FAQ Category: Cervical Spine

There are several things to consider here. First, allografts (donor bone from a bone bank) have had some problems in the past. But with new techniology, improved sterilization, and the ability to reduce viruses and bacteria, allografts are chosen by surgeons more often than autografts.

Autografts use bone harvested from the patient — usually from the pelvic bone. There is less risk of donor rejection but many times the donor site is more painful and problematic than the surgical site. The patient can end up with more days of pain and misery from the autograft bone harvest than if an allograft had been used.

In fact, studies show that more than half of all patients who have bone harvested from the pelvic bone have difficulty walking. Chronic pain in the donor site area is present in one-fourth of all patients. Half of these patients end up taking pain medication on a long-term basis.

Then there’s the cosmetic appearance of the donor site. Many patients think the scarring won’t bother them but the results can be unacceptable after the fact. And finally, harvesting bone from the patient adds time in the operating room and under the effects of anesthesia.

With the improved safety and effectiveness of allografts, you may want to rethink your decision. The best one to advise you is your surgeon. He or she can give you all the pros and cons from his or her experience as well as take into consideration any personal factors that are unique to you.

You are referring to the concept of adjacent segment disease (ASD) — a possible long-term complication of vertebral fusion. This is something that has been studied in relation to the lumber spine (low back) and well as cervical spine (neck) fusions.

It’s clear from many studies that adjacent segment disease is a real phenomenon. It’s not entirely clear why this happens. The idea that fusing one level will transfer load to the next higher or lower segment makes some sense.

The stress, force, or load through the spine during motion is the same with or without a fusion. In other words, having a fusion doesn’t take away the load placed on the spine during compression or movement. And according to all we know about movement and physics, load applied to the vertebrae is shared and does transfer from one segment to another.

When a segment can’t move because of a fusion, there is a certain amount of stress or load that is absorbed by the vertebral segment on either side. But studies don’t show equal amounts of adjacent segment disease on both sides of the fusion so there may be other factors involved.

For example, there is a report from a recent study done at the University of Washington in Seattle that the spine tries to restore normal range-of-motion as much as possible, especially after a cervical (neck)fusion. That may mean increasing motion at other segments to the point of becoming hypermobile (too much motion).

It is thought that this hypermobility contributes significantly to adjacent disease (i.e., the segment next to the disc fusion starts to deteriorate). Hypermobility combined with increased load transferred to the adjacent segments affects more than just those levels.

Based on the results of this study, the authors suggest that there are more biomechanical effects on the entire cervical spine after a two-level fusion compared with either one-level fusion. Greater muscular effort in an attempt to maintain full motion after a two-level fusion may be the reason patients develop muscle fatigue and pain.

These are very good questions! The use of total disc replacements versus fusion and the replacement of a fusion with disc replacement implants is one currently being studied. Likewise, the idea of a disc replacement for adjacent disc disease following a fusion is under investigation.

In fact, a recent study at the University of Washington Medical Center in Seattle explored some of these questions. The study was done with nine cadaver necks. Cadavers are human bodies preserved after death for use in studies like this.

The surgeon fused some necks and compared cervical spine (neck) movement with other necks that had a one-level fusion plus a one-level disc replacement. The fusion and disc replacement were at adjacent levels. The combination fusion-disc replacement is referred to as a hybrid. As part of the study, they did perform a fusion at one level and then reversed the procedure. This involved removing the fusion and replacing it with a disc replacement.

There were three significant findings from this study:

There are different types of manipulation procedures that can be done on the spine. Some techniques can be done in more than one position. The location of the problem and the patient’s individual anatomic variations may direct some of the chiropractor’s decision about the techniques (and positions) used.

For some patients, it may be possible to get better leverage by using a supine (on your back) position. The force of the patient’s body along with the downward thrust of the manipulation may be needed to make the necessary correction of spinal alignment.

Sometimes the chiropractor’s size (compared with the patient’s size) figures in on the equation. The more specific the manipulative treatment can be, the better the results. These are just some general thoughts on your experience. You will have to ask in order to know for sure why your chiropractor uses different positions and techniques.

