Lumbar Intervertebral Disc Herniation
International Publicized Data
GMCD Instructional Course Lectures
Dr. med. Guy MC 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 Therapy (IAAT)
Copywriter / Translator: Filip Vanhaecke PhD
Illustrative expertise: Jasper Baele, HHP
Review scientific literature: Medical Consulting Advice, Ostend, Flanders, Belgium
Support: International Association of Andullation Therapy
Legal advice: Anthony De Zutter, kornukopia.be
Dedication to Jean-Marie Dedecker. January 2014.
Internationally well-known judo coach, Flemish politician and senator, and founder of the political party Lijst Dedecker.
In all circumstances, an uniquely understanding and real honest friend! Hearing my commotion regarding my professional goals but not prompted by calculation, without arrogance and without financial purposes, but as an unwitting accomplice he stimulated me to finalize this subject. And I don’t care who gets the credit
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 (*). If the science of a body of work is solid, it serves publication regardless of who produced it.
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
Table of contents
1. How I define the herniating pathway
Hernia comes from Latin. It refers to a more centrally localized part of an organ ‘voyaging through’ an opening in the wall of that organ that normally surrounds it. There exist multiple types of herniations: epigastric, diaphragmatic, inguinal, umbilical, etc … hernias.
The term disc ‘herniation’ stands for two evolving entities and one potential final outcome: disc protrusion, disc extrusion and potential final sequestration. For a fragment of the central part of the intervertebral disc - the nucleus pulposus (NP) and sometimes parts of the endplate - to voyage through the wall (protrudere in Latin) of an IVD and finally migrate out of it (extrudere in Latin), the surrounding outer part - the annulus fibrosus - must break down (Fig. 1).
Fig. 1. Schematic illustration of the herniating pathway. Compression forces on the NP are translated in tension forces of the AF. It gradually results in in-to-out annular tears. This nuclear herniating pathway leads to protrusion, extrusion and sequestration of the NP
(Declerck / Taylor / Kakulas, Neuropathology, Perth, Western Australia)
Except when a traumatic event causes the protecting annular ring to rupture (e.g. road traffic accident or extreme spinal loading in young individuals), in an intact and normal lumbar IVD it is simply impossible for nuclear (and endplate) tissue to herniate.
All herniating disc protrusions and extrusions then are primarily the consequence of irreversibly progressing degenerative processes inside the IVD. Step-by-step the ongoing destructive and inflammatory processes break down the different collagenous (type I) annular layers in an in-to-out direction initiating the herniating pathway of mostly the nuclear material.
Because degenerative annular tears predominantly develop in the lower part of the lumbar spine (Declerck), most disc protrusions and extrusions are confined to the L4-5 and L5-S1 levels (80%).
2. Mechanical failure of annulus fibrosus (AF)
It is known since 1962 that a mechanical failure of the AF needs to be present (Naylor) for a protrusion or extrusion of the NP (and sometimes parts of the endplate) to arise.
3. Herniating pathway in normal intervertebral discs (IVD)
As a consequence of trauma, and especially in the young individual, an annular rupture associated with a protrusion or extrusion of the healthy NP may occur suddenly in an absolutely normal IVD (Fig. 3) with no signs of disc aging on MRI (e.g. nucleus dehydration or desiccation with signal intensity loss, dark disc, annular bulging, internal annular high intensity zones, etc ...) and no MRI signs of disc degeneration (e.g. disc space narrowing, endplate ruptures, complete radial annular fissures, annular narrowing, inwards collapse of the annulus, etc …).
Fig. 3. Strictly normal intervertebral discs between the vertebral bodies L4 and L5 in a one month old individual (left) and in a 42 year aged male. VB = vertebral body, EP = endplate, NP = nucleus pulposus, AF = annulus fibrosus.
Above: original (Declerck / Kakulas, Neuropathology, Perth, Western Australia, X83/478, M, aged 1/12). Middle: artistic presentation by Alonso Ríos Vanegas, sculptor and pintor, Medellín, Colombia.
Below: original (Declerck / Kakulas, Neuropathology, Perth, Western Australia, X90/1420, M, aged 42 yr)
4. Herniating pathway in degenerating IVD’s
In a mature IVD, a continuous chain of biochemical degenerative changes at cellular and molecular level must evolve for the NP to dehydrate and lose its viscoelastic gel-type behavior. When the NP starts fragmenting (Fig. 4), it no longer can maintain its ability to evenly distribute stresses transmitted to the NP. In such situations spot-loadings occur at the level of the nuclear fragments which may cause low back pain (Mulholland). However, the more the degenerative processes progress, the more the nuclear material gets digested and resorbed. By the end there, there simply is no nuclear material left. An extrusion simply becomes impossible.
Fig. 4. Degenerative intervertebral disc L4-L5 with fragmentation of the nucleus pulposus and clear endplate disruption. Further IVD narrowing due to inflammatory digestion and resorption of nuclear material makes it gradually impossible to produce extrusions
(Declerck / Kakulas, Neuropathology, Perth, Western Australia – A90/139 / M / 50 yrs)
The creation of herniating pathway occurs in a stepwise fashion for the NP to protrude or extrude through the AF. Our daily lumbar spinal mechanical wear-and-tear loading patterns during varying sitting and standing positions, non-stochastic and high frequency industrial and vehicle vibrations, and intensive repetitive pulling and lifting activities put the type-I collagen fibers in the annular layers under an increased shear strain. Gradual annular tearing develops in a peripheral posterior and postero-lateral direction. The (remaining) degenerating nuclear material can start migrating through these radial annular fissures and create a protrusion. Usually, a minor incident (a cough/sneeze) is sufficient for a weakening AF to finally cause the evolving and degenerative annular fissure to tear completely (= annular rupture). From that moment nuclear material may choose this path of least resistance to protrude and extrude into the spinal canal. Further increase of the intradiscal degenerative processes even enhance the opening of the created annular tears (Wognum).
5. Genetic predisposition for the herniating pathway
It is extremely rare for a healthy, non-degenerative, and well-hydrated juvenile AF to fissure. Except when trauma causes an accidental annular rupture, an intact and non-fragmented NP remains contained in the center of the IVD (Fig. 3).
Nonetheless, the occurrence of a symptomatic disc protrusion and extrusion is 20 times higher if members of a family show severe degenerative IVD changes (internal disc disruption, tears of the annulus fibrosus and of the endplates) (Fig. 4).
Some of the genes which may induce the development of disc degeneration are known (e.g. collagen type I and IX genes, vitamin D receptor genes, matrix metalloproteinase genes, genes for coding interleukin-1 and interleukin-6). Supplementary genetic evidence for specifically developing a nuclear disc protrusion and extrusion is continuously being researched. Till now, no ‘herniating pathway’ genes have been discovered.
Indeed, every man and woman will develop the strictly normal aging processes into his or her IVD’s. Only a very small percentage of people never will develop degenerative changes whatever the loads subjected on them. Indeed, some individuals are ‘protected’ by Nature and the absence of deteriorating genes.
6. Normal aging processes may be accompanied by degenerative processes
Low back pain is an unfortunate effect of belonging to the erect species because the IVDs are loaded constantly. Walking upright, standing, sitting and certainly bending forwards elicit lifelong combined compression and rotational stresses (F/a = N/m² = Pa = Pascal) on the lumbar IVDs. For example, the pressure on these discs accounts for 80 kg/cm² during a static upright rest position and 210 kg/cm² during a forwards bending position in 10° flexion. To make this statement very clear, these pressures can be compared to the pressure exerted by 8 respectively 21 cases of 24 full bottles of beer on one cm²!
These repetitive daily mechanical loading factors influence and alter the biochemical aging processes in the IVD’s. Except for a few genetically ‘protected’ individuals, the daily physical activities will cause degenerative and damaging structural changes in the three parts of the IVD: the NP, the endplates and the AF.
The highest situated L1-L2 and L2-L3 IVD’s eventually evidence rather degenerative vertebral endplate fissures and fractures (Fig. 6a). The degenerative internal nuclear disruptions in the lowermost L4-L5 and L5-S1 IVD’s rather result in fissuring and tearing the posterior AF through which herniation of nuclear material may occur (Fig. 6b, 7a and 7b).
Fig. 6a. X83/593 - M- 57 – IVD L1-2. Degenerative endplate fissures originate rather in the intervertebral discs between the L1 and L2 and the L2 and L3 lumbar vertebrae
(Declerck / Kakulas / Taylor, Neuropathology, Perth, Western Australia)
Fig. 6b. A83/40 - M – 64. Degenerative internal nuclear disruptions in a lower lumbar IVD without evidence of endplate involvement
(Declerck / Kakulas / Taylor, Neuropathology, Perth, Western Australia)
Noteworthy is that the conversion of lumbar IVD’s from normal structures to abnormal ones not necessarily explains the clinical degenerative discogenic syndrome. More physiological elements need to occur to cause pain such as the invasion of small blood vessels accompanied by nociceptive nerve fibers and hotspot loading mechanisms (Mulholland).
7. Lumbar intervertebral disc herniation is always the result of ‘something else’!
Overtime the internal nuclear mass of the IVD disintegrates and loses its hydrostatic properties. Step by step, the material capabilities of the collagens (type I) in the AF alter as well. These aging events result in the daily mechanical compression forces on the NP no being completely resisted by equivalent developing tension forces in the AF. When the AF no longer can withstand the high intradiscal loading pressures, its collagenous layers start tearing in-outwards and therefor will lose their viscoelastic capabilities to return to its original status.
Fig. 7a. Body weight and daily activities result in compression forces on the nucleus pulposus. Because water is incompressible, the hydrostatic pressure in the nucleus will increase. This results in more tension forces in the annulus fibrosus. Compression forces on the NP can be resisted by the AF until tears occur. These biomechanical phenomena are nicely shown at the L3-L4 IVD level. The resulting effects are seen at the L4-5 IVD level
(Declerck / Kakulas, Neuropathology, Perth, Western Australia – A90/139)
CAT- and of course MRI-investigations may reveal the well-known bulges and protrusions of the AF into the spinal canal (Fig. 7b).
