Causes Of An Acute Locked Back

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• A natural 'window of weakness' early in a bend

• Segmental stiffness predisposes to facet locking

• Muscle weakness contributes to facet locking

A natural 'window of weakness' early in a bend

All spines experience a natural vulnerability on bending until they get themselves properly braced. I believe that facet locking occurs when the spine is caught momentarily ill-prepared as it passes through a fleeting 'window of weakness' in the early part of range.

Bracing happens when the muscles at the back and front of the abdomen contract in unison to stiffen the spine. They create a valuable tensile strength which keeps the spinal segments secure until they can be passed into the care of the strong system of muscles and ligaments running down the back of the spine. These then pay out slowly and lower the spine forward like a mechanical crane. However, the powerful erector spinae muscles and the 'posterior ligamentous lock' do not come into their own until the spine is well forward into a hoop when at last they generate sufficient tension to make the spine safe.

A locking incident often happens when people are recovering from a viral illness. Generalised debility is the most likely explanation, when the reflexes are dulled and the tummy muscles (in particular) cannot generate a quick enough response to keep the spine braced.

Facet locking can also happen a day or so after some form of serious exertion such as laying paving stones, cutting timber or digging in the garden. In these circumstances, it is probably the overactivity of the long back muscles and their residual raised tone which disturbs the natural harmony of the two deeper groups working underneath. The story is always the same: your back has been feeling stiff for a day or so when it was harder than usual to keep the tummy pulled in. Then some minor incident—almost too incidental to be taken seriously—catches unexpectedly and brings you down.

Segmental stiffness predisposes to facet locking

Segmental stiffness, even when benign and painless, can predispose your back to locking if the intervertebral disc between the two segments has already lost its oomph.

One of the specific roles of the multifidus muscle (with its willing helper the 'muscular' ligamentum flavum on the other side of the facet) is to pre-tense the intervertebral disc at each lumbar level. As soon as your spine starts to move, the disc should be as tense and plump as possible to prevent any wobble of the vertebra. If the disc has already lost fluid and the intradiscal pressure has dropped, it is much harder for the facet muscles to get the disc primed. Thus a spine already in line to develop symptoms from a stiff segment is also more likely to suffer a facet locking incident.

If the disc has already dropped in height and the other ligaments holding the segment in place have become slack, the segment is additionally vulnerable. The bone-against-bone locking of the facets (which provides a more basic tier of stability) is not specific enough to prevent minute movement of a vertebra and the facet can slip slightly askew unless the volitional muscular hold (the tummy) is compensating well. In fluke circumstances, an ill-prepared tummy can bring the whole lot down.

Up until this time the spine passes through an un-sprung phase when it must rely on the tummy muscles to tense the abdomen and slightly hump the spine to get it across the wobbly part. This slight tensing and rounding of the lower back in preparation for bending plays a subtle but invaluable role in putting the important multifidus and transversus abdominus muscles at a better angle of pull. They control the tipping of the segment by being intimately involved in the gapping apart of the facets to allow the segments to go forward.

Figure 4.3 It is important to have the tummy switched on to keep the spine braced and the segments stable through the 'window of weakness' in the early part of bending.

But even the slightest delay of one or other partner in the co-contraction can cause a glitch in the movement. When the spine starts to move before both systems are ready, it is caught off-guard and minutely disjoints somewhere in the column at one of its facets. The threat this poses to the spine causes a massive protective response from the muscles which jams the slipping facet before it can go any further. This is the reaction which brings you to your knees.

Figure 4.3 It is important to have the tummy switched on to keep the spine braced and the segments stable through the 'window of weakness' in the early part of bending.

the lift offloads

Muscle weakness contributes to facet locking

Longstanding segmental stiffness often makes the muscles weak. When a segment is too stiff to be active the small muscles which work it have less to do, which makes them atrophy. This particularly applies to the deeper fibres of multifidus which lie right on the back of the facets, acting as their special protector.

Figure 4.4 Contraction of the two muscles closest to the disc (multifidus and ligamentum flavum) clamps the segment which 'primes' the disc and prevents wobble during early bend.

In its moment of need, multifidus may find when its segment goes to slip it is not up to the task of keeping its joint under control. This is particularly important when a back has been suffering underlying trouble for some time. When there is low-grade inflammation of a facet, there is evidence to suggest that multifidus 'deliberately' under-performs to spare the irritable joint excessive compression. Although this might be for the prevailing comfort of the inflamed facet in the short term, in the long term it leaves it without the muscular control to compensate for other inefficiencies. A problem facet is wide open to a future locking episode.

