Risks and Complications

Risks and Complications 2023-04-02T12:19:09+00:00

All procedures and operations, no matter how minimal, carry risks and complications. However when these occur in spinal surgery, although they are rare, they can be very serious. Therefore it is very important that you fully understand all the risks and complications involved in your surgery. Mr Hilton will take time to fully explain the potential problems involved and allow you time to decide whether you wish to proceed with surgery. Mr Hilton works closely with the consent procedure and guidelines set out by the British Association of Spinal Surgeons.

Summary of Risks and Complications Of Surgery

  • Bleeding (minor and major vascular damage)
  • Infection
  • DVT/Pulmonary Embolism
  • Minor and Major Nerve Damage (including foot drop, cauda equina syndrome, paralysis)
  • Dural Tear/CSF leak
  • Failure of Bone Fusion
  • Perineural Fibrosis (scar tissue forming around nerves)
  • Failure to Relieve or Recurrence of Symptoms
  • Worse Pain or Symptoms
  • Back Pain
  • Failure of Implants and Misplacement of Implants
  • Medical Complications including CVA (stroke), MI (heart attack), Blindness and Death


A small amount of bleeding is expected and the operation does not finish until the bleeding has stopped. However very occasionally patients will continue to slowly bleed/ooze and a collection of the blood can build up. If this continues, the collection of blood may press on the spinal nerves which can cause Cauda Equina Syndrome. If this occurs a further urgent operation will be required to remove the blood collection.

Major vascular injury causes significant bleeding which is potentially life threatening. Significant blood loss is rare; in lumbar spine surgery the risk is about 0.05 – 4%. If this occurs, repair would be immediate however the bleeding is life threatening.


Infections following surgery can be superficial wound infections or deep spinal infections. Superficial wound infections are not common but can occur in  2 – 4% of spinal operations. Risks of infection are increased in diabetic patients, patients who smoke, patients on steroids, patients with lowered resistance to infection (immunosuppressed) and patients on disease-modifying anti rheumatic drugs (DMARDs) and biologic drugs.

Most superficial infections are easily treated with antibiotics.

Deep infections are much more serious but also much less common. A deep spinal infection occurs in less than 1% of cases. If a deep infection occurs it usually requires another operation to ‘washout’ the infection and a long course of antibiotics.

Minor and Major Nerve Damage

During the operation the spinal nerves have to be moved and protected in order to remove the disc which lies under the nerve. During this process the nerve can be stretched or the nerve can be damaged by direct surgical trauma or by pressure effects necessary to control bleeding.

Furthermore the spinal nerve causing the pain may already be intrinsically damaged by the disease process. The disc prolapse can cause scarring with in the nerve such that it is unable to recover despite technically successful surgery.

Just moving and protecting the nerve can cause minor nerve damage for example loss of sensation, altered sensation, pain or pins and needles. These symptoms are usually only temporary but maybe permanent.

Major nerve damage can result in a foot drop, cauda equina syndrome (double incontinence and loss of sexual function) and paralysis. Again, these maybe temporary or permanent.

Paralysis is understandably one of the most feared complications of spine surgery however it is also one of the least complications to occur especially in lumbar spinal surgery. The risk of paralysis, which means loss of use of the legs, loss of sensation and loss of control of bowels and bladder is low and is reported to occur in less than one in 300 of all spinal operations. Paralysis can be caused by the following reasons:

  • Bleeding into the spinal canal after surgery (an extradural spinal haematoma). The risk of paralysis is higher if patients are taking blood thinning medication (warfarin). If this happened every effort would be made to reverse this situation which would include re-operating.
  • An incidental durotomy (leak of spinal fluid). Again, if adverse event of this nature was to occur every effort would be made to reverse the situation.
  • Sometimes paralysis can occur as a result of damage to the blood supply of the nerves or spinal cord, and this is not reversible.
  • In the presence of pre-existing nerve or spinal cord damage causing muscle weakness or where a nerve or the spinal cord is already squashed there is an increased risk of these structures being injured further because of the manipulation needed to try to free the nerve or spinal cord.
  • The risk of paralysis is also increased by the area of the spine being operated on and the complexity of the surgery.

Cauda Equina Syndrome

Cauda Equina Syndrome (CES) can cause double incontinence, loss of sexual function and paralysis. The symptoms can start as numbness or loss of sensation around the bottom area (back passage, perineum, testes and penis) and loss of sensation whilst passing urine/opening bowels or incontinence. CES following a spinal operation can be caused by bleeding into the spinal canal or due to a leak of CSF (spinal fluid) after the surgery. Urgent surgery is required in order to attempt to reverse these symptoms.

Dural Tear and CSF Leak

The brain, spinal cord and spinal nerves are surrounded by a thin membrane called the dura. The dura also contains the CSF (cerebrospinal fluid). During spinal surgery the nerves usually have to be moved in order to protect them and this can result in a small tear in the dura due to it being stuck onto the disc or bone. A small amount of CSF may leak out but be reassured, CSF is being replaced constantly.

The dural tear is repaired at the time of surgery, usually with small stitches or a patch. Following the surgery, some patients may have no symptoms however others may experience a headache and in these cases, a few days of bed rest is usually all that is needed. Very occassionally a patient needs to be taken back to theatre.

