Lumbar Pedicle Screw Fixation
What is a lumbar pedicle screw fixation?
A spinal fusion is performed in cases where the spine is unstable and can’t maintain the functional alignment between all of its key parts, or if the abnormal movements cause pain and put adjacent structures at risk of injury. Spinal instability can be caused by degenerative joint disease, spondylolysis, fractures, infections and tumours. A spinal fusion joins two vertebrae together to make one large bone. The surgeon roughens up the external surfaces of the two vertebrae to make the body’s natural repair system think that one large bone has broken. The surgeon then adds bone to fill the gap and the body joins the mass together, like a normal fracture. While the bone is healing it is held in position by means of screws and plates or rods and full fusion generally takes 3 months. Given the numerous reasons for a lumbar fusion, the success rate varies widely. In degenerative joint disease, surgery is always optional, but with cancer and fractures, there is often no choice but to have a fusion.
Bone chips can be taken from the patient’s hip at the time of the operation and then grafted onto the vertebra. Alternatively, bone can be harvested from other patients and stored until needed in a bone bank. Using bone from the bank spares the patient the pain of the harvesting surgery, but it doesn’t produce as high a fusion rate as using the patient’s own bone would. Artificial and natural bone substitutes are also available and Bone Morphogenetic Proteins may be used to accelerate the fusion rate.
- Avoid bending, lifting, twisting and prolonged sitting
- Pain relieving medications
- Physical therapy
- Weight loss
- Steroid and local anaesthetic injections around the nerves or into the facet joints
- Lumbar disc replacement (less common)
Smoking damages every part of the body and decreases the chance of a successful procedure. If you smoke, you should stop now.
Before the procedure
- Your doctor will complete a medical exam to ensure that you are in good general health before continuing with the operation.
- You will be advised when to stop any medications that will increase your risk of bleeding, including aspirin, anti-inflammatories, vitamin E, and some herbal remedies such as chamomile, gingko and fish oil, among others.
- You may be admitted the day of, or the day before, your procedure.
- Don’t eat or drink anything 6 hours before the procedure.
- Wear comfortable, loose-fitting clothing and leave all jewellery at home.
- An intravenous line will be inserted into a vein in your arm for ease of fluid administration.
- You may be given a sedative to make you drowsy before being given your anaesthetic.
- You will be given a general anaesthetic to put you to sleep.
- Let your doctor know if you develop a cold, fever or flu-like symptoms before your operation.
The patient is placed in a kneeling position and the skin is cleaned. An incision is made in the middle of the back and the overlying muscles are moved to the side. Using X-ray imaging, the surgeon confirms the correct vertebrae for the procedure. The ligamentum flavum is separated from the lamina and then removed. The spinous process and lamina are removed at each level needing to be decompressed. Next, the tracks for the pedicle screws are prepared. The hard bone surface is removed. A guide track is inserted under X-ray guidance. Its depth and position are checked. Then a thread is tapped into the bone and the pedicle screw is placed. The vertebrae are prepared for the other pedicle screws, and the transverse processes and facet joint are prepared for the bone graft. The bone graft and the remaining pedicle screws are then placed and the brackets and rods are installed. X-rays are used to check the position of the screws and rods. The muscles are replaced and the wound is closed with sutures.
- A lumbar pedicle screw infusion typically takes 4 to 8 hours.
- You may need to spend 1 to 2 nights in intensive care and a total of 5 to 10 days in hospital.
- An epidural anaesthesia can be used to prevent pain for the first 24 hours. Thereafter, patient-controlled analgesia is available. A bladder catheter is used for the first few days.
- On day 2 or 3, you will start standing and walking with help. Your surgeon may require that you wear a lumbar brace every time you are out of bed for the first 3 months.
- Your bowels may not open for a few days after the procedure, so pain medication, muscle relaxers and laxatives can be used as directed.
- Limit exercise to walking only for the first 6 to 12 weeks.
- Avoid bending, twisting, lifting or making any other sudden movements as they can break the screws and cause non-fusion to occur.
