Causes Of A Stiff Spinal Segment

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• Unremitting spinal compression reduces disc metabolism

• Gravity squeezes fluid from the discs

• Abdominal (tummy) weakness allows the spine to 'sink'

• Sustained postures accelerate fluid loss and poor varieties of movement prevent fluid replacement

• Chronic protective muscle spasm compresses the problem disc

• Abnormal postures increase neurocentral compression and reduce metabolic activity of the discs

• Injury can rupture the cartilage endplate between vertebra and disc

Unremitting spinal compression reduces disc metabolism

The synthesis of proteoglycans diminishes when a disc fails to undergo adequate pressure changes. As the concentration of proteo-glycans falls the disc loses its ability to attract fluid. The powerful osmotic or 'diffusion' pump gradually loses power, making the disc less efficient at nourishing itself. A starvation cycle sets up as the disc fails to attract water, and stiffens as it dries thus further reducing its mobility and its ability to physically suck fluid in, thus further lowering its metabolic rate. As the stiff disc progressively loses height the health of the entire segment gradually erodes.

Disc de-vitalisation happens more rapidly when the spine is subject to sustained high loads, such as experienced during lengthy periods of sitting, or when the spine is vertically clenched by muscle spasm. It also happens at low loads of the type encountered with lengthy periods of resting in bed. On the other hand, extremes of pressure within physiological range stimulate disc metabolism. Pressure variations within this range are most succinctly delivered by everyday spinal activity.

In addition to the natural squash-suck activity stimulating proteo-glycans manufacture, routine movement also exerts a slight pumping through the discs to move nutritional molecules, particularly the larger ones which have difficulty diffusing. The same convection pumping also helps the disc eliminate waste products and lactates

(the by-products of cellular activity) which depress metabolic activity if their concentration rises.

Once a certain level of disc turgidity sets in, the very immobility of the dry, inelastic disc reduces the gradient of the pressure changes and the volume of fluid passing through. Both the osmotic and physical pumping engines struggle to circulate fluid and the disc shrinks. Drying and thinning of the discs has immediate ramifications in the cascade of breakdown, making it easy to see why therapy for back problems must focus on disc hydration and nutrition.

Aside from the physiological realities which make disc viability borderline, there are several 'outside' factors that make discs more susceptible to breakdown, thus speeding degeneration of the entire spinal segment.

Gravity squeezes fluid from the discs

All discs lose fluid through the day and replace it during sleep. Gradually, fluids ooze out when we are upright and the spine is compressed, with fresh quantities imbibed again when we are relaxed and horizontal overnight with the segments un-weighted. The slow diurnal pattern of pushing stale fluids out by day and recouping fresh amounts at night is the main way discs circulate fluid, and this stately exchange is only possible because the metabolic rate of discs is so low.

Figure 2.2 Fluid is pressed out of the spine's discs through the day while we are upright and is imbibed at night as we rest horizontally.

gravity exerts pressure through axial load gravity exerts pressure through axial load

Daschund Anatomy

Figure 2.2 Fluid is pressed out of the spine's discs through the day while we are upright and is imbibed at night as we rest horizontally.

L5 endures the greatest compression as the brick at the bottom of the stack. To tolerate this throughout a lifetime L5's disc starts off thicker than the rest. Over time, constant downward forces can cause incremental fluid loss, for the reasons given above, and low lumbar discs usually flatten faster than elsewhere in the spine. It is common for L5 disc to end up the thinnest.

Intradiscal pressures are highest with sitting because this posture exerts the greatest compression on the spine's base. With long hours of sitting, metabolic activity of the low lumbar discs slows as fluid is relentlessly squeezed out. Discs lose approximately 10 per cent of their fluid within the first two hours of sitting, when the stacked bony segments slowly settle in to closer contact. After this time, fluid loss continues at a slower rate until the osmotic pull exerted by the proteoglycans in the nucleus equals the squashing effect of gravity and fluid loss stops.

The bearing down force of gravity squeezes fluid from every disc in the spine, from the sacrum to the base of the skull. This means we all go to bed appreciably shorter than when we got up. As our muscles relax and our discs swell overnight we are all taller by morning, with our discs primed and plumped up with nutrients, ready to take on another day.

