Neurosurgeon

The spine

The spinal column consists of 33 vertebrae (figure 1A):

• 7 cervical (neck)(figure 1B)

• 12 thoracic (each connects to the 12 pairs of ribs)

• 5 lumbar (low back)

• 5 sacral (in an adult they are joined together as one bone called the sacrum, which does not contain any discs)

• 4 coccygeal (joined to form the single coccyx, also called the tailbone)

The bones are numbered from above down - e.g. L1 is the highest lumbar bone, L5 is the lowest. The spinal cord actually finishes at the level of the L1/2 disc in most people.

Lower down there are only spinal nerves running in the central spinal canal, looking like strings of spaghetti and referred to as the cauda equina ("horse's tail").

The lumbar spine has five pieces (vertebrae) stacked like bricks one on top of another. The "bricks" are called the bodies. The lumbar spine sits on top of the sacrum. The sacrum also has five segments numbered S1 to S5 but in the adult these five bones are joined together and do not contain discs. Likewise, the coccyx has four pieces but is one bone in the adult, and is also called the tailbone.

Between each vertebra there are three joints - the disc between the bodies at the front, and two smaller facet joints at the back. The nerves run down together in the spinal canal between the discs at the front and facet joints behind, and then at each level leave the bony spine through holes called the intervertebral foramina (single = foramen, meaning window). Outside the spine, the lumbar and sacral nerves join together to form the large sciatic nerve, which runs down the lower limb.

The lumbar bodies are separated by thick cushions called discs. A disc is made of special cartilage and acts like a shock absorber between the bodies. The disc is made of two parts - the outer layers form the annulus (meaning "belt"), which is like layers of onion rings and makes up 75% of the disc. In the centre of the disc is the nucleus, which makes up 25% of the disc and is like crab meat. The facet joints are like tiles on a roof, overlapping one another. Problems with a disc or facet joint can cause pressure on the adjacent nerve.

Disc rupture

Outpouching of the disc nucleus through an annulus tear is referred to as a "ruptured", "herniated", "prolapsed" or "slipped" disc. When a disc fragment extrudes to press on a nerve, the patient experiences a condition called sciatica, meaning pain along the sciatic nerve.

The fresh prolapse is initially well hydrated (like a grape) but with time it usually shrinks due to dehydration (like a sultana). This is why most disc prolapses improve without surgery. The principles of treatment are to relieve pain until this natural improvement occurs.

Osteophytes

As we get older the joints in the spine often form bony spurs, called osteophytes, as can be seen in some people's thickened finger joints. These spurs may grow from the edge of the discs and facet joints. This condition is called osteoarthritis or osteoarthrosis and is the commonest form of arthritis in our community.

If osteophytes develop in the spine, the condition is called spondylosis, meaning osteoarthritis of the spine. The spurs may grow and press on a spinal nerve to cause sciatica, which is less likely to settle because of its gradual onset.

Symptoms

Disc and facet disease can cause low back pain directly, or may cause "referred" pain, meaning pain from the lumbar spine which is felt elsewhere - into the pelvis, hips and/or thighs. It is uncommon for disc pain to radiate down to the foot, but it does occur. Facet joint pain rarely radiates down past the thigh.

Pressure on a spinal nerve may cause pain, weakness, tingling and/or numbness in the leg, which is called sciatica. Pain, tingling or numbness tend to occur in specific sites in your lower limb, depending on which nerve is affected - e.g. L5 sciatica classically radiates into the big toe.

The adjacent figure shows the pattern (called dermatome) of nerve sensation down the leg, which can be quite variable between patients.

Sciatica is actually a type of referred pain due to pain radiating down the course of the sciatic nerve. The further that pain travels down the leg, the more likely it is to be sciatica, and is very likely if there is tingling or numbness. Straight leg raising (lifting the whole lower limb up by bending only at the hip) tends to be reduced and painful when there is pressure on a spinal nerve.

Investigations

If any type of x-rays are to be performed then plain x-rays should be done on every patient with low back pain or sciatica, ideally including functional studies - meaning x-rays with bending forwards and backwards.

CT scan is very helpful if there is leg pain and can identify most cases of disc prolapse or bony spur pressing on a nerve to cause sciatica. CT is very good for looking at bone, as opposed to soft tissue such as disc and nerves.

MRI is the most sensitive type of investigation but is often not necessary, particularly because of its expense and lack of availability. MRI is very good for looking at soft tissue such as disc and nerves, and is not as good as CT for looking at bone. MRI is not associated with any radiation exposure. Your GP cannot order an MRI scan without it costing you a lot more money than if it were ordered by a specialist.

