R.W. Porter. Royal College of Surgeons Edinburgh, Nicolson Street,
Edinburgh EH8 9DW.
More than 20 00 spinal operations are carried out in the UK each
year. The decision when and whether to operate requires mature judgement.
Spinal surgery is technically difficult, demanding a high level
of surgical skill. It is learnt only by lengthy apprenticeship.
The after-care is equally important. The personal supervision of
the surgeon who leads a coordinated team of clinicians, nurses and
physiotherapists will ensure the best results. It is inevitable
and unfortunate that mistakes will occasionally be made and only
careful attention to detail in the pre-operative assessment, meticulous
surgical care and supervised post-operative management will ensure
consistently good results. The spinal surgeon needs to remain up-to-date,
be disciplined with a systematic and careful approach and lead a
coordinated team to maintain the highest standards.
What is a patient entitled to expect at the present time and what
are the standards that are recognized by the general body of spinal
Avoid unreasonable haste.
Spinal surgery offers the patient a life-threatening procedure
for a non-life threatening condition. There are always potential
surgical complications, and although the benefits of surgery can
be considerable, all reasonable conservative approaches should have
been attempted first. When to operate is a difficult decision demanding
fine judgement. There is a spectrum of opinion amongst surgeons
for most spinal conditions. Some prefer a radical approach offering
early surgery in order to hasten recovery of normal function. Others
adopt a more conservative attitude. In the long term, most spinal
conditions have a good natural history but disability can be protracted
with conservative management. For example, there is no absolute
indication for a surgical discectomy unless the patient has bladder
symptoms. Even with severe sciatica and marked root tension signs,
surgical treatment is not mandatory. With time symptoms will resolve,
perhaps not completely, but at least to a manageable level. If symptoms
have been present for only two weeks, it is not possible to predict
the natural resolution. Without surgery, many of these patients
will recover over a 3-month period with complete relief of symptoms
and a return to work. If there has been no improvement over a 6-week
period, however, the prognosis is less optimistic. Most spine surgeons
would argue therefore that disc surgery for a patient who has had
less than 6-weeks of symptoms is not good practice. They would say
that unless there were bladder symptoms it was operating with unreasonable
haste to offer surgery to a patient with less than 2-weeks of symptoms
and this would not be a practice adopted by any reasonable spine
Avoid unacceptable delay.
Patients are sometimes distressed because they believe that there
has been unnecessary delay in referral to a spinal unit. They may
have suffered for many years with chronic back pain until finally
they find an expert who is able to offer them successful spine surgery.
They may remember years of pain and suffering, and at some time
having been told the problem is psychological, and they might seek
redress. Such a claim, however is unlikely to succeed because the
surgery for chronic back pain is very unpredictable. There is always
a body of reputable clinicians who would not recommend surgery for
chronic low back pain. It is reasonable to operate but it is also
reasonable to encourage patients to avoid surgery.
A more frequent claim for potential medical negligence is an unacceptable
delay in a patient who has a bladder problem. Spinal pathology which
compromises the sacral nerves supplying the bladder generally requires
emergency treatment. Every surgeon knows that a patient who is unable
to pass urine or alternatively is incontinent of urine has a potentially
serious condition. Involvement of the L5 nerve may leave a patient
with a foot drop and some numbness of the foot. It is a disability,
but not serious even if it does not recover. However, involvement
of the sacral nerves which supply the bladder is a major problem.
When the symptoms have been there for more than a few hours the
problem tends to be permanent, with loss of normal bladder function
for a lifetime. The same nerves supply the bowel and sexual function,
which are also permanently affected.
Pathology which affects the conus can cause these problems. The
conus is the lower end of the spinal cord at the level of the second
lumbar vertebra and this can be compressed by fractures at this
site. The conus may be compressed mechanically or its blood supply
may be affected by the fracture. The sacral nerves can also be affected
in the mid-or lower-lumbar spine. These nerves form the lower posterior
part of the caudia equina. They lie fairly close to the lamina and
they can be damaged by decompressive surgery at this level. A massive
disc herniation can so compress the cauda equina that the sacral
roots are pressed tightly against the lamina (cauda equina lesion).
It is therefore an emergency situation when a patient presents
with back pain and bladder symptoms. These patients require rapid
and comprehensive neurological assessment. The sacral nerves also
supply the skin around the anus and perineal region. They are responsible
for the tone of the anal sphincter muscles. Clinical assessment
of this region confirms that there is significant problem with the
sacral roots and early surgery is imperative.