Fig. 7b. A routine finding during CAT-investigations. The visualised protrusion is not at all the reason for pain because these protrusions are routinely seen in nearly every CAT-scan and in individuals without pain. Low back pain is related to other underlying mechanisms
In the later stages of the degradation processes complete annular tears, annular protrusions with ‘contained’ nuclear material and nuclear extrusions may become radiologically visible signs on MRI (Fig. 7c).
Fig. 7c. MRI-images of the lower part of the lumbar spine. Visually ‘normal’ IVD between the vertebral bodies VB 3 and VB 4. Degenerated and narrowed IVD between VB 5 and the sacrum (S1) with irregularities at the level of the lower endplate of the VB 5 and an annular protrusion. Clear extrusion of the nucleus pulposus at the L4-5 IVD-level
8. Annular protrusions and extrusions: always pain?
The annular protrusions and nuclear extrusions may arise in all lumbar IVD’s with or without complaints of (chronic) low back pain. Most individuals don’t even know they possess these - mostly temporarily - expressions of the herniating pathway.
In the elderly population, nearly all examined postmortem lower lumbar discs comprise various types of complete fissures and gross ruptures in the AF. However, extrusions of nuclear material are extremely rare. The complete nuclear matrix has been digested and resorbed by the degenerative and inflammatory processes. Not only the central part of the NP but all potentially existing extrusions of nuclear material - symptomatic or not - have been ‘eaten away’. As no NP is left inside the IVD, a nuclear disc protrusion or extrusion of course no longer is possible (Fig. 8).
Fig. 8. Most degenerative nucleus pulposus material has already been ‘eaten’ away by the degenerative and inflammatory processes in the IVD. In the posterior part, only a normal annular protrusion is visible. There is no nuclear material in the epidural space. There is no contact with the spinal nerve root which is not compressed. Trying to surgically ‘clean out’ the protrusion and some intervertebral nuclear material will lead to a catastrophic end result.
(Declerck / Kakulas, Neuropathology, Perth, Western Australia – A90/149 – M – 79)
9. Mechanism for resorbing the herniating nuclear material
It is known since 1950 that protruding and extruding degenerative nuclear disc tissues mostly are digested (Lindblom). The size of a nuclear ‘herniation’ regresses for approximately 50 % or more over a period of three months in up to 80 % to 90 % of cases when controlled by MRI. The speed and the degree of resorption of degenerated nuclear disc material is directly related to the intensity of the inflammatory progresses which proceed in the herniating nuclear (not annular) segments.
Protruded and extruded fragments of the degenerating NP are close to epidural vessels. Electron microscopic investigations show extensive neovascularisation and macrophages surrounding the disc fragments. The most potent proinflammatory cytokines (tumor-necrosis factor-α or TNF-α) and leading factors in the inflammatory processes of the degenerating IVD fine-tune the phagocytic performances of the macrophages which will ‘eat’ the nuclear hernia away. The endothelial cells of the bloodvessels contain so-called angiocrine signals which activate proteolytic enzymes (Ding; Tashimo) for resorbing the nuclear proteoglycans away.
10. No leg pain?
Then … don’t treat a radiological disc ‘herniation’!
Up to 70 % of all radiological disc protrusions and extrusions are not associated with leg pain. The nuclear herniations simply are the expressions of the normal aging and abnormal degenerative pathways of the IVD. Surgically removing such an innocent disc ‘herniation’, incidentally found on radiology and without leg pains, solely is an aesthetic procedure. In the long term, it simply changes nothing.
When a nerve root becomes compressed, motor and sensory disturbances may ensue. However, mechanical compression is insufficient to produce pain.
It is well known that the degenerated NP material contains different cytokines (e.g. TNF-alpha) which may induce potent inflammatory activity in the spinal nerve roots. The production of such nitric oxide (NO) induces endoneural edema and decreases nerve conduction velocity in the spinal nerve root (Olmarker). Inflammatory mediators (NO) not only induce nerve function impairment but are essential to cause the excruciating neuropathic pains in the leg (Olmarker). In the long term, significant ultrastructural axonal changes will occur locally: Schwann cell damage, intracellular edema, and vesicular swelling of the Schmidt-Lanterman incisures (Olmarker).
11. Evolution of inflammatory radicular leg pain
The inflammatory type of radicular sciatic pain related to solely lumbar disc protrusions and extrusions may be excruciatingly painful and debilitating.
When absolutely nothing particular is done to such a typical symptomatic disc ‘herniation’ and when its related nerve root signs and symptoms do not increase, then Mother Nature dictates that the sciatic pain will spontaneously disappear in approximately 80 % to 90 % of all such instances within 6 to 12 weeks.
Although it is extremely difficult to impart simple virtues to low back pain patients, in such circumstances patience undeniably can lead to the avoidance of totally unnecessary discectomy.
There is absolutely no doubt that in the long term (+/- 2 years) surgical removal of a lumbar disc protrusion or extrusion causes more harm than good even if the initial surgical result may be absolutely perfect. Just ask a mason what will happen to a wall in 4 years’ time when cement is removed from between two of its bricks. Millions of disc ‘herniation’ patients all over the world are now suffering the consequences of simple but devastating discectomy procedures.
12. The Dynasty of the IVD herniation
Reason for tragic human wreckage
For totally unknown reasons and without any scientific basis whatsoever, most doctors and surgeons still continue to accept the indoctrinated and archaic principle of a disc ‘herniation’ as the only explanation for nearly all low back pain.
For approximately 150 years and during the periods of the Industrial Revolutions, reasons were sought to explain the increasing incidence and prevalence of low back pain.
In 1934/1935 the neurosurgeons Mixter and Barr described a very clear and detailed clinical condition :‘rupture or herniation of an intervertebral disc’. Unfortunately and again for totally unknown reasons in a matter of few years this ‘new’ condition became the mainstream for explaining the whole range of lumbar spinal conditions for which there was no explanation. All low back pain was suddenly explained by a ‘disc herniation’. Nothing could have been crazier!
But the Dynasty of disc herniation was born and an explosion of discectomy surgery ensued which in most countries still continues till today.
When in the 1950’s neurogenic claudication was outlined as another evident reason for a radicular syndrome, it became clear that the discectomy procedures ‘for all kind of reasons’ had been and were responsible for ‘leaving the largest prevalence of tragic human wreckage than any other operation in history’. Repetitive negative surgical explorations, interventional failures, continuing reports of clinical disasters, and ensuing salvage procedures finally resulted in the recognition of disc herniations as the most illogical explanations for chronic low back pain.
13. ‘Medical ignorance’ versus ‘perfect surgery’
Strangely enough, still a lot of surgeons cannot understand why their high-tech guided and thus perfectly performed discectomies could be associated with the persistence of postoperative low back pain.
Who never heard the following statement? ‘My dear! Look at the postoperative picture! The herniation has been nicely removed! The MRI shows no evidence of a protrusion, extrusion or sequestration! Your spinal canal is ‘clean’! I can’t see the reasons why you still have low back pain. I think you must have … familial, social, relational, economic, or ….. psychological problems?’ And sometimes the patient receives ‘a higher level of scientific explanation ’: ‘you know, dear, we know it since a very long time: there are three groups of patients: those who heal up all the time, those who will heal up overtime, and those who never will heal up!’ And there we go! Millions all over the world have been confronted with this statement.
But could it still be that highly educated and technically skilled surgeons:
(1) are unaware of the strictly normal aging processes in the IVD’s?
(2) have no idea of the primary underlying degenerative discogenic processes?
(3) don’t know the scientific basis of the degenerative herniating pathway?
(4) do not realize that discectomy surgery stimulates and accelerates intradiscal degenerative processes?
(5) do not know that increased degeneration enhances the diameters of annular tears (Wognum)?
(6) do not realise that discectomies lead to secondary degenerative spondylolisthesis and spinal stenosis?
The author has been confronted day and night with hundreds of these patients in multiple countries, all telling exactly the same history …
14. Misinterpretation of the radiological images
Most of the discogenic protrusions and extrusions observed by radiological means (XR, CAT, MRI) are incidental findings in individuals who are asymptomatic or only have a small amount of low back pain. Why then do so many people mention that they have disc ‘herniations’?
It certainly can be due to misinterpretation of the normal posterior anatomy of the IVD’s. At the thoracolumbar junction, the IVD has no tendency to bulge into the canal. Whereas the L1-L2 and L2-L3 IVD’s have a straight posterior margin, the most distal localized L3-L4, L4-L5, and L5-S1 discs have a distinct posteriorly convex bulging configuration (Fig. 14).
Fig. 14. Normal posterior margins of the lumbar intervertebral discs. There is no bulging at the level of T12-L1. The posterior margins at L1-L2 and L2-3 are ‘straight’. At the level of L3-L4, L4-L5 and L5-S1, the posterior margins, and for biomechanical reasons, must have a convex configuration. If not, there is a problem!
By no means should this normal anatomy be confused with a pathological bulging of these IVD’s due to degeneration and hypermobility even in the presence of a ‘black’ disc (Rauschning). Indeed,
For making the presumptive diagnosis of a lumbar disc disorder, the major determining factors are essentially the characteristics of leg pain rather than those of low back pain (see above: point 10).
The essentials in a patient’s history and clinical examination to conclude that a radiological disc protrusion or extrusion is the causing symptomatic leg pain factor include:
(a) a history of intense functionally incapacitating and unremitting sciatic leg pain extending below the knee largely in excess of low back and/or buttock pain which may be totally absent,
(b) neurological motor and sensory disturbances in a radicular distribution (= radiculopathy),
(c) presence of disturbed neuromeningeal tension signs and qualifying tests reproducing the typical sciatic pain (e.g. disturbed straight-leg tension test, dorsiflexion of the ankle, medial hip rotation test, slump test), and
(d) manifestation of disturbed neuromeningeal compression signs (especially profound muscular weakness) in the radicular distribution.
The presence of neuromeningeal compression signs, mainly expressed by sensory disturbances (numbness and dysesthesias) but only minor motor weaknesses without pain below the knee, never present indications for removal of a disc protrusion or extrusion. The sensory dysfunctions still remain present in a high percentage (up to 35 %) independently of the chosen treatment, traditional or surgical.