Nuclear bone scan, despite its name, involves very little radiation. It involves an injection of radioactive material followed by a scan a few hours later. It is very good at detecting bone rubbing on bone and so is very sensitive at picking up painful facet joints which might otherwise look abnormal on x-rays, CT and MRI.

MRI scan showing a black (dehydrated) L5/S1 disc. Note the white dots at the back of the abnormal disc, indicating disc tears. The arrow points to the S1 body.

Nuclear bone scan

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Treatment

The best treatment is prevention - taking good care of your back. The spine is strongest when the vertebrae are vertical rather than when tilted or twisted. You should imagine that your back is a stack of building blocks and how you would best balance the blocks. Therefore, the spine is best used to carry a load if it is vertical, which is why you should bend your knees with your back as vertical as possible when lifting something from the ground. Similarly, if you have low back problems you should not twist or rotate from side to side, especially when lifting something.

Pressure in the disc is least when you lay flat, higher when you stand and, surprisingly, highest when you sit, and obviously higher if you carry a load. Therefore, standing is usually better than sitting if you have a painful disc. If there is low back pain from a damaged disc, the pain is usually least if you lay flat. If pain is particularly bad you may have to rest in bed but for as short a time as possible. Heat packs or a hot shower or bath can be quite helpful. If there is a lot of back muscle spasm (particularly noticeable if you are bent forward or to the side), your doctor can prescribe diazepam tablets. You should try to keep mobile by walking, which requires comfortable flat shoes (not high heels), walking twice a day about a kilometre at a time. Walking is an excellent low impact activity. Jogging is unwise as there are repetitive high impact loads on your spine. Swimming freestyle or breaststroke is an ideal exercise because your back is horizontal, with the least load on the discs, and it helps strengthen the back and abdominal ("core") muscles to help support your spine. If you are unable to swim, you can get into a pool with a kickboard and use your legs to kick in the water. Out of the water, a simple exercise can be done any time of the day and as often as you like - tighten your abdominal muscles and hold them tight (like straining) for as long as you can - say, 15 seconds. This activity simultaneously makes your low back muscles tighten and therefore strengthens them, helping support your lower spine. This exercise needs to be practised long-term in order to get real benefit.

Early on, it is very helpful to see a physiotherapist who can give you local treatment such as heat, massage, ultrasound, acupuncture and hydrotherapy (mobilisation and exercises in a pool). There are techniques of posture positioning where you can bend into a certain position to relieve your back pain (and sciatica). This technique is the basis of the McKenzie system of treatment and can be very beneficial. Most often lumbar extension (back arching) can relieve disc problems causing low back pain or sciatica. The physiotherapist can guide your recovery and may advise you to go to a gym for appropriate exercises. Not all exercises are good for your back. Sit ups are a bad exercise but you can learn to "think smart" and strengthen your abdominal muscles in other ways - e.g. you can lay flat and straight leg raise both legs together, tightening your abdomen without bending your back.

A brace can sometimes be of benefit if there is a lot of back pain which is worsened by movements, but generally you are advised not to have a brace because your core muscles can become lazier and weaker. A brace can be useful to protect your back if you need to do some heavy work. A comfortable, firm bed is helpful if you have a lumbar spine problem. Most beds are satisfactory but you are advised not to have a water bed or any bed which sags a lot with your body weight.

I do not understand the principles of chiropractic treatment but there are many good chiropractors around who can certainly help with back pain. Physiotherapists, chiropractors and osteopaths may manipulate ("crack") the spine. I believe that plain x-rays should be done prior to any manipulation, if only for medicolegal reasons. I am more apprehensive about manipulation of the spine if there is any neurologic deficit - i.e. any weakness or numbness due to pressure on a spinal nerve, and in this situation I would suggest that at least a CT scan be done in order to rule out significant pressure on a nerve.