The patient with the massive disc protrusion and bladder problems
requires urgent imaging with MRI and rapid removal of the herniated
disc, decompressing the cauda equina. The patient who has had spine
surgery and in the post-operative period has evidence of sacral
nerve dysfunction also requires urgent investigation and re-exploration
for a treatable condition. The patient with an upper lumbar fracture
and conus lesion similarly requires urgent decompression after appropriate
It is agreed that the longer the sacral nerve roots are compressed
the less likely is their recovery and therefore, for the best result
early surgery is required. It takes only a few minutes of complete
loss of blood supply to the nerve roots for permanent damage to
occur. Thus if compression is complete, in practice early surgery
is generally too late. However the majority of patients have incomplete
compression, when surgery within the first few hours can be fairly
effective. The longer the delay, the less chance there is of recovery.
Adequate pre-operative investigation.
The diagnosis of back pain syndromes is made from the history and
the examination. Investigations are supplementary, usually to identify
the level at which surgery will be required. A plain radiograph
is helpful in a negative sense. It can exclude advanced ankylosing
spondylitis where the sacroiliac joints are sclerosed. It can demonstrate
a spondylolisthesis which may be a hidden cause for back pain. It
can also show up spinal metastasis from primary tumors elsewhere
when these have progressed to an advanced stage. It will also show
the presence of an osteoporotic fracture. However, for the majority
of patients with low back pain syndromes the plain radiograph is
negative. There is no good correlation between degenerative change
in the lumbar spine and back pain.
The image of choice is the MRI scan. This will identify a disc
protrusion, degenerative discs, spinal stenosis, infection and neurological
tumors. It is so sensitive that pathology is often demonstrated
which is asymptomatic. It is only of positive value when the images
correlate with the clinical features in the history and examination.
When MRI is unavailable, a CT scan is the next best imaging modality,
followed by myelography. It is unacceptable to operate on a patient
without one of these supplementary investigations. Spinal surgery
should be a once-in-a-lifetime experience. It is not an exploratory
procedure in order to make a diagnosis; rather, there should be
as much information available to the surgeon as possible prior to
There are no reliable procedures which tell us where the pain is
coming from. Some clinicians will carry out facet joint injections
or a provocative discography in the hope that this will identify
the pain source by reproducing the pain. However none of these are
Depending on the patient's clinical problem, other investigations
may be necessary. For example, a patient with osteoporosis requires
blood investigations to exclude other sources of demineralization.
They need blood tests for osteomalacia and hyperparathyroidism,
tests of the liver function and renal studies. However, for most
of the patients having spine surgery, the history and examination
often followed by MRI scan is the main pre-operative assessment.
It may sometimes be supplemented by other studies.
Operate in the patient's best interest.
It may seem obvious that surgery should be offered only when it
is in the patient's best interest. However, it is unusual to have
an absolute indication for surgery on the spine. The natural history
of spinal disorders without surgery is generally good although disability
can be protracted. It is necessary therefore for the surgeon to
have a complete understanding of the patient's past history and
social history to understand their lifestyle and occupational requirements
before recommending surgery. It is important to understand the patient's
expectations and whether these are realistic, and to ask whether
surgery should be carried out at all. Simply because it is possible
to change pathology by a surgical approach, does not mean that it
is indicated. It is justified, however, in the patient who requires
a rapid return to normal function because of the family or occupational
Operative management and competent surgery.
At the present time, there are few full-time spine surgeons in
the UK. Most of the spine surgery is carried out by orthopaedic
surgeons or neurosurgeons who besides having a general practice
take an interest in the spine. In previous years, most orthopaedic
and neurosurgeons would do an occasional spine operation but it
is now becoming an acceptable practice for spine surgery to be the
preserve of those who have a special interest. This means that the
majority of spinal surgery for degenerative conditions is carried
out by a surgeon doing at least 20 spine operations per year. There
is no agreed minimum limit but competence is maintained by continued
There are occasions when a surgeon can predict technical difficulties.
For example, obesity will add to the operative difficulties and
repeat spinal surgery is more complicated than the first procedure.
It can be anticipated that a grossly displaced spondylolisthesis
will be difficult to fuse, and extensive spinal stenosis with gross
degenerative change is not easy to decompress. With such problems
a good surgeon will refer to one of his more experienced colleagues.
Failure to do so, and particularly failure to inform the patient
of potential hazards, is poor practice.
