ANEXOS
Anexo 02 MAESTRÍA EN ADMINISTRACION EDUCATIVA
V.- CALIFICACIÒN
In the massive literature on this subject, the greater majority of contributors have concerned themselves with the lumbar discs, and because of the importance of patho
logical change in all tissues of this spinal region, the changes occurring in thoracic and cervical interbody joints are described under 'Regional variations of combined degenerative change' (pp. 1 25, 1 35).
Like other tissue, most discs degenerate to a greater or lesser degree. They:
I. Desiccate and may lose turgidity
2. May form combined osseocartilaginous bars pos
teriorly, with exostosis of adjacent vertebral body marginsl17
3. Develop concentric or circumferential tears between laminae of the posterolateral annulus, and radial tears be
ginning at the nucleus and inner annulusJ2tJ
4. Partially disrupt their annular attachments together with portions of hyaline cartilaginous plate780
5. Herniate up and/or down into the spongiosa of ver
tebral body (microscopically and macroscopically)'O"
6. Be themselves invaded by vascular tissue from the spongiosa 1044
7. Undergo internal disruption or isolated resorption, and be slowly ground into rubble'"
8. Develop a vacuum or gas within the disctJ07.b68 9. Become calcifiedll5
10. Bulge into the neural canal70, '52,818,820. 1)71
I I . Extrude nuclear pulp into the same space either as a pedunculated mass, a sequestrum or a massive escape (burst) of nuclear contents together with rupture of the posterior longitudinal ligament.608
With the exception of the last-named, the relationship between these events and clinical evidence of their pre
sence is by no means direct.
That the intervertebral disc and the vertebral bodies de
velop, grow and age together has been emphasised by indolent clinical workers to consider the disc as an impor
tant interposed washer between unimportant vertebral bodies.
A clear distinction between intervertebral disc degeneration and intervertebral disc disease remains to be established, albeit our detailed knowledge of the physical and biochemical changes increases almost weekly.4.49Q.II08.
892. 1270 The vertebral column undergoes a fairly predictable sequence of morphological changes from infancy to old age but by no means do all individuals showing these changes suffer significant spinal pain or disability.
Our essential mode of distinction, between ageing and
disease, remains that of clinical criteria, and even this dis
tinction is blurred by the fac t that an individual with demonstrable vertebral changes and painful disability is very frequently relieved of symptoms and signs while the vertebral changes persist and slowly multiply.o98
Sciatica was first described by the early Greek and Roman physicians. However, it was not related to dysfunction of the sciatic nerve until 1764, when Domenico Cotugno of Naples published his De Ischiade Nervosa Comme,llarills. Irritation of the sciatic nerve and its component nerve roots was subsequently found to result from different underlying conditions, such as spi
nal arthritis, intraspinal and extraspinal neoplasms, and spondylo
listhesis. More recemly, it became apparent that sciatica is often caused by nerve root compression from a herniated nucleus pul
posus of a lumbar intervertebral disc. 1)14
Although the first disc lesion ( 1 893) to be described had occurred in a dog and was reported by a veterinary sur
geon,'" Nachemson ( 1976) observed,
. . . we have our heritage from Doctor Barr of Bosran who, one Sunday morning in 1932 in the Pathology Laboratory of Massa
chusetts General Hospital, was the first person to understand that the material recently removed from one of his patients as chon
droma was in reality a disc hernia. He solved one important part of the low-back pain problem, but, as we all know by now, it was only a minor part. 889b
Wyke ( 1976)'''' considers it should be emphasised (contrary to popular impression) that less than 5 per cent of patients with backache have prolapsed intervertebral discs ; about three-quarters of the small handful affiicted in this way will have backache as the initial symptom. This leaves only the occasional patient representing that group whose pain will begin in haunch or lower limb, without backache.