Sciatica

Because most cases of sciatica noticeably improve over several weeks, the aim of treatment is to manage the pain while waiting for this natural recovery. The first symptom to improve is pain, followed by weakness and finally numbness, so don't worry if numbness persists - this is a nuisance rather than anything serious. Sciatica is less likely to settle if the pain has come on gradually rather than rapidly, if the sciatica has been unchanged or worsening over several weeks, if there is a large disc prolapse on x-rays or if it is due to a bony spur. With acute onset of severe sciatica you may be advised to have strict rest in bed for up to two weeks, with bathroom (toilet and shower) privileges only. Otherwise and as for low back pain, you will be encouraged to be active. Treatment is otherwise much the same as for low back pain and you are recommended to see a physiotherapist. Occasionally, sciatica can be helped by a Nerve Root Sleeve Injection:

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Nerve Root Sleeve Injection (NRSI)

NRSI means an injection around a nerve root in the spine. Usually the injection consists of local anaesthetic mixed with a steroid. The local anaesthetic gives immediate but short lasting pain relief from half to several hours. The steroid is an anti-inflammatory drug which reduces swelling and which may take several days to have its full effect.

The effect of a NRSI usually lasts days to a few weeks, but may be very brief or help for months. NRSI can be ordered by your General Practitioner or specialist. NRSI is usually done using a CT scan, in which case an x-ray doctor (radiologist) gives the injection. Otherwise, it may be given by a pain specialist, in which case it is done in an operating theatre under x-ray control, often with the patient sedated. The advantage of a NRSI being given by a pain specialist is that it is usually more comfortable because there is also an anaesthetist present, but the disadvantage is that it usually takes some weeks or months to get in to see the pain specialist. A NRSI performed by a radiologist can usually be organised within a few days. An epidural (meaning the space outside the spinal nerves but still within the central spinal canal) injection is similar to a NRSI but is given deeper - closer to the spinal canal - and is therefore able to help several nerves, not just one.

NRSI is used for two main reasons: Therapy - to help severe leg pain (sciatica) due to a compressed nerve in the spine, usually from a disc prolapse or bony compression. Most times these pains will settle over a number of weeks. NRSI is one way to help relieve the pain while the condition naturally improves. NRSI can be very helpful for the severe pain that might otherwise require surgery. For this reason it is helpful in elderly or frail patients on whom we would wish to avoid surgery. Diagnosis - it may not be clear which nerve is causing the pain. For example, leg pain going into the foot may be due to L4, L5 or S1 nerve compression. X-rays may not be clear as to which nerve is compressed. In these cases it can be helpful to perform a NRSI to see if the pain is helped by the injection. For example, the doctor may suspect that S1 nerve is the problem because pain radiates into the sole of the foot. If an S1 NRSI helps the pain, even for a few minutes, then this indicates that S1 is the likely problem. This is helpful if the surgeon is considering which nerve to operate upon.

Complications from NRSI - Complications are very rare. However, sticking a needle into any part of the body must have a risk, particularly infection. Rarely, a nerve may be injured if it is injected into, instead of next to.

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Pain specialist

The pain specialist is a doctor, often an anaesthetist, with a special interest in the management of pain, particularly with skills to inject various parts of the body to help relieve pain. In patients with pain that is not easy to control, the pain specialist can advise which pain medications to take, including stronger narcotic (morphine-like) medications, as well as other pain-modifying medications such as amitriptyline and the anticonvulsant (antiepileptic) drugs which also help control pain.

The term "pain management" refers to the entire range of treatments used to help relieve pain, not just medications. The pain specialist has a particular interest in pain management, which also includes cognitive and behavioural techniques to help pain, and may work with other therapists such as psychologists and exercise physiologists who help with such techniques as pacing. Pacing simply refers to doing activities in smaller amounts, up to the level of pain tolerable.

Sometimes the cause of pain has gone but the pain continues - e.g. pain persists even though the pressure has been released from a nerve after removal of a prolapsed disc - or the cause of pain may not be obvious despite all investigations. In these situations, the pain specialist (or any other doctor) should reinforce that there is nothing seriously wrong but pain is persisting and is now the problem without any curable underlying cause.

The pain specialist also has a range of procedures to help work out the source of neck pain and/or to help this pain. Such procedures include NRSI, radiofrequency (RF) nerve injections, epidural injections, disc blocks (blocking pain from the disc annulus), medial branch blocks (to deaden pain from facet joints), facet joint injections and epiduroscopy (looking in the epidural space through an endoscope). RF injections are made directly into the nerve which is then heated slightly, only enough to deaden the pain but not enough to cause numbness or weakness. RF injection is typically used for facial pain due to trigeminal neuralgia.

Surgery

Surgery is generally a last resort option.

