Lumbar Total Disc Replacement
This surgery is used to treat chronic low back pain resulting from disc degeneration.
The intervertebral disc is a soft tissue located between two vertebrae (spinal bones). The intervertebral disc consists of a soft jelly-like substance (nucleus pulposus) surrounded by layers of collagen tissue (annulus fibrosis). In its healthy state, the nucleus pulposus is well hydrated and acts like a shock absorber. Occasionally, the nucleus pulposus can undergo degeneration due to a variety of causes (some of which are not well understood) and loses its ability to hold water and becomes stiff. The loss of the shock absorber action (like a flat tyre) places abnormal strain on the surrounding annulus fibrosis leading to damage. Disc degeneration can cause low back pain.
Lumbar disc replacement model - Side view
Role of lumbar disc replacement
The surgery involves the removal of the degenerated and painful disc, thereby reducing the back pain, and restoration of the movement of the spine using an artificial disc. The three-piece prosthesis consists of two cobalt-chromium-molybdenum plates spray-coated with titanium that are attached to the vertebrae by a keel. A polyethylene (plastic) core is located between the two metal plates and allows for spinal mobility.
About the surgery
Anaesthesia: The surgery is performed under a general anaesthetic with the patient lying on the back.
Procedure: A 7-10cm incision is made in the abdomen and the abdominal muscles (rectus abdominis) are retracted to the side. The abdominal contents (intestines) that lie inside a large sack (peritoneum) are retracted to allow access to the front of the spine. The large blood vessels that continue to the legs (aorta and vena cava) lie in front of the spine and have to be moved out of the way to access the spine. After the blood vessels have been moved aside, the intervertebral disc is excised and the resultant space fitted with the artificial disc. The two metal plates of the artificial disc are inserted, followed by the polyethylene (plastic) core. The incision is closed with dissolvable sutures and a drain tube removes the blood that collects at the surgical site.
Lumbar disc replacement model - Front view
In the recovery room: Following surgery, you will be transferred to the recovery room and may feel some pain at the operated site when you wake up. You will be given pain medications, antibiotics, intravenous fluids to keep you hydrated and a urinary catheter will empty your bladder. When you are comfortable you will be transferred to your room.
In the ward: Since the abdomen was opened during surgery, you will be advised not to eat or drink anything for the first 12 -24 hours. You will then be commenced on a clear fluid diet and gradually progress to a light diet. Medications will be provided to reduce your pain after surgery and at home for the first 1-2 weeks. However, if you have excessive pain while you are in the hospital, the attending nurses should be informed. The day after surgery, the drain tube and the urinary catheter will be removed and you will be encouraged to walk wearing a brace to support your spine. You will stay in the hospital for approximately 3-5 days and your surgeon will decide when you can go home.
At home: Once you are at home, it is important to stay active and take short walks at regular intervals to help reduce pain and hasten your recovery. Gradually increase the distance you walk each day but avoid strenuous activities, heavy lifting and twisting. You may require some help with chores and errands for the first few weeks and it is advisable to have someone to help with these activities.
Risks and complications
All surgical procedures are associated with a risk of complications and all risks should be discussed with your surgeon. Allergic reaction to the anaesthetic or other medications and unforeseen complications such as pneumonia, stroke or heart attack are not caused by the surgical treatment and although rare it may have serious consequences. Please let your surgeon and anaesthetist know if you are allergic to medications and if you have any medical problems (relating to your heart, lungs, diabetes or increased blood pressure) and provide a list of your current and past medications.
Surgical complications can include bleeding, infection, spinal fluid leak, injury to the veins and arteries near the spine or injury to the spine's nerve tissue or its surrounding protective layer. Injury to the spinal cord or the nerves may occur during surgery and can result in complete paralysis of all four limbs or paralysis of certain muscles in the arms or legs, with loss of normal sensation. Loss of bowel and bladder control can also occur following injury to the nerves. An injury to the covering layers of the nerves (dura) can result in a leak of spinal fluid and this may occasionally require a repeat surgery. Great care is taken to ensure the accurate placement of the screws, including the use of intra-operative fluoroscopy (x-rays).
Although antibiotics are given before and after surgery, there is a 1-5% incidence of wound infection. Superficial mild infections can be treated with antibiotics, while deep infections may require a wound wash-out under anaesthesia. If you have had an infection in any other region (urinary bladder, chest and skin) immediately prior to surgery, you may be at a higher risk of post-operative infection in the spine, so let your surgeon know.
Venous thrombosis (DVT: clotting of blood in your calf muscles) and pulmonary embolism are uncommon after an elective spine surgery, particularly when you are out of bed and walking within 24 hours after surgery. We use calf compressors and TED stockings to prevent the clotting of blood in legs; we do not routinely use medications. However, if you have had an episode of DVT in the past, let your surgeon know.
A major risk that is unique to the anterior disc surgery is damage to the large blood vessels that lie in close proximity to the spine leading to excessive blood loss. Quoted rates in the medical literature put this risk at 1% - 2%.
For males, another risk unique to this approach occurs while approaching the L5-S1 disc. There are small nerves directly over the disc interspace that control a valve that causes the ejaculate to be expelled outward during intercourse. By dissecting over the disc space the nerves can stop working, and without this coordinating innervation to the valve, the ejaculate takes the path of least resistance, which is up into the bladder - a condition known as retrograde ejaculation. The sensation of ejaculating is largely the same, but it makes conception very difficult (special harvesting techniques can be utilized). Fortunately, retrograde ejaculation happens in less than 1% of cases and tends to resolve over time (a few months to a year). This complication does not result in impotence as these nerves do not control erection.
Notify your surgeon at once if you notice the following after surgery
- Excessive bleeding
- Redness or discharge from the wound
- Persistent headache
- Weakness or numbness in the arms and legs
- Difficulty in passing urine
Talk to your surgeon
This is a brief overview and does not contain all the known facts about your condition and the treatment options. Feel free to seek any clarifications from your surgeon and his team. It is important for you to obtain a clear understanding of your condition and the risks, benefits and limitations of the surgical procedure before proceeding.