Following the papers of Goldthwait,'" Dandy,'" and more especially Mixter and Barr861 there has been an ava
lanche of published material on the intervertebral disc ; an estimated 3000 papers have appeared since the war, i.e.
more than 100 a year, or 2 every week. In the face of this inexorable How, it is understandable that a senior ortho
paedic surgeon should have been moved to observe, .. . have found in the intervertebral disc not a jelly-like nucleus but a glittering nugget of gold.9N
For a long time it has been evident that the attention of the medical profession in general has been mesmerized by the dis
covery of the radiologically visible gross changes in intervertebral discs associated with regional spinal disorders, in some cases to the point at which some medical men seemed to have regarded a pain in the back and the word 'disc' as synonymous. It is of course evident that there are many Structures in the spine in which pain can arise. 1 100
A commonly expressed regret of orthopaedic and neurosurgeons is the wide discrepancy between much of what is said and written about the disc and what is actually observed by them during open surgical procedures. I t also
PATHOLOGICAL CHANGES-GENERAL 89 becomes very difficult to remember that there are other equally important articular tissues in the spinal column.445 ... In the same year, Mixter and Barr published their pioneer
ing paper in the widely read New England Journal of Medicille and brought to medical anemion ruptured discs, which for the next decade and a half after 1934 were thought by many to explain just about everything abnormal in the lower spine. 1 }()()
Sunderland ( 1978)"04 has summarised the changing approach to common vertebral joint problems as follows : When investigating the problem oflow back pain, one cautions against concentrating exclusively on the intervertebral disc as the site of the offending lesion lest this obscure the significance of aetiological factors originating elsewhere in the vicinity. In this respect the passage of the medial branch of the lumbar dorsal ramus and its accompanying vessels through an osseo-fibrous tunnel and the intimate relationship of this neurovascular bundle to the capsule of the apophyseal joint represents a potemial site of fixation and entrapment following pathological changes involv
ing the joint.
The observations of Arnoldi (I972)" are relevant, . . . Pain in the lumbar area can originate in a number of different structural elements, and if we except the apparently clear-cut syn
dromes with nerve root affection caused by disc herniation we can
not say that our understanding has gained substantially from the impressive pool of detailed information.
There is no clinical sign, nor combination of signs, which prove diagnostic of a disc protrusion, other than the signs of a space-occupying lesion.'" Radiographically demonstrated lumbar disc 'lesions', for example, and demonstration by epidurography that alterations in the profile of disc 'lesions' may be produced by rotatory manipulation and/or traction,8l7, 1171 provide interesting corroboration of the ordinary physical changes these pro
cedures might be expected to produce, since discs are sub
ject to physical laws like everything else, yet this does not dispose of our difficulties of confidently ascribing the cause of clinical manifestations, with any real certainty, to changes in a particular tissue.
Barker (1977)" describes the incidence of back prob
lems in a general practice with 3000 patients, and a con
sultation rate of about 10 000 per year; musculoskeletal and connective tissue disorders accounted for some 750 consultations annually. About one-third of these were concerned specifically with complaints of back and leg pain. Over a 2-year period, the data on all patients with back and leg pain were recorded in a standardised way, i.e. 1 97 cases, and it was suggested by the investigator that the intervertebral disc could account for only a small pro
portion of these problems.
Brown (1971)1]7 reminds us that even more perplexing is the circumstance that enucleation of an intervertebral disc relieves the syndrome of low back pain and sciatica when true mechanical impingement of the nerve rOOt is not evident during surgery.
90 COMMON VERTEBRAL JOINT PROBLEMS
One of the earlier (and perhaps the fullest) accounts of intervertebral disc pathology presented in British litera
ture was that made by Beadle (1931).76 in which he de
scribed and illustrated the now classic image of posterior or posterolateral bulges in the dorsal aspect of (he longi
(udinal ligamenr, this perhaps leading to the common con
cept that nuclear protrusion represents a breach at about the middle of the annulus with extrusion of nuclear material through the breach. Thjs is not necessarily COf
rect/so very frequently the essential physical damage is that to the hyaline cartilage plate, a detached segment of which slides or is shifted centrifugally under traction exerted by intact annular fibres, themselves under tension of stress produced by flexion, rotation and compression forces upon a tissue-system in which concentric annular disruption has very probably already begun.
Degenerative changes (see 'Applied anatomy', p. 18) The nature of structural disturbance of the disc is more complex and varied than is sometimes conveyed by simple diagrams and by the hydrostatic theory of disc pro
trusion. )20
. . . the word <disc' has been used so loosely as to lose all clinical and pathological significance.78o
The physical properties of intervertebral discs have been conceived as depending mainly upon the water
binding capacity of the nuclear pulp, the hydration of the nucleus being predominantly due to the imbibition pressure exerted by the mucopolysaccharide gel. '" Nor
mal function of the disc has been observed to require the presence of a fluid nuclear gel to distribute pressure evenly, together with the tensile strength and elastic prop
erties of the pulp-retaining annulus fibrosus, which does contain elastic fihres. 1J9 The gel distributes the pressure
put upon it in an isotropic manner.