People who sit for long hours may develop progressively more torpid lumbar discs which cannot accept a full quota of fluid overnight. They often feel cast when they rise in the morning, with their back feeling as brittle as a pretzel, and it can take several minutes of being up and about to evacuate sufficient fluid to make movement easier. More significantly, the reduced fluid exchange and gradual disc stiffening is setting up these lumbar discs for breakdown.

Jogging is particularly damaging for low backs because the forces of compression are so much greater. Marathon running eliminates greater amounts of fluid from the discs and overall height loss can be up to 5 cm. Faster running is less dehydrating because the forward stance braces the tummy and draws up the pelvic floor which buoys up the spine and dampens the jarring of the basal discs.

Abdominal (tummy) weakness allows the spine to 'sink'

Strongly contracted tummy muscles play a critical role as a retaining wall when the spine bends. A powerful 'drawing-in' contraction of all three layers of the abdominal muscles creates a higher intraabdominal pressure which lengthens the spine from within and increases the tensile linkage strength of the disc walls. This provides more security for the segments as the spine goes over, lessening their tendency to shear. Strong abdominal tone also does important things just as you sit there. A co-contraction with the back muscles buoys the spine up and stops the segments squashing down into the pelvis and compressing the lumbar discs.

Kapandji Physiology

Figure 2.3 Strong drawing in of the abdominal muscle corsetry raises the intra-abdominal pressure and bears the spine aloft which alleviates compression of the lumbar segments. (I. A. Kapandji, 'The Physiology of the Joints')

When the abdominal retaining wall is weak, it cannot generate sufficient up-thrust to offset the downward forces of gravity. As the girth expands and the belly distends over the belt like a sagging bag of chaff the abdominal contents spill forward, further dragging the spine downwards. As the multi-segmented column ploughs down ever more firmly onto the sacrum the loading pressure on the lower segments increases, adding to the unremitting load that lessens the metabolic activity, particularly of the L5 disc.

Figure 2.4 During protracted periods of sitting a lax abdominal wall allows the lumbar spinal segments to plough down into the sacrum which compresses the lower discs.

It is worth noting that carrying loads balanced on the head— another time-honoured custom of less developed societies—invokes a superb dynamic response from the tummy and back muscles working in tandem. The abdominals automatically pull in to brace, converting the lower abdomen into a taut, supportive cylinder. The raised pressure within the abdominal cavity creates extra lift for the spine and safeguards the lower segments from excessive compression. We might do well to copy this way of carrying!

Sustained postures accelerate fluid loss and poor varieties of movement prevent fluid replacement

Sustained postures keep the evacuation pump going one way whereas routine activity alternately raises and lowers intradiscal pressures to help suck fluids in and out. In the normal lordotic posture of upright standing the facets bear some load which spares the disc at the front excessive compression and fluid loss. Sustained bending forward disengages the lumbar vertebrae from the compression protection provided by the facet joints and loads the discs more. With sustained leaning over, the facets pull apart and the discs at the front are excessively 'milked'.

Lengthy periods of leaning forward, concentrating the gaze over a small field of vision are commonplace in our work lives, whether it be seated at a keyboard, working on a production line or sowing a paddy field with rice. The forward flexed posture pinches the lumbar spinal segments together at the front and subjects the lumbar discs to sustained compression. High loading is one of the chief factors in paving the way to breakdown of the lumbar spinal segments.

You can see from Figure 2.5 below that the flexed posture of diagram B causes ten times the fluid loss from the nucleus and 50 per cent more from the disc wall than that of the lordotic posture of diagram A. This makes it abundantly clear why sitting in a relaxed way with a pillow behind the low back to keep it arched is so necessary, particularly if you have a bad back.

Lordotic posture Flexed posture

Lordotic posture Flexed posture

Flexed Back Position

Figure 2.5 Flexed postures of the lumbar spine (B) cause greater discal fluid loss than arched or lordotic postures (A).

(M. A. Adams, The Biomechanics of Back Pain)

Figure 2.5 Flexed postures of the lumbar spine (B) cause greater discal fluid loss than arched or lordotic postures (A).

