DEGENERATIVE DISCOGENIC SYNDROME

Genetics, Lifestyle, Environmental Factors

International Publicized Data

GMCD Instructional  Course Lectures

Author :  

Dr. med. Guy M.C. Declerck MD (GMCD)

Medical FRCS-, FRCS Ed Orth-, M Ch Orth-, PhD-studies

Spinal Surgical and Research Fellow, Perth, Western Australia

Spinal Orthopaedic Surgeon and Surgical Instructor

Consultant R&D Innovative & Restorative Spinal Technologies

President International Association of Andullation Technology (IAAT)

Copywriter / Translator:   Filip Vanhaecke PhD

Illustrative expertise & page layout:   Lennart Benoot, Mincko, Halle, Flanders, Belgium

Review scientific literature:   Medical Consulting Advice, Ostend, Flanders, Belgium

Support:   International Association of Andullation Therapy (IAAT)

Legal advice:   Anthony De Zutter, kornukopia.be

Dedication to the Colombian Family Gloria Rúa Meneses and her sons Andres David and Juan Camilo Hinestroza, both members of the National Colombian Waterpolo Team. For their friendship and hospitality. August 2014.

Acknowledgements

Relying on the work of giants is the lifeblood of scientific research. Indeed, if I have seen further, it is by standing on the shoulders of giants. One might even say that I have always depended on the kindness of strangers in this regard (*).

The continuous support by professor BA Kakulas (Neuropathology), professor JR Taylor (Spinal Anatomy and Human Biology), and Sir George M Bedbrook (Spinal Orthopaedic and Rehabilitation Surgeon) made it possible to analyse 27539 post-mortem human spines, normal and pathological, in the Department of Neuropathology, Royal Perth Hospital/University Western Australia, Perth.

Note: in order not to disturb easy reading of the underneath scientifically based chapters, only a few authors are mentioned in the text where dr. Guy considered it essential. Their names are placed between brackets. Further information on their individual research can be read in the last chapter ‘Literature Encyclopedia’.

(*) Mirsky Steve. Technology is making it harder for word thieves to earn outrageous fortunes.Scientific American, February 2014, p. 64

Contents

1. Aging processes, genetic factors, and physical activities

2. Aging processes and routine daily activities

3. Combined genetic-mechanic influences

4. Combination of genetic and environmental factors

5. Influence of unfavorable, abnormal, or aberrant genes

6. Upper versus lower lumbar degenerative changes

7. Socioeconomic lifestyle factors

8. Influence of traumatic accidents

9. Repetitive heavy and physically demanding jobs

10. Literature Encyclopaedia

1. Aging processes, genetic factors, physical activities

All tissues, including the intervertebral discs (IVD), will age. The aging processes occur at the same time in all IVDs and are irreversible. But aging is not synonymous with degeneration.

It is known since a long time that familial heredity, which includes genetic factors, plays a substantial role in the development of major degenerative changes and lesions in the IVDs. The presence or absence of a certain genetic inheritance determines who will develop the intradiscal degenerative cascade and when. But on their own, abnormal genes will not generate degenerative processes in all IVDs at the same time and in the same proportion.

Although the genetic influence is the same in all IVDs of a particular human spinal column, some repetitive daily and lifetime physical environmental factors are essential to trigger the development of degenerative structural features. However, each IVD is influenced differently by the performed physical activities. In other words, the characteristics of each activity finally will determine which intradiscal levels become more affected. Repetitive daily routine activities including mechanical spinal loading factors during sitting, standing and walking differ from the influence of repetitive daily, heavy physical and spinal overloading activities (Fig. 1a and 1b).

Fig. 1a. A90/139. Although the genetic influence for developing degenerative changes is identical for all lumbar intervertebral discs (IVD), the degenerative intradiscal cascade evolves differently in each of these discs depending on the characteristics of routine daily activities. In this 50 year old male, heavy labourer, the aging processes are responsible for the typical brown colour in the nucleus pulposus at the L3-4 IVD. The L4-5 IVD presents the typical degenerative signs: disc height loss with fragmented nucleus pulposus, ruptures of the endplate and the annulus fibrosus. An anterior ‘herniating’ pathway is present as well. At the L5-S1 IVD level the posterior annulus is ruptured with subsequent protrusion and disc height loss. Inflammatory reactions compatible with the MRI Modic signs are visible at L4-L5 and L5-S1 (subchondral intraosseous light brown discoloration).

