The Way This Back Behaves

There is a world of difference between the acute and chronic forms of the stiff spinal segment. Strange to say, the more advanced pathologies are often less painful. This is because the segment is so stiff it is almost fused, and where there is little movement there is little pain. At this stage, however, the low internal pressure of the disc means that it retains the inherent risk of knocking loose from its jammed impaction and very quickly becoming unstable. Its lack of intrinsic tensile strength means, quite literally, that if the segment is not stiffly stuck together it is vulnerable to instability.

The sub-clinical phase

In its sub-clinical form this back is hardly a problem. It may be stiff after a long car trip or sleeping in a different bed, but it is never painful. There may be a vague awareness that something is not right with your back, but for years it may come to nothing more than this.

A typical sub-clinical problem is the 'jumpy legs' syndrome, which feels as if two live wires touch when you sit for too long. A lesser form of the affliction is not being able to keep your legs still when sitting, usually combined with a dull sense of pressure in your back. Both conditions are more a nuisance than a problem, and although there is never any pain, it is unnerving and indicates a degree of compression of the spine which is an ill omen for the future.

Sub-clinical disorders wait in the wings to cause trouble. The causing mishap is often trivial, yet brings about an extraordinary pain response. People are often perplexed at how their back became painful so quickly with so little provocation. But they actually had it coming; their back was silently protecting a rusty level and adjusting for its lack of mobility by over-compensating at the levels above and below. For some reason, the ricking incident bypasses all the usual defenses, and unavoidably targets the semi-rigid link.

The acute phase

There is no greater back pain than acute inflammation of a spinal segment. It causes an intense smarting, aching soreness right across the centre of the back which is often too tender to touch. It is often described as screamingly painful with a hot throbbing sensation under the skin, like a boil about to burst. (When this bad it is common to suspect you have cancer.) If the vertebra is locked one way, twisted on its axis, the pain will still be central but focused to one side as well.

At the height of an acute condition your back feels as fragile as a Dresden doll. Jarring it can be so painful it almost makes you sick. Even deviating in your path to avoid a collision on the footpath can make you so weak you almost crumple at the knees. Someone brushing past behind you can make you flinch and automatically move out of the way. Staying upright may be nearly impossible, although pressing the flat of your back into the wall can give relief. Cooking the dinner can be a panicky race against time, until the pain makes you lie down.

Figure 2.16 With acute segmental stiffness the spine does not like being 'sat on'—you either lie back in a slung-out position, taking weight on the back of your sacrum, or over-arch to relieve the pressure.

Sitting is uncomfortable and your spine does not like being compressed. You constantly shift positions from slumping deeply and resting on the low slung-out back (to take the pressure off the neurocentral core) to perching forward and making it over-arch (so the facets take more weight). Either way, your back is uncomfortable again within moments. Even lying down can be painful because your back feels too tender to take the pressure. The locked vertebra seem pushed up by the muscles, as if you are lying on a stone.

Figure 2.16 With acute segmental stiffness the spine does not like being 'sat on'—you either lie back in a slung-out position, taking weight on the back of your sacrum, or over-arch to relieve the pressure.

Acute palpation

When I use my hands to palpate, the vertebra can be highly sensitive to light pressure but surprisingly less so to deep. En masse, the vertebrae feel bunched together, like a row of beads threaded too tightly on elastic. Sometimes the segments feel hard to depress like piano keys where the spring underneath is too stiff. Often the surrounding tissues have a puffy, water-logged feel with a deep inflammatory heat smoldering up from below.

What causes the acute pain?

With acute segmental stiffness there are multifarious reasons for the pain and there is plenty of it.

The injury which first hurts your back can be likened to a ligament strain of the disc. It is similar to spraining an ankle though on a smaller scale. Chemical toxins are released when the fibres are damaged which irritate 'nociceptors' or free nerve endings in the disc wall. Messages are relayed to the brain from the injured part, which are interpreted as pain.

Having said this, the disc is poorly sensitive to pain. Only the outer layers of its wall have a nerve supply which makes it unlikely to bring about intense pain on its own. This rather points to the cramp of local muscles in spasm and the accumulation of waste products around the injury as additional sources of pain.

Although the muscle spasm is protective it can be too unrelenting. Unabated, it physically jams the segments together and increases the pain coming from the sore interbody joint. Mechanical receptors with bulbous or globular nerve endings in the disc wall are stimulated by the excessive compression. These are situated between the fibres and are sensitive to physical distortion. They are flattened when the disc is flattened and this too is perceived as pain. Sometimes this stimulates more protective reaction from the muscles and the painful cycle intensifies.

