Discogenic low back pain is a common cause of disability, but its pathogenesis is poorly understood. We collected 19 specimens of lumbar intervertebral discs from 17 patients with discogenic low back pain during posterior lumbar interbody fusion, 12 from physiologically ageing discs and ten from normal control discs. We investigated the histological features and assessed the immunoreactive activity of neurofilament (NF200) and neuropeptides such as substance P (SP) and vasoactive-intestinal peptide (VIP) in the nerve fibres. The distinct histological characteristic of the painful disc was the formation of a zone of vascularised granulation tissue from the nucleus pulposus to the outer part of the annulus fibrosus along the edges of the fissures. SP-, NF- and VIP-immunoreactive nerve fibres in the painful discs were more extensive than in the control discs. Growth of nerves deep into the annulus fibrosus and nucleus pulposus was observed mainly along the zone of granulation tissue in the painful discs. This suggests that the zone of granulation tissue with extensive innervation along the tears in the posterior part of the painful disc may be responsible for causing the pain of discography and of discogenic low back pain

1. Compression forces are mainly absorbed by the vertebral body. The nucleus pulposus, being liquid, is incompressible. The tense annulus bulges very little. On compression the vertebral end-plate bulges and blood is forced out of the cancellous bone of the vertebral body into the perivertebral sinuses. This appears to be the normal energy-dissipating mechanism on compression. 2. The normal disc is very resistant to compression. The nucleus pulposus does not alter in shape or position on compression or flexion. It plays no active part in producing a disc prolapse. On compression the vertebral body always breaks before the normal disc gives way. The vertebral end-plate bulges and then breaks, leading to a vertical fracture. If the nucleus pulposus has lost its turgor there is abnormal mobility between the vertebral bodies. On very gentle compression or flexion movement the annulus protrudes on the concave aspect–not on the convex side as has been supposed. 3. Disc prolapse consists primarily of annulus; it occurs only if the nucleus pulposus has lost its turgor. It then occurs very easily as the annulus now bulges like a flat tyre. 4. I have never succeeded in producing rupture of normal spinal ligaments by hyperextension or hyperflexion. Before rupture occurs the bone sustains a compression fracture. On the other hand horizontal shear, and particularly rotation forces, can easily cause ligamentous rupture and dislocation. 5. A combination of rotation and compression can produce almost every variety of spinal injury. In the cervical region subluxation with spontaneous reduction can be easily produced by rotation. If disc turgor is impaired this may occur with an intact anterior longitudinal ligament and explains those cases of tetraplegia without radiological changes or a torn anterior longitudinal ligament. The anterior longitudinal ligament can easily be ruptured by a rotation force and in my experience the so-called hyperextension and hyperflexion injuries are really rotation injuries. 6. Hyperflexion of the cervical spine or upper thoracic spine is an anatomical impossibility. In all spinal dislocations a body fracture may or may not occur with the dislocation, depending upon the degree of associated compression. In general, rotation forces produce dislocations, whereas compression forces produce fractures

1. The normal anatomy of the intervertebral disc of immature rabbits is described. 2. An account is given of the changes that occur after an operative incision in the ventral part of the intervertebral discs of rabbits which allowed the escape of the nucleus pulposus. The account is based on observations made on fifty-five young animals killed at intervals during the twenty-five months after operation. 3. The superficial part of the wound in the annulus heals rapidly by active fibrosis. Thereafter there is a chondrification of the ventral region of the disc, followed by ossification. A prominent bony ridge ultimately ankyloses the vertebrae adjoining the disc. 4. The site of the nucleus pulposus is eventually occupied by a dense pad of fibrocartilage. A tongue of this tissue projects into the deep median part of the wound which remains unhealed. 5. A hypothesis is submitted regarding the mechanism of rupture of the annulus fibrosus and prolapse of the nucleus pulposus in man; this hypothesis is based in part on the observations of lesions in discs not subjected to operation

Magnetic resonance imaging (MRI) was used to compare the appearance of the spine in 20 adolescents with proven symptomatic intervertebral disc herniations with that in 20 asymptomatic patients who acted as controls. Abnormality in the signal from the nucleus pulposus of one or more discs was present in all patients, while only four of the 20 controls had any abnormal signals. In all the patients the symptomatic disc produced an abnormal signal and in most a herniated fragment of the nucleus pulposus was identified. Fifteen of the 20 patients had multiple-disc abnormality: six had three abnormal discs and nine had two. This suggests there was an underlying diathesis in patients who later developed disc herniation

1. A hypothesis outlining an auto-immune mechanism for antibody production against autogenous nucleus pulposus is presented. 2. Auto-antibodies to autogenous nucleus pulposus have been experimentally produced in rabbits. 3. These antibodies are cell-bound within lymphoid cells and are greatest in primary lymph nodes. This antibody is demonstrated by a positive pyronin reaction. 4. Lymphoid cells fixed in Carnoy's fluid and stained for pyronins also show a distinct natural yellow fluorescence. This fluorescence occurs only in the cytoplasm of those cells which are pyronin-positive and presumably producing antibody. 5. The lymph node phase of the reaction is greatest at four days and is sustained for three weeks. A secondary generalised lymph node response occurs in all lymph nodes at six weeks