Actually, there are some studies that support the use of thrust manipulation of the upper back in the treatment of neck pain. Using manipulation to realign the mid-to-upper spine has been shown to provide immediate neck pain relief.

There are also some studies that show neck motion improves following this type of treatment. The results are measurable and last for at least six months (that’s as long as the studies followed patients).

It’s possible there are continued good long-term benefits but this hasn’t been studied yet. It’s also possible that there is one type of thrust manipulation (i.e., specific technique) that works better than another.

In addition, the differences in treatment outcomes may be based on the location of the problem within the spine. Perhaps the position the patient is in (sitting, lying down) when the manipulation is done makes a difference, too.

There’s plenty of room for additional studies but for the moment it looks clear that your idea has been investigated and has some merit!

It makes sense that patients having anterior cervical spine surgery (from the front of the neck) might experience difficulty swallowing for a few weeks after the procedure. This symptom of painful swallowing is called dysphagia. As you have discovered, some patients develop this transient (temporary) symptom and others don’t.

Post-operative dysphagia seems to be a fairly common problem. As many as 60 per cent of all patients having the anterior cervical discectomy and fusion (ACDF) procedure report this as an annoying and sometimes disabling symptom. Although the dysphagia usually goes away in the first three weeks after ACDF, there are cases of chronic (permanent) dysphagia.

These was a recent study by surgeons from the University of Pittsburgh looking for some answers about this problem. They wondered if the process of intubation (tube down the throat) during anesthesia might be part of the problem.

To find out the effect of intubation on swallowing, they compared a small number of patients who had an anterior cervical discectomy and fusion (ACDF) with a similar-sized group of patients who had a lumbar spine (low back) fusion.

ACDF refers to the surgical removal of a damaged disc from between two vertebrae with fusion of those two vertebrae to each other using bone grafts, titanium cages, or other similar fixation devices. The word anterior in the name tells us the surgeon made the incision and performed the procedure from the front of the spine.

The lumbar procedure was done from the back or posterior aspect of the spine. For some patients it was just a matter of removing the damaged disc while others had a disc removal and fusion. They used lumbar spine patients as the comparison group because they had spine surgery but not from the front of the neck and they were intubated during anesthesia.

They found that the anterior cervical discectomy and fusion group were much more likely to experience dysphagia after surgery than the lumbar surgical group. When all the data was analyzed, it wasn’t the patient’s age, length of surgery (intubation), history of diabetes or rheumatoid arthritis or even body size that put patients at risk of dysphagia.

This symptom was more likely to develop in women and in patients who had a history of smoking and especially those who had a history of chronic obstructive pulmonary disease (COPD). The authors concluded that post-operative dysphagia is related to the anterior cervical spine surgery and not the intubation process. The risk factors listed here may help explain why some people (but not all) develop difficulty swallowing after neck surgery.

Baseball pitchers are always at increased risk of shoulder and neck injuries compared with other players. The high-speed, twisting motions required with each and every pitch multiplied by hundreds of pitches during practice and games can put quite a torsional strain and load on discs.

For those reasons, disc herniations are not uncommon in this group. Getting back to normal function and level of performance expected in major league ball can be a challenge. But the overall prognosis is good. These kinds of injuries are not an automatic ticket into retirement for most pitchers.

In fact, a recent review of the public record on major league baseball pitchers experiencing disc herniations, the treatment, and recovery gave a very optimistic report. Out of the 40 pitchers reported with cervical (neck) or lumbar (low back) disc herniations, 88 per cent of the players treated for a cervical disk herniation and 100 per cent of the players with a lumbar disc herniation returned to a preinjury level of play after surgical treatment.

That’s the good news. The downside of those statistics is that it took anywhere from seven to 12 months for the players to rehab and return. So although it’s possible to return to sports action in the same season as the injury, the experience of other players in similar situations suggest it might not happen.

In the meantime, don’t be swayed by what you hear or read from sports writers. They seem to reflect a negative prognosis despite medical reports that recovery from disc herniations is possible and even very likely in elite sports athletes.