- If you’re given a brace to wear, it should be worn whenever you are out of bed. However, you don’t need to wear it while you are sleeping, or to go to the bathroom in the middle of the night.
- Don’t drive for 6 weeks. You can be a passenger for up to 120 minutes maximum. If you do have to travel for a longer period, take several stops so that you can stretch your legs. Reclining the passenger seat will provide you with the greatest comfort during travel.
- Don’t sit for longer than 30 minutes. You can gradually increase this time as you become more comfortable.
- Walk as much as possible. Stairs are good but climb them slowly. You can use a treadmill but avoid running. If you were discharged from hospital with a walker, or cane, you may stop using it once you feel safe and comfortable.
- A follow-up appointment with your surgeon will be booked for 6 weeks after the surgery. Repeat spine X- rays are usually taken at 6 weeks, 3 and 6 months and 1and 2 years.
- The wound must be checked daily. If you notice any redness, swelling, green or yellow discharge, or opening of the wound, or if the dressing becomes soaked with a large volume of fluid contact your GP immediately and call your surgeon.
- If you have small bandages on your incision, it’s important to keep these dry. Once they start peeling off, you may remove them (typically after 2 weeks). All external sutures will be removed in 1 to 2 weeks.
- Keep the wound dry. While you may shower with a water-occlusive wound dressing, avoid bathing, swimming or using creams for 2 weeks.
- The incision site may be gently cleaned using soap and water. Rub gently and avoid using perfumed soaps.
- If your incision has staples or sutures that need removing, your nurse or local doctor can take them out after 2 weeks.
Despite having surgery, your back will never return to full strength. You will always have a weak spot and you will need to commit to lifelong care to prevent further injury. Maintain correct posture, eliminate excess body fat, follow a daily exercise program and avoid unnecessary stresses to your back.
The right to refuse
You have the right to informed refusal, which means you can delay or reject the recommended treatment of your condition. Be mindful however that this may lead to the worsening of your neck pain and ask your doctor to detail what may happen should you choose not to undertake the recommended treatment.
Allergic reaction to medication
This can cause a rash, swelling of the hands, joints, eyelids and throat, difficulty breathing, low blood pressure and death. An allergic reaction is easily controlled with the correct equipment and medication.
Adjacent Segment Syndrome
When a part of the spine has been fused – limiting movement in that area – stress can be transferred to the adjacent segments. This can increase wear and tear in these adjacent intervertebral discs, facet joints, pars articularis and ligamentum flava, and can lead to increased mobility and pain. Known as adjacent segment syndrome, or transitional syndrome, it is more likely when multiple segments are fused, abnormal alignment, facet joint injury during surgery, increased age and pre-existing degenerative changes. Up to 20% of fusion patients might need another operation to treat the symptoms related to the adjacent segment degeneration. A degree of pre-existing degenerative disease might be present in the adjacent segments and it is sometimes difficult to determine if abnormalities in the adjacent segments are due to adjacent segment disease or progression of pre-existing disease or a combination of both.
There are a number of different types of anaesthesia:
Local: the medication is injected into the skin around the site of the surgery to numb only surrounding tissues.
Regional: where the body part is anaesthetised by numbing major nerves or part of the spinal cord.
Conscious sedation: where a full anaesthetic is not given, rather, medications are used to create a near-sleep relaxed state.
General: where you are rendered unconscious and temporarily paralysed. In this instance, medication is given to you through an IV line, and machines breathe for you and monitor you together with the anaesthesiologist. Most spinal operations require general anaesthesia, so that you can’t move during the operation.
There are many possible complications associated with a general anaesthetic. 1 to 10% of these include:
Post-operative nausea and vomiting: this may last a few hours to several days. It can be the result of the operation, anaesthetic and pain killers.
Aches: as a result of lying immobile on a firm operation table for a long period of time.
Blurred vision/dizziness: due to low blood pressure from fluid loss or medication. Can be treated with fluid replacement and medications.
Bruising/pain: around injection and intravenous cannula sites. This usually settles by itself and the cannula can be moved if necessary.
Headaches: due to the anaesthetic, dehydration or anxiety. These may last a few hours but can be treated with medication.
