Possible Complications

General risks

All surgery carries with it the general risks associated with wound infection and having an anaesthetic. These will vary to some degree depending on your age, your general state of health and any other specific medical problems that affect you. Although the risks are low, they should not be ignored and it must always be remembered that some complications, although rare, can be very serious and certain unforeseen circumstances can even lead to death. However, clinical experience and many studies have shown that these severe risks are extremely low and, for the vast majority of patients, surgery proceeds entirely smoothly. If you have concerns about your specific risks or feel any issues have not been addressed, please feel free to ask Mr Boeree or his team at any stage.

Risks related to the surgery

Gaining access to the intervertebral disc does involve retracting some large blood vessels, which carries the small risk that one of the vessels could be torn leading to heavy bleeding. Moving these vessels also results in a slight increase in the risk of a deep vein thrombosis.

Passing down in front of the lowest disc (L5/S1) are a number of very thin nerves which need to be moved to one side before the disc itself is removed. There is a very small risk that this action could damage these nerves. In men this can result in retrograde ejaculation, as the nerves control sphincters which prevent the ejaculate from passing backwards into the bladder. Although erection and orgasm would not be affected, the abnormal ejaculation caused by damaged nerves can impair fertility. It was once thought that this problem occurred in 1% of men having this type of surgery, but studies now show the risk to be much lower thanks to current surgical techniques (particularly the retroperitoneal approach). Nonetheless, if this risk is of particular concern for you then at The Spine Clinic we can arrange sperm banking on your behalf.

There is also a very small chance that a nerve root could be injured during the extraction of the disc. If this occurs it could affect either leg, resulting in a patch of numbness, some weakness of certain muscles, or sciatic pain. The nerve roots are not uncommonly affected by some bruising or swelling around the operation site, or by being a little stretched as the disc height is restored. This again may cause some discomfort radiating into the leg but these symptoms will usually resolve quite quickly.

Finally, there is also a very small risk of a haematoma (blood clot) forming under the skin, although this will normally resolve itself spontaneously. The likelihood is increased in patients who are overweight, in which case a drain may be inserted to minimize the risk.

Risks associated with the Disc Replacement Prosthesis

The downside of using an artificial disc which will be subjected to continuing stress and movement is that, like any mechanical component, it could potentially wear out or fail in some way. Studies suggest that wear is not a problem in the medium term (10 to 15 years) but we do not yet have enough clinical data to comment on the very long term.

The disc replacement is very firmly held together by natural tensions between the vertebrae. It is also fixed to the bone, at first by the teeth on the back of the endplates, but in the long term by bone bonding to the metal surfaces. As such, it is extremely unlikely that the disc replacement will come apart or displace but this still remains a very small risk.

If the vertebral bone is soft or is overloaded (for example, by a heavy fall) there is a small risk that the endplate could sink into the vertebra. This is called subsidence and is the reason why disc replacement should not be performed if you have osteoporosis. However, subsidence is very unlikely once the metal endplates become bonded to the vertebral bone even if a degree of osteoporosis develops many years later. Moreover, even when subsidence does occur it is not particularly problematic. If any of these issues arise and cause clinical complications, further surgery may be needed. Sometimes this will simply involve a fusion operation from the back.

Risks arising from allowing continuing movement

Although in principal, movement in the spine seems natural and a good thing to maintain, in a few cases this can actually be associated with continuing symptoms. Discomfort may be felt in the facet joints or soft tissue structures, such as the ligaments between the vertebrae. Therapeutic injections can be helpful in these instances but, in a small proportion of cases, the clinical outcome from disc replacement may be disappointing because of these problems. Occasionally, conversion to a fusion may then be suggested.

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