Dysphagia (difficulty swallowing) and odynophagia (painful swallowing) are common problems following anterior (from the front) cervical spine (neck) surgery. Surgeons are actively researching to figure out why this happens so they can put a stop to it.

What do we know so far? Studies have shown us that performing spine surgery from the front or the back each has its own advantages and disadvantages. Coming in from the front avoids damaging the spinal cord and spinal nerve roots. The posterior (from the back) approach is much more likely to be linked with this type of damage to the nerve tissue.

But moving the esophagus aside during anterior surgery and/or accidentally cutting the nerves to the vocal cords can result in some serious problems. Difficulty swallowing, painful swallowing, and loss of voice control are some of those potentially disabling complications.

It’s also possible that bone spurs present even before the cervical spine surgical procedure is done may contribute to the problem after surgery. Other studies have pointed to older age as a possible risk factor for dysphagia after anterior cervical surgery but not all study results agree on this one. Vertebral fusion at more than one level may also be a risk factor for dysphagia.

Once we know what the risk factors are for postsurgical dysphagia, then we can start to predict who might develop such problems and prevent them. Careful patient selection is part of the process (i.e., avoiding doing anterior spine surgery on anyone with significant risk factors). Developing improved surgical tools and techniques is also part of the solution.

Most of the time, the symptoms are transient temporary and only last for up to three weeks. But that’s not very comforting for patients who develop chronic or permanent dysphagia. Be assured that efforts are being made to study this problem and prevent it from happening.

Ossification refers to the formation of bone within soft tissue structures such as muscles and ligaments. It develops after surgeries that involve cutting or disrupting the soft tissues (e.g., muscles, tendons, ligaments) around bone anywhere in the body.

The exact cause of ossification isn’t quite clear. It could be part of the healing response of the soft tissues after being cut and moved away from the bones. There is some thought that pins or screws used in orthopedic procedures (like spinal fusion) might generate this type of response.

Changing the biomechanics of the spinal segment may have a role in the development of ossification. Some researchers are looking at the amount of pressure inside the discs (called intradiscal pressure) as a possible contributing factor.

Not everyone develops ossification. When they do, there aren’t always any symptoms (such as pain) or obvious effects (further loss of motion). So just how much of a problem this problem is remains under investigation.

There is some research to support the idea that if you haven’t developed ossification after 12 months (and especially after 24 months), then your risk decreases considerably. Efforts are underway to figure out just why ossification develops, who it is most likely to occur in, and ways to prevent its development.

It sounds like you might be planning to have an anterior cervical discectomy and fusion otherwise known as an ACDF. In this procedure, the surgeon comes in from the front of the neck (anterior) and removes the disc (discectomy).

Then the two vertebrae (one above the disc and one below the disc) are held together (fused) with a metal plate and screws (also called pins). The procedure is usually done at one spinal level but it can be done on more than one level, a process called multi-level fusion.

The ACDF procedure has been around since the 1950s. Many studies have been done to look at results and improve outcomes. The technique isn’t perfect or always 100 per cent successful but for the most part, it does the job. The major disadvantage to cervical fusion is the loss of motion.

Two other potential complications of cervical fusion include the development of ossification (bone formation in the soft tissues) and adjacent disc disease. Adjacent disc disease refers to the degeneration of the disc above or below the disc already removed.

As a result of the disadvantages and potential problems that could develop with arthrodesis, many surgeons are going with disc replacements now. The early results of this procedure are fairly favorable. Ossification can still develop but seems to be an much less of a problem after disc replacement when compared with disc fusion.

The disc replacement preserves motion and may decrease the incidence of adjacent disc degeneration. Many studies are underway to examine and compare the features of disc removal and spinal fusion versus disc replacement. Studies show that in the hands of an experienced surgeon who performs many of these procedures, the anterior cervical discectomy and fusion (ACDF) is quite safe and very effective.

Whiplash is defined as a sudden extension of the cervical spine (backward movement of the neck) and flexion (forward movement of the neck). This type of trauma is also referred to as a cervical acceleration-deceleration (CAD) injury. Rear-end or side-impact motor vehicle collisions are the number one cause of whiplash with injury to the muscles, ligaments, tendons, joints, and discs of the cervical spine.