(M. A. Adams, The Biomechanics of Back Pain)

Repetitive bending is doubly destructive when it co-exists with a meagre variety of 'other' activities to take the skeleton out of its habitual stoop. Sometimes when sitting at a computer we obey our instincts momentarily and stretch back into a wide, non-functional releasing posture but these respites are often fleeting and too infrequent to provide the much-needed pressure alternatives. I believe slumped sitting postures in today's world are the most frequent underlying cause of low-back problems. Sustained low loading also slows the discs' metabolic rate, though in reality, lying horizontal in bed where the discs are not loaded is a much less potent form of disc destruction.

The second important engine for transacting disc nutrition is physical activity. To some extent, discs hydrate themselves by using grand-scale spinal activity to pull the segments apart, thus creating a slight suction effect to entice fluids in from the vertebral bodies. Unfortunately, the relative stability of L5 equates to lack of mobility, which makes it harder for this segment in particular to recoup lost fluids. As the most squashed disc, it is also the most disadvantaged; the trade-off between mobility and stability makes it harder for L5 to keep itself puffed up and buoyant.

This is more significant if the spine is less active for some reason. If you have pain, or more importantly if you fear movement, your lower discs flatten faster. With insufficient bending and straightening, the pressure pump is less adequate for shunting fluids in and out and disc nutrition suffers. Low levels of physical activity hasten the decline of lumbar discs.

You will see from the diagram A below that stretching into a lordotic (arched) posture increases fluid diffusion into the front of the discs, whereas diagram B shows that bending pulls a greater quantity of fluid into the back of the discs. Thus, both extremes of bending forward and back take turns at sucking fluid in.

Lordotic posture Flexed posture

Lordotic posture Flexed posture

Figure 2.6 With low-back arching-backwards movements (A) fluid is sucked into the front disc wall. With bending movements (B) fluid is sucked into the back wall and pressed out the front.

(M. A. Adams, The Biomechanics of Back Pain)

Figure 2.6 With low-back arching-backwards movements (A) fluid is sucked into the front disc wall. With bending movements (B) fluid is sucked into the back wall and pressed out the front.

(M. A. Adams, The Biomechanics of Back Pain)

Movement is the life blood of the discs. Studies in the past have also shown that patients confined to bed for non-back-related reasons lose disc bulk. Height measurements before and after confinement showed that even healthy discs become steadily thinner with protracted inactivity and reduced gravitational stresses. This is particularly relevant to spinal therapy, where grand-scale movement must deliberately compensate for the reduced proteoglycans concentration and permeability of the vertebral endplates so typical of the ageing process.

Lack of physical vigour throughout daylight hours also allows our muscles and other soft tissues to become less yielding and stretchable, which makes the spine less free to unravel when it tries to 'grow' overnight. Thus overall body stiffness indirectly increases the compression of our discs. When they are not put through their paces by day they are too stiff to let fluid seep in by night, and for this reason I like patients to deliberately stretch to decompress their spine before going to bed.

Healthy discs take in fluid faster than they expel it. It takes 6-8 hours overnight to regain the fluid volume squeezed out the previous day. Settling discs can gulp in small quantities of fluid by stretching and twisting during upright hours, though you can make this up more quickly if you lie on your back and bring your knees to your chest. This explains why the simple 'knees-rocking' exercise is so important in your daily treatment plan. 'Squatting' through the day also helps counteract discal fluid loss, mainly by hinging open the back of your spine.

Lying draped backwards over a BackBlock passively arches (hyper-extends) the lumbar spine which potentiates the effect of bouncing your knees to your chest. The distractive force is the antithesis of compression and it sucks fluid in as it pulls the segments open at the front. At the same time, the lower intradiscal pressure stimulates disc metabolism.

People who deliberately spare their backs by bending their knees instead, are actually doing themselves harm. It starves the discs of drink. Certainly, if a weight is very heavy you should lift it like a weightlifter, but for most daily travails—bending down to get the detergent from under the sink, reaching up to the top cupboard—you must make your back do the work, knowing that it is positively good for it! If you persist with a straight back you will be bringing on your own demise; it makes your back stiffer, the discs cannot feed themselves as well, you become more fragile and more likely to develop instability at the problem level.

