Decompressive Lumbar Laminectomy

A decompressive lumbar laminectomy is a surgical procedure where the posterior aspect of the lumbar spine is exposed and a central area of bone at the back of the spine, along with any overgrown ligament which is narrowing the spinal canal, is removed. The most common reason for this procedure is to relieve nerve compression due to degenerative spinal canal stenosis.

Anatomy of the Lumbar Spine

The lumbar spine consists mainly of the vertebrae or bone of the spine with a disc in between each bone. There are five lumbar vertebrae (referred to as L1-5) .The main part of the vertebra is called the body and is located towards the front. The disc is located between the vertebral bodies. Each disc is referred to by the bones between which it sits. For example the L4/5 disc is located between the L4 and L5 vertebral bodies.

Behind the vertebral bodies there is a ring of bone that contains the bottom of the spinal cord which ends at L1/2 and the nerve roots. The back of this ring is made of the lamina and spinous processes to which several muscles are attached. For most of the lumbar spine, there are a group of nerve roots which trail down from the bottom of the spinal cord. The nerve roots, which are surrounded by spinal fluid and which are enclosed in a sac called the dura, are referred to as the cauda equina which translates to ‘horse’s tail’. At each level a nerve root exits the spine through a hole between each bone called the intervertebral foramen. That nerve root will supply feeling (sensation) to a particular area and will also supply particular muscles that perform different movements.

The disc is made of two main elements. The first is the annulus fibrosis. This is a strong outer layer made of criss-crossing fibres. The inside of the disc, or nucleus pulposis, is the soft gel-like centre which normally provides the cushioning functions of the disc. When a disc becomes unhealthy the nucleus can become shrunken and loose its normal water content. As a result the annulus tends to bulge and in some cases can rupture leading to protrusion of the unhealthy nucleus into the spinal canal.

Indications for Surgery

There are numerous reasons for which a lumbar laminectomy is performed. For instance it may be the first part of a more extensive procedure such as spinal fusion or may be performed to gain access to a spinal tumour. However, by far the most common indication for the operation is to decompress the nerve roots in the lumbar spine.

Degenerative Spinal Canal Stenosis: This is a common condition in which the space or spinal canal for the spinal nerve roots (cauda equina) becomes too small. This occurs due to a combination of three factors. The first is usually broad bulging of the discs. The second is the overgrowth of the facet joints at the back of the spine on each side. Finally the ligament that runs between each of the bones also thickens and in some cases buckles inwardly. The stenosis is usually most severe at the L4/5 level with the L3/4 level being the second most affected. The aim of the operation is therefore to create more room for the nerve roots by removing the overgrown ligament and bone at the lack of the spine called the lamina – hence the term laminectomy. The laminectomy normally extends from L3-L5 but can be longer (or shorter) depending on the imaging findings.

The two main conditions that may occur as a result of spinal canal stenosis are:

Neurogenic claudication: This term refers to pain, numbness or paraesthesia (pins and needles) that occurs during walking. Typically, the symptoms begin when the patient walks long distances only and is relieved by a few minutes of rest after which they can walk again for a similar distances. Over time, as the condition progresses the distance for which the patient is able to walk, or time that they can stand for, reduces. Eventually the symptoms become so severe that they occur at rest and may significantly limit mobility. The most common reason for this condition is a spinal canal stenosis. This means that the space inside the spinal canal has become too small for the nerves. Essentially they become crowded together and compressed.

Many patients with spinal canal stenosis will also experience a degree of low back pain which has a variable response to surgery. Patients and their relatives notice that they walk with stooped posture in order to attempt to compensate for spinal canal stenosis. This often does improve with surgery.

Radiculopathy: It is a clinical condition usually due to compression of a nerve root. The nerve root is the start of a nerve as it exits from the spinal cord and spinal canal. It usually will join with other nerve roots outside of the spinal canal to form various peripheral nerves. Nerve roots normally supply sensation to a particular area of the body as well as supply various muscles to make them move. Radiculopathy is most commonly painful and the area in which the patient experiences pain will often indicate the particular nerve involved. In addition there is often numbness and paraesthesia. Paraesthesia is commonly referred to as pins and needles. Again these may indicate the nerve root that is affected. Finally there may be weakness of a particular muscle or of a particular movement.

Before Surgery

Prior to surgery, patients may be asked to attend a preadmission clinic. This will involve routine blood tests and for some patients an ECG and chest X-ray. Patients that have significant co-morbidities or illness may require extra assessment. Patients at Westmead Private Hospital will have a pre-operative Doppler of the lower limbs which will be repeated after surgery. This is to assess patients for the presence of deep vein thrombosis (DVT).