There is a problem called whiplash associated disorder (WAD). Patients with this problem experience neck pain, stiffness, and tenderness over the neck muscles. Sometimes there is a decrease in neck and/or shoulder motion. When these symptoms persist beyond the expected time for an acute injury, they become chronic. This time period is usually anything past three months.

Whiplash associated disorder (WAD) doesn’t usually cause widespread pain (throughout the body) like fibromyalgia does. Pain in fibromyalgia is present in soft tissues throughout the body. Pain and stiffness concentrate in spots such as the neck, chest, shoulders, elbows, knees, buttocks, and lower back. The tender spots don’t seem to be inflamed. Most tests show nothing out of the ordinary in the anatomy of people with fibromyalgia.

Tenderness or painful points of specific muscles in the upper neck point to WAD. A similar painful response of the lower neck and upper shoulder are more common in people with fibromyalgia,

Obviously, the cause of whiplash associated disorder is the extension-flexion injury. The causes of fibromyalgia are unknown. Sometimes fibromyalgia occurs as a result of an injury like a whiplash or some other medical condition. So fibromyalgia can be primary (the main problem) or secondary (caused by other problems).

There has been some considerable debate over this point. Do patients with chronic neck and/or shoulder pain from whiplash really have fibromyalgia? As you probably know, fibromyalgia, a common painful disorder among women in their middle years (40 to 60 years old) is no longer considered a “disease” but rather a syndrome.

The term syndrome is used to represent a group of symptoms that tend to occur together either at the same time or in close proximity to one another. Sometimes fibromyalgia is referred to as fibromyalgia syndrome (FMS).

The most common symptom is widespread pain throughout the body, with especially tender spots near certain joints. The pain stops people with fibromyalgia from functioning normally, partly because they feel exhausted most of the time.

Fibromyalgia is a chronic (meaning long-lasting) condition that usually requires many years of treatment. It can occur along with other forms of arthritis or all by itself. It can occur after an injury or out of the blue.

The history of an injury like a car accident is where the long-term effects of whiplash (called whiplash associated disorder or WAD) can get confused with fibromyalgia. With both conditions, there are tender points (TPs) in the neck and shoulder region.

According to a recent study, using tender points as the test in people who have chronic pain after a motor vehicle accident will often yield a diagnosis of fibromyalgia. Yet when retested six months later, the symptoms are gone for many people. The majority no longer have fibromyalgia.

Fibromyalgia is usually a long-lasting problem that doesn’t just go away six months later — not even after treatment. And it is characterized by tender points all over the body, not just in the neck and shoulder areas. As a general rule, people with whiplash associated disorder tend to have local tender points (i.e., just in the neck and shoulder and not anywhere else).

As you already know, a stinger is an injury to a nerve in the neck. It’s a common injury among players involved in contact sports (football players being the most commonly affected athletes). Getting hit on the head from one side is usually enough to do it. A cervical nerve (coming from the spinal cord to the arm in the neck) gets stretched or pinched.

Besides neck and shoulder pain, there may be additional symptoms of arm weakness and numbness. The symptoms are usually transient (temporary) and go away within 24-hours. But repeated stingers over time can eventually lead to a chronic stinger syndrome. With a chronic stinger, symptoms of neck and shoulder pain with numbness, tingling, and weakness don’t go away.

Most players who do experience persistent symptoms from a chronic stinger recover. With conservative care, they are able to return to 100 per cent participation in their sport. Anyone suffering an acute stinger should be advised to rest and avoid contact sports (anything that could cause traction, compression, or direct blow to the head/neck).

Some players use a special collar called a Cowboy Collar to protect the neck. This is worn during play and practice. It is a cervical collar (fits around the neck) underneath the shoulder pads. The Cowboy Collar fills the gap between the helmet and the shoulder pads. When worn with regular shoulder pads, the Cowboy Collar helps absorb shock.

Special exercises to help stabilize the head and neck are encouraged. You should be aware that multiple stingers and chronic stinger syndrome are linked with degenerative changes in the spine that can cause problems much later in life. If you have further questions about this condition, don’t hesitate to ask your team physician for more information.

