Abstract

Background: Discs are avascular. Oxygen and nutrients are diffused from capillaries in endplates into thick discs. Calcified layers begin to fortify the cartilaginous endplates around age 16, (1) blocking many capillaries, (2) reducing diffusion depths, (3) causing starvation and hypoxia in the mid-disc layer. Starvation triggers enzymatic degradation of proteoglycans in mid-disc layer, leading to desiccation and voids in nucleus, and fissure in annulus. Hypoxia triggers production inflammatory cytokines and lactic acid, leading to pH 5.5-6.5 in mid-disc layer, 5-50X acidity of blood plasma. Lactic acid leaks through the annulus fissure to cause discogenic pain from lactic acid burn, as shown in Figure 1. Conversely, disc matrixes near superior and inferior endplates are in the diffusion zones of bicarbonate (pH buffer), oxygen and nutrients from body circulation, and have neutral pH 7.2.

Proposed Intervention: Percutaneous Disc Scaffold (PDS) is a multi-spiral fluid absorbing filament, a braided nylon #3 suture, for bridging between diffusion zones near superior and inferior endplates to re-establish interstitial fluid exchange between the mid-disc and body circulation. Bicarbonate in blood plasma neutralizes the lactic acid. Oxygen inhibits hypoxic inflammation and is essential to biosynthesize the most water-retaining chondroitin sulfate in proteoglycans. Constant supply of nutrients relieves starvation, Figure 2.

Methods: In-vitro and in-vivo studies are used to verify the intended use, safety and efficacy of the PDS. (1) Fluid transport through the #3 braided nylon suture is verified by capillary action of drawing pork blood. (2) Lactic acid neutralization is verified by titration with fresh pork blood. (3) Safety is verified in sheep discs by histology on tissue response at euthanized time point 1, 3, 12 and 30 months. (4) Efficacy is verified in a pilot clinical study after confirming discogenic pain. PDS is implanted through the discography needle. Visual Analog Pain Score (VAS) and Oswestry Disability Index (ODI) are used to evaluate therapeutic efficacy of PDS at 1-week, 3-, 12- and 24-months.

Results: (1) Fluid transport through the #3 braided nylon suture as PDS is demonstrated by capillary action of drawing pork blood 10.3 +/- 1.2 cm against gravity. (2) Approximately 0.51-1.51 cc of pork blood is required to neutralize 1 cc of 2-6 mM lactic-acid, common concentration in painful disc. (3) PDS is inert, elicited no immune response in sheep discs euthanized at 1, 3, 12 and 30-months. (4) Baseline or pre-PDS VAS was 6.1±1.6, and 2- Year VAS after PDS is 1.2±0.7. Baseline ODI was 37.9±15.1%, and 2-Year ODI is 9.8±5.1%.

Conclusion: Acid-base neutralization is instantaneous, which may be the reason for rapid reduction of discogenic pain from lactic acid burn.

This special Issue on Minimally Invasive Spine Surgery II was put together to provide updated information that is lacking in high profile established journals where published articles are subject to review by established Spine Journals with the highest ratings. These Journals usually only publish articles subject to their restrictive guidelines of level I and II EBM validated, and powered by statistical analysis. Level I and II EBM, however, always starts with level 5 expert opinion EBM that deserves access to the literature.

Open access Journals supported by publication fees after peer review provide important timely scientific information tend to reflect more recent contemporary research, and opinions ultimately become listed and cited by PUB Med 5-10 years later with meta-analysis, statistically powered numbers, and consolidation of multiple case series. By the time these articles become part of the established literature, it is often outdated.

This special Issue has topics and opinions by authors offering level 5 opinions that will eventually work its way to Level I and II EBM or establish a more contemporary collection of EBM articles.

16 Patients undergoing Lumbar Selective Endoscopic Discectomy (SED) using the Y.E.S.S. method was monitored intraoperatively for SEP (somatosensory evoked potentials) and EMG (electromyography) activity. 18 cases were analyzed. Questions: Is Intraoperative Neuromonitoring of SEP and EMG safe, effective and useful in SED cases? What information does it yield, if any?

Endoscopic spine surgery is emerging as an effective intervention for the minimally invasive treatment of symptomatic degenerative disease of the cervical and lumbar spine. There are an increasing number of sound indications for the use of endoscopic techniques, including, but not limited to: extruded and contained disc herniations, annular tears, facets cysts, central, lateral recess, and neuroforaminal stenosis. The same goals of safe and effective decompression of the neural elements with equivalent clinical results can be achieved endoscopically with less tissue disruption, less post-operative pain, and faster recovery than traditional open or microscopic approaches in the hands of well-trained surgeons. Navigating the learning curve is a critical part of the process of adopting endoscopic techniques. A thoughtful plan for the sequential acquisition of endoscopic skills and appropriately graduated technical difficulty of cases increases the likelihood of success.

Progress within the various surgical fields has been facilitated by the use of minimally invasive procedures to achieve the same clinical outcomes as traditional techniques. Spine surgery is no different, and endoscopic spine surgery continues to demonstrate extensive applications while minimizing collateral tissue damage. Endoscopic spine surgery blends skill sets, technology, and clinical applications from both surgical spine and interventional spine. Clinicians from these fields have adopted endoscopic spine surgery. This has created a dilemma: there are now physicians providing surgical care who have not had formal spine surgical training. Some interventional spine practitioners are able to offer safe and effective endoscopic spine surgery, but training standards and practice standards are necessary for the field to progress. This article provides suggestions for a pragmatic approach to endoscopic spine surgery training and credentialing for physicians who practice interventional spine.