Patients who are on aspirin or clopidogrel should cease those medications 7 days before surgery. For patients who are on warfarin, management will depend on the original reason for their warfarin. Some patients will require early admission and be started on heparin, for example, patients with mechanical heart valves. Others will just need to stop taking warfarin 2 days before surgery. The INR will be checked before surgery.

Other medications should be continued including those usually taken on the morning of surgery. These medications should be taken with a sip of water even though the patients may be nil by mouth otherwise

All patients undergoing a general anaesthetic will need to fast. That is, they should have nothing to eat or drink for around 8 hours prior to surgery. Failure to comply with this may necessitate cancellation of the procedure as it may expose the patient to significant risk. As most patients are admitted on the day of the surgery, the hospital will contact them to inform them of the time for admission, likely time of surgery and the required fasting times on the day before the surgery.

Hospital Admission

Most patients are admitted to hospital on the day of the surgery. Patients need to ensure that their latest X-rays, CT scans and MRI scans are with them when they come to hospital. These scans are the surgeon’s road map and without them the operation cannot proceed. If you do not have your pictures with you when you are admitted the operation may need to be cancelled. Except in rare circumstances, patients are responsible for these films, and are normally given back to them at the time of consultation. Patients at Westmead Public Hospital who have images taken at that hospital will usually have their films at the hospital.

Operation

The operation is performed under a general anaesthetic with patient laying face down on a specialised operating table. The incision is marked and the patient prepared. The incision is made in the middle of the back and the length will depend on the patient and the number of levels that require surgery.

The muscles are dissected from the posterior aspect of the vertebrae. The spinous process and lamina of the level in question are moved. This also normally includes part of the facet joint on each side at that level – a medical facetectomy. This exposes the main dural sac containing the fluid and nerve roots. The nerve roots as they pass through their foramen and the nerve roots going down to exist at the next level are also exposed and decompressed.

At the end of the operation a drain is left in the wound. The wound is then closed using dissolving sutures. A dressing is applied and the patient is returned to the supine position before they are awoken from the anaesthetic. Once awake the patient goes either to the recovery room before being transferred back to the ward.

Hospital stay

The hospital stay is normally around 3-7 days in total but varies depending on the patient and their underlying condition. During the hospital stay the patient receives daily physiotherapy. Patients will receive prophylactic subcutaneous heparin injections and are required to wear stockings to prevent DVTs. At Westmead Private Hospital DVT scans are routinely performed before and after surgery.

After surgery there is normally some discomfort and analgesia is provided. Constipation is a common complaint after surgery and is usually due to analgesics. You should inform staff if this becomes an issue.

The wound is normally cleaned and the dressing changed each day. There is normally a drain left in the wound which is removed after 24 hours. After discharge no dressing is required. You may shower and then pat the wound dry with a clean towel afterwards. While the wound may get wet, do not soak it in the bath or in a pool for at least 2 weeks after the surgery. Do not rub the wound. If there are any concerns such as excessive redness, pain or ooze then you should have your GP review the wound as the first step.

Most patients are able to be discharged directly home as they are independently mobile and self-caring. However, some patients, particularly those who are older or who live alone may benefit from a short stay in a rehabilitation facility such as Westmead Private Rehabilitation, Mt Wilga or Lady Davidson Hospitals.

At home

After discharge, it is advisable to rest for 2 weeks which should consist of normal daily activities. One should maintain a good posture as advised by the physiotherapists, For example, you should not slouch in a chair. You should not spend too long in any one position. Once you feel more confident then activities such as driving can resume. Normally one can drive after 2 weeks from the date of surgery. A return to work depends on the work environment. Those with sedentary jobs can usually begin to go back to work after 4-6 weeks. Those with more manual jobs should wait at least 6-8 weeks but it should be discussed with A/Prof Owler prior to surgery and again at the follow-up appointment.

Post-operative follow-up

You should make an appointment to see A/Prof Owler 6 weeks from the date of surgery or thereabouts. At that visit any concerns can be discussed and the wound will be checked. If there are any significant problems then you should contact his office earlier.

Risks of the surgery

All surgical procedures have risk. There are risks common to all surgeries such as infection, bleeding, deep vein thrombosis (DVT), pulmonary embolism and those associated with a general anaesthetic.

Most infections that occur are superficial and easily treated with antibiotics. Pre-existing diabetes increases the risk of this complication.