Stingers are common injuries among players involved in contact sports. Getting hit on the head from one side is usually enough to do it. A cervical nerve (coming from the spinal cord to the arm in the neck) gets stretched or pinched. In fact, up to 65 per cent of all football players get at least one stinger.

Burning pain down the arm after getting hit is the main symptom. There may be additional symptoms of arm weakness and numbness. The symptoms are usually transient (temporary) and go away within 24-hours. But repeated stingers over time can eventually lead to a chronic stinger syndrome. With a chronic stinger, symptoms of neck and shoulder pain with numbness, tingling, and weakness don’t go away.

Having a means of predicting who might develop a chronic stinger syndrome would be helpful. With this information, athletes could be advised on the risks associated with repeated stingers. This is important because many athletes who suffer from one stinger will have more than one.

Imaging studies (e.g., X-rays, MRIs) are used to help predict who might develop a chronic stinger syndrome. In the past, a ratio called the Torg ratio was used. This is a way of using X-rays to assess the diameter of the opening for the spinal cord and spinal nerve(s). Narrowing of the spinal canal (where the spinal cord is located) causes a condition called stenosis. It’s the stenosis that puts pressure on the cord or nerves causing symptoms.

It turns out that the Torg ratio is highly sensitive (it accurately tells who has the problem). But it has a poor positive predictive value, which means it doesn’t predict who (with stenosis) will develop actual neurologic symptoms. The Torg ratio doesn’t account for the effect of the surrounding soft tissues. In using statistical measurements like this, positive predictive values are more clinically meaningful than sensitivity.

So, surgeons have turned to the mean subaxial cervical space available for the cord (MSCSAC) index to predict chronic stinger syndrome. This is a measurement made using MRIs that looks at the diameter of the spinal cord in comparison to the diameter of the spinal canal. It gives a much more accurate picture of what’s going on and who might develop a chronic stinger syndrome.

The tests will show if you have stenosis (narrowing), where it’s located, and how severe it is. The results will also give your surgeon an idea of the likelihood of developing a chronic problem (one that doesn’t go away).

With an acute (first time) injury, most players are back on the field within 24 hours. After eight stingers, the amount of damage to the spine will help determine treatment. The good news is that you will in all likelihood recover full function and return-to-play. But it might take a bit more than a day or two.

We assume you are referring to the cervical spine (neck) disc replacement surgery that is now available. The vertebral bones are not removed and replaced, but the disc between the bones is. The goal is to preserve and restore normal spinal movement.

After the disc is removed, the ends of the vertebral bodies (called endplates) are smoothed down. The artificial implant is then inserted into the empty disc space and positioned properly. The surgeon uses fluoroscopy (special three-dimensional, real-time X-ray) to guide the implant in place.

The surgeon is careful to choose the correct size of implant for each patient and to maintain the proper disc height. Special “teeth” built in to the implant help hold it in place until bone fills in around it. There is no need for a bone graft.

You could have had the more traditional procedure called anterior cervical discectomy and fusion (ACDF). With ACDF, the surgeon removes the degenerative disc and fuses the two vertebral bones on either side of the disc together. The hope with arterial disc replacement is that it will reduce the strain placed on the disc and spinal joints as well as provide improved neck motion.

Your age is a definite factor. But cervical disc implants have been used in patients from 34 to 67 years old. The cervical implants are new enough that we don’t know how well they will hold up over time for each age group. Long-term studies to report on the possibility of adjacent disc disease have been very limited so far. Adjacent disc disease refers to the potential effect of disc replacement on the spinal segments above and below the implant.

The definite advantage disc replacement has over fusion is that if it isn’t successful, you can always convert (change over) to a fusion. The only way you will know if you are a good candidate for this procedure is to see a spinal surgeon who performs both cervical fusion as well as disc implantation.

After a proper evaluation, the choices available to you will be discussed and a decision can be made together. Your age, general health, occupation, activity level, personal goals, and other important factors will be included in that process.