We studied the presence of anabolic growth factors in human herniated intervertebral discs (IVD) using a reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. Messenger RNA (mRNA) was isolated from the nucleus pulposus using oligo (dT). 25. superparamagnetic beads and probing with gene-specific primers in RT-PCR. mRNA coding for TGF-α (3/10), EGF (0/10), TGF-β1 (0/10) and TGF-β3 (2/10) or the EGF receptor (EGF-R; 0/10) and TGF-β type-II receptor (0/10) was found only occasionally. Beta-actin was always present and positive sample controls confirmed the validity of the RT-PCR assay. These RT-PCR findings were confirmed using immunohistochemical staining of EGF and TFG-β, whereas TGF-α protein was always found associated with discocytes. We conclude that the nucleus pulposus of the herniated IVD is vulnerable to proteolytic degradation and depletion of proteoglycans due to the lack and/or low production of anabolic growth factors/receptors which could increase the local synthesis of the extracellular matrix

Percutaneous nucleotomy is a relatively new technique for treating lumbar disc herniation. There is no agreement as to the volume of disc material to be removed. A long-term study of clinical and radiological data from patients treated by percutaneous nucleotomy was designed to identify the factors associated with favourable and unfavourable outcomes. We studied 42 patients for at least ten years; the mean follow-up was 10.9 years. They were divided into two subgroups to assess the value of preserving the nucleus pulposus in the central area of the disc. The overall success rate for both subgroups was 50%. A decrease in disc height on plain radiography and a decrease in signal intensity on MRI were observed more infrequently in patients in whom the nucleus pulposus in the central area of the disc had been preserved, than in those in whom it had been extensively removed. These adverse radiological findings correlated closely with increased low back pain during the first one to two years after operation and a poorer overall outcome. We conclude that percutaneous nucleotomy is most likely to be successful when the central area of the disc is preserved

1. In this investigation one was impressed by the close relationship that exists between the constituent parts of the intervertebral discs and the surrounding supporting structures. The part that is responsible for the maintenance of a co-ordinated balance between these structures, and hence for the effective mechanism of the spine, is the nucleus pulposus. 2. The cruciate arrangement of the annulus fibrosus is related to spinal function, and the angle of intersection of consecutive laminae of the annulus fibrosus is more or less constant. 3. In the Bantu it was found that the interspinous and supraspinous ligaments differ from the classical descriptions given in anatomical text-books. 4. The movements taking place between two vertebrae are comparable to those of a rocking-horse. 5. Narrowing of a disc is a progressive process which is the result of the disturbances in the balance between the components of the force to which a disc is subjected. The process is initiated by the loss of nucleus pulposus content. 6. With the approximation of two adjacent vertebrae a disturbance of the relations of the structures in the intervertebral foramen was noted. On anatomical grounds, when a disc is narrowed it appears that the most likely structures to cause pressure on the nerve root are not the disc itself, but the superior articular processes with their overlying ligamentum flavum

The anatomical studies, basic to our understanding of lumbar spine innervation through the sinu-vertebral nerves, are reviewed. Research in the 1980s suggested that pain sensation was conducted in part via the sympathetic system. These sensory pathways have now been clarified using sophisticated experimental and histochemical techniques confirming a dual pattern. One route enters the adjacent dorsal root segmentally, whereas the other supply is non-segmental ascending through the paravertebral sympathetic chain with re-entry through the thoracolumbar white rami communicantes. Sensory nerve endings in the degenerative lumbar disc penetrate deep into the disrupted nucleus pulposus, insensitive in the normal lumbar spine. Complex as well as free nerve endings would appear to contribute to pain transmission. The nature and mechanism of discogenic pain is still speculative but there is growing evidence to support a ‘visceral pain’ hypothesis, unique in the muscloskeletal system. This mechanism is open to ‘peripheral sensitisation’ and possibly ‘central sensitisation’ as a potential cause of chronic back pain

1. The technique of nucleography, in which a radio-opaque watery solution of iodine is injected into the nucleus pulposus for contrast-radiography, is described. 2. The merits of the procedure in demonstrating the shape and condition of nucleus are discussed

A description is given of a mutation in the mouse which reduces the size of the nucleus pulposus in the intervertebral disc of the adults. The discs of these mice show greatly accelerated age changes. The consequences of a similar mutation in man are discussed

One hundred and twenty-seven cases of intervertebral disc calcification in children, including 11 previously unreported cases, have been analysed. A distinction is made between symptomatic and asymptomatic patients, whose age, sex and spinal distributions of the calcifications have been shown to differ. Radiologically detectable protrusions and later resorption of the calcifications are common events in symptomatic children, but are unrecorded in asymptomatic children. The spinal distribution of paediatric calcifications is quite different to that of adult and canine calcifications of the nucleus pulposus

