The spine is made up of many bones called vertebrae. These vertebrae surround and protect the spinal nerves and lower part of the spinal cord from damage. Discs are located in between the spinal vertebrae and are made up of a tough outer shell called the annulus fibrosis and a soft spongy gel-like center called the nucleus pulposus. You can think of the disc like a jelly donut. The annulus is formed by many layers like “tape” stuck together. The discs are named in reference to the spinal vertebrae. The disc between L4 and L5 vertebrae is called the L4-5 disc. Similarly, the disc between L5 and S1 vertebrae is called the L5-S1 disc.
If too much stress is placed on the disc, the annulus – the outer shell – may rip, forming an annular tear. There are three types of annular tears:
1. Radial tears – A radial tear is a tear that goes all the way through the annulus, forming a channel connecting the inside to the outside of the disc. The nucleus pulposus – the gel-like center of the disc – may extend into the tear and prevent it from healing. Radial tears are the most important annular tears because they often cause back pain. Back pain caused by injured discs is called discogenic back pain. Radial tears may also cause leg pain by leaking inflammatory chemicals (such as tumor necrosis factor) from the nucleus pulposus onto spinal nerves. This causes irritation and inflammation, resulting in pain.
2. Concentric or circumferential tears – The wearing out of the annulus may lead to separation of the annular fiber layers like the layers of an onion, leading to weakening of the annulus. This results in a bulging of the disc. Concentric tears do not usually cause back pain.
3. Transverse tears – The tearing of the annulus’ connection to the vertebral body. These do not usually cause back pain.
Annular tears may be diagnosed on a work up for back and leg pain. They are seen as a white spot on MRI called a High Intensity Zone. Discogram and CT scans best demonstrate annular tears and may indicate if it is the cause of a patient’s back pain. Discogram is an interventional pain procedure done under X-ray guidance to determine which disc is causing pain.
Annular tears that are not successfully resolved with conservative treatment may be treated surgically. The treatment of annular tears must be individualized. Unfortunately not every patient will be a candidate for surgical treatment.
Traditional surgery involves a large incision, muscle retraction and bone removal to expose the spine for disc removal and fusion. This may be done through the abdomen [anterior lumbar interbody fusion(ALIF)], side [direct lateral interbody fusion (DLIF)] or back [posterior lumbar interbody fusion (PLIF) or transforaminal lumbar interbody fusion (TLIF)]. The spine is then held together with pedicle screws or clamps. Today there are many minimally invasive options, from injections to endoscopic disc surgery and minimally invasive fusions. The most promising new procedure appears to be endoscopic discectomy.
The endoscopic discectomy treats pain resulting from a torn disc by removing the painful disc with the annular tear. This disc is found and removed through the endoscope, which provides rapid pain relief and a shorter recovery time than traditional back surgeries.