Apart from this automatic inhibition, primary weakness of muscles can also cause facet locking. General indolence or unfitness can so impair our streamlined coordination that the tummy and back muscles fail to cooperate simultaneously in holding the spine supported. In a brief blip of control they perform out of sync, also

Facet Locked

the disc is tensed


contracting ligamentum flavum and multifidus

Figure 4.4 Contraction of the two muscles closest to the disc (multifidus and ligamentum flavum) clamps the segment which 'primes' the disc and prevents wobble during early bend.

the disc is tensed


contracting ligamentum flavum and multifidus making it difficult for the deeper intrinsics to come in at just the right time. If they fail to hump the back in its imperceptible first few degrees of bending, and the two important deep muscles cannot develop an optimal line of pull, the fundamental unit at the centre of the motion segment—the disc—does not get primed properly, and the segment can slip.

As a first cause, a weak tummy is easy to blame because it affects so many of us. Most of us have weakness (to varying degrees) of both the abdominal wall and pelvic floor. Weakness here creates a sloppy hydraulic sack which is less efficient at forcing the spine skywards. With a weaker up-thrusting force within the abdominal cavity and failure to round the back, there is a reduced tensile strength between the spinal links, leaving them more susceptible to jostling about when the spine goes to move.

Women are particularly susceptible to this in late pregnancy and early motherhood. When the muscles are stretched and weak and the ligaments still soft from the pregnancy hormones, it is easy to be less prepared for spinal action. This can also happen to any of us suffering from exhaustion, lack of fitness or recent weight gain. Getting up after an illness is also a time for suffering an acute locking incident, probably because of generalised weakness. Food poisoning and the flu are also commonly mentioned as predisposing factors.

The relative weakness of multifidus in its role of preventing sideways twist of a vertebra may also contribute to facet locking. Since all functional bending movements incorporate a twisting component (unlike robots which have an up-down and left-right action only) multifidus is like David versus Goliath in steadying the torque of the heavy trunk above. Even though the available range of segmental rotation is a few degrees only, multifidus (acting one-sidedly) is the only muscle which directly controls its vertebra. It does so at the very beginning of range by hanging on to its tail and preventing it from going both forward and twisting sideways. (Iliocostalis, another intrinsic muscle, also controls the vertebra twisting but only deeper into the forward bend.) All the other muscles controlling spinal rotation are in large sheets on the surface of the trunk with no direct attachment to the spine.

Figure 4.5 Multifidus is the 'bending' muscle. As we bend down to the left, the left-sided multifidus hangs on to the tails of the vertebrae and steadies them from swinging to the right.


The acute phase

The electric jolt of pain comes at the beginning of a movement— almost before it has started. In a split second there is an ominous sort of 'uh ohhhh' feeling, as if your spine is about to do something it shouldn't. The action is usually inconsequential—you can be leaning forward to pick up a coffee cup and your whole world stops. Apart from the suddenness, you are incredulous that something so trivial could have brought you so undone.

The sudden clench of pain completely takes your strength away. You clutch furniture for support and then, with your hands sliding down your thighs, you might slither helplessly to the floor. There at least you are more comfortable but you are like a beached whale and cannot be moved. If you are alone when it happens, it can take hours to crawl to the telephone to call for help.

The pain at this stage can alternate between a cramp hovering in the background and excruciating jolts whenever you try to move. If you need to move a leg you have to inch it across using a sideways heel-toe action on the floor. If you attempt to lift the leg or jerk in any way the pain will zap you again and leave you gasping.

What causes the acute pain?

The grabs of pain in the acute phase come from the muscles locking up the whole spine to trap the individual joint. They jump instantaneously into a high-pitched clench whenever they sense the joint going to move. The muscle contraction stops the mini-dislocation going any further but it also prevents the joint disengaging and repositioning correctly. The muscles keep on keeping on, like a dog with a bone, and they are a major part of the problem.

The intense compression of the joint while it is still out of kilter sends out the usual alarm signals of any traumatically twisted joint. The back does not let you off as lightly as a twisted ankle, probably because of the complexity of the workings inside and the relative size of the tiny joint compared to the bulk of the muscles guarding the spine. Until they are satisfied they can relax, they stay guarding the joint, keeping it out of action and locked away in the machinery of the spine.

The special mechano-receptors in the capsule let the brain know the joint is locked under pressure. They do so the instant the joint freezes and repeat the message every time there is even so much as a flicker from the muscles. A different sort of lower grade pain creeps in several hours later from stimulation of the chemical receptors in the joint capsule. They register the build-up of toxins in the tissues, both from the original capsule-wrenching damage and the stagnation of circulation through the capsule. As the concentration of toxins rises, the protective spasm increases, which intensifies the hold on the joint, and the pain coming from it.

