Annular Tears and Fragments – Part 1

What causes an annular tear?   Here is my theory.

When I first started doing discography and CT scans to visualize annular tears in a painful lumbar spine, I thought it was wear and tear that caused all the fissures. I initially believed that the annulus was breaking down because of all of the various loads on the disc. This certainly made the most sense when looking at an isolated peripheral tear, but the majority of annular tears are not isolated peripheral tears. The majority of annular tears extend from the center of the disc and move outward.

I began placing an endoscope in the disc and noticed free floating fragments moving around inside of the disc. The continuous water flow of the endoscope caused the fragments to float out where they could be captured on a sponge. I noticed that I could move the tubular retractor in and out of the disc to mobilize more and more loose fragments, but I didn’t really have a sense of where the fragments were coming from or the magnitude of the problem until I included one more thing. 

I started staining the inside of the disc with the disco needle used for the guide wire placement. The guide wire was used to position the obturator into the disc for the tubular retractor to slide over. 

The dye I used initially and for many years, was indigo carmine, an acidophilic dye. The acidophilic property of the dye meant it would stain the nucleic acids of the cells that were breaking down or were already dead. Eventually I switched to methylene blue when there was a shortage of indigo carmine, since methylene blue had similar acidophilic properties.  

The staining of the disc introduced a 3 dimensional perspective to the annular tear problem. For the first time, I could see stained fragments in the fissures that sometimes went right out to the periphery of the annulus. The stained fragments would, in some cases, extend all the way out to the posterior longitudinal ligament (PLL). Where were these fragments coming from ?

The most intense concentrations of stained material occurred towards the center of the disc where the nucleus is located. 

This observation led me to believe that “disc degeneration” and “internal disc disruption” popularized by Henry Crock in 1970 was really a process of fragmentation of the degenerating nucleus.  

It appeared that these small (1-2mm) fragments had no way out of the disc and were not being effectively resorbed, so they were left to migrate to the periphery of the disc with the force of intradiscal pressures. This concept correlates well with the most painful position of sitting being the position that generates the highest intradiscal pressures. The only way for these particles to get to the periphery of the disc was for the fragments to burrow through the annulus, thus creating the annular tears. 

This endoscopic spine surgery experience with acidophilic staining of the disc leads me to believe that it is the loose degenerative fragments that contribute to the annular tears. The fragments are a mechanical cause of annular injury and chronic recurring low back pain. Fortunately these stained fragments can be seen and removed in part with endoscopic spine surgery techniques.  

I will be back with Part 2 next time…