Itchiness: can be an allergic reaction to drugs, sterilising fluid or sutures, or as a side effect of strong pain-relieving medication (opiates).
Memory loss/confusion: this is more common in older people who have had a general anaesthetic. There are many causes and may last a few days or even weeks.
Pain from drug injection: some drugs cause pain when they are injected.
Shivering: can be caused by medication, stress or low body temperature during the surgery. Shivering can be treated with a hot air blanket or medication.
Sore throat: from the breathing tube. This may last a few hours to a few days. Can be treated with pain-relieving lozenges.
Uncommon complications (0.1%) include:
Anaesthetic awareness: if you are ill, your anaesthesiologist may use more muscle relaxants and less general anaesthetic to reduce your risk. However, this may lead to you being aware of your body and your surroundings during the operation. Anaesthesiologists use monitors to observe your body’s reactions and adjust the medication doses. If you think you’ve been aware during the operation, it’s important to tell your anaesthesiologist afterwards.
Bladder problems: depending on the operation and the medications, men may find it difficult to urinate, while women tend to leak after the operation. If necessary, a urinary catheter is used to drain the bladder until control returns.
Chest infection: this may lead to breathing problems, but can be treated with antibiotics. This is more likely to occur in people who smoke.
Lip, teeth, tongue injury or jaw dislocation: this can be caused by difficulty placing the breathing tube, or by clenching your teeth as you recover from the anaesthetic.
Muscle pain: can be caused by a muscle-relaxing drug that is used to prevent vomiting during emergency surgery.
Slow breathing: can be due to some painkillers or muscle relaxants. Can be treated with medications.
Worsening of existing medical condition: your Anaesthesiologist will monitor your body closely and act to eliminate or reduce any medical complications.
Very rare complications (0.0005 to 0.01% of general anaesthetics) include:
Death: is very rare and usually occurs when 4 or more complication occur simultaneously. Death from anaesthesia occurs in 1 of every 200 000 cases,
Equipment failure: vital equipment can fail, but this is very rare, and monitors give immediate warnings.
Eye damage: eyelids are taped shut to protect them during surgery. Rarely, sterilizing fluid may leak under the eyelids, or you may rub your eyes while waking from the anaesthetic. Any discomfort is usually temporary.
Nerve damage – stretch, compression, incision or puncture: recovery usually occurs within 3 months of the procedure.
Serious allergic reaction to medication: This is noticed and treated quickly, but can very rarely cause death, even in healthy people.
Back pain (that is similar or different to the original back pain) after the procedure is to be expected and is usually temporary. Sometimes the original back pain can persist or can even be worse.
Bone Graft Displacement
During a bone graft, bone fragments are placed in the space between two bones. If the bones are kept still for long enough, the fragments fuse with one another – and the adjacent bones – to form a solid and pain-free single bone. However, if excess movement occurs before fusion has occurred, the graft can become displaced. This can result in pain, injury to adjacent tissues, mal-alignment of the bones or non-fusion, which is known as non-union or pseudo-arthrosis.
Bone Graft Misplacement
Every effort is made to ensure that bone grafts are placed in optimum positions. However, there are rare instances where these implants are not optimally placed and a further procedure may be required to correct this. Misplacement may be the result of anatomical variations, equipment limitations or system failures.
Bone morphogenetic proteins
Bone morphogenetic proteins (BMP) stimulate bone growth naturally in the human body. These proteins that exist in the body can be produced, concentrated and placed in the fusion site in surgery to attract bone-forming cells and to stimulate cells to form bone. More importantly, they can create a fusion without the need for any use of the patient’s own bone.
Although MPS are more expensive in comparison to bone graft, the advantages are numerous:
- They decrease fusion time by a third. This means faster hospital discharge and a faster return to day-to-day activities.
- They increase the successful fusion rate to up to 90%.
- They bypass the pain, blood loss and risk of infection and nerve damage that may occur during the bone graft harvesting procedure.
- Bone growth in unwanted sites.
- Transient desorption of adjacent bone.
- Seroma formation or local oedema.
- Local inflammatory reaction.
- Potential development of an immune reaction, particularly if used in subsequent surgeries.