One of the most common causes for medical negligence is operating
at the wrong level. Most patients have five lumbar vertebrae followed
by the solid segments of the sacrum. About 5% of the population
will have six lumbar vertebrae where one of the sacral segments
is lumbarized or four lumbar vertebrae where the lowest lumbar segment
is sacralized. This can confuse the surgeon. The radiographs may
show the disc protrusion say at L4/5 level. If the fifth lumbar
vertebra is sacralizred and fixed to the sacrum, the surgeon may
be confused and operate at the L3/4 disc by mistake. It is imperative
therefore that the surgeon adopts a safe practice to identify the
operative level. There are two methods. One is to expose the sacrum
in the operative field. It is possible to identify the solid sacrum
by vision and by palpation and the work up the spine identifying
each of the lower levels. When using a minimal exposure, the correct
level can be identified radiographically on the operating table
by introducing a needle down to the appropriate segment and checking
the level on the radiograph. Sometime, methelene blue dye can be
injected through the needle and this mark recognized when the area
is exposed. There really is no defence for operating at the wrong
Human error is responsible for operating on the wrong side. It
is not defensible, but the surgeon can mistake the laterality when
the patient is lying prone. Good practice requires a skin marker
on the back identifying the side required for surgery.
There has been long debate how much disc material should be removed
in a patient who has a disc protrusion. A consensus is developing
that only the loose fragmented material needs to be removed, along
with any other loose fragments within the disc space. The surgeon
is operating through a deep hole and cannot visualize the centre
of the disc space. Loose fragments are extracted by rongeurs and
sometimes by a blunt curette. Previously, surgeons would remove
large amounts of disc material from within the disc space to avoid
a recurrence, but this is now considered unnecessary. It is a balance
of clinical judgement as to how much or how little material should
be removed and there are as yet no absolute guide lines.
When carrying out a discectomy the symptomatic lesion is usually
at one level. Not uncommonly, imaging will show protrusion at perhaps
two levels, and there is then a dilemma about which one is symptomatic.
The surgeon usually operates at the level which is compatible with
the clinical features of the nerve root involved. It is good practice
to limit the surgery to as little as possible compatible with the
Spinal decompression for spinal stenosis requires removal of the
tight bony lamina to allow more room for the underlying nerves of
the cauda equina. In previous years surgeons were very radical,
sometimes removing the lamina of all five lumbar vertebrae. In the
last few years, surgery has become much more conservative, frequently
recommending only partial laminectomy at a selective level where
stenosis is most significant. If decompressive surgery is too extensive,
it runs the risk of the development of post-operative scar tissue
causing further stenosis and also the risk of instability and post-operative
back pain. However, if the decompression is too limited, the nerve
roots may not be adequately decompressed. In addition bony ridges
can develop post-operatively, tightening up the canal again.
Damage to nerves.
Disc surgery is surgery for the nerve root, and decompessive surgery
removes bony structures where spinal stenosis is causing nerve problems.
These nerves are already vulnerable, having been partially compressed,
and they need to be handled with great care. Even gentle retraction
of the nerves in order to expose a disc or to remove tight bone
can further affect nerve root function. Even when these nerves are
satisfactorily decompressed the patient may be left with some abnormal
nerve function. This can occur even in the best hands and is unavoidable.
There are, however, occasions where nerves are crushed or bruised
by surgical instruments and sometimes a nerve can be severed. This
is the result of poor surgical technique and is generally not to
be expected from a competent spine surgeon. There are occasions,
however, when an experienced surgeon is attempting to decompress
a tight spinal canal, the nerves cannot be fully visualized and
unavoidable contusion can occur. The surgeon may or may not be aware
of this injury at the time.
The most popular method of performing a spinal fusion is to support
the bone graft by using pedicle screws. These screws are inserted
posteriorly through the pedicle of the vertebrae into the vertebral
body. This is done blindly with an understanding of the direction
of the pedicles. Studies have shown that even in expert hands, 20%
of the pedicle screws transgress the pedicle to some degree. Frequently
this is not clinically important but from time to time there may
be a serious transgression of the pedicle and the screw can damage
one of the nerve roots. This occurs when the anatomy of the spine
is slightly abnormal and the surgeon will not usually be aware that
the screw is not within the pedicle. It is only when the patient
recovers from the anaesthetic complaining of leg pain that the surgeon
is aware of this complication.
Radiographs do not usually help to confirm whether or not the screw
has transgressed the pedicle because of so many overlapping shadows.
CT scans and MRI are similarly unhelpful because the metal scatters
images and impairs good definition. Nerve root damage as a result
of a pedicle screw is a clinical diagnosis which can sometimes be
difficult. Nerve root pain can be present post-operatively because
of mechanical disturbance to a nerve root during an associated decompression.