With ageing, the soluble polymer content slowly pre
cipitates to form a collagen matrix, and isotropy decreases with the diminution of gel viscosity.499 Ageing is accom
panied by a gradual increase in the collagen content of the pulposus and this takes place at the expense of the gel structures. The lessening of the degree of hydration from early life is progressive, a gel water-content of almost 90 per cent in children slowly decreasing to about 70 per cent in later life. There is generally a sharp rise in severity of degenerative changes in the fifth decade, among those mature people who do come to the notice of clinicians.
Degenerative changes usually become visible in the nucleus before the age of 20, but whether these are evi
dence of normal age involution or pathological degenera
tion is not certain.'" Hirsch and Schajowicz ( 1 953)'" de
scribed changes recognisable as early as the 14th year, apparent as concentric cracks and fissures occurring more commonly in the posterior annulus of the lower two lumbar levels.
Splitting and cleft formation in discs are frequently the
artefacts of preparation for pathological examination 1270 but these should not be compared with the macroscopic evidence of annular separations following torsionaJ stresses applied to fresh cadaver material. Farfan (1973)'" reported disc degeneration, presumably trau
matic in origin, in an 8-year-old boy, and there are many reports of disc prolapse in children, adolescents and young aduits,77.2?6. 322,4 )5.929,I066 yet Farfan also observed that nor
mal discs may be found at autopsy in patients of 80, 90 or over. I n many instances, these discs have experiment
ally been subjected to compression and torsional loads, and they behave in a manner indistinguishable from younger discs ; injections under high pressure failed to show any annular damage or end-plate fractures.
As degenerative change proceeds:
J. The borders between pulp and annulus begin to become less definable and islands of cartilage cells begin to appear among the now more fibrous pulp. In the later stages of disc ageing the collagen of the nucleus and that of the inner annulus tend to coalesce ; separation of the two elements becomes more difficult.499
2. The annulus progressively loses its elasticity as its cartilage content increases.
3. Degeneration of disc tissue appears to be accelerated if the disc becomes vascularised, as may happen when car
tilage end-plates are damaged. Trespass into the disc by vascular tissue, through the previously closed apertures in the cartilaginous end plates, has been described by Ritchie and Farhni ( 1970)."" The more central nucleus becomes typically discoloured, 'brown degeneration', believed in the past to be due to blood pigments from small haemorrages of spongiosa vessels penetrating through minute defects in the hyaline cartilage plate. This 'brown degeneration' is usually associated with a desiccated and friable consistency of the nuclear pulp. 1270 In elderly discs, sites of previous tears are frequently occupied by fibrovas
cular tissue, providing evidence of previous disruption and of repair processes. 194, 195,508
4. Concentric or circumferential tears in the peripheraJ annulus, as separations of the annular laminae, notably in the posterolateral part of the disc, become evident before the more central radiating fissures begin to track outwards through the peripheral nucleus and inner laminae of the annulus. 1044 Lateral or anterior ruptures are probably rare.I27O Fragmentation and disruption of the disc have commenced ; thus the nucleus pulposus, with the retain
ing annulus, cannot act as a fluid suspension and shock
absorbing system with its former efficiency, and is less able to redistribute the stresses placed upon it, although nuclear herniation and protrusion do not necessarily fol
low because of this. The water-binding capacity is more markedly depressed in more degenerated discs ; for example, when changes normally seen in the fifth decade of life occur at 40 years, degenerative joint disease, as
opposed to simple ageing, can be considered to be present.
The difference between normal discs and those showing frank pathological changes are greater than when young and aged discs are compared.
5. The fissures initially affecting the deeper layers of the annulus extend later to the peripheral layers. This age
ing process is frequently hastened by particular types of stress, especially rotation stress, and as a rule the posterior and posterolateral annulus arc the sites most often in
volved in attenuation, disruption and failure, i.e. disc pro
lapse, most common in the lumbar spine. Extrusion of the nucleus pulposus seldom occurs in normal discs.