You see this awkward bending with long-term back sufferers all the time—and sadly they believe they are doing what's best! As they bend over to wipe the table or tune the radio they keep their backs rigid and bend sideways in preference to going forward; otherwise they squat on their haunches with their spines ramrod straight. The oft-cited reason for doing it this way is so as not to 'pop the disc out'. This is also wrong. It has been shown that the intradiscal pressure is just the same with bending (and lifting) whether the knees are bent or not.

Extreme stiffness often makes you misread the cues; you are more likely to interpret bending as a no-go area if your back is painful. But be warned. Protecting your back in this way only makes matters worse. It emphasises the use of the wrong muscles and makes the deep muscles of your spine and tummy so weak they cannot hold the segments together (see Chapters 4 and 6). Most importantly, it makes the problem levels vulnerable to shearing strains as the spine bends and lifts. One mishap when your back is working under duress can transform a benign correctable problem into a tragically incurable one.

Opening the front of the discs by lying passively draped backwards with a BackBlock under the sacrum helps drag fluid in. It is a powerfully effective 'anti-sitting measure' which also reverses soft-tissue contracture acquired by hours spent slumped in a chair. Apart from stretching the front wall of the discs it stretches the powerful hip flexor muscles at the front of your pelvis which are apt to shorten when they spend hours in a puckered state. Their tightness creates a lack of give across the front of the groin and down the thighs which makes it difficult to assume a 'normal posture' when you stand up.

In the long term this tightness has adverse consequences because it causes the pelvis to tilt down at the front, which throws the spine out of balance and creates a typical 'bottom out' appearance. Tight hip flexors also make you take much shorter steps because the legs cannot angle back properly at the hips. Again this is bad for the back because in making a decent stride, the spine must twist left and right to compensate for the poor hip mobility.

If the sitting posture is especially slumped it causes adaptive contracture of the anterior longitudinal ligament which runs down

low back crumples into a 'C' bend

Figure 2.7 Slumped sitting fails to invoke the tummy muscles and is one of the chief compressors of the spine's base.

the front of the vertebral bodies like a long elastic tape. In healthy circumstances, its role is to limit the backward-arching movement of the spine, but when it adaptively shortens it tethers the spine forward in a hoop, like an over-tight bowstring. People are often aware of their worsening posture, and feel they are being kept stooped, as if their shirt is tucked too tightly into their waistband.

Bear in mind that sitting, or parking one's pelvis on a chair, is a recent and fairly unnatural phenomenon. Many indigenous people still squat rather than use high-backed support. Even though their day may involve running or carrying heavy loads, both of which compress the base of the spine, they can easily disimpact it again come nightfall by squatting to prepare food and eat. Would you see a Masai warrior slumped on a sofa? Frequent squatting exercises form a large part of the self-treatment program.

If you move forward more to the front of the seat, the abdominal wall works more dynamically and gives better support. If you sit slumped your tummy balloons forward, flaccid and inert. If you sit up free of back support you can feel the internal corsetry of your tummy reefing in the retaining wall and making your lower abdomen into a firm, flexible cylinder. It also makes the top of your spine better balanced and freewheeling to work more efficiently over its base.

The best sitting arrangement at a desk is the kneeling chair. Its seat is inclined forward a few degrees which promotes optimal hollowing of the lumbar spine instead of a slumped 'C'. A degree of weight taken through the knees and lower legs on the upholstered cushion minimises that taken through your sitting bones and lower back. Ingenious as they are, it is important to use caution when first using these chairs, particularly if you already have a back problem. The sudden unaccustomed activity of the back muscles trying to hold you up can intensify your pain in the short term. You should start with ten-minute periods per day only and gradually build up the time. It is also important to hasten slowly if you have knee or ankle problems.

Figure 2.8 The kneeling chair creates an 'almost perfect' sitting posture where the spinal and abdominal muscles work together to hold you up.