The spinal mechanics may have been slightly altered, compressing
the nerve root, and it is sometimes difficult to be confident that
a pedicle screw is responsible. If a screw has completely transfixed
a root then surgical removal of the screw is not likely to significantly
affect the symptoms. If, however, the nerve root is being irritated
or contused by the screw, the removal will be beneficial. The surgeon
tends to re-operate because of a high level of suspicion and sometimes
is rewarded with a relief of the symptoms. On other occasions permanent
damage will have resulted from this misfortune. Although the surgeon
can not reasonably be blamed for this problem, the patient should
be warned pre-operatively that there is a slight risk of nerve damage
when pedicle screws are to be inserted.
The dural membrane surrounds the cauda equina and the nerve roots
bathed in cerebrospinal fluid. There are two layers of the dura.
If both layers are cut or torn cerebrospinal fluid will leak into
the wound. The extradural veins are usually compressed by the tight
dura and when the cerebrospinal fluid leaks, the dural pressure
falls and the veins become congested. The operation then becomes
difficult because of cerebrospinal fluid and venous blood filling
the wound. Damage to the dura occurs in about 5% of lumbar spine
operation and it is considered an accepted complication that is
sometimes difficult to avoid. Some surgeons then recommend a wider
exposure followed by suturing the dura and others recommend that
the dura not be repaired. These surgeons rely rather on a secure
muscular repair to avoid post-operative leak.
If the dura is contused and torn, the nerve roots which lie posteriorly
in the cauda equina are the sacral roots which supply the bladder
and bowel and sexual functions. The surgeon is therefore particularly
cautious when decompressing at the back of the spinal canal. Rough
handling of the tissues at this level is of course poor practice,
but the surgery can be difficult in the obese patient with marked
A few patients who have a dural leak at the time of operation continue
to have a discharging sinus of cerebrospinal fluid. In the majority
of these the sinus will become dry over a few days, while on other
occasions it will produce a chronic leaking sinus which requires
further surgery. Occasionally a pseudo-menigocele will form with
a large cyst of cerebrospinal fluid, which requires surgical closure.
Damage to blood vessels.
Most patients have minimal blood loss during spine surgery and
do not require a blood transfusion. Extensive decompression and
a spinal fusion using a bone graft from the pelvis will, however,
frequently cause sufficient blood loss to require a blood transfusion.
It is only when a major vessel is damaged that serious complications
occur. The superior gluteal artery leaves the pelvis into the buttock
through the lower part of the pelvis (the greater sciatic foramen).
When taking a bone graft from the back of the pelvis it is possible
to damage this vessel and the surgeon will therefore avoid this
particular region. Bleeding from the superior gluteal artery is
not the result of poor practice, but failure to ligate the vessel
is not acceptable. Sometimes the help of a vascular surgeon is required
to identify and secure the bleeding vessel.
It is possible to damage the aorta or the inferior vena cava when
carrying out a discectomy, if the disc extractor penetrates through
the anterior annulus of the disc. If the surgeon relies on removing
only the loose fragment this complication is not likely to occur.
However, if there is a radical excision of the disc space it is
possible to penetrate through the anterior annulus. This may already
be torn pathologically.
The surgeon is therefore particularly cautious when operating towards
the front of the disc space. It is difficult to defend this injury.
The surgeon is aware that there has been some damage to a blood
vessel anterior to the disc space when there is a small amount of
blood on the instruments. The disc space is avascular and the instruments
should be dry. The anaesthetist may note that there is a drop in
blood pressure and an increase in the pulse rate. There should be
no delay in turning the patient into the supine position and with
the help of a vascular surgeon exposing the damaged vessels. Tragedies
occur when the surgeon procrastinates and hopes the injury is minimal.
It is then frequently too late to avoid a fatal outcome.
Infection can occur from time to time. This can be an airborne
infection or bacteria transmitted from instrument. The surgeon's
gloves can perforate with infection being transmitted from the surgeon's
hands. Sometimes bacteria in the patients own blood (bacteraemia)
can settle in the wound, producing the infection. These are occasional
hazards which are difficult to avoid. Some surgeons recommend perioperative
prophylactic antibiotics, but this is not routine practice.
