During the operation of the intervertebral disc prosthesis, the degenerated intervertebral disc is completely