16. Annular location of lumbar disc ‘herniations’
Laboratory experiments and mathematical finite element methods (FEM), investigations nearly exclusively understood by engineers, (doctors are not at all trained in understanding research data!), substantiate that the risk for nuclear migrations is highest in the posterior and posterolateral annulus fibrosus especially in mildly degenerated IVD’s. Severely degenerated IVD’s show a lower risk.
The degenerated NP may also protrude or extrude in other directions: anteriorly, (far) laterally, through the endplates (Schmörl’s node) (Fig. 16), and intradurally.
Fig. 16. Evidence of the ‘herniating pathway’ of the nucleus pulposus through an endplate (nodule of Schmörl)
(Declerck / Kakulas / Taylor, Neuropathology, Perth, Western Australia, dossier A90/148)
17. Radiological imaging: nuclear protrusion
A disc protrusion (protrudere in Latin) represents the herniation of NP material through an incomplete defect in the AF (Fig. 17a and 17b). The annular margin is locally extended but the outermost annular collagen type I layers remain totally intact. These types of annular disc bulgings are extremely common, but do not at all represent ‘pain’.
Fig. 17a. The annulus fibrosus shows concentric tears and disruption of the inner collagenous layers. The outer layers remain intact. The nucleus pulposus moves outwards but is halted by the intact layers of the AF. This ‘moving’ process of nuclear material is called ‘protrudere’ in Latin. The protrusion is depicted. This herniating state may or may be associated with low back pain. However, the typical excruciating sciatic leg pain, essential for making the correct diagnosis of a ‘hernia’, cannot be present because the spinal nerve root has no contact with the different cytokines inside the degenerating NP (Internal Spinal Course – Kyphon International)
They may or may not be associated with an incomplete annular tear. If the tears are fluid-filled, which varies along the spinal loading patterns, they present a high intensity zone (= HIZ) on MRI (Fig. 17c). And again, HIZ’s are not necessarily the reason for pain.
It is important to realise that this type of radiological herniation - the disc protrusion - mostly is an incidental finding in totally asymptomatic individuals.
Fig. 17b. MRI-image of a disc protrusion. The nucleus pulposus (‘black disc’) herniates through incomplete defects in the inner collagenous layers of the annulus fibrosus. The annular margin is locally extended but the outermost annular layers remain totally intact
Fig. 17c. The formation of an protrusion may be associated with a visible fluid-filled incomplete tear in the annulus fibrosus. On the left: the high intensity zone (HIZ) is visible on MRI. On the right: pathological section through such a developing in-to-out tear in the annulus
(Declerck / Kakulas, Neuropathology, Perth, Western Australia – A90/149)
18. Radiological imaging: nuclear extrusion
Once a complete in-to-out annular radial defect has been established, degenerating nuclear material may migrate through it and appear into the anterior epidural space. As long as this herniating nuclear material still remains attached to the parent NP via a pedicle of nuclear material, the radiological presentation is defined as a disc extrusion (extrudere in Latin) (Fig. 18a and 18b).
Fig. 18a. The annulus fibrosus is teared completely. The nuclear material migrates through the annular tear into the epidural space. This process is called ‘extrudere’ in Latin. The herniating extrusion is depicted. This situation can provoke low back pain can be responsible for the development of excruciating leg pain
(Internal Spinal Course – Kyphon International)
When the pedicular attachment no longer exists, the free floating nuclear fragment is described as a disc sequester (sequestrare in Latin).
Fig. 18b. MRI of the lower part of the lumbar spine. Degenerative extruding nuclear material is present at the L4-L5 IVD level. The herniated material still remains attached to the parent NP via a pedicle of nuclear material
It is important to realise that this type of radiological herniation - the disc extrusion - may be an incidental finding as well in totally asymptomatic individuals.
19. Traditional conservative treatments do not influence the natural history
Except if the radicular leg pain symptoms and clinical neuromeningeal compression signs due to a protrusion or extrusion of nuclear material increase or worse rapidly and dangerously, patients should be thoroughly observed for 3 months before a definite surgical decision is taken. Mother Nature, responsible for the ‘natural history’, does Her uppermost best not only to resorb the ‘herniation’ but to spontaneously resolve the associated symptoms in approximately 80 % of individuals over a period of twelve weeks!
While Mother Nature takes this average period of time to cure, the patient may and should remain as active as possible. Nonoperative measures may be initiated but only to - hopefully - avoid unnecessary discectomy surgery.
20. Huge variety of nonoperative measures
A huge variety of all kind of management methods is tried, used, and combined worldwide. Traditional and non-traditional exercises, medications, injections, etc … may of course be initiated in an attempt to alleviate the pain associated with inflammation. Sometimes, injected epidural steroids may decrease pain as they inhibit the prostaglandin synthesis and block nociceptive C-fibers.
21. Conservative measures: what can be expected?
It finally remains up to Mother Nature to decide if She will ‘centralize’ or not the patient’s symptoms from the distal radicular locations in the leg into only the lower lumbar spine. As the primarily underlying degenerative destructive enzymatic and inflammatory processes in the IVD cannot be neutralised, low back pain always will evolve into a chronic intermittent (Fig. 20a) or chronic undulating pattern (Fig. 20b).
Fig. 21a. Schematic presentation of chronic intermittent low back pain. Frequently recurring and suddenly occurring episodes of low back pain followed by varying painless periods (Graph by Natacha Monstrey)
Fig. 21b. Schematic presentation of chronic undulating low back pain. Low back pain is always present but the intensity varies enormously (Graph by Natacha Monstrey)
22. Conservative measures: what cannot be expected?
It should be well realized that - till now - none of the non-surgical strategies has ever succeeded in directly and handsomely dissolving the volume of the protrusion or of the extrusion more rapidly than does Mother Nature!
None of all the existing non-operative treatment possibilities will accelerate the spontaneous resorption and regression of the ‘herniation’.
None of the conservative methods interferes or can stop the progressing intradiscal degenerative processes. Whatever the type of treatment, it will not and cannot interfere with the cellular and molecular processes of degeneration.
Then, it must be understood that ‘TIME and PATIENCE’- but not too long and not too much - are primordial to avoid unnecessary discectomy.
On the other hand, when (a) Mother Nature fails - for as jet unknown reasons - to resolve the clinical signs and symptoms, when (b) the radicular leg pain intensifies, when (c) the neurologic motor deficits progress and paralysis occurs, a new MRI is required to confirm the diagnosis before proceeding with discectomy surgery.
23. Surgical discectomy rarely is an urgent procedure
There is no doubt that discectomy is an urgent and absolute surgical procedure to treat severe and intensifying disabling radicular leg pain.
When this history is associated with a MRI imaging an extruded disc fragment impinging and inflaming the neural structures (the so called dural conus medullaris and different dural cauda equina syndromes) and causing:
a) progressing and worsening neuromeningeal compression signs,
b) bilateral radicular pain,
c) saddle anesthesia and
d) adversely affecting the bladder, bowel and sexual functions, hesitation to perform a discectomy may lead to irreversible lesions of the myelin sheath of the nerve roots with irreversible clinical consequences (see point 10 - Olmarker).
24. What to do in the absence of worsening signs and symptoms?
In the absence of progressing disabling leg pain and motor paralysis, removal of disc tissue rarely should be performed if the clinical signs and symptoms do not meet the typical definition of a ‘herniation’. Surely, discectomy never is indicated when low back pain is the only and major complaint.
Since years, the underneath mentioned remarks regarding surgical discectomy are repeated over and over again in the spinal literature and during international spinal meetings:
a) if the surgical decision is only based on a rapid interpretation of a radiological image (CAT and/or MRI) in the absence of a typical history and clinical examination, discectomy surgery has no sense at all and will fail to produce a relief,
b) an incidental finding of a protrusion or extrusion on CAT or MRI and thus without pain nor symptoms, is not at all a panacea for removing the ‘offending’ part: nor for minimally nor for generously removing disc material from the intervertebral disc space,
c) if the surgical decision is solely based on ‘failure’ of traditional and conservative treatments in cases of low back pain without (increasing) leg pain, discectomy has nothing to offer,
d) if surgery is decided upon to resolve chronic distress and illness behavior of the patient who has no evidence of objective pathological neuromeningeal compression signs, the outcome is totally unpredictable.
Whatever the reasons for performing a surgical discectomy, Nature never will cooperate. Surgical discectomy is like throwing oil on an existing fire. Surgery never will neutralise the destructive enzymatic and inflammatory mediators associated with the existing degenerative processes and therefore …. low back pain will become more prominent!
25. Discectomy for low back pain without leg pain?
As already mentioned, each of the L3-4, L4-L5, and L5-S1 IVD’s has a normal posterior convex configuration and should not be considered ‘abnormal’. Don’t touch bulging discs!
Evolving disc protrusions are due to the progressing destructive degeneration of the IVD (nucleus and endplate) and are related to the advancing in-to-out breakdown of the type I collagenous layers of the annulus. Surgically perforating and rupturing these incomplete annular lesions to remove part of the degenerating NP only will result in the development of chronic low back pain because discectomy creates more high spot-loading areas inside the emptied disc space (Mulholland).
Radiological visible extrusions and sequestrations may or may not be the reasons for low back pain. But low back pain will continue to exist and even increase following discectomy surgery.
It is essential to realise that a lumbar disc ‘herniation’ is not at all a major primary cause of low back pain. To the contrary, discectomy increases low back pain in the long term.
26. Primary goal of discectomy surgery
The primary goal of discectomy surgery still remains the same since its first descriptions in the 1930s. The only purpose of a lumbar discectomy is to remove the ‘herniating’ NP and taking away the compression from the affected nerve root. Then, hoping that inflammation settles and improves the leg pain.
To stimulate this process, it was and still is a routine to supplement the procedure with anti-inflammatory corticoids (injected inside the emptied intervertebral space and on the affected nerve roots).
But because the reasons of failure of discectomy procedures have till recently not been sought where they should be, new instruments and modified techniques for ‘discectomy’ are still been developed.