A prospective study of 480 patients who underwent enzymatic dissolution of the nucleus pulposus with chymopapain is reported. Seventy per cent of patients with the clincial criteria for a disc herniation had a favourable response to chemonucleolysis. The commonest cause of failure was persistent back pain. In patients with sequestered discs or lateral recess stenosis surgical intervention was not made more difficult by chemonucleolysis. Those with a previous operation, spinal stenosis or psychogenic components to the disability had very poor results. Complications were few and easily managed

By polarising microscope and x-ray crystallographic techniques the annulus fibrosus has been shown to consist of regularly oriented sheets of collagen fibres. These results have been interpreted in terms of an elastic mechanism whereby thrust from the nucleus causes increased girth in the annulus. It is suggested that this is accomplished by a change in the angle between the axis of the fibres in adjacent uniaxial layers of the annulus. Furthermore, the loss of elasticity of the intervertebral disc associated with age would seem to be mainly due to changes occurring in the nucleus pulposus

We reviewed the magnetic resonance (MR) images of eight adults with acute hyperextension-dislocation of the cervical spine. The images were obtained to evaluate damage to the spinal cord. All eight patients had disruption of the anterior longitudinal ligament and of the annulus of the intervertebral disc, and separation of the posterior longitudinal ligament from the subjacent vertebra. Some, but not all, showed widening of the disc space, posterior bulging or herniation of the nucleus pulposus, and disruption of the ligamentum flavum. The MR demonstration of these ligament injuries, taken with the clinical and radiographic findings, establishes the mechanism of hyperextension-dislocation, confirms the diagnosis, and is relevant to management

1. As a result of degenerative changes in the intervertebral disc, nuclear tissue often herniates through its confining structures. These lesions are common, even in children, and often lead to difficulty in diagnosis. 2. The radiological manifestations of nuclear herniations into the spongiosa of the vertebral body, through the anterior part of the annulus fibrosus, beneath the epiphysial ring, and through the posterior part of the annulus are described and illustrated. The clinical significance of these radiological appearances and their pathological basis is indicated. 3. An understanding of the significance of the radiological findings in herniation of the nucleus pulposus and a careful correlation with the clinical features of the case are necessary for accurate diagnosis

The follow-up of these seventy-three cases suggested the following conclusions:. 1. The clinical signs alone are not always sufficient to make the diagnosis of herniated nucleus pulposus with sufficient accuracy. 2. When positive, myelography was reliable as a means of localising the hernia. 3. In doubtful cases in which conservative treatment failed a clearly positive myelography turned the scale for a well-indicated operation. 4. In doubtful cases a clearly negative myelography has often rightly been a contra-indication for laminectomy. 5. No serious complication from the use of water-soluble contrast medium for myelography has been encountered

The role of antibiotics in the treatment of disc-space infection is controversial. This study assessed the tissue penetration of flucloxacillin and cephradine into the normal intervertebral disc after intravenous administration of a bolus dose of antibiotic. Twenty-five discs were removed from 12 adolescent patients having anterior spinal surgery to correct scoliosis; antibiotic had been administered between 30 minutes and four hours before operation. Despite high blood levels, no antibiotic could be detected by bioassay or by high-pressure liquid chromatography (h.p.l.c.) in any of the specimens from the nucleus pulposus or the annulus fibrosus

A series of experiments showing how posture affects the lumbar spine is reviewed. Postures which flatten (that is, flex) the lumbar spine are compared with those that preserve the lumbar lordosis. Our review shows that flexed postures have several advantages: flexion improves the transport of metabolites in the intervertebral discs, reduces the stresses on the apophyseal joints and on the posterior half of the annulus fibrosus, and gives the spine a high compressive strength. Flexion also has disadvantages: it increases the stress on the anterior annulus and increases the hydrostatic pressure in the nucleus pulposus at low load levels. The disadvantages are not of much significance and we conclude that it is mechanically and nutritionally advantageous to flatten the lumbar spine when sitting and when lifting heavy weights

We studied 135 lumbar discs from 27 spines removed post-mortem from subjects of an average age of 31.5 years. Defects of the annulus fibrosus were classified as peripheral, circumferential or radiating; the nucleus pulposus as normal, moderately or severely degenerate. Peripheral tears were more frequent in the anterior annulus, except in the L5-S1 disc. Circumferential tears were equally distributed between the anterior and the posterior annulus. Almost all the radiating tears were in the posterior annulus, and closely related to the presence of severe nuclear degeneration. Histology suggested that peripheral tears were due to trauma rather than biochemical degradation, and that they developed independently of nuclear degeneration. The association of peripheral annular lesions with low back pain is uncertain but our study suggests that they may have a role in the pathogenesis of discogenic pain