- Effects on developing embryo in pregnancy are unknown.
Cauda Equina Syndrome
Cauda equina syndrome (CES) is a rare but serious condition that describes extreme pressure and swelling of the cauda equina bundle of nerves located at the base of the spinal cord in the spinal canal. These nerves transmit movement and sensation information to and from the lower body and also manage the bladder, bowels and sexual function. Should pressure be applied to these nerves as a result of damaged disc or bone, tumour, infection or bleeding, they can become inhibited. If the pressure is not rapidly alleviated, permanent nerve damage can occur. Cauda equine syndrome can cause leg paralysis and numbness, impaired bladder or bowel control, loss of sexual sensation and other problems.
This is when the dura (which contains the spinal cord and the cerebrospinal fluid) is torn and cerebrospinal fluid leaks out of the sac. Symptoms include a headache when standing, back or limb pain, nausea, vomiting, dizziness, ringing in the ears or sensitivity to bright light, including a risk of infection and meningitis. The dural tear may reseal spontaneously or it may need best rest, drainage or surgery to repair.
No operation is risk-free. Complications resulting from a procedure can range from minor troubles to major disability. Even when a surgery has gone well, serious problems can still arise and result in pneumonia, heart attack, stroke or even death. The entire medical team is highly trained and committed to eliminating all risk pre-, during and post-surgery as much as is humanly possible.
Deep Vein Thrombosis
Any surgery can put you at an increased risk of deep vein thrombosis (a blood clot that forms inside the large deep veins of the legs). The reason for this is twofold: The blood’s clotting mechanism is activated by surgery, injury to blood vessels, immobility and anaesthetic effects during and after the surgery make it easier for clots to develop.
The danger of a DVT is that it can block the blood flow from the legs back to the heart, causing swelling of the legs with resultant pain. If the clot doesn’t dissolve properly, the swelling and discomfort can become permanent. Alternatively, the clot in the leg can detach and travel up the veins to the lungs, where it blocks the smaller lung blood vessels and stops the blood flow. This is called a pulmonary embolus, or PE. If the PE is large enough, or there are many of them, it can cause death.
Patients who are at additional risk of DVT are: over the age of 50, have varicose veins, have had a previous heart attack, cancer, atrial fibrillation, an ischemic stroke, diabetes, previous DVT, heart failure, combined oral contraceptive pill use, smoking, obesity, leg weakness and inherited clotting abnormalities.
Discitis is an infection of the intervertebral disc and can occur spontaneously or post-operative. Risk factors for discitis include age, smoking, smoking, obesity, diabetes, malignancy, chemotherapy, immune suppression, malnutrition, indwelling venous catheters, concurrent infections and extended hospitalisation. Post-operative discitis can occur up to 6 weeks after a disc operation or injection, and in most instances causes worsening pain after an initial period of relief. Discitis is treated with antibiotics over a long period of time (months).
The dura is a thin layer of tissue that forms a sac containing the brain, spinal cord and nerve roots. This sac is filled with cerebrospinal fluid and can be torn during spinal surgery. It’s a complication that is more difficult to avoid during repeat surgery in the same location, or when operating on severe spinal narrowing or a large disc herniation. A dural tear – and the subsequent leakage of cerebrospinal fluid – can cause a headache when standing, back or limb pain, nausea, vomiting, dizziness, ringing in the ears or eye pain from bright light. A continual leak can lead to a cerebrospinal fluid cyst under the skin or leakage of fluid from the wound. Dural tears can reseal spontaneously, or it may need bed rest, a blood patch procedure, draining or an additional operation to repair.
Dysesthetic Leg Pain
Sometimes a burning hypersensitivity leg pain occurs after the procedure. This dysesthetic pain may resolve over a few days, but it can also be permanent. The cause of dysesthetic leg pain is unclear.
Should bleeding occur into the epidural space around the spinal cord, it can form a blood clot known as an epidural hematoma. If the hematoma is large, it can compress the spinal cord and nerve roots leading to pain, weakness, numbness and bowel and bladder problems. A surgical procedure may be needed to stem the bleeding and remove the hematoma.