In vain! Discectomies on their own never will neutralise the destructive enzymatic and inflammatory mediators associated with the existing degenerative processes. On top of that, discectomy procedures create multiple high hot-spot loading zones because the normal daily loads on the IVD during sitting and standing no longer can be equally distributed.
27. What needs to be realised if a lumbar discectomy will be performed?
When the ultimate surgical approach is decided upon, it is essential to realize the underneath data:
(1) the highly organized structure of the annulus is severely damaged as a result of the primary degenerative discogenic herniating pathway,
(2) the discectomy procedure causes further laceration to the outer annular layers,
(3) nuclear and/or annular reconstruction is still totally impossible,
(4) all even perfectly performed techniques of disc removal benefit only good short-term effects,
(5) the removal of nuclear material decreases the intradiscal hydrostatic pressure and stimulates the degradative enzyme production (MMP’s) accelerating the underlying primary degenerative disc processes,
(6) the denucleation always will result in subsequent loss of intervertebral disc height,
(7) the ablation of nuclear material increases segmental hypermobility between two vertebrae,
(8) the denucleation leads to more biomechanical stress in the remaining AF and in the zygapophyseal facetal joints causing new episodes of low back pain,
(9) recurrent herniation at the same location occurs in up to 30 % of cases,
(10) the amount of recurrent disc herniations after ‘microdiscectomy’ is highest when MRI only indicates a minor disc degeneration,
(11) approximately 30% of all disc herniation operated patients decide to undergo another operation within 10 years, and
(12) older patients undergoing discectomies for degenerative disc ‘herniations’ have higher rates of morbidity and mortality than younger individuals (Stolke).
28. Multitude of minimally invasive intradiscal discectomies
It remains an enigma why the removal of a ‘herniated’ disc still is the most commonly performed spinal surgical procedure although lumbar discectomy relentlessly leads to the further destruction of the remaining intervertebral cartilaginous structures (AF, NP and the endplates).
Since the late 1970’s, it is well known that the conventional ‘open’ midline muscle stripping discectomy procedures have been responsible for ‘leaving the largest prevalence of tragic human wreckage than any other operation in history’.
In the meantime a multitude of minimally invasive lumbar intradiscal discectomies has been invented (percutaneous, endoscopic, laser, etc …). Because irreversible and significant paravertebral muscle damage (Fig. 28a and 28b) can now be prevented, there is no doubt that these innovative strategies have benefited the patients in the short term.
Fig. 28a and b. Muscle histopathology (see other chapter: Paraspinal Musculature)
Left slide: normal paraspinal muscle fibers (M - 40 years - X90/368 - EM 90/56)
Right slide: non-specific myopathy changes (M - 73 years - X90/346 - EM 90/52)
(Declerck / Kakulas, Neuromuscular Pathology, Perth, Western Australia)
The use of one of these various discectomy techniques depends on
a) the professional formation of the surgeon in one or more countries,
b) his understanding of spinal biochemistry and biomechanics,
c) his inherent technical skills, experience, but not at least
d) the impact of the marketeering skills of the surgical companies.
None of all these various discectomy methods is superior to the other:
a) all these modern manipulations still need additional surgical annular perforations, fenestrations or annulotomies to explore and ablate the central NP,
b) none of these modern procedures can be performed without further damaging the intervertebral disc texture,
c) none is capable of preventing the progression of the underlying primary causing intradiscal degenerative processes
d) to the contrary, the removal of nuclear disc material always results in a further activation of the degenerative processes and an increased incidence and prevalence of inflammatory mediators.
Mother ‘Nature’ will continue to revolt against this destructive approach by causing more inflammatory low back pain.
29. How to evaluate results of lumbar discectomy surgery?
For a throughout evaluation of a particular spinal treatment and certainly for ablative procedures of degenerative discogenic ‘herniations’, a minimum of at least 10-year follow-up is essential to judge the validity of a peculiar management approach.
Cheap comparative effectiveness research (CER website) should be performed to evaluate the potential boost of the intradiscal degenerative steps by different treatment modalities for lumbar disc ‘herniations’. However and because this research will need to include repetitive scanning (MRI) at regular follow-up intervals, it will never be performed. On the other hand and in comparison, similar and longitudinal evaluations on the effects of aging processes in homogeneous life circumstances are done since years (Riley; Tyas; Shock).
30. Discectomy results: only two long-term evaluations since 1934
Since the Dynasty of disc herniation started in the late 1930’s, only two 10-year studies (Weber; Atlas) have been performed.
As can be expected, the early one-year and two-year results always resulted and still result in an exceptionally good leg pain relieving effect with ratings varying from 79 % to 97 % (Table 30).
Two 10-year follow-up studies since 1934: results
At 1 – 2 years
exceptional good low back pain relief
At 4 years
At 10 years
no difference between operated and non-operated patients
Table 30. One year, 4 years, and 10 years evaluation of patients operated with discectomies
Most patients have been found to be ‘ok’ for approximately 4 years! By that time and because the underlying causative factors were never dealt with initially, it became clear that the long term results were the same whether the patient was treated with surgery or was left alone with non-operative means.
At 10 years the disability outcomes were similar for both groups, operated on or not. It was calculated that up to 27 % of all previously discectomy patients decided to undergo another spinal operation within 10 years.
And funny enough, all studies - short and long term - evaluating the results of lumbar disc hernia surgery emphasize inappropriate patient selection as the leading cause of surgical failure. Indeed, Mother ‘Nature’ will continue to revolt as long as the causes which lead to the formation and progression of the herniating pathway are not considered: IVD degeneration.
31. The removed parts of the disc under the microscope
Macro- and microscopic analysis of ‘herniated’ lumbar disc material following surgical removal and during postmortem evaluations never shows a normal hydrated viscous material expected to be present in a healthy nucleus of the IV disc.
The removed parts of the IVD always contain dehydrated and fibrous elements originating from the NP, the AF and the endplates as well.
Chemical analysis of the ‘herniated’ fragments clearly show that they possess the same degenerative profile as the degenerating NP. Disc ‘herniations’ contain identical degradative enzymes (matrix metalloproteinases) and identical potent proinflammatory cytokines (i.e. tumor-necrosis factor-α). These enzymatic and inflammatory mediators not only are responsible for causing low back pain and/or radicular pains but they stimulate macrophages for eating the ‘hernia’ away. None of all the developed techniques for lumbar discectomy can neutralise these complex mechanisms which induce chemical inflammatory pain.
32. Low back pain continues following lumbar discectomy
Surgical ablation of a ‘hernia’ can resolve the radicular type of leg pain, but the low back pain will rarely disappear. Only 1 % of patients who suffer discogenic low back pain as well will experience an immediate and complete disappearance of low back pain following surgery.
To the contrary, extirpation irreversibly stimulates the degenerative and inflammatory processes further resorbing the remaining NP. Chronic low back pain persists! This evolution consolidates the degenerative discogenic syndrome and finally will result in its secondary pathologic events: degenerative spondylolisthesis and degenerative spinal stenosis.
33. Medical personnel apparently is not willing to understand why postoperative low back pain increases and continues to think in … other terms
Strangely enough, a lot of surgeons do not consider the occurrence of persistent postoperative low back pain a component of poor surgical outcome. And they are right! With the most modern high tech guiding machinery, they performed a straightforward and uncomplicated removal of a ‘herniation’, without muscle destruction and without intraoperative complications.
Then, there is no reason at all to expect bad results. And qualifying a patient as somebody ‘who will heal all the time, who will heal over time, and who never will heal’ only can be done in the postoperative phase. And by that time, lack of scientific knowledge evidently is only the responsibility of the patient! But patients have no clue about the underlying and primary processes ……
Because of the increasing requested familial, social, professional, leisure, and economic pressures and responsibilities dictated by the ‘evolutions’ in modern industrialised societies, Mother Nature will continue to revolt. Mother Nature hates interference in her own healing potential. She does not agree with this financially rewarding indication for surgery.
A price will always be paid for the performed discectomy and nucleotomy:
1) intradiscal inflammatory processes are stimulated,
2) intradiscal pressure will decrease,
3) disc height will decrease,
4) more tension stress will occur in the remaining annulus,
5) circumferential radial bulging will increase (apparently in a proportion similar to the mass of the excised nucleus tissue),
6) ‘reherniations’ will present,
7) an abnormal range of motion between the two vertebral bodies (initially hyper- and later hypomobility) will occur (because the center of rotation and centrode between two adjacent vertebrae will shift),
8) stress in the facets of the zygapophyseal joints (ZGA’s) increases,
9) accelerated osteoarthritic-like changes will occur in the cartilage of the ZGA’s,
10) vertebrae will slip against each other and result in a degenerative spondylolisthesis,
11) the spinal canal will narrow and cause neurogenic claudication due to the development of degenerative spinal stenosis,
12) sexual impotence can ensue as well as disability, socioeconomic and financial misery, and more surgery.
34. Future perspectives
But the patients shouldn’t worry too much. Modern innovative brains in cooperation with exiting technology have responded to the unrelenting postoperative destructive processes. Research and development continuously invents new ‘salvage’ surgical procedures and implants in an effort to interfere again with the caused tragic human wreckage.
But to no avail! Unless an innovative biological concept evolves stabilising the intradiscal degenerative and inflammatory processes, in accordance to Mother Nature’s Biological Laws, everybody will continue to suffer the consequences of the normal aging processes and its degenerative complications!
Intensive research is going on to understand and to neutralize the primary intradiscal degenerative processes.
35. Literature Encyclopaedia
The role of activity in the therapeutic management of back pain. Report of the International Paris Task Force on Back Pain
Spine, 2000, 25 (Suppl 4):1S
Mechanical initiation of intervertebral disc degeneration
Spine, 2000, 25:1625
Adams MA, Hutton WC
Gradual disc prolapse
Spine, 1985, 10:524
Adams MA, Hutton WC
Prolapsed intervertebral disc. A hyperflexion injury. 1981 Volvo Award in Basic Science
Spine, 1982, 7:184
Adams MA, Roughley PJ
What is intervertebral disc degeneration, and what causes it?