Chronic protective muscle spasm compresses the problem disc

Sometimes, a back over-protecting itself can make a problem snowball. After injury, major or minor, protective guarding by the muscles surrounding the injured segment keeps it out of action until the inflammation subsides. Usually this only takes a day or so and seat ang forward perfect lumbar hollowii seat ang forward perfect lumbar hollowii

Figure 2.8 The kneeling chair creates an 'almost perfect' sitting posture where the spinal and abdominal muscles work together to hold you up.

then the muscles relax by degrees, letting in just enough movement to coax the injured fibres to heal. Tentatively at first and then with more gusto, they let the injured segment join in with the rest of the spine. All going well, movement introduced at just the right rate brings the injured segment back to full function with no legacy of pain. But if the injured link never gets going again properly, it will remain an ongoing focus of trouble.

Overzealous muscle spasm can create a stiff link in the spine, even though the original injury was minor. The vertical clench compresses the spine throughout its length, especially at the problem level. Over time, the tissues develop adaptive shortening across the spinal interspace (like the childhood fable where the changing wind fixes a grimace on the face). Thus one vertebra acts like a rusty link in the sleek spinal chain, clonking as the spine goes around and sending out screeches of pain.

There can be a similar outcome if the muscle spasm remains self-fuelling, well after the initial irritability has faded away. This is usually related to subliminal anxieties and a fear of moving the back, when it seems as if the muscles develop a mind of their own. They remain rigidly on guard (the muscles do not pulsate, which is a common misconception), restricting all spinal movement and making everything stiffer and more painful. The cycle is never easy to interrupt and in the self-treatment section you will see how you may have to trick the muscles physiologically into switching off before progress can start.

Pain from simple segmental stiffness has no doubt been around since we evolved to stand upright. Using the hands to get all the vertebrae in line and equally mobile probably went on when we were cave dwellers in a way, believe it or not, which is still appropriate today. On the wall in my clinic I have a print of an ancient Egyptian text with diagrams of human spines being pushed around by the feet, a method I still use today.

However, this book is about self-treatment and I will explain how doing a variety of exercises, using a block of wood, a tennis ball, or perhaps a convoluted rolling pin, can prise individual segments free using your own efforts. All that comes later. Meanwhile, back to what is wrong.

Abnormal postures increase neurocentral compression and reduce metabolic activity of the discs

Deviant spinal alignment can be a potent cause of segmental stiffening. Anomalies can stem from poor postural habits, just as much as from congenital curvatures like spinal scoliosis.

As a rule, spinal segments stiffen more readily in zones where the spine's function alters; where it changes from neck to thorax to low back. These are called the 'transition zones' and they correspond to where 'S' curves (viewed sideways on) change direction. Hence, the common trouble spots in the spine are the lumbo-sacral level (where the spine joins the fixed pelvis), the thoraco-lumbar level (where the thorax becomes the low back), the cervico-thoracic level (where the neck joins the thorax) and the atlanto-occipital joint (where the base of the skull sits on the neck).

A rounded (kyphotic) low back

All transition zones give greater trouble if the natural 'S' bend of the spine deviates too far from normal. However, a fixed kyphotic low back (rounded into a hump instead of a hollow) is particularly troublesome for the neurocentral core because the facet joints at the back are pulled apart by the humping posture and bear no weight at all. This means that the discs themselves take a direct hit of compression, with no mitigation from the facets. The rigid rounding of the low back also obliterates the dynamic bowing forward on the impact of heel strike. Denied the natural sink-and-spring of a working lordosis many spinal levels develop segmental stiffness.

As a further consequence, reduced metabolic activity of the inner 'pinched' sides of the lumbar discs makes them wedge-shaped at the front, thus increasing the severity of the spinal hump. At a time when all the lumbar discs are forced to shoulder a more than usual load they have to make do with reduced nutritional exchange to carry out vital running repairs.

There is another ill effect of lumbar kyphosis: the weight of the upper body is carried too far forward, in front of the line of gravity. Consequently, the spine cannot stack itself with minimum effort and a 'turning moment' (a tendency for the upper spine to slump) comes

Concertina Collapse
Figure 2.9 Greater fluid loss and reduced proteoglycans synthesis on the pinched (concave) side of a lumbar discs hasten the development of a more stooped (kyphotic) posture.

about around the thoraco-lumbar junction. With the shoulders stooped, the lumbar segments incrementally slide forward, jamming the spine at mid-lumbar level. A lumbar kyphosis creates a similar tendency for the whole body to tip forward on the pelvis, also contributing to the typical 'bottom out' appearance.