The surgeon and the surgical team need to be vigilant in the post-operative
period. As soon as the patient is awake from the anaesthetic it
is important to carry out a neurological assessment, particularly
to confirm that there is not abnormal neurology which was not present
before surgery. If there is an area of anaesthesia in the lower
leg and foot or some weakness of the lower leg, this suggests some
nerve root damage by surgery. If the patient has severe pain in
the root distribution which was not present before surgery this
is again evidence of some nerve root damage. A complete transgression
of the nerve root is not usually painful but will give some motor
weakness and sensory loss. Root pain, however, suggests some degree
of nerve compression or irritation.
Sacral anaesthesia and some loss of anal tone suggests sacral nerve
root damage and a possible bladder disfunction. This is a serious
sign which usually requires urgent repeat surgery. If there is sacral
nerve root damage there may be a haematoma pressing on the nerve
roots which can be relieved by decompression. However, if the sacral
roots have been contused by the surgery, further exploration will
In the next few days, if the patient continues with severe root
pain or root pain which was not previously present, it is worth
re-exploring the spine after suitable imaging. It is possible that
the surgery has been carried out at the wrong level or the wrong
side or that the decompression, although at the correct site, has
not been adequate. Further surgery is likely to be helpful. If,
however, nerve root symptoms develop some days after surgery, after
a pain-free interval, this suggests that there has been a fragment
of disc material previously missed which has now extruded and is
pressing on a nerve root. It is no fault of the surgeon. Further
surgery for this fragment after suitable imaging can be helpful.
However, depending on the severity of the symptoms, the pain may
be left to resolve naturally.
If there is a leak of cerebrospinal fluid after surgery the patient
should remain in bed receiving appropriate antibiotics and routine
dressings until the wound becomes dry. If after a few days the wound
is continuing to discharge cerebrospinal fluid, exploration may
Post-operative infection can be the result of a chest infection
or urinary infection. If these can be excluded then the infection
of the wound is the most likely source. There should be no delay
in identifying the source and giving appropriate antibiotics. If
there is a high temperature a blood culture is indicated. Post-operative
discitis is an infection in the disc space. It is associated with
severe low back pain and usually spasm of the spinal muscles. The
patient is in severe pain when attempting to stand. The radiographs
are normal for a few weeks but the MRI scan is very sensitive to
discitis and is the image of choice. A blood culture or needle biopsy
will identify the organism and its sensitivity.
It is a difficult decision to know whether or not to operate again
in the post-operative period. The complications of the second operation
are greater than the first, but provided the indications are correct
there can be a considerable bonus in performing this procedure.
The inexperienced spine surgeon should seek a second opinion before
embarking upon repeat surgery.
One of the most common causes of patient dissatisfaction is failure
to receive sufficient information about surgery and its risks. At
the present time, spine surgeons would agree that every patient
should be given information about risks and benefits. In broad terms
patients should be informed of the changes of improvement by surgery.
For example, when performing a discectomy for nerve root pain there
is something like a 90% chance of relief of leg pain by surgery.
When decompressing the spine for neurogenic claudication there is
a 60% chance of reducing the symptoms and perhaps a 60% chance of
relieving chronic back pain by a spinal fusion.
The patient should also be told in general terms, the risk of not
being improved by surgery. For example, in discectomy there is a
10% chance that some leg pain will persist in the short term. The
nerve has been bruised for a long time and even though the fragment
of disc has been removed the nerve can remain sensitive and painful.
When offering fusion for low back pain, 40% may continue with their
There is always a remote risk that the patient could be worse.
They should be told of this possibility. In disc surgery 2 or 3%
can be worse as a result of damage to a nerve root, a leak from
the dura or some post-operative infection, and there is always the
chance of some anaesthetic complication. Patients are not usually
told about these remote risks in great detail, or why they could
be worse by surgery. If, however, they specifically ask how they
could be worse, then it is the surgeon's responsibility to explain
some of these problems. When carrying out decompression for neurogenic
claudication or a fusion for chronic back pain, patients are told
that not only may their symptoms not be relieved but they could
have more pain and over a period of time things could get steadily
worse. There is about a 5% chance of having repeat surgery after
discectomy and 10 to 20% chance of having further surgery after
decompression for neurogenic claudication. There is a similar risk
of repeat fusion for chronic low-back pain. The broad concept of
improvement, failure to relieve symptoms and the change of being
worse should be explained to every patient and also recorded.
In spite of these many pitfalls most patients do well. Fortunately
those patients who have careful pre-operative selection, competent
surgery and good post-operative management are significantly helped
by their operation, and provide they are aware of potential risks,
patients usually accept that the surgeon and the surgical team have
done their best in a very difficult area of medical care.
Taken from the Journal of the Royal College of Surgeons Edinburgh.
1997; 42: 376-380.