During general anaesthesia the patient’s eyes are taped shut to protect them from the risk of drying or scratching. Should they become dry or scratched however, they typically heal within a day or two. Blindness is a rare complication that can be caused by too much pressure on the eyeball or decreased blood flow through the eye (ischemic optic neuropathy (ION)). Blindness due to ION is a 0,1% risk and is associated with emboli, prolonged spine surgery in patients older than 70, a face-down operating position, diabetes, intraoperative blood loss/hypotension and ankylosing spondylitis (poor position owing to a deformity of the neck).
Fluoroscopy is similar to an “X-ray movie”. A continuous X-ray beam is passed through the body part being examined, affording the surgeon instant imagery of the inside of a patient during a procedure enabling him or her to accurately position any devices. The disadvantage of fluoroscopy is that X-rays can potentially cause cancer, reproductive abnormalities, cataracts and radiation dermatitis. That said, the exposure during surgical procedures is usually not significant and doctors make use of protective lead shields and minimize the intensity and duration of exposure.
During any surgery, some blood vessels will be cut. And although the surgeon stops all significant bleeding before closing the wound, there are instances in which bleeding restarts and forms a collection of blood in the tissues. Known as a hematoma, this can cause pain, put pressure on the adjacent tissues or become infected. A drainage tube may need to be inserted or a surgical operation performed.
Surgeons may need to cut some blood vessels in order to access the spinal operation site. The surgeon will plan the surgical route to avoid large blood vessels and will make sure that all bleeding has stopped before finishing the operation. Occasionally, one of these vessels can re-bleed after the procedure and if the rate, or the location of the bleed is problematic, a further procedure may be needed to stem the bleeding and drain the accumulated blood clot.
Post-operative ileus is a temporary paralysis of the bowel. This condition is usually caused by narcotic pain-killing medications, intra-abdominal, spine or chest surgery. Symptoms include abdominal discomfort and bloating, constipation, nausea or vomiting. Through fasting and minimising the use of narcotic medication most cases will settle within three days. Occasionally though the stomach may need to be emptied using nasogastric suction tubes and intravenous feeding and fluid is required.
Spinal fusion operations use screws, plates, rods and spacers to hold the vertebrae in correct alignment while the bone fuses together over the first few months. Once the bone fuses these implants are no longer necessary but are often left in place. Sometimes, before the bone has fused, an implant may break or shift from its correct position, causing pain, injury to adjacent tissues, mal-alignment (of bones) or non-fusion of bones (non-union, pseudoarthrosis). Another operation may be needed to remove or replace the implant.
Spinal fusion operations use screws, plates, rods and spacers to hold the vertebrae in correct alignment while the bone fuses together over the first few months. Rarely, because of anatomical variations, equipment limitations or system failures, the implants are not optimally placed and a follow-up procedure is needed.
Infections occur in less than 1% of spinal operations and are more likely in patients that smoke, have diabetes, are overweight, or had a hematoma. Symptoms of an infected wound include: increased pain, swelling, tenderness, redness, oozing (clear or yellow fluid), slowness to heal, or if the patient experiences fever or chills.
Infections can be superficial (involving the skin), which usually respond to oral antibiotics and washing of the site. Sometimes the wound needs cleaning and re-suturing. Deep infections (involving the vertebrae or spinal cord) are more serious and may need intravenous antibiotics and an operation to drain the infection. On rare occasions, infected bone graft or hardware may need to be removed.
This rare life-threatening condition is passed down through families and can be triggered by some drugs that are used for general anaesthesia. In susceptible people, the drugs can cause an uncontrolled increase in skeletal muscle calcium levels and muscle contraction, leading to decreased blood oxygen and increased blood carbon dioxide and body temperature. This can lead to circulatory collapse and death if not quickly treated. Symptoms usually develop within an hour of drug administration. As yet, there is no simple test to diagnose susceptibility but it is usually found during drug administration or suspected if a family member develops the symptoms. While treatment is effective, it is critical that patients, who have a family history of malignant hyperthermia, discuss this with their doctor so that the use of the potential trigger drugs can be avoided.