Figure 2.10 A humped lower back (as opposed to lordotic) puts the upper body in front of the line of gravity and causes excessive loading of the lumbar discs.

This is a great source of strain. Pain can emanate from two sites— the bottom and top ends of the lumbar spine—at the same time. Upper lumbar problems often refer pain down lower in the back over the lumbo-sacral junction. When isolating your problem levels it is important not to assume that all your trouble is coming from L5, where the pain is. Both levels must be dealt with if you are to get better.

Figure 2.11 Segments of both the high and low lumbar spine refer pain to a similar area across the top of the buttocks.

Running with a humped low back is an exceptional hazard. Even walking can be juddering instead of feline and youthful, with the head no longer tracing an imaginary wavy line along through the air as the spine bounces along with every step.

Even the most youthful spines collapse into a 'C' shape when sitting, though it is better if they keep a proper lordosis, if that is possible with minimal effort. This applies even more when sitting in a vehicle when the added vibration causes greater fluid loss. Accordingly, car seats should have a firm and pronounced upholstered bulge filling out the entire lumbar hollow (to the extent that it feels too referred pain from upper lumbar problem

Perirectal Abscess Locations

Figure 2.11 Segments of both the high and low lumbar spine refer pain to a similar area across the top of the buttocks.

referred pain from upper lumbar problem referred pain from low lumbar problem much when you first sit down) and the seat should not be tipped down at the back which throws you into slumped sitting on the neurocentral core.

Incidentally, the correct horse-riding attitude is almost the perfect sitting posture for the back to disperse weight. Providing the stirrups are the right length, the low back assumes the optimum alignment to ride out shock and balance the upper body over the pelvis.

A sideways-twisted (scoliotic) spine

Spinal scoliosis is a lateral 'S'-shaped bending-twist through the spine which is obvious when viewed from behind. The lateral angulation of the vertebrae near the apex of the curve pinches them together on one side, reducing metabolic activity and the synthesis of proteoglycans on that side of the discs only. Thus the discs lose viability and their ability to rehydrate, right at the point where they are thinnest. This dramatic one-sided reduction in metabolic activity explains why the discs of scoliotic children deform so quickly and their curves get so dramatically worse during their growth spurt. In effect, the rest of their body keeps growing, except at these focal points on one side of the spine. As growth continues, their body hunches and their chest cage buckles around the spine, as if their growing body is tethered to the Earth by a string of wire from inside the spine.

Figure 2.12 A scoliosis is a 'windswept', lateral 'S' bend through the spine when

Scoliosis can be a congenital abnormality or acquired through the presence of a shorter leg. If a scoliotic curve is relatively stable and does not involve rotation of the vertebrae, the pathology will limit itself to segmental jamming. If however the spine twists as well as deviates laterally, the disorder will include 'facet joint arthropathy' (see Chapter 3). Here, the facets become chronically inflamed in their role of locking the spinal segments together to prevent them twisting off centre. With scoliotic curvature, there is usually a primary curve in the lower back and a secondary curve higher up. The upper curve develops to compensate for the lower one, throwing the spine back across the central line so the head at the top of the column can sit squarely on the shoulders and the eyes can focus to judge distance.

When one leg is shorter, the spine twists one way then the other, compensating in a fairly predictable way. Usually, though not always, the scoliotic lumbar curve will be concave towards the side of the longer leg.

Lateral curves in the spine also develop trouble because the liga-mentous shoring of the sides of the column is so weak. Unlike the various structures which keep it stable in the forwards-backwards direction, there is little impediment to the segments sliding sideways off-centre, except the disc wall itself.

The vertebrae themselves develop lateral wedging of the bone, particularly at the apex of the curve. The pinching of the apical vertebra also compresses its intervertebral disc beneath it. In addition, the segments above the apex tend to slide laterally one way and the other way below. As the creeping vertebrae move off-centre their discs also drag sideways, thinning as they go. Thus several discs in the scol-iotic curve are thinner, though the apical one more so. As several levels become 'stiff spinal segments' it is easy to see why the distribution of pain from scoliotic spines can be so diffuse.