Left: Declerck / Kakulas, Neuropathology, Perth, Western Australia

Right: Detailed artistic illustration by the Colombian sculptor Alonso Ríos Vanegas - www.alonsoriosescultor.com)

Fig. 1b. X90/1437. Male, 63 years old. Osteoporotic L5 vertebral body and sacrum. The L4-5 IVD displays normal aging processes with swelling pressure in the still hydrophilic nucleus which reflects the ‘aging’ brown colour due to the accumulation of metabolic catabolic products. Degenerative annular and endplate lesions are not present in the L4-5 IVD. The L5-S1 IVD shows degenerative features: an asymmetrical posterior disc height narrowing, a large posterior internal disc tear with protruding nuclear tissue through a degenerated and ruptured annulus.

(Declerck / Kakulas, Neuropathology, Perth, Western Australia)

2. Aging processes and routine daily activities

Intervertebral disc aging is not similar to disc degeneration. While the daily mechanical influences of activities continue, all IVDs undergo extensive aging changes as a consequence of

(1) declined nutrition of the IVD through the endplates,

(2) suicidal apoptotic cellular processes,

(3) cell cluster formation,

(4) cell necrosis,

(5) increasing number of senescent cells, and

(6) degradation of major molecules in the extracellular matrix, the proteoglycans and collagens.

Aging processes result in dehydration and desiccation of the nucleus pulposus. Signs of IVD aging can be seen on magnetic resonance images (MRI): loss of signal intensity, ‘dark’ disc, annular bulging, high intensity zones as a result of incomplete radial in-to-out developing annular fissures, and vertebral rim osteophytes. These aging signs in the intervertebral disc are no similar to disc degeneration.

3. Combined genetic-mechanic influences

In the presence of unfavorable genes, the daily routine mechanical loading patterns on the intervertebral discs accelerate the aging processes in these discs. This genetic-mechanic combination finally remains the major causative factor for the formation of degenerative lesions routinely seen at autopsy (Fig. 1a and 1b) and on magnetic resonance images (MRI) as well. The degenerative damage typically includes endplate fissures and defects, complete in-to-out radial annular tears, important disappearance of nuclear material due to the resorbing inflammatory processes, and loss of nuclear and annular height. All these lesions eventually lead to the destruction and dysfunction of the IVD and may potentially result in the degenerative discogenic syndrome (DDS).

4. Combination of genetic and environmental factors

Except for spinal traumata which cause direct accidental and incidental lesions to the IVDs, ruptures of the endplates, internal destruction of the nuclei, and tears in the annuli are determined by the combination of genetic, mechanical, and environmental factors.

A few facts are scientifically proven. Structural degenerative IVD changes are not seen in some ethnic groups when their individuals life in identical circumstances. Disc degeneration is more commonly found in men and women who already developed arthritis in other synovial joints (hips, knees, shoulders, etc …). The L4-5 and L5-S1 IVDs consistently exhibit more degenerative intradiscal and annular changes than the L1-2 and L2-3 lumbar IVDs. Degenerative discogenic lesions are more routinely seen from the fourth decade on. Lumbar discs of twins show similar aging and degenerative findings on MRI whatever their professional activities. These findings underline a complex interplay between genetic,  mechanical and environmental factors.

5. Unfavorable, abnormal, or aberrant genes

The presence of unfavorable genes influences the development of degenerative processes in the IVDs. The aberrant genes code for synthesis of abnormal proteins, proteoglycans, collagens, proteinases and cytokines. Higher concentrations of aberrant molecules alter the structural and functional properties of the extracellular matrices and may lead to the development of degenerative lesions in the endplates, annuli and nuclei.

In animals, typical examples of these genetically based phenomena occur in the IVDs of the so-called chondrodystrophoid dogs (the dachshund and the basset hound dogs with short limbs).

In humans, it is suggested that approximately 70 % to 75 % of all individuals contain abnormal genes which induce degenerative changes in the extracellular matrix of disc cells. Aberrant vitamin D receptor genes (VDR) impair the sulfation of the chondroitin and keratan chains and build abnormal proteoglycans (PGs). No longer able to retain the normal amount of water molecules, the changed VDR-genes are responsible for decreased MRI intensity signals of the IVD. Variants of the collagen IX gene (= COL9A2 and COL9A3 genes) produce unstable type IX collagens which no longer are able to stabilize the type II collagens. The presence of these genes leads to aberrations in the endplate, nucleus and inner annulus. Variants of the aggrecan gene construct abnormal types of the most important proteoglycan. Variants of the matrix metalloproteinase genes (MMP genes) accelerate the degenerative processes in the elderly. Abnormal collagen type I genes (COL1A1 gene) interfere in the production of the type I collagens which are important for the annular resistance of the annulus to tension forces. Abnormal genes for coding interleukin-1 and interleukin-6 stimulate the function of these pro-inflammatory cytokine molecules.

