The disk is the soft cushion between the vertebrae that provides a lot of the shock-absorbing qualities of the spine. There is one between every two vertebrae, for a total of 23.
The disk is not just a solid piece of material. It is composed of an inner core of jelly-like material surrounded by a tough “tire” of fibrous tissue. It is the job of the core to provide the shock absorbing qualities, and the job of the “tire” to contain the core. Just like everything else in the body, something can go wrong with the disks. What happens when that occurs?
Most people know about disks which are herniated (or ruptured, in layman’s terms). This happens when the fibrous wall of the disk tears (from one big trauma, such as a fall or car accident, or from repetitive small ones throughout daily living). If the tear is big enough, the jelly-like core will escape backwards into the spinal canal, and press on the nerves. This usually causes pain traveling down one leg, as usually only one nerve is pressed on. Most (more than 75%) herniated disks heal by themselves within 3 months.
The body is able to absorb the ruptured material and relieve the pressure on the nerves. In a minority of patients, time and simple treatments such as therapy and medication are not enough; surgery is needed to surgically remove the piece of disk that is pressing on the nerve.
A more common, but less well-known problem in disks is simple degeneration. In other words, wear and tear. Over the years aging and minor traumas accumulate in the disks. They slowly dry out and get thin, like a tire slowly losing its tread. Eventually, the disk can disappear almost entirely and the bone of one vertebra can rub on another, causing pain. Most cases of degenerative disk disease cause pain which is annoying but not incapacitating, and it can be treated with simple medication or therapy. In a small minority of patients the pain becomes incapacitating and debilitating. This actually happens more in younger people in their forties and fifties. In this small minority of patients, there are operations that can help. Most of them involve eliminating the deteriorated disk by eliminating it and fusing the two adjacent vertebrae together with bone and special titanium cages. This surgery can work very well to alleviate severe pain, but it takes several months to recover from and it is not by any means a pleasant experience. That is why we reserve it for those who are truly miserable and for whom all nonsurgical treatment has failed.