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 involves retracting the pharynx (the gullet) and keeping this protected during the surgery. There is a very small risk that the pharynx may be injured which can result in the patient needing to wear a naso-gastric tube for a few days. Running close to the pharynx is one of two small nerves, one on each side, that supply the vocal cords. There is a small risk of injury to this nerve (called the 'recurrent laryngeal nerve') which could affect your voice slightly. If problems do occur, they often recover but this risk is clearly of importance to people such as professional singers.

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 the patient's arm, resulting in a patch of numbness, some weakness of certain muscles, or pain extending into the arm. 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.

The spinal cord runs quite close behind the discs, such that there is a very small risk of spinal cord injury or compression. This is clearly a very serious complication but it is also extremely rare.

There is also a very small risk of a haematoma (blood clot) forming under the skin so a drain will be left in place for the first 24 hours after your surgery.

Risks associated with the Disc Replacement Prosthesis

An artificial disc will be subjected to everyday stress and movement as you move your head and neck normally. As a result, like any mechanical component, it could potentially wear out or fail in some way. However, most clinical studies of cervical artificial disc replacements suggest that wear has not been a problem in the medium term (10-15 years) but we do not yet know about the very long term. In the lab the M6-C has been tested to over 50 million cycles, that is 50 million full movements in all directions under physiological loads, which equates to many, many years of normal use. Again, the issue of wear and tear did not give any cause for concern in these studies.

The disc replacement is very firmly held in place by natural tensions between the vertebrae. It is also fixed to the bone, at first by the keel ridges on the back of the endplates, but in the long term by bone bonding to the metal surfaces. In fact, even during surgery once the disc replacement is implanted it is very difficult to remove! As such, it is extremely unlikely that the disc replacement will displace but this still remains a very small risk.

Unlike other forms of cervical artificial disc replacement where the separate components are held together only by the natural tension between the vertebrae, the M6-C components are completely bonded together. There is really no conceivable risk that the disc replacement will come apart.

If the vertebral bone is soft or is overloaded (for example, by a heavy fall) there is a small risk that the prosthesis 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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