Concentric tears frequently occur without breaching the outer annulus, reducing the normal resilient stiffness of the mobile segment and allowing a certain 'sloppi
ness',872 with consequently reduced ability to withstand the normal strains of movement, and the possibility of in
creased wear and tear on all the ligamentous and joint structures of that segment. Intervertebral joints with degenerated discs have been found to have appreciable lateral motion (lateral shear of 0.1 to 0.4 inches) at the disc when subjected to torsion ; this lateral shear is not observ
able to any appreciable extent in joints with intact discs. 326 (See Lumbar instability, p. 1 39.)
Disc prolapse is frequently preceded by episodes of simple bulging, i.e. herniation, as the annulus, without actually being breached, becomes attenuated by rotational stress, and the circumferential tensile stress exerted by compression forces, acting on the nucleus pulposus and annulus.
Farfan ( 1 973)'" believes the hydrostatic theory of lumbar disc protrusion (i.e. that axial compression will be transmitted as hoop tension to the annulus, and increasing compression may ultimately cause rupture of it, the rupture commencing on its inner side) has many failings ; when subjected to experimental proof, the predicted out
come does not occur. In compression tests, the vertebral body always collapses before the disc is damaged to any significant degree.324 In mechanical torsional tests, of a magnitude which did not injure vertebral bone, it was demonstrated that the orientation of posterior facet-joints protected the discs from torsional stress, the resistance of isolated discs being much less than the discs of an intact lumbar segment. During testing, concentric tears appeared in the annulus, and these were similar to those occurring naturally. The change in facet-orientation at the lower lumbar spine appears to lessen the resistance to torsional stress and the development of circumferential or concentric annular tears. This would accord with the segmental incidence of annular disruption which is, of course, very much greater at the lower two levels.
An apparently logical assumption that the magnitude of weight-bearing stress is directly related to the segmen
tal incidence, because of the higher compression loading at L4-5 and L5-S 1 , may not be valid. Compression loads
PATHOLOGICAL CHANGES�ENERAL 9 1 may cause failure of the disc i n the sense that end-plate fracture may occur, but this is not failure of the annulus.
Torque strength of isolated discs is not appreciably changed by compression, but experimental torsion of in
tact joints with compression amounting to 50 per cent of the body weight increased the ability to withstand torsional stress by a similar 50 per cent. This may be because facet
joints are more approximated and provide more protec
tion'" by locking.
Clinicians have known for a considerable time that rotational stress figures largely in patients' descriptions of incidents causing lumbar joint problems, and Farfan readily produced annular failure, as separation of laminae, when applying torsion.
The relatively small twisting force required to injure the inter
vertebral joint probably occurs in everyday life; for example.
using the flexed thigh as a lever to manipulate the spine, a manipu
lator could easily attain 1000 inch-pounds of torque by applying a 50 Ib force to a femur 20 inches long. In this way, he could easily damage the intervertebral joint. 325
The development of laminar separations in the annulus precedes that of radial perforating fissures, and the torsional stress concentration occurs mainly at the pos
terolateral portions of the annulus.
Farfan's326 hypothesis of predisposing factors in degenerative change, and factors preventing the likelihood of lumbar disc damage, might be summarised as follows : The integrity of the neural arch is a factor of immense importance for the torque strength of the lumbar vertebral segments.
Facet-joint orientation exerts an influence on stresses applied to the intervertebral joint, and is partly respon
sible for the pattern of degenerative change.
The initial changes of disc degeneration are the result of torsion forced beyond the normal range of motion, which is probably less than 5 .
The distortion of the annulus during experimental rota
tion strains is most commonly maximal at the posterior surface and especially the posterolateral angle.
Rotation also induces a forward tilt (ftexion), forcing the neural arches apart and increasing the interpedicular dis
tance. The posterolateral annul us is distracted.
When torsion is removed, the distortion largely dis
appears, but the disc has lost stiffness and become Isoft.' Abnormally increased motion at a joint is usually a sign of severe degeneration, and can be observed in radio
graphic studies in about 1 5 per cent of patients with back
ache.J26 (Morgan and King, 1 957,872 found the incidence to be 28.6 per cent j those especially practised in evaluation of segmental mobility by palpation would probably detect a higher proportion ; see p. 328.)
Lack of motion at a lumbar intervertebral joint is usually a sign of stability of that joint, and repeated attempts to attain 'normal' range will predictably result in sprain.
92 COMMON VERTEBRAL JOINT PROBLEMS
Spines with four segments will rotate less than those with
Spines with four segments will rotate less than those with