Probably most of the pain comes from the intense vascular engorgement around the injured part when the muscles prevent free movement. The disc stays compressed and the circulation of blood becomes sluggish because there is no pumping action from free movement to sluice it on. Pain comes from the physical engorgement of the neighbouring pain-sensitive structures and also from the rising concentration of waste products in the stale blood.

This engorgement is a potent source of discomfort. It accounts for the steadily increasing pain, several hours after injury, just like when you twist an ankle. There is a wrench of pain when the mishap first happens which then passes off, but several hours later the pain worsens. As the joint gets stiffer and more tense with swelling, there is a frightening inexorability about the way the pain gets worse.

The sub-acute phase

In this phase, the discomfort from the low back is more bearable. The lumbar spine feels permanently clenched, with peaks of stinging pain or twinges whenever it gets tired. It suddenly gets uncomfortable being in one position for too long and is only relieved by moving about. Rubbing with the flat of the hand is a relief, although direct pressure on the vertebra feels tender, as if the bone itself is bruised. The aching stiffness can be relieved by heat, sometimes so hot it works like a counter-irritant. (Using a hot-water bottle is common but often leaves a mottled discolouration of the skin which takes years to fade.)

Movement is painful because the muscles are tight and the back fails to let go as you try to push through their clench. Standing becomes more painful as the spine becomes more cast. It worsens into brittle impaction if you stay there and then it hurts to sit down. The spine cannot pull its segments apart to get itself rounded, and folding up to get into the car after standing at a cocktail party, for example, can be excruciating.

From the sub-acute phase, the problem can pitch back into acute flare-ups when the jammed link is disturbed or it can become more subdued and move into the chronic phase. It typically see-saws between the two with painful spates and remissions, and shorter respites in between. At this stage, avoiding hurting your back can become life's obsession. You take the long way round doing everything, just to avoid setting it off, and often the whole family must come to terms with accommodating your back.

Sub-acute palpation

When I palpate with my hands the segments have usually lost their bunched-together feel, but there will be a tubular rigidity across a local section of the neurocentral core. The spine feels brittle, as if the cotton reels are welded together and the surrounding tissues may have the rubbery feel of longstanding inflammation. With the flat of my hand I feel the drag of moisture on the skin which indicates a deep seated, low-grade inflammation. After manually mobilising the vertebrae the skin often flushes up red with the blood rushing to the surface. (The degree of redness gives some indication of the degree of inflammation.)

The chronic phase

The chronic phase of segmental stiffness makes you feel years older than you are. Rather than frank pain you have a deep, aching, armour-plated stiffness across your low back. Arching backwards gives relief, but bending forward is always awkward and stiff; your back feels so rigid you sense you shouldn't do it. It is difficult drying your toes and putting your socks on in the morning but activity gets easier as the day goes on. You feel creaky getting out of a chair or car and you often have to winch yourself straight before moving off.

Chronic palpation

Delving around in a spine like this, it seems the fire has gone out leaving only the cold embers. There is no soupy inflammatory feel of the tissues because they are so inert and lacking in juice they barely react. The vertebral column feels like a semi-rigid mass with thickened bars of bone across the segmental junctions. Often the bone of the vertebrae feels enlarged, like barnacles encrusted on an anchor chain, and the segments have a rock-hard blocking resistance to passive, gliding pressures from me.

What causes the chronic pain?

When a stiff spinal segment passes from its acute to chronic phase the pain comes about for different reasons.

During the course of everyday activity most of the weight through the segment is taken by the disc wall. This causes the wall to pucker and bulge, and the bulbous mechanical receptors hidden between the fibres are stimulated. If fibres are pulverised and broken by excessive compression the chemical receptors will be activated by the toxins of injury. Thus the brain receives two different pain messages.

Pain can also be provoked by the stiff disc wall being stretched. When the disc is inelastic and not free to pull apart with the other segments, the mechano-receptors pick up the lack of give in the fibres and interpret it as pain. If fibres are broken through being stretched beyond their limit, the chemo-receptors pick up the toxins released by the injured tissue.

Figure 2.17 Bulbous mechano-receptors between the fibres of the anulus pick up both compression and tensile stretch of the wall.

embedde mechanc receptor;

fibres of disc wall embedde mechanc receptor;

fibres of disc wall

Figure 2.17 Bulbous mechano-receptors between the fibres of the anulus pick up both compression and tensile stretch of the wall.

Pain from tissue tightness can also be registered in the other ligaments which help the disc hold the vertebral space together, in particular the posterior longitudinal ligament. As the problem disc drops in height during the degenerative process there is adaptive shortening of the ligament across the interspace.

The posterior longitudinal ligament in particular has a highly sophisticated nerve supply and, once a tight band develops, the ligament will register pain—just like the disc only more so—when provoked by stretch. Because it runs right down the back of the vertebral bodies, its tightness makes bending forward particularly painful.

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