In primary microdiscectomies for sciatica, dural tears occur in about 3% of operations. In decompression surgery it is more common, happening in 8% of operations. In revision surgery, the risk of a dural tear is much higher due to scar tissue which means that the nerves are more likely to be stuck onto the disc and bone.

Failure of Bone Fusion

The risk of non-bony fusion is 5%. There are a number of factors that increase the risk of not getting a solid fusion following surgery and these include:
• smoking
• diabetes or chronic illnesses
• obesity
• malnutrition
• osteoporosis
• post-surgery activities eg. heavy lifting
• long-term  steroid use and post-operative regular NSAIDs (non-steroidal anti-inflammatory drugs)

Of all these factors, the one that can compromise fusion rate the most is smoking. Nicotine has been shown to be a bone toxin and stops the bone-growing cells in the body to grow bone. Patients should make a every effort to allow their body the best chance for their bone to heal by not smoking, ideally 2-3 months before the operation. Some surgeons may be delay surgery if you have not stopped smoking beforehand.

Perineural Fibrosis

As much as we scar on the outside of our bodies we also scar on the inside of our bodies. It can be difficult to predict the degree of scaring and in whom scarring will occur most. Perineural fibrosis simply means ‘scar tissue that develops around nerves’ and can cause pain and/or altered sensation. Unfortunately scar tissue is very difficult to treat because further surgery can result in more scar tissue forming.

Perineural fibrosis also increases the risk of other complications in revision surgery, for example dural tears.

Recurrence, Failure to Relieve or Worse Symptoms

  • 70% of patients should have their pain reduced by 50% following a spinal fusion
  • 25% of patients may not have any change in their pain or symptoms
  • 5% of patients maybe worse

Back pain

The majority of lumbar spine operations is to help leg pain or symptoms rather than back pain. Furthermore, since the operation is performed through the back, patients maybe left with some back pain they did not have before. Rehabilitation and re-conditioning exercises are very important to help reduce this risk.

Misplacement or Failure of Implants

Difficulty with screw placement can cause injury to the nerves or screw breakage cage / implant movement can occur in up to 2 out of 100 cases, with 1 out of 100 requiring an operation. In extremely rare cases, cage movement can cause severe damage and cauda equina syndrome (paralysis, bladder or bowel incontinence)

Medical Complications Of Surgery

Patients undergoing spinal surgery are at risk of medial complications. The risk depends upon an individual patients current health and past medical history and as a general rule, surgery is less risky and is safer on fit and healthy patients. Therefore it is common sense to take responsibility as a patient to reduce the risks whenever possible. Simple measures such as stopping smoking, losing weight and improving aerobic fitness all help.

Older patients may have specific risk factors such as heart disease. Tablets used to thin the blood such as Warfarin, Aspirin or Clopidogrel increase the risks of bleeding and you must inform Mr Hilton and his team if you are taking any of these.

Your specific relative risks will be discussed in detail with Mr Hilton before making the decision to proceed with surgery.

Myocardial Infarction (MI)

MI or heart attack occurs when there insufficient blood supply to the heart. This is more likely to occur if a patient has had previous heart problems.

Cerebrovascular Accident (CVA)

CVA or Stoke is when there is inadequate blood supply to the brain, which leads to an area of the brain becoming damaged. This is more likely if a patient has had a previous problem.


Death during or following planned/elective spinal surgery is extremely rare, however death can occur with any surgery and usually occurs after the operation. The most common reasons are myocardial infarct (heart attack) due to the stress of the surgery, blood loss, a rare reaction to a drug (anaphylaxis) or pulmonary embolus.

Death following General Anaesthetic (GA) complications have been reported in 1 out of 250,000 cases.


Loss of vision (blindness) following spinal surgery is a very rare complication that has an estimated incidence of 0.01–1%. Patients with preoperative risk factors (glaucoma, hypertension, diabetes, smoking and atherosclerosis) having prone spinal surgery at risk of severe blood loss are now known to be at significantly increased risk of postoperative visual loss secondary to ischaemic optic neuropathy, and consideration should be given to warning them of such a risk.

Retinal artery thrombosis  or central retinal vein occlusion reduction of pressure


Smoking reduces the success rate of fusion due to interfering with the development of new blood vessels and inhibits bone forming cells (osteoblasts) which are essential for developing new bone.

Patients who smoke are also at higher risk of wound infections (both superficial and deep), chest infections,

Over Weight and Obesity

Complications following spinal surgery occur more commonly in people who are overweight and obese. Being overweight makes makes the operation technically more difficult to access the correct area in the spine that is being operated on. There is a higher risk with the general anaesthetic and therefore the anaesthetist will be involved with decision to operate in elective cases and our goal is to not only help patients to be pain-free but to also to keep them safe during the operation.

Following the operation, the risk of infection, DVT, PE, chest infections/pneumonia, heart complications, nerve injury and post-operative swelling.

Evidence from The American Academy of Neurosurgeons shows that spinal fusion failure and failure to relieve symptoms (Failed Back Surgery) is higher in obese patients.

Ideally a patient’s Body Mass Index (BMI) should be less than 35.


Patients who have diabetes have a slightly increased risk of infection generally and the nerves in diabetic patients may not recover as well as patients without diabetes.