Nerve Injury – Lateral Femoral Cutaneous
The lateral femoral cutaneous nerve supplies sensation to the front of the thigh. It usually passes under the inguinal ligament in front of the hip, however, in some people it passes over the anterior iliac crest, near the site of bone graft removal. This nerve can be injured during bone graft removal or by prolonged pressure while lying in surgery. Injury can cause pain, pins and needles or numbness on the front to the thigh called meralgia paresthetica. Pressure injuries usually resolve within 3 months, but if the nerve has been cut, the symptoms may be permanent.
Nerve injury – Lumbar
Vertebrae surround the spinal nerve roots. This means that accessing or repairing damaged vertebra can potentially bruise, stretch, tear or cut these nerves roots – either within the spinal canal – or as they leave the spinal canal through the invertebral foramen. Locating, protecting and mobilising the spinal nerves can be the most sensitive and time-consuming part of spinal surgeries. If a nerve is damaged, the injury can cause temporary or permanent pain or bladder and bowel dysfunction as well as partial or complete loss of sensation or movement in the patient’s leg.
Nerve Injury – Ulnar
During surgery the medical team carefully positions the patient’s body so that the injured region is easily accessible. This can result in the ulnar nerve (located in the arm) being compressed or stretched at the elbow. Symptoms of pain, numbness or weakness in the hand can appear up to 4 days after surgery and usually disappear over a few weeks.
Failure of the two vertebrae to fuse into one solid bone is called non-union or pseudo arthritis This occurs in about 10% of spine fusion operations. Nicotine products, including chewing tobacco, and cigarette and cigar smoking, can slow bone healing and significantly increase the likelihood of non-union. Consuming high doses of non-steroidal anti-inflammatory drugs after the operation can also increase the risk of non-union. Other causes are excessive alcohol intake, the location and number of segments fused, osteoporosis and some medical diseases. Non-union can cause worsening pain and may cause the supporting hardware to break. Additional surgery may be required to add more bone graft, replace the hardware or add an electrical stimulator to encourage the fusion to heal.
Osteomyelitis is a bacterial infection of bone or the bone marrow. It can occur as a result of surgery, especially after the replacement of foreign material in the bone, or as a result of an adjacent infection. Symptoms can take up to 4 weeks to appear after surgery – the most common of which is worsening pain after an initial period of relief. Risk factors include age, smoking, obesity, diabetes, malignancy, chemotherapy, immune suppression, malnutrition, indwelling venous catheters, concurrent infections and extended hospitalization. Osteomyelitis is difficult to treat and often requires weeks or months of intravenous antibiotics and a surgical procedure to clean the area.
The spine surrounds and protects the spinal cord. This means that any surgery to the spine carries a degree of risk and the surgeon takes great care when working on the operation site. Damage to the thoracic, lunar or sacral spinal cord can cause loss of movement and sensation in the lower half of the body. It can be complete, with no movement or sensation below the level of the spinal cord injury, or incomplete with some movement or sensation. Paraplegic patients generally need to use wheelchairs or other walking aids. Urinary and faecal incontinence and impotence are common and paraplegics are at an increased risk of pressure sores, thrombosis and pneumonia.
Prolonged surgery and bed rest can result in the formation of skin pressure sores over prominent bones. The nursing team carefully place, pad and manoeuvre the patient to prevent this from happening.
Surgery can’t restore the back to a pre-diseased state. This means that some remaining post-procedural pain is very common. Furthermore, a degree of discomfort from the operation site – and pain from adjacent areas already damaged by the disease or by their own degenerative problems – can be expected. Usually, any residual pain is mild, but it may be severe or even worse than the original problem.
Urinary Tract Infection
Given that patients undergo general anaesthetic during surgery and are confined to recuperative bed rest, they aren’t able to go to the toilet to urinate. As such, a urinary catheter is passed along the urethra to freely drain the bladder and avoid bladder discomfort. The presence of a urinary catheter does increase the risk of bacteria entering the bladder and causing a urinary tract infection. Treatment usually requires the catheter to be removed, followed by a course of antibiotics.