You are quite right that Computer Aided Design (referred to as CAD models) is widely used in many areas of study from theatre lighting to engineering bridges. In the field of orthopedics, it has been applied to the study of new surgical procedures like the cervical artificial disc replacement (CADR).

The use of cervical artificial disc replacements (CADR) is still in the first decade (10 years) of study. Before conducting studies on humans, computer simulation can be used to assess the biomechanical effects on movement. This concept is referred to as kinematics.

In a recent study from Korea, mathematicians joined mechanical engineers and orthopedic surgeons to compare different types of cervical disc implants using a computer-aided design model. They used the CT scans of a young, healthy 21-year-old man to build the spinal model. With a computer-aided model, everything is done in three-dimensions. The effect of force and load with motion is calculated by the computer rather than on a live subject.

Two different types of artificial disc implants were compared. Both were made of cobalt-crome with a polypropylene (plastic) core (inner piece). The artificial device mimicked the natural anatomy of a disc with its outer layer (annulus fibrosus) and the inner core (nucleus propulsus). Placement was at the C56 level where the majority of disc implants are currently placed.

All material and mechanical properties of the implanted device were programmed into the computer-aided design model. Likewise, force, load, friction, tension, and angles were included in the model. In this way, the model could be put through thousands of spinal movements normally available in the human body. The results could be studied without subjecting a live human to that kind of experimentation.

Range-of-motion and load placed on the facet (spinal) joints were measured. The effects of load on spinal flexion-extension were evaluated. Data was also collected on the effects of side-bending load, rotational (twisting) load, force on the spinal (facet) joints, and stress on the spinal ligaments. Tension on the polyethylene core was also measured.

As this study showed, the use of computer-aided design (CAD) provided a biomechanical comparison between two different types of artificial disc implants. Long-term human studies will be needed to assess final outcomes but this is a good place to start. It’s noninvasive and allows for many different choices of force and load application without causing injury to anyone. CAD is a natural fit for something like this.

Each patient undergoing this surgical procedure to replace a degenerated or otherwise damaged disc in the cervical spine (neck) is evaluated by the surgeon. It’s important to select the correct size and shape of implant that will best suit each individual.

But there are also different types of implants. The main difference is whether or not the device has a moveable center. If it has a core that shifts, glides, or moves over the lower plate, it is referred to as an unconstrained implant with a mobile core. If the center does not move, it is constrained with a fixed core.

The moveable core tends to put more pressure on the facet (spinal) joints. The fixed core takes more of the pressure and load on itself and translates only half as much pressure to the spinal joints compared with the replacement with the mobile core.

Whether or not these differences result in more (or less) pressure on the adjacent vertebral segments is currrently being studied. Likewise, the long-term effects and differences with these two different types of implants is under investigation.

Most surgeons train using one particular type of implant so your choices may be determined by the surgeon you see. The type of degenerative damage and number of disc/vertebral levels affected may impact the type of implant you receive. Once the surgeon evaluates you and reviews imaging studies, then the specifics of the surgery can be discussed. That would be a good time to bring this question up.

Surgeons in Europe have been using artificial disc replacements for the low back and neck much longer than in the United States. In the history of disc replacements, devices for the lumbar spine came first. When they were successful, efforts to design an equally good implant for the cervical spine were begun.

The first trials using disc replacements for the neck were started in the spring of 2002 here in the U.S. Since then, more than one company has produced a cervical disc prosthesis. Studies with small numbers of patients are being reported with good-to-excellent results.

One recent study from China followed a group of 25 adults who received the newer Discover implant. The implant (manufactured by DePuy) is made of titanium with a polyethylene (plastic) insert to mimic the natural disc. It is designed to restore full motion and even incorporates the lordotic angle (curvature) of the natural spine.

Results were assessed 12 to 18 months later using a variety of different measures. Pain relief was good-to-excellent. Motion was improved and both measures (pain relief and motion) stayed improved throughout the follow-up period. The implants remained in good position with no evidence of subsidence (sinking down into the bone).

Further studies are needed before any particular system is given the thumbs up approval by all. For example, larger groups of patients receiving the cervical disc replacement must be evaluated over a longer period of time. Studies comparing results between artificial disc replacements and the anterior cervical discectomy and fusion (ACDF) procedure will be important as well.