Spine, 2006, 31:2151
Effect of anular repair on the healing strength of the intervertebral disc. A sheep model
Spine, 2000, 25:2165
Annular incision technique on the strength and multidirectional flexibility of the healing intervertebral disc
Spine, 1994, 19:948
The potential and limitations of a cell-seeded collagen/hyaluronan scaffold to engineer an intervertebral disc-like matrix
Spine, 2003, 28:446
Allan DB, Waddell G
The dynasty of the disc
In: Understanding and management of low back pain
Acta Orthop Scand, 1989, 60 (Suppl 234):6
Preclinical evaluation of a poly (vinyl alcohol) hydrogel implant as a replacement for the nucleus pulposus
Spine, 2004, 29:515
Ando T, Mimatsu K
Traumatic lumbar disc herniation. A case report
Spine, 1993, 18:2355
Aoki Y, Rydevik B, Kikuchi S, Olmarker K
Local application of disc-related cytokines on spinal nerve roots
Spine, 2002, 27:1614
Atlas SJ, Keller RB, Wu YA, Deyo RA, Singer DE
Long-term outcomes of surgical and nonsurgical management of sciatica secondary to a lumbar disc herniation. 10 Year results from the Maine lumbar spine study
Spine, 2005, 30:927
Barth M, Diepers M, Weiss C, Thomé C
Two-year outcome after lumbar microdiscectomy versus microscopic sequestrectomy. Part 2. Radiographic evaluation and correlation with clinical outcome
Spine, 2008, 33:273
Two-year outcome after lumbar microdiscectomy versus microscopic sequestrectomy. Part 1. Evaluation of clinical outcome
Spine, 2008, 33:265
Battié MC, Videman T, Gibbons LE, Fisher LD, Manninen H, Gill K
1995 Volvo award in clinical sciences. Determinants of lumbar disc degeneration. A study relating lifetime exposures and magnetic resonance imaging findings in identical twins
Spine, 1995, 20:2601
Diagnosis of lumbar disc disease
Seminars in Spine Surgery, 1994, 6:186
Bhardwaj R, Midha R
Synchronous lumbar disc herniation in adult twins. Case report
Can J Neurol Sci, 2004, 31:554
Abnormal magnetic-resonance scans of the lumbar spine in asymptomatic subjects. A prospective investigation
J Bone Joint Surg, 1990,72A:403
Boden SD, Wiesel SW, Laws ER Jr, Rothman RM
The pathophysiology of the aging spine
In: The Aging Spine. Essentials of pathophysiology. Diagnosis and treatment
WB Saunders, Philadelphia, 1991:21
The value of magnetic resonance imaging of the lumbar spine to predict low-back pain in asymptomatic subjects. A seven-year follow-up study
J Bone Joint Surg, 2001, 83A:1306
Treatment of sciatica. A comparative survey of complications of surgical treatment and nucleolysis with chymopapain
Clin Orthop Relat Res, 1990, 251:144
Lumbar disk herniation. MR imaging assessment of natural history in patients treated without surgery
Radiology, 1992, 185:135
Breig A, Troup JD
Biomechanical considerations in the straight-leg-raising test. Cadaveric and clinical studies of the effects of medial hip rotation
Spine, 1979, 4:242
Brickley-Parsons D, Glimcher MJ
Is the chemistry of collagen in intervertebral discs an expression of Wolff's Law? A study of the human lumbar spine
Spine, 1984, 9:148
Injury of the annulus fibrosus and disc protrusions. An in vitro investigation on human lumbar discs
Brinckmann P, Grootenboer H
Change of disc height, radial disc bulge, and intradiscal pressure from discectomy. An in vitro investigation on human lumbar discs
Spine, 1991, 16:641
Burke JG, Watson RW, Conhyea D, McCormack D, Dowling FE, Walsh MG
Human nucleus pulposus can respond to a pro-inflammatory stimulus
Spine, 2003, 28:2685
Burke JG, Watson RWG, McCormack D, Dowling FE, Walsh MG, Fitzpatrick JM
Intervertebral discs which cause low back pain secrete high levels of proinflammatory mediators
J Bone Joint Surg, 2002, 84B:196
Callaghan JP, McGill SM
Intervertebral disc herniation. Studies on a porcine model exposed to highly repetitive flexion/extension motion with compressive force
Clin Biomech, 2001, 16:28
Carragee EJ, Han MY, Suen PW, Kim D
Clinical outcomes after lumbar discectomy for sciatica. The effects of fragment type and anular competence
J Bone Joint Surg, 2003, 85A:102
Choy DS, Ascher PW, Ranu HS, Saddekni S, Alkaitis D, Liebler W, Hughes J, Diwan S, Altman P
Percutaneous laser disc decompression. A new therapeutic modality
Spine, 1992, 17:949
Internal disc disruption.
A challenge to disc prolapse fifty years on
Spine, 1986, 11:650
Isolated lumbar disk resorption as a cause of nerve root canal stenosis
Clin Orthop Related Res, 1976, 115:109
The presidential address, ISSLS. Internal disc disruption. A challenge to disc prolapse fifty years on
Spine, 1986, 11:650
Dabezies EJ, Langford K, Morris J, Shields CB, Wilkinson HA
Safety and efficacy of chymopapain (Disease) in the treatment of sciatica due to a herniated nucleus pulposus results of a randomized, double-blind study
Spine, 1988, 13:561
‘Neuropathologic spinal anatomy of all cervical, thoracic and lumbar intervertebral discs in 23.539 consecutive
sagittal vertebral autopsies in different types of pathologies. A continuous observation during 50 years’ Observations made at the Department of Neuropathology, University of Western Australia
In cooperation with the professors BA Kakulas & JR Taylor and Sir George M. Bedbrook
Serial publications on the website www.guydeclerck.com
Declerck GMC, Hoogmartens M
Chymopapain chemonucleolysis. A follow-up study of 100 consecutive cases
Acta Orthop Belg, 1984, 50:54
De Palma AF, Rothman RH
The intervertebral disc
WB Saunders, Philadelphia, 1970
Derby R, Kine G, Saal JA, Reynolds J, Goldthwaite N, White AH, Hsu K, Zucherman J
Response to steroid and duration of radicular pain as predictors of surgical outcome
Spine, 1992, 17 (Suppl 6):S176
Devillé WL, van der Windt DA, Dzaferagić A, Bezemer PD, Bouter LM
The test of Lasègue. Systematic review of the accuracy in diagnosing herniated discs
Spine, 2000, 25:1140
Deyo RA, Cherkin DC, Loeser JD, Bigos SJ, Ciol MA
Morbidity and mortality in association with operations on the lumbar spine. The influence of age, diagnosis, and procedure
J Bone Joint Surg, 1992, 74A:536
Di Martino A, Vaccaro AR, Lee JY, Denaro V, Lim MR
Nucleus pulposus replacement. Basic science and indications for clinical use
Spine, 2005, 30(Suppl 16):S16
Ding L, Saunders TL, Enikolopov G, Morrison SJ
Endothelial and perivascular cells maintain haematopoietic stem cells
Nature, 2012, 481:457
Doita M, Kanatani T, Harada T, Mizuno K
Immunohistologic study of the ruptured intervertebral disc of the lumbar spine
Spine, 1996, 21:235
Donelson R, Aprill C, Metcalf R, Grant W
A prospective study of centralization of lumbar and referred pain. A predictor of symptomatic discs and anular
Spine, 1997, 22:1115
Dora C, Schmid MR, Elfering A, Zanetti M, Hodler J, Boos N
Lumbar disk herniation. Do MR imaging findings predict recurrence after surgical diskectomy?
Radiology, 2005, 235:562
Dunlop RB, Adams MA, Hutton WC
Disc space narrowing and the lumbar facet joints
J Bone Joint Surg, 1984, 66B:706
Ebeling U, Kalbarcyk H, Reulen HJ
Microsurgical reoperation following lumbar disc surgery. Timing, surgical findings, and outcome in 92 patients
Neurosurg, 1989, 70:397
Edwards WT, Ordway NR, Zheng Y, McCullen G, Han Z, Yuan HA
Peak stresses observed in the posterior lateral anulus
Spine, 2001, 26:1753
Epstein JA, Epstein NE, Marc J, Rosenthal AD, Lavine LS
Lumbar intervertebral disk herniation in teenage children. Recognition and management of associated anomalies
Spine, 1984, 9:427
Exercises. Which ones are worth trying, for which patients, and when?