The three reasons why you might need surgery are:

1. The pain is too severe to cope with in the short term, e.g. you need hospitalisation; or,

2. The pain is persisting for too long, interfering with your quality of life; or,

3. If there is significant muscle weakness from pressure on a nerve - e.g. a foot drop (inability to lift the foot up).

Generally, if your problem is #1 or #2, it is basically your decision as to whether surgery is needed. You should not be pushed into an operation if your problem is purely pain. However, if you have problem #3, your surgeon may advise surgery because the nerve pressure is too great and the nerve may not recover if the pressure is not taken away from it. Cauda equina syndrome is an example of when surgery must be done, and done urgently.

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Lumbar disc surgery Broadly speaking, there are three types of surgery for lumbar disc disease: Microdiscectomy - This is the most common spine operation. It means removal of the offending disc prolapse and is done either under a microscope or, rarely, with an endoscope. At the same time, some of the nucleus may also be removed, referred to as an internal discectomy. In either case the annulus is largely preserved, meaning that most of the disc remains. The rationale for internal discectomy is to try to reduce the future risk of further nucleus material rupturing out, called a recurrent disc prolapse. A recurrent disc prolapse occurs in about 5% of patients, developing any time from immediately after surgery to many years later. The only way to prevent a recurrent disc prolapse is to remove most of the disc - subtotal discectomy, which is a bigger operation and often not indicated.

Subtotal discectomy - Nearly all of the disc is removed, which can be performed from behind (posterior) or in front (anterior - through the abdomen). Some of the outermost portion of the annulus remains. If there is a problem with pain from a disc tear, which is virtually always at the back of the disc, it is important to remove the tear. After a subtotal discectomy the disc space will collapse if something isn't put in its place, causing instability and back pain.

Therefore, the disc needs to be filled with bone and/or a device that holds the disc space open, such as a cage, spacer or artificial disc replacement. If bone is placed in the disc, the intention is to form a bony bridge across the disc space, which is called a fusion. Fusion simply means joining one bone to another and is what occurs naturally when a broken bone heals. Fusion may be done from behind or in front and may be accompanied by a cage or spacer placed in the disc. (See PLIF and ALIF). Currently, artificial disc replacement is only done from the front.

Dynamic stabilisation - Dynamic stabilisation (DS) is a new change in thinking about the lumbar spine. DS basically means strengthening or repairing a damaged joint without fusing it. Years ago, hip osteoarthritis was treated with fusion but nowadays many people have the movement preserved and have a hip joint replacement. This is an example of DS. The idea behind DS is that a damaged disc is supported without fusing it, placing less stress on the adjacent disc and facet joints above and below, compared to a fusion. The range of movement is not as much as normal but is more than with a fusion. I believe that DS reduces future back pain and recurrent disc prolapse, not as effectively as fusion but the operation is not as major.

In the spine there are now three techniques of dynamic stabilisation:

1) Interspinous buttress (or spacer)

A block of material is placed between two spinous processes (the pointy part of the vertebra that can be felt through the skin).

Lumbar spine and interspinous spacer viewed from the left

This spacer reduces back extension. I also like to pass strong cords from the spacer around the two spinous processes, tightening them together so that back flexion (bending) is also restricted. This is much the simplest type of DS and can be done at multiple levels. The procedure takes about 20 minutes on its own or can be combined with a microdiscectomy. There are a number of devices on the market - Diam, X-Stop, Wallis and Impala. I tend to use the Diam device, as illustrated in the two adjoining figures. The first Diam device in the world was inserted in 1996. The downside is that since July 2008 the Federal Government no longer allows private insurance companies to cover the cost of the device. This means the patient has to pay $3,500 out of pocket, which goes entirely to the instrument company. Prior to July 2008 I had been performing this procedure for three years without any extra cost to the patient. Hopefully, this situation will be rectified within the next year.

2) Dynamic pedicle screw stabilisation

Dynamic pedicle screw stabilisation is a significantly bigger operation than insertion of an interspinous spacer, but it is also much more stable and is more effective when there is some instability (abnormal movement) at a joint (See Spondylolisthesis).

There is currently only one system available in Australia - Dynesys. This procedure involves placement of a pair of screws above and below the operated disc segment (i.e. a total of four screws per disc), as would be done in a posterior fusion. However, instead of using metal rods to cross the disc segment, as would be done in a fusion, a pair of firm plastic rods are used which allow a small amount of movement at this level. Both interspinous stabilisation and dynamic pedicle screw fixation are performed by a posterior approach (from behind).

3) Artificial Disc Replacement (Read more)

Of all the three forms of DS, artificial disc replacement preserves the most amount of movement at the disc and therefore is not as restrictive as interspinous or dynamic pedicle screw stabilisation.