Of course, no one can say for sure how long cervical disk arthroplasty (disc replacements) will last or how well they will hold up. That’s for two reasons — one, they haven’t been around that long to see what happens. And two, most of the studies published so far only go out two to four years.

There is a recent study from France using the Bryan disc replacement system with reported results eight years out. The Bryan disc system mimics the normal protective disc that acts like a cushion between two vertebral bodies. It is made of titanium on the outside with a plastic inside. The titanium endplate shells are covered in a double layer of porous coating to allow for better grip between the vertebrae.

Everyone in the study had good spinal alignment without any sign of instability. They had all tried conservative care without good enough results to bypass surgery. Patients ranged in age from 26 to 65 years old.

Results were measured using a variety of outcomes such as work status, activity level, symptoms (neck and/or arm pain), and neck motion. X-rays were used to assess the position of the device and to look for heterotopic ossification (HO).

With heterotopic ossification, there is additional bone formed outside the skeletal system. The extra bone usually forms in the surrounding soft tissues, especially the nearby muscles. It’s a problem because the artificial disc replacement (ADR) is designed to maintain joint motion. The heterotopic ossification reduces soft tissue mobility and causes increased stiffness.

The eight-year results were excellent. Three-fourths of the patients (18 of the 21) were free of neck and/or arm pain. They could perform all daily activities and chores without any problems. There were no neurological symptoms (e.g., no numbness or tingling down the arms, no change in deep tendon reflexes or sensation).

Heterotopic ossification (HO) was a problem in almost half of the patients. More HO seems to develop as time goes by. Not only do more patients show evidence of HO in time, those who develop it early start to progress to more severe cases. Having a two-level disc replacement is also a risk factor for HO.

As far as the other common complications developing (loosening, migration, subsidence, implant failure), there were none! There were three cases of spontaneous fusion (bone filling in around the implant) but no symptoms or functional problems as a result. No one had any further follow-up surgery.

About 19 per cent of the group did develop adjacent segment disease (ASD). That’s a striking finding since it has been believed that fusion is what causes increased degeneration at the vertebral segments on either side of the fusion. There is some speculation that ASD develops because there were already some degenerative changes present before disc replacement.

In conclusion, artificial disc replacement for the cervical spine (neck) is safe and effective. But it may not be without its problems. It’s good that you have had such excellent results. Keep up with your follow-up appointments and watch for more suggestions and guidelines as other long-term studies are published.

Artificial disc replacements were developed to avoid neck fusions and thus preserve neck motion. The idea came about when studies showed that cervical spine fusion often resulted in added wear and tear and degeneration of the adjacent (next level above or below) segment.

But there are concerns with the disc implants. They can migrate or move backwards in the spine. A position too far back can increase the risk of spinal cord or spinal nerve root compression. There is the possibility of subsidence (disc sinks down into the vertebral bone). Loosening of the implant and adjacent segment degeneration round out the list of possible problems or complications that can occur.

But it turns out the biggest problem is heterotopic ossification. With heterotopic ossification, there is additional bone formed outside the skeletal system. The extra bone usually forms in the surrounding soft tissues, especially the nearby muscles.

It’s a problem because the artificial disc replacement (ADR) is designed to maintain joint motion. The heterotopic ossification reduces soft tissue mobility and causes increased pain and stiffness and decreased neck motion.

There are several reasons why heterotopic ossification develops — especially after multiple-level cervical disc implantation. First, the disruption of soft tissues and damage to the muscles is greater when more than one level is involved.

Second, the risk of heterotopic ossification (HO) increases when patients are not given antiinflammatory medications (known to reduce the risk of HO). And third, removing the diseased disc and damaged bone involves a special milling process, which may contribute to the body’s response making more bone.

There aren’t a lot of long-term studies to show for sure how often the problem of HO develops. From what has been reported, it looks like almost half of all patients will develop HO after cervical disc replacements. More HO seems to develop as time goes by. Not only do more patients show evidence of HO in time, those who develop it early start to progress to more severe cases.