The muscle spasm itself can cause a similar type of residual pain. When blood must be squeezed through tonically contracted fibres, the metabolic waste products cannot get away. As their concentration rises, their irritation of the free nerve endings in the joint's tissues is read as pain. Cramping muscles also experience another type of pain from lack of oxygen (anoxia). The over-working muscles cannot get sufficient fresh supplies through, creating a typical tired pain with peaking pin-prick twinges.

Pain begets more spasm which begets more pain and the cycle intensifies unless you get the joint moving. For this reason, reducing the muscle spasm and restoring activity is very important early in the treatment regimen.

When you have just been struck down however, any sort of therapy seems a long way off. At the time, the pain seems to come from everywhere and the back feels frighteningly locked.

At this stage, the best course of action is an intra-muscular injection of pethidine (a strong painkiller) and a muscle relaxant such as Valium as well. The first priority is to get you off the floor and into bed and the quicker a doctor is called the better. For your future rehabilitation you need to get over the incapacity stage as soon as possible, almost as much for your head as your back.

If the first attack is not handled properly you may never get over it, physically, mentally or emotionally. Many people with ongoing troubles claim their problem started with an incident like this which was never properly resolved. Twenty or thirty years later they can remember every detail and let you know that their back has never been right since.

The sub-acute phase

Within a matter of a few days, the crisis of the acute condition should pass. With resting in bed and proper medication the muscle spasm relaxes and it is easier to move. Your own attitude makes a big difference here. The more fearful and tense you are the more you hold things up. Breathing quietly, keeping calm and deliberately making your spine move again helps break through the physical and mental barriers and relieves the pressure on the jammed joint. The more anxious you are, the slower this resolution is.

As the muscles relax, it becomes easier to lift your bottom off the bed although it is still painful to turn over. Slowly the guarding reaction loses intensity and the back softens its over-vigilant armour-plated hold. There are no crippling jolts of pain if you move slowly. Unless you make a sudden jerking movement or sneeze or cough you will be able to get up, although it is difficult doing something complicated like getting out of bed.

Slowly the broad expanse of pain retracts to a localised area of soreness and it is easier to pinpoint the focus of the trouble. By this stage your back usually feels bruised and fragile, as if it has been through an ordeal. Even though it is weak, it is ready to get moving.

The chronic phase

In its chronic phase this problem behaves the same as facet joint arthropathy (see Chapter 3). When the blanket of protective spasm lifts, the dysfunctional joint underneath emerges through the mist. It needs to be mobilised as soon as possible and brought up to par with the rest of the joints, otherwise the problem becomes chronic and continues off and on indefinitely.

When the damaged facet is slow getting going the protective muscle spasm hangs around and the condition worsens. There is shrinkage of the joint capsule as a legacy of the scar tissue formation but, in a seemingly contradictory way, the capsule may also be left weak. Microscopic scarring cobbles the joint and pinches it tight, which leaves it stiff, but the original renting of the joint capsule and the weakness of the local muscles around it leave it vulnerable and easier to re-injure.

Taken to its extreme, the facet joint may eventually become unstable (see Chapter 6). This condition brings with it a conundrum for the joint's management. How do you strengthen the stiff, inelastic joint capsule when its very stiffness may be the only thing holding it together? This is the problem facing all facet instabilities, and it is not an easy one to deal with. Better therefore to handle it early on—after the first facet locking episode—so you never have to deal with the difficult end.

The aim is to get the joint going early to lessen the scarring. Even if your problem is longstanding (when you fear that loosening the joint will allow it to it slip again), the joint must, nevertheless, be mobilised, while making sure to cover the new-found freedom with improved power of the segmental muscles (mainly multifidus). The most effective way of doing this is by intrinsic exercises, unfurling the trunk off the end of a table, but an earlier and easier version (though with shorter leverage and less empowering) is simply bending forwards to touch your toes and uncurling cog by cog up to vertical.

If the intrinsic power of the segment is not restored quickly you are left with a back you keep hurting with twisting movement. You bend down to help an elderly lady with her shopping and you feel the familiar tweak as you overtax the weak facet. By next day your back has stiffened and developed its familiar lateral 'S' bend with one hip protruding. It feels tighter and caught up on one side and you keep digging your fingers in to find relief.

People often seek treatment at this point because they find they can do progressively less before they tweak the facet again, with it taking longer each time to recover. Whereas it used to be two or three days in bed now it takes ten and you are barely over one attack before the next one comes along. One episode seems to merge with the next.

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  • daniel
    How can you treat a locked back?
    10 months ago
  • nicole
    What causes lower back to get locked up?
    7 months ago
  • Galdino Fanucci
    What causes my lower back to lock up?
    2 months ago

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