disc.
- In individuals over 60 years old, both the nucleus and the annulus are affected, signifying advanced stages of degeneration where herniation and further disc degradation are more likely, causing potential pain and muscle weakness.
A key factor in DDD is the weakening of the anulus fibrosus which can lead to herniation or protrusion of the nucleus pulposus. This can compress spinal nerves, resulting in pain and muscle weakness in dependent body regions. The L4/L5 and L5/S1 intervertebral discs are common sites for herniation, often causing sciatica. Similarly, damage to the C5/C6 or C6/C7 discs can cause neck, shoulder, and upper limb pain.