The jammed apical segment is always the most painful, though several segments may be involved, depending how many times the spine twists back and forth as it goes up. Various spinal segments emitting pain simultaneously account for the wide variety of symptoms typical of scoliosis. There can be neck discomfort (sometimes including headaches), pain in the shoulder blade area (sometimes down the arm), pain at waist level (sometimes referred

Thinning Spinal Disc

the disc may develop wedging in addition to thinning can be wedge-shaped the vertebra

Figure 2.13 Poor lateral shoring of the spine allows the vertebrae to creep sideways, one way above the curve's apex and the other below. The apical disc and vertebra are compressed by the spine buckling.

the disc may develop wedging in addition to thinning can be wedge-shaped the vertebra

Figure 2.13 Poor lateral shoring of the spine allows the vertebrae to creep sideways, one way above the curve's apex and the other below. The apical disc and vertebra are compressed by the spine buckling.

to the groin), and low-back pain (sometimes referred down the leg). With so much pain, mild scoliotic patients in particular are rarely taken seriously and often wrongly dismissed as making a fuss.

Symptoms from exaggerated spinal curves (lordotic and kyphotic low backs) usually emerge during the third decade of life as the internal make-up of the tissues changes and they become more fibrous. Pain from scoliosis, on the other hand, can come on as early as nine or ten years old and be with you for life, getting progressively worse, unless something is done about it.

Injury can rupture the cartilage endplate between vertebra and disc

Unlike the hard cortical bone making up the sides of the vertebral bodies, the vertebral endplates of the roof and floor of the disc are a thin cartilaginous interface. As the spine alternately compresses and off-loads like a concertina during weight-bearing activity, the trapped internal pressure of the discs causes the endplates to belly outwards with the force, like wind billowing up under a tarpaulin. This imparts a lovely buoyant spring to our step as we romp along the pavement, but it also illustrates how weak the endplates are. In fact, they are the weakest component part of the spine.

Vertebral endplates have many tiny holes which allow the diffusion of discal fluids from nearby blood reservoirs in the vertebral bodies. They are pinpoints of weakness and can easily perforate under pressure. It is easily possible to damage the endplates within the limits of normal activity (physiological range) as reverberating shock passes up through the central core rupturing a small vent through the fibro-cartilage interface.

I ICCll LI II ucleus

Figure 2.14 It is relatively easy to punch a vent through the vertebral endplate during normal daily (physiological range) activities.

The tiny fracture can allow blood from the vertebra to seep into the sterile bloodless outer environs of the disc. In a process similar to a cold abscess, a low grade 'discitis' (or inflammatory reaction) sets up in the disc as it reacts to the invasion of blood. The process may be completely painless because it is contained within the insensitive disc interior but the segment stiffens afterwards. The disc converts to an inert fibrous 'washer' which pads out the interspace and gives the disc bulk, but thereafter it simply acts as a primitive spacer instead of ruptui endph ruptui endph

I ICCll LI II ucleus

Figure 2.14 It is relatively easy to punch a vent through the vertebral endplate during normal daily (physiological range) activities.

a buoyant tipping ball. It separates the vertebrae well enough but it has none of the highly resilient spinal connector properties which make a healthy disc so brilliant at what it does.

There are many ways you can puncture a vent in the bone, but the most common is stepping off a wall while carrying a heavy weight (particularly on your shoulder) or falling down hard on your bottom (especially if you were expecting a chair to be there). You may also do it wrenching up a sash window which is stuck, or standing up suddenly and hitting your head on an overhead beam (although this is more likely to injure the thoracic part of the spine).

Dramatic as the original trauma may be at the time, it rarely causes severe pain. It jars the spine but discomfort is usually short-lived. Your back may feel stiff and sore for a few days, possibly with leg pain caused by the trauma to the facets. However, you are often aware, in a vague sort of way, that your back is never quite the same again. The injury usually hastens the development of a 'stiff spinal segment', as the disc hardens and narrows.

The process is even less painful when it happens higher up the spine. Often you are unaware of anything wrong until X-rays reveal a typical tear-drop anomaly in the main body of a vertebra called a Schmorl's node. But lower down where the gravitational stresses are higher the sick disc may degenerate much faster, sometimes fast-tracking to entirely different symptoms of 'segmental instability' (see Chapter 6).

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