There is a small risk of significant bleeding with this surgery and occasionally patients may require a blood transfusion. Post-operative haematoma formation is rare but can cause significant neurological problems. The use of a wound drain minimises the risk of this complication.

The spinal cord is normally well clear of the site of the surgery. In the lower lumbar spine the spinal cord has changed into a group of nerve roots called the cauda equina. While patients commonly worry about complications such as paraplegia and incontinence, such problems are very rare. More common is the chance of injuring one nerve root at the site of the surgery and the risk of this is approximately 1% and may result in numbness or weakness of the leg which may be permanent.

Persistent or recurrent pain in the leg can occur for several reasons. Some patients will experience leg pain because of changes that occur in the nerve itself after it has been compressed severely or for an extended period, i.e., neuropathic pain. Some patients will develop scar tissue around the nerve. Some scarring is normal as it is the body's natural response to healing. However excessive scar tissue is thought to be a reason for recurrence of pain as well.

During the procedure a small tear may occur in the covering of the nerves (dura). This dural tear will result in leakage of spinal fluid. Therefore when it occurs it is repaired with sutures. The tear happens because the spinal canal can be very tight and because adhesions may develop between the degenerative structures and the dura. If this occurs, it is repaired at the time. The patients is normally asked to stay flat in bed for 24 hours after surgery and the drain will be kept in for a longer period. In the majority of cases there are no other consequences and the recovery proceeds as normal. However in some patients the leak will continue and this may necessitate a return to the operating theatre to resuture or repair the leak.

As the spine is degenerative, and the operation involves removing some of the bone at the back of the spine, there is a small risk that instability of the spine will be introduced requiring surgery to correct it in the form of a fusion. This is very unusual but patients should be aware of the possibility.

There are numerous other very rare complications that may also occur including those associated with a general anaesthetic such as reactions to medication, visual loss, and operation at the incorrect level despite the use of x-rays.

This is not an exhaustive list of potential complications but this information provides an overview of the more common complications that patients may be exposed to.

Expectations of surgery

The outcome of surgery is dependent on the indication for surgery and often the severity and duration of symptoms prior to surgery. No guarantees can be given in relation to the surgery.

Neurogenic claudication normally responds well to surgery. Over 80% of patients are expected to improve significantly with surgery. With successful surgery they can normally begin to increase their fitness and increase the distances that they are able to walk and the time that they are able to stand for. About 80% of patients will experience significant improvement in their pain allowing them to reduce their analgesic requirements and resume their normal activities.

Pain is the most common symptom of radiculopathy and, in most cases, is the first symptom to improve; often immediately after the surgery. Pins and needles may take longer but tend to improve quickly. Numbness takes the longest period to recover, perhaps even over 12 months and some patients may not experience full recovery of numbness. Weakness has variable recovery depending on severity and duration before surgery. Some patients will experience recovery immediately while others may have persistent weakness despite the surgery. Normally physiotherapy is required to treat weakness. Overall about 80% of patients will experience significant improvement in pre-operative symptoms while a further 20% will not improve as much as is hoped and 1-2% percentage will be worse off in relation pain or some other problem.

On-going care of the spine

A/Prof Owler’s philosophy is to attempt to return the patient to a normal active life rather than place onerous restrictions on the patient. However there are two aspects of spinal care that are important to patient’s that have undergone surgery.

The first, and somewhat obvious, advice is to avoid activities that may reinjure the spine. In the simplest form this includes not lifting heavy or awkward objects. As a general rule no-one should generally be lifting weights above 20Kg. In the short term the lifting restrictions are much less (see above). When lifting, good technique should be used such as keeping the knees bent and back straight while keeping the object being lifted close to the body. People should avoid simultaneous lifting and twisting. Those who are golf enthusiasts should wait 3 months after surgery before resuming golf.

The second aspect to long term care is maintaining spinal fitness. This includes weight loss, core strengthening and on-going exercise. The best exercises are those which are non impact such as swimming and cycling. All patients are normally taught core-strengthening exercises. These should be continued independently by the patient at home indefinitely.

Important Information

This information was provided to assist you. While it has been prepared to provide accurate information the practice and techniques of surgery will differ between surgeons. Likewise the information is a generalisation in relation to the surgery and will vary between patients depending on the individual and their pathology. This information cannot cover all aspects of the surgery especially in relation to surgical risks and should not be considered an exhaustive explanation. Please contact A/Prof Owler’s office if there are any further concerns or questions.