6. Upper versus lower lumbar degenerative lesions

The individuals who carry some or all of the disadvantageous genes will weaken the integrity of the extracellular matrix of the lumbar IVDs more extensively and earlier than ‘intact’ individuals. However, the lumbar IVDs react differently to the impact of the environmental and mechanical loading factors. Postmortem investigations indicate different degenerative IVD patterns at the upper and lower IVD levels. The upper lumbar IVDs exhibit rather degenerative endplate defects at the L1-L2 and L2-3 levels while the lower lumbar IVDs display rather degenerative annular tears at the L4-5 and L5-S1 levels (Declerck).

7. Socioeconomic lifestyle factors

The contribution of a variety of socioeconomic lifestyle factors to IVD degeneration is clearly controversial and overestimated. These factors may determine which spinal levels become affected but not in which individual.

There is no evidence or insufficient evidence that lifestyle factors such as eating, drinking, sports, sedentary activity, work, smoking, obesity and drugs may induce the degenerative intradiscal processes.

Strangely enough, identical physical activities are considered to be harmful when performed during professional duties while they are propagated to be beneficial during the exertion of sports.

There is no evidence or insufficient evidence that the presence or absence of physical factors such as physical fitness, mobility, flexibility and muscle strength lead to IVD degeneration.

Atherosclerosis is only thought to be a risk of discogenic degeneration but has never been proven.

There is no consistent evidence that wearing school bags initiates degeneration of IVDs and that all kind of furniture will prevent these processes. Other unknown and underlying factors make the difference.

There is no evidence at all that psychosocial factors such as happiness, health perspective, well-being, parental support, tiredness, anger, violence, disobedience and so on result in degeneration of the IVD.

8. Influence of traumatic accidents

Accidental spinal injuries with vertebral fractures and dislocations are a frequent reason for developing chronic low back pain in the long term. Once these spinal conditions have been completely restored or healed, the usually non-diagnosed but associated traumatic ruptures in the endplates and annuli develop into full-blown degenerative lesions (Fig. 8a and 8b).

 

Fig. 8a. A90/139, man, 62-year old. He suffered chronic undulating and disabling thoracolumbar pains. All radiological investigations showed a healed minimal anterior vertebral body (VB) T11 fracture. He was considered a lunatic, crazy, psychologically disturbed and of course a compensation seeking person. Postmortem analysis ordered by the coroner showed a clearly healed fracture of the T11 VB. At the T10-T11 intervertebral disc level, the typical ‘aging’ brown colour is evident. A small intradiscal lesion in the nucleus above the inferior but intact endplate is visible (any significance?). However, at the T11-T12 IVD level, a large anteroposterior internal disc rupture is documented as well as disrupted superior endplate lesions with an anterior inflammatory subchondral osseous reaction and, more posteriorly, the formation of an intraosseous nuclear protrusion (not yet a Schmorl nodule) in T11 VB.

(Declerck / Kakulas, Neuropathology, Perth, Western Australia)

 

Fig. 8b. Female, 53 years. ‘Chance’ type fracture of the T11 vertebral body (VB). The postmortem image shows the healed VB following postoperative (Knodt rod) fixation. The complete detachment of the T12 VB from its proximal T11-T12 disc junction and the ruptured superior endplate of T12 were never diagnosed radiologically. Internal T11-T12 intervertebral disc degeneration (necrosis?) is evident

(Declerck / Kakulas, Neuropathology, Perth, Western Australia)

9. Repetitive heavy and physically demanding jobs

People with repetitive, heavy and physically demanding jobs leading to abnormal load torsion (manual lifting) and whole-body vibration (truck driving), no doubt, experience unfavourable distribution and transmission of mechanical stresses on their IVDs. Then, it seems logical that their IVDs may develop more severe signs of degeneration. However, this is not a correct statement and not at all an universal phenomenon. Most heavy labourers simply have no more but no less degenerative discogenic signs than those who have sedentary jobs (sitting). Annular bulging is closely associated with heavy lifting but not at all with other spinal degenerative features.

Although such professional exposures may certainly lead to the development of degenerative lesions in the endplate and in the annulus leading to chronic low back pain, there exists no directly related evidence between these heavy loading activities and the origin nor the evolution of these visible degenerating disc signs – at least on magnetic resonance imaging (MRI).

A clear relationship between heavy physical loading activities and degeneration of the discs has never been shown. If their discs showed evidence of degenerative tears in the endplates and/or in the annuli, weightlifters would be unable to lift their Olympic weights.

Although important and significant degenerative structural defects in the lumbar disc may occur as a consequence of repetitive bending, twisting, fatigue loading and heavy physical work, they are more frequently the result of a sedentary environment that implies hypomobility. Studies on monozygotic twins demonstrate that the additional effects of heavy physical loading patterns only contribute for a small portion to the development, the presence and the degree of disc degeneration.

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