Herniated Disc: Understanding Disc Herniations

Herniated Disc: Understanding Disc Herniations

I am Yeliana Mayor Pinchevski, a physician assistant. Today I will be talking to you about understanding disc herniations and what that means for your spine. The spine is your body's main support structure, so let us take a closer look at the spine's anatomy. The vertebral column is made up of many bony subunits called vertebrae, and their cushions are the intervertebral discs. Discs act like shock absorbers between those bones. It has a natural curvature and is broken down into 4 different segments based on anatomy and its curvature. To begin, you have the cervical region, which has 7 vertebral bodies. Then the thoracic region, which has 12, your lumbar region, which has 5, and the sacrum and coccyx are fuzed with no intervertebral discs. For this presentation, we will focus on the lumbar spine since it is the most common location for disc herniations due to degeneration from a combination of factors.

Looking at the lumbar spine, it is the most robust part of the spine due to having the greatest weight load. Important structures here are the spinous process, which you can feel if you run your hand down your spine; the interlaminar window; your disc space; central canal; and your intervertebral foramen. The foramen become larger as you go up the spine, which is important for certain procedures, and the interlaminar window become larger as you descend the spine.

Now, in regards to the nerves, the nerve roots course down through the spinal canal until they exit their respective neural foramen. In the green figure, you can see the spinal cord ends at L1-L2 called the conus medullaris and once you pass that level, you have the cauda equina, or horse's tail, which is encased by thecal sac. You can think of all of this like a highway with the exiting route named after the vertebral body above. The vertebral body is covered in a cartilage end plate, and the intervertebral disc is a fibrocartilaginous cylinder that lies between the vertebrae, joining them together. They permit some flexibility in the spine. The discs are well hydrated and receive their nutrition via diffusion from vertebral vessels. With age and activity, these processes wane and the discs lose their hydration. Being largely avascular, they have little to no ability to heal or restore.

What exactly is a disc herniation? A herniation of a disc occurs when the nucleus pulposus, the center part, ruptures, breaking through the annulus fibrosis at varying degrees. The very first thing to understand is that the word herniation is a parent category that has 4 subcategories beneath it. The first is the bulging disc; the second is a protrusion; the third considered an extrusion, and the fourth a sequestration when there is a free fragment in the canal. There are many different locations of disc herniations. They typically occur in the posterolateral direction.

That is where the nucleus pulposus can irritate nearby spinal nerves, resulting in a variety of neurologic and muscular symptoms. You can have a central herniation, a paracentral herniation, a far lateral as well. As I mentioned before, the lumbar spine is the most common location for disc herniations. Here, we see an image of a left-sided paracentral L5-S1 disc herniation, specifically an extrusion on MRI T2 sequence. Common causes of disc herniations are aging and degeneration, normal wear and tear; genetics; heavy lifting; and poor posture. Injuries and accidents also increase your risk of herniation, and smoking does as well.

How do patients present? Patients with a disc herniation may present with back or neck pain; pain that travels down arms or legs, which is named radiculopathy; numbness or tingling; muscle weakness, and symptoms vary depending on the location of the herniation. Diagnosis is made with a thorough history and physical exam, special tests, diagnostic testing and at times epidural steroid injections to confirm. Multiple spinal imaging modalities may be used for patients with lumbosacral radiculopathy, but magnetic resonance imaging, MRI, is typically the gold standard. It helps to identify bony and soft tissue abnormalities. Computed tomografty, which is CT, can be used as an alternative for patients with a contraindication to MRI.

With nonsurgical management, up to 90% of patients improve with conservative care within those first 4 months. First line management includes patient education, NSAIDs, physical therapy up to 12 weeks, and activity modification. This includes maintaining good posture, exercise regularly, and lift objects safely. If these conservative measures fail, then it is fair to reassess the condition. Surgical management is reserved for patients with persistent symptoms beyond 6 weeks. Also, if they have severe or progressive neurologic deficits or cauda equina syndrome.

Surgical options include open surgery versus minimally invasive surgery, and lastly, ultra minimally invasive surgery. Starting with open surgery, open spinal surgery involves a large incision to access and operate directly on the spine. While this approach provides the surgeon a wide view, it can lead to significant muscle and tissue damage, which often results in a longer recovery period for patients. Here is an example of an open lumbar incision, which is quite sizable.

Moving on to minimally invasive techniques, the conventional microdiscectomy is a good option for localized and unilateral lumbar disc herniations. The same goal as accomplished as with open, just with a smaller incision and usually done under a microscope. Tubular microdiscectomy is another type of technique where surgeons use a series of dilators and tubular retractors to complete the surgery using microinstruments as well. Here is an example of a tubular microdiscectomy incision with a visible tube. With tubular cases, whether you use a microscope or not, it can be difficult to gain good visualization. There is significant charred tissue and soft tissue disruption, as seen here on the right.

Finally, there is your ultra minimally invasive spine techniques, which enable surgeons to use spine specific endoscopes in order to access the space and target pathology. The discectomy here can be accessed via a transforaminal or interlaminar approach. It minimizes soft tissue disruption, resulting in less postoperative pain. Additionally, studies have shown that approximately 85% of patients who underwent endoscopic lumbar discectomy returned to activity in as few as 6-8 weeks. Here is an example of how clear it looks during an ultra minimally invasive spine case, and how you can better visualize the anatomy around. Here you have a comparison of the skin incision sizes, where your traditional microdiscectomy is to the left, and an endoscopic case is to the right. The surgeon is able to target many different pathologies and disc herniations that might have not been possible without a fusion. You are reaching a larger population of patients in need. Endoscopic spine procedures continue to evolve with better instrumentation, accuracy, and safety. It certainly is the future of spine surgery. Thank you for tuning in to OrthoPedia.