Spine, 1996, 21:2874
Foley KT, Smith MM
Tech Neurosurg, 1997, 3:301
Freemont AJ, Peacock TE, Goupille P, Hoyland JA, O'Brien J, Jayson MI
Nerve ingrowth into diseased intervertebral disc in chronic back pain
The Lancet, 1997, 350:178
Frei H, Oxland TR, Rathonyi GC, Nolte LP
The effect of nucleotomy on lumbar spine mechanics in compression and shear loading
Spine, 2001, 26:2080
Friberg S, Hirsch C
Anatomical and clinical studies on lumbar disc degeneration. 1950
Clin Orthop Relat Res, 1992, 279:3
Fritsch EW, Heisel J, Rupp S
The failed back surgery syndrome. Reasons, intraoperative findings, and long-term results. A report of 182 operative treatments
Spine, 1996, 21:626
Gertzbein SD, Seligman J, Holtby R, Chan KH, Kapasouri A, Tile M, Cruickshank B
Centrode patterns and segmental instability in degenerative disc disease
Spine, 1985, 10:257
Gibson JA, Waddell G
Surgical interventions for lumbar disc prolapse
Cochrane database of systematic reviews, 2007, 2:CD001350
Goel VK, Goyal S, Clark C, Nishiyama K, Nye T
Kinematics of the whole lumbar spine. Effect of discectomy
Spine, 1985, 10:543
Goel VK, Nishiyama K, Weinstein JN, Liu YK
Mechanical properties of lumbar spinal motion segments as affected by partial disc removal
Spine, 1986, 11:1008
Gogan WJ, Fraser RD
Chymopapain. A 10-year, double blind study
Spine, 1992, 17:388
Gordon SJ, Yang KH, Mayer PJ, Mace AH Jr, Kish VL, Radin EL
Mechanism of disc rupture. A preliminary report
Spine, 1991, 16:450
Gotfried Y, Bradford DS, Oegema TR Jr
Facet joint changes after chemonucleolysis-induced disc space narrowing
Spine, 1986, 11:944
Grevitt MP, McLaren A, Shackleford IM, Mulholland RC
Automated percutaneous lumbar discectomy. An outcome study
J Bone Joint Surg, 1995, 77B:626
Prognosis in sciatica. A clinical follow-up of surgical and non-surgical treatment
Acta Orthop Scand, 1970, 129:Suppl
Handa T, Ishihara H, Ohshima H, Osada R, Tsuji H, Obata K
Effects of hydrostatic pressure on matrix synthesis and matrix metalloproteinase production in the human lumbar intervertebral disc
Spine, 1997, 22:1085
Hanley EN, Shapiro DE
The development of low-back pain after excision of a lumbar disc
J Bone Joint Surg, 1989, 71A:719
Harada Y, Nakahara S
A pathologic study of lumbar disc herniation in the elderly
Spine, 1989, 14:1020
Hayden JA, van Tulder MW, Tomlinson G
Systematic review. Strategies for using exercise therapy to improve outcomes in chronic low back pain
Ann Intern Med, 2005, 142:776
Heikkilä JK, Koskenvuo M, Heliövaara M, Kurppa K, Riihimäki H, Heikkilä K, Rita H, Videman T
Genetic and environmental factors in sciatica. Evidence from a nationwide panel of 9365 adult twin pairs
An Med, 1989, 21:393
Heliövaara M, Vanharanta H, Korpi J, Troup JD
Herniated lumbar disc syndrome and vertebral canals
Spine, 1986, 11:433
Occupation and risk of herniated lumbar intervertebral disk or sciatica leading to hospitalization
J Chron Dis, 1987, 40:259
Heliövaara M, Mäkelä M, Knekt P, Impivaara O, Aromaa A
Determinants of sciatica and low-back pain
Spine, 1991, 16:608
Hermantin FU, Peters T, Quartararo L, Kambin P
A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy
J Bone Joint Surg, 1999, 81A:958
Hickey DS, Hukins DW
Relation between the structure of the annulus fibrosus and the function and failure of the intervertebral disc
Spine, 1980, 5:106
Hirsch C, Schajowicz F
Studies on structural changes in the lumbar annulus fibrosus
Acta Orthop Scand, 1952, 22:184
Hukins DW, Meakin JR, Oxland TR, Frei H
The effect of nucleotomy on lumbar spine mechanics in compression and shear loading
Spine, 2002, 27:1126
Ikeda T, Nakamura T, Kikuchi T, Umeda S, Senda H, Takagi K
Pathomechanism of spontaneous regression of the herniated lumbar disc. Histologic and immunohistochemical study
J Spinal Disord, 1996, 9:136
Ito M, Incorvaia KM, Yu SF, Fredrickson BE, Yuan HA, Rosenbaum AE
Predictive signs of discogenic lumbar pain on magnetic resonance imaging with discography correlation
Spine, 1988, 23:1252
Ito T, Takano Y, Yuasa N
Types of lumbar herniated disc and clinical course
Spine, 2001, 26:648
Janssen ME, Bertrand Sl, Joe C, Levine MI
Orthopedics lumbar herniated disk disease. Comparison of MRI, myelography, and post-myelographic CT scan with surgical findings
Orthopedics, 1994, 17:121
Janssson KA, Németh G, Granath F, Blomqvist P
Surgery for herniation of a lumbar disc in Sweden between 1987 and 1999. An analysis of 27,576 operations
J Bone Joint Surg, 2004, 86B:841
Janssson KA, Németh G, Granath F, Jönsson B, Blomqvist P
Health-related quality of life in patients before and after surgery for a herniated lumbar disc
J Bone Joint Surg, 2005, 87B:959
Javid MJ, Nordby EJ, Ford LT, Hejna WJ, Whisler WW, Burton C, Millett DK, Wiltse LL, Widell EH Jr, Boyd RJ,
Newton SE, Thisted R
Safety and efficacy of chymopapain (Chymodiactin) in herniated nucleus pulposus with sciatica. Results of a randomized, double-blind study
J Amer Med Assoc, 1983, 249:2489
The role of vascular damage and fibrosis in the pathogenesis of nerve root damage
Clin Orthop Relat Res, 1992, 279:40
Jensen MC, Brant-Zawadzki MN, Obuchowski N, Modic MT, Malkasian D, Ross JS
Magnetic resonance imaging of the lumbar spine in people without back pain
N Engl J Med, 1994, 331:69
Jönsson B, Strömqvist B
Influence of age on symptoms and signs in lumbar disc herniation
Eur Spine J, 1995, 4:202
Kambin P, Casey K, O’Brien E, Zhou L
Transforaminal arthroscopic decompression of lateral recess stenosis
J Neurosurg, 1996, 84:462
Kambin P, Zhou L
History and current status of percutaneous arthroscopic disc surgery
Spine, 1996, 21(Suppl 24):57S
Kang JD, Georgescu HI, McIntyre-Larkin L, Stefanovic-Racic M, Donaldson WF 3rd, Evans CH
Herniated lumbar intervertebral discs spontaneously produce matrix metalloproteinases, nitric oxide, interleukin-6,
and prostaglandin E2
Katayama Y, Matsuyama Y, Yoshihara H, Sakai Y, Nakamura H, Nakashima S, Ito Z, Ishiguro N
Comparison of surgical outcomes between macro discectomy and microdiscectomy for lumbar disc herniation. A prospective randomized study with surgery performed by the same spine surgeon
J Spin Disord Tech, 2006, 19:344
Kawaguchi Y, Osada R, Kanamori M, Ishihara H, Ohmori K, Matsui H, Kimura T
Association between an aggrecan gene polymorphism and lumbar disc degeneration
Spine, 1999, 24:2456
Kelsey JL, Hardy RJ
Driving of motor vehicles as a risk factor for acute herniated lumbar intervertebral discs
Am J Epidemiol, 1975, 102:63
Klara PM, Ray CD
Artificial nucleus replacement. Clinical experience
Spine, 2002, 27:1374
Koike Y, Uzuki M, Kokubun S, Sawai T
Angiogenesis and inflammatory cell infiltration in lumbar disc herniation
Spine, 2003, 28:1928
Korge A, Nydegger T, Polard JL, Mayer HM, Husson JL
A spiral implant as nucleus prosthesis in the lumbar spine
Eur Spine J, 2002, 11(Suppl 2):S149
Korhonen T, Karppinen J, Paimela L, Malmivaara A, Lindgren KA, Bowman C, Hammond A, Kirkham B, Järvinen S,
Niinimäki J, Veeger N, Haapea M, Torkki M, Tervonen O, Seitsalo S, Hurri H
The treatment of disc-herniation-induced sciatica with infliximab. One-year follow-up results of FIRST II, a randomized controlled trial
Spine, 2006, 31:2759
Korhonen T, Karppinen J, Paimela L, Malmivaara A, Lindgren KA, Järvinen S, Niinimäki J, Veeger N, Seitsalo S, Hurri H
The treatment of disc herniation-induced sciatica with infliximab. Results of a randomized, controlled, 3-month follow-up study
Spine, 2005, 30:2724
Kozaci LD, Guner A, Oktay G, Guner G
Alterations in biochemical components of extracellular matrix in intervertebral disc herniation. Role of MMP-2 and TIMP-2 in type II collagen loss
Cell Biochem Funct, 2006, 24:431
Kraemer R, Wild A, Haak H, Herdmann J, Krauspe R, Kraemer J
Classification and management of early complications in open lumbar microdiscectomy
Eur Spine J, 2003, 12 :239
Krag MH, Seroussi RE, Wilder DG, Pope MH
Internal displacement distribution from in vitro loading of human thoracic and lumbar spinal motion segments:
experimental results and theoretical predictions
Spine, 1987, 12 :1001
Kurihara A, Kataoka O
Lumbar disc herniation in children and adolescents. A review of 70 operated cases and their minimum 5-year follow-up studies
Spine, 1980, 5:443
Kuslich SD, Ulstrom CL, Michael CJ
The tissue origin of low back pain and sciatica. A report of pain response to tissue stimulation during operations on the lumbar spine using local anesthesia
Orthop Clin North Am, 1991, 22:181
Lebkowski WJ, Dziecioł J
Degenerated lumbar intervertebral disc. A morphological study
Pol J Pathol, 2002, 53:83
Le Maitre CL, Freemont AJ, Hoyland JA
Localization of degradative enzymes and their inhibitors in the degenerate human intervertebral disc
J Pathol, 2004, 204:47
Lew SM, Mehalic TF, Fagone KL
Transforaminal percutaneous endoscopic discectomy in the treatment of far-lateral and foraminal lumbar disc
J Neurosurg, 2001, 94(Suppl 2):216
Lindblom K, Hultqvist G
Absorption of protruded disc tissue
J Bone Joint Surg, 1950, 32A:557
Lippitt AB Fracture of a vertebral body end plate and disk protrusion causing subarachnoid block in an adolescent
Clin Orthop Relat Res, 1976, 116:112
The centralization phenomenon. Its usefulness as a predictor or outcome in conservative treatment of chronic
low back pain (a pilot study)
Spine, 1995, 20:2513
Machado LA, de Sousa MS, Ferreira PH, Ferreira ML
The McKenzie method for low back pain. A systematic review of the literature with a meta-analysis approach
Spine, 2006, 31:E254
Maroon JC, Onik G
Percutaneous automated discectomy. A new method for lumbar disc removal. Technical note
J Neurosurg, 1987, 66:143
Masaryk TJ, Ross JS, Modic MT, Boumphrey F, Bohlman H, Wilber G
Am J Roentgenol, 1988, 150:1155
Transforaminal endoscopic microdiscectomy Neurosurg
Clin N Am, 1996, 7:59
Matsui H, Kanamori M, Ishihara H, Yudoh K, Naruse Y, Tsuji H
Familial predisposition for lumbar degenerative disc disease. A case-control study
Spine, 1998, 23:1029
Matsui H, Terahata N, Tsuji H, Hirano N, Naruse Y
Familial predisposition and clustering for juvenile lumbar disc herniation
Spine, 1992, 17:1323
McCombe PF, Fairbank JC, Cockersole BC, Pynsent PB
1989 Volvo Award in clinical sciences. Reproducibility of physical signs in low-back pain
Spine, 1989, 14:908
McKenzie RA The lumbar spine. Mechanical diagnosis and therapy
Spinal Publications Ltd, New Zealand, 1989
McNally DS, Adams MA, Goodship AE
Can intervertebral disc prolapse be predicted by disc mechanics?
Spine, 1993, 18:1525
Meakin JR, Hukins DWL
Effect of removing the nucleus pulposus on the deformation of the annulus fibrosus during compression of the intervertebral disc
J Biomech, 2000, 33:575
Meakin JR, Reid JE, Hukins DW
Replacing the nucleus pulposus of the intervertebral disc
Clin Biomech, 2001, 16:560
Mitchell PEG, Hendry NGC, Billewicz WZ
The chemical background of intervertebral disc prolapse
J Bone Joint Surg, 1961, 43B:141
Mixter WJ, Ayer JB
Herniation or rupture of the intervertebral disc into the spinal canal. Report of thirty-four cases
N Engl J Med, 1935, 213:385
Mixter WJ, Barr JS
Rupture of the intervertebral disc with involvement of the spinal canal
New Engl J Med, 1934, 211:210
Mochida J, Toh E, Nomura T, Nishimura K
The risks and benefits of percutaneous nucleotomy for lumbar disc herniation. A 10-year longitudinal study
J Bone Joint Surg, 2001, 83B:501
Exercises for back pain
In: Back Pain. New approaches to rehabilitation and education
Roland MO, Jenner JR (eds)
Manchester University Press, Manchester, 1989:50
Moneta GB, Videman T, Kaivanto K, Aprill C, Spivey M, Vanharanta H, Sachs BL, Guyer RD, Hochschuler SH,
Raschbaum RF, et al.
Reported pain during lumbar discography as a function of anular ruptures and disc degeneration. A re-analysis
of 833 discograms
Spine, 1994, 19:1968
Moore RJ, Vernon-Roberts B, Fraser RD, Osti OL, Schembri M
The origin and fate of herniated lumbar intervertebral disc tissue
Spine, 1996, 21:2149
Morgan G Jr, Mikhail M, Murray M
Pain management In: Clinical Anesthesiology (4th ed) McGraw-Hill, New York, 2002:3094
The myth of lumbar instability. The importance of abnormal loading as a cause of low back pain
Eur Spine J, 2008, 17:619
The load on lumbar disks in different positions of the body
Clin Orthop Relat Res, 1966, 45:107
Natarajan RN, Andersson GB, Patwardhan AG, Verma S
Effect of annular incision type on the change in biomechanical properties in a herniated lumbar intervertebral
J Biomech Eng, 2002, 124:229
The biophysical and biochemical aspects of intervertebral disc herniation and degeneration
Ann R Coll Surg Engl, 1962, 31:91
Neidlinger-Wilke C, Würtz K, Liedert A, Schmidt C, Börm W, Ignatius A, Wilke HJ, Claes L
A three-dimensional collagen matrix as a suitable culture system for the comparison of cyclic strain and hydrostatic pressure effects on intervertebral disc cells
J Neurosurg Spine, 2005, 2:457
Nerlich AG, Weiler C, Zipperer J, Narozny M, Boos N
Immunolocalization of phagocytic cells in normal and degenerated intervertebral discs
Spine, 2002, 27:2484
Nerubay J, Caspi I, Levinkopf M, Tadmor A, Bubis JJ
Percutaneous laser nucleolysis of the intervertebral lumbar disc. An experimental study
Clin Orthop Relat Res, 1997, 337:42
Nesti LJ, Li WJ, Shanti RM, Jiang YJ, Jackson W, Freedman BA, Kuklo TR, Giuliani JR, Tuan RS
Intervertebral disc tissue engineering using a novel hyaluronic acid–nanofibrous scaffold (HANFS) amalgam
Tissue Eng Part A, 2008, 14:1527
Nishimura K, Mochida J
Percutaneous reinsertion of the nucleus pulposus. An experimental study
Spine, 1998, 23:1531
Nomura T, Mochida J, Okuma M, Nishimura K, Sakabe K
Nucleus pulposus allograft retards intervertebral disc degeneration
Clin Orthop Relat Res, 2001, 389:94
O'Connell GD, Malhotra NR, Vresilovic EJ, Elliott DM
The effect of nucleotomy and the dependence of degeneration of human intervertebral disc strain in axial compression
Spine, 2011, 36:1765
Office of Health Economics
Okuma M, Mochida J, Nishimura K, Sakabe K, Seiki K
Reinsertion of stimulated nucleus pulposus cells retards intervertebral disc degeneration. An in vitro and in vivo experimental study
J Orthop Res, 2000, 18:988
Spinal nerve root compression. Nutrition and function of the porcine cauda equina compressed in vivo
Acta Orthop Scand Suppl, 1991, 242:1
Olmarker K, Rydevik B
Selective inhibition of tumor necrosis factor-alpha prevents nucleus pulposus-induced thrombus formation, intraneural edema, and reduction of nerve conduction velocity. Possible implications for future pharmacologic treatment strategies of sciatica
Spine, 2001, 26:863
Olmarker K, Rydevik B
Single- versus double-level nerve root compression. An experimental study on the porcine cauda equina with
analyses of nerve impulse conduction properties
Clin Orthop Relat Res, 1992, 279:35
Olmarker K, Rydevik B, Hansson T, Holm S
Compression-induced changes of the nutritional supply to the porcine cauda equina
J Spinal Disord, 1990, 3:25
Olmarker K, Rydevik B, Holm S
Edema formation in spinal nerve roots induced by experimental, graded compression. An experimental study on the pig cauda equina with special reference to differences in effects between rapid and slow onset of compression Spine, 1989, 14:569
Olmarker K, Rydevik B, Holm S, Bagge U
Effects of experimental graded compression on blood flow in spinal nerve roots. A vital microscopic study on the porcine cauda equina
J Orthop Res, 1989, 7:817
Onik G, Mooney V, Maroon JC, Wiltse L, Helms C, Schweigel J, Watkins R, Kahanovitz N, Day A, Morris J, McCullough JA, Reicher M, Croissant P, Dunsker S, Davis WG, Brown C, Hochschuler S, Saul T, Ray C
Automated percutaneous discectomy. A prospective multi-institutional study
Neurosurg, 1990, 26:228
Otani K, Arai I, Mao GP, Konno S, Olmarker K, Kikuchi S
Experimental disc herniation. Evaluation of the natural course
Spine, 1997, 22:2894
PernerA, Andersen JT, Juhler M
Lower urinary tract symptoms in lumbar root compression syndromes. A prospective survey
Spine, 1997, 22:2693
Petersen T, Kryger P, Ekdahl C, Olsen S, Jacobsen S
The effect of McKenzie therapy as compared with that of intensive strengthening training for the treatment of patients with subacute or chronic low back pain. A randomized controlled trial
Spine, 2002, 27:1702
Postacchini F, Lami R, Pugliese O
Familial predisposition to discogenic low-back pain. An epidemiologic and immunogenetic study
Spine, 1988, 13:1403
Variations in size of the bony lumbar canal in patients with prolapse of lumbar intervertebral discs
Clin Radiol, 1976, 27:301
Ramberg N, Sahlstrand T
Early course and long-term follow-up after automated percutaneous lumbar discectomy
J Spinal Disord, 2001, 14:511
Rantanen J, Hurme M, Falck B
The lumbar multifidus muscle five years after surgery for a lumbar intervertebral disc herniation
Spine, 1993, 18:568
Anatomy and pathology of the lumbar spine
In: The adult spine. Principles and practice
Frymoyer JW, Ducker TB, Hadler NM, Kostuik JP, Weinstein JN, Whitecloud III TS (eds)
Raven Press, New York, 1991:1465
Normal and pathologic anatomy of the lumbar root canals
Spine, 1987, 12:1008
Pathoanatomy of lumbar disc degeneration and stenosis
Acta Orthop Scand, 1993, Suppl 251:2
Surgical anatomy of the thoracic and lumbar spine
In: Manual of internal fixation of the spine
Thalgott JS, Aebi M (eds)
Lippincott-Raven Publishers, Philadelphia, 1996:9
The PDN Prosthetic disc-nucleus device
Eur Spine J, 2002, 11(Suppl 2):S137
Ren Y, Savill J Apoptosis. The importance of being eaten
Cell Death Differ, 1998, 5:563
Reyentovich A, Abdu WA
Multiple independent, sequential, and spontaneously resolving lumbar intervertebral disc herniations. A case report
Spine, 2002, 27:549
Rhee JM, Schaufele M, Abdu WA
Radiculopathy and the herniated lumbar disc. Controversies regarding pathophysiology and management
J Bone Joint Surg, 2006, 88A:2070
Richardson JK, Chung T, Schultz JS, Hurvitz E
A familial predisposition toward lumbar disc injury
Spine, 1997, 22:1487
Ricketson R, Simmons JW, Hauser BO
The prolapsed intervertebral disc. The high-intensity zone with discography correlation
Spine, 1996, 21:2758
Riley KP, Snowdon DA, Desrosiers MF, Markesbery WR
Early life linguistic ability, late life cognitive function, and neuropathology. Findings from the Nun study
Neurobiol Aging, 2005, 26:341
Motion of the lumbar spine with special reference to the stabilizing effect of posterior fusion. An experimental study on autopsy specimens
Acta Orthop Scand, 1966, Suppl 90:1-144
Saal JA, Saal JS, Herzog RJ
The natural history of lumbar intervertebral disc extrusions treated nonoperatively
Spine, 1990, 15:683
Saban KL, Penckofer SM, Androwich I, Bryant FB
Health-related quality of life of patients following selected types of lumbar spinal surgery. A pilot study
Health Qual Life Outcomes, 2007, 5:71
Saifuddin A, Braitwaite I, White J, Taylor BA, Renton P
The value of lumbar spine magnetic resonance imaging in the demonstration of anular tears
Spine, 1998, 23:453
Sasaoka R, Nakamura H, Konishi S, Nagayama R, Suzuki E, Terai H, Takaoka K
Objective assessment of reduced invasiveness in MED. Compared with conventional one-level laminotomy
Eur Spine J, 2006, 15:577
Sato M, Asazuma T, Ishihara M, Ishihara M, Kikuchi T, Kikuchi M, Fujikawa K
An experimental study of the regeneration of the intervertebral disc with an allograft of cultured annulus fibrosus cells using a tissue-engineering method
Spine, 2003, 28:548
Recognition and phagocytosis of cells undergoing apoptosis
Br Med Bull, 1997, 53:491
Failed back surgery syndrome. The role of symptomatic segmental single-level instability after lumbar microdiscectomy
Eur Spine J, 2004, 13:193
Schechtman H, Robertson PA, Broom ND
Failure strength of the bovine caudal disc under internal hydrostatic pressure
J Biomech, 2006, 39:1401
Schmidt H, Kettler A, Heuer F, Simon U, Claes L, Wilke HJ
Intradiscal pressure, shear strain, and fiber strain in the intervertebral disc under combined loading
Spine, 2007, 32:748
Schmidt H, Kettler A, Rohlmann A, Claes L, Wilke HJ
The risk of disc prolapses with complex loading in different degrees of disc degeneration. A finite element analysis
Clin Biomech, 2007, 22:988
Shock NW, Greulich RC, Costa PT Jr, Reubin A, Lakatta EG, Arenberg D, Tobin JD
Normal human aging. The Baltimore longitudinal study on aging
NIH Publication, Washington DC, 1984
Simunic DI, Broom ND, Robertson PA
Biomechanical factors influencing nuclear disruption of the intervertebral disc
Spine, 2001, 26:1223
Enzyme dissolution of the nucleus pulposus in humans
J Amer Med Assoc, 1964, 187:137
The lumbar disc herniation. A computer-aided analysis of 2,504 operations
Acta Orthop Scand (Suppl), 1972, 142:1
Stolke D, Sollmann WP, Seifert V
Intra- and postoperative complications in lumbar disc surgery
Spine, 1989, 14:56
Schwarzer AC, Aprill CN, Derby R, Fortin J, Kine G, Bogduk N
The prevalence and clinical features of internal disc disruption in patients with chronic low back pain
Spine, 1995, 20:1878
Tanaka M, Nakahara S, Inoue H
A pathologic study of discs in the elderly. Separation between the cartilaginous endplate and the vertebral body
Spine, 1993, 18:1456
Tashiro Y, Nishida C, Sato-Kusubata K et al.
Inhibition of PAI-1 induces neutrophil-driven neoangiogenesis and promotes tissue regeneration via production of angiocrine factors in mice
Blood, 2012, 119:6382
Teplick JG, Haskin ME
Spontaneous regression of herniated nucleus pulposus
Am J Roentgenol, 1985, 145:371
Biomechanics of the lumbar spinal canal
Clin Biomech, 1986, 1:31
Straight-leg-raising (SLR) and the qualifying tests for increased root tension
Spine, 1981, 6:526
Trout JJ, Buckwalter JA, Moore KC
Ultrastructure of the human intervertebral disc. II. Cells of the nucleus pulposus
Anat Rec, 1982, 204:307
Tyas SL, Snowdon DA, Desrosiers MF, Riley KP, Markesbery WR
Healthy ageing in the Nun study. Definition and neuropathologic correlates
Age Ageing, 2007, 36:650
Vad VB, Bhat AL, Lutz GE, Cammissa F
Transforaminal epidural steroid injections in lumbosacral radiculopathy
Spine, 2002, 27:11
van Tulder MW, Koes B, Malmivaara A
Outcome of non-invasive treatment modalities on back pain. An evidence-based review
Eur Spine J, 2006, 15 (Suppl 1):S64
Varlotta GP, Brown MD, Kelsey JL, Golden AL
Familial predisposition for herniation of a lumbar disc in patients who are less than twenty-one years old
J Bone Joint Surg, 1991, 73A:124
A radicular syndrome from developmental narrowing of the lumbar vertebral canal
J Bone Joint Surg, 1954, 36B:230
Further experiences on the pathological influence of a developmental narrowness of the bony lumbar vertebral canal
J Bone Joint Surg, 1955, 37B:576
Virri J, Sk S, Grönblad M, Tolonen J, Seitsalo S, Kankare J, Karaharju EO
Concomitant immunocytochemical study of macrophage cells and blood vessels in disc herniation tissue
Eur Spine J, 1994, 3:336
A new clinical model for the treatment of low-back pain. 1987 Volvo award in clinical sciences
Spine, 1987, 12:632
Waddell G, Morris EW, Di Paola MP, Bircher M, Finlayson D
A concept of illness tested as an improved basis for surgical decisions in low-back disorders
Spine, 1986, 11:712
1982 Volvo award in clinical science. Lumbar disc herniation. A controlled, prospective study with ten years of observation
Spine, 1983, 8:131
Weidner N, Rice DT
Intervertebral disk material. Criteria for determining probable prolapse
Hum Pathol, 1988, 19:406
Weiler C, Nerlich AG, Bachmeier BE, Boos N
Expression and distribution of tumor necrosis factor alpha in human lumbar intervertebral discs. A study in surgical
specimen and autopsy controls
Spine, 2005, 30:44
Weinstein JN, Lurie JD, Tosteson TD, Skinner JS, Hanscom B, Tosteson ANA, Herkowitz H, Fischgrund J, Cammisa FP,
Albert T, MD, Deyo RA
Surgical vs nonoperative treatment for lumbar disk herniation. The Spine Patient Outcomes Research Trial (SPORT) Observational Cohort
J Amer Med Assoc, 2006, 296:2451
Weinstein JN, Lurie JD, Tosteson TD, Tosteson AN, Blood EA, Abdu WA, Herkowitz H, Hilibrand A, Albert T, Fischgrund J
Surgical versus nonoperative treatment for lumbar disc herniation: four-year results for the Spine Patient Outcomes Research Trial (SPORT)
Spine, 2008, 33:2789
Weinstein JN, Tosteson TD, Lurie JD, Tosteson ANA, Hanscom B, Skinner JS, Abdu WA, Hilibrand AS, Boden SD, Deyo RA
Surgical vs nonoperative treatment for lumbar disk herniation. The Spine Patient Outcomes Research Trial (SPORT). A randomized trial
J Amer Med Assoc, 2006, 296:2441
Weishaupt D, Zanetti M, Hodler J, Boos N
MR imaging of the lumbar spine. Prevalence of intervertebral disk extrusion and sequestration, nerve root
compression, end plate abnormalities, and osteoarthritis of the facet joints in asymptomatic volunteers
Radiology, 1998, 209:661
Wera GD, Marcus RE, Ghanayem AJ, Bohlman HH
Failure within one year following subtotal lumbar discectomy
J Bone Joint Surg, 2008, 90A:10
Werneke M, Hart DL, Cook D
A descriptive study of the centralization phenomenon. A prospective analysis
Spine, 1999, 24:676
Wilder DG, Pope MH, Frymoyer JW
The biomechanics of lumbar disc herniation and the effect of overload and instability
J Spinal Disord, 1988, 1:16
Wilke HJ, Heuer F, Neidlinger-Wilke C, Claes L
Is a collagen scaffold for a tissue engineered nucleus replacement capable of restoring disc height and stability in an animal model?
Eur Spine J, 2006, 15(Suppl 3):S433
Wilke HJ, Kavanagh S, Neller S, Haid C, Claes LE
Effect of a prosthetic disc nucleus on the mobility and disc height of the L4-5 intervertebral disc postnucleotomy
Neurosurg, 2001, 95(Suppl 2):208
Winston K, Rumbaugh C, Colucci V
The vertebral canals in disc disease
Spine, 1984, 9:414
Wognum S, Huyghe JMRJ, Baaijens FPT
Influence of osmotic pressure changes on the opening of existing cracks in two intervertebral disc models
Spine, 2006, 31:1783
Wu X, Zhuang S, Mao Z, Chen H
Microendoscopic discectomy for lumbar disc herniation. Surgical technique and outcome in 873 consecutive cases
Spine, 2006, 31:2689
What is comparative effectiveness research?
Answers to frequently asked questions by the agency for healthcare research and quality
Yasuma T, Arai K, Yamauchi Y
The histology of lumbar intervertebral disc herniation. The significance of small blood vessels in the extruded tissue
Spine, 1993, 18 :1761
Yasuma T, Makino E, Saito S, Inui M
Histological development of intervertebral disc herniation
J Bone Joint Surg, 1986, 68A:1066
Yeung AT, Tsou PM
Posterolateral endoscopic excision for lumbar disc herniation. Surgical technique, outcome, and complications in
307 consecutive cases Spine, 2002, 27:722 Yorimitsu E, Chiba K, Toyama Y, Hirabayashi K Long-term outcomes of standard discectomy for lumbar disc herniation. A follow-up study of more than 10 years
Spine, 2001, 26:652
Yukawa Y, Kato F, Matsubara Y, Kajino G, Nakamura S, Nitta H
Serial magnetic resonance imaging follow-up study of lumbar disc herniation conservatively treated for average 30
months. Relation between reduction of herniation and degeneration of disc
J Spinal Dis, 1996, 9:251
Yu SW, Haughton VM, Sether LA, Wagner M
Anulus fibrosus in bulging intervertebral disks
Radiology 1988, 169:761
Yu SW, Sether LA, Ho PS, Wagner M, Haughton VM
Tears of the anulus fibrosus. Correlation between MR and pathologic findings in cadavers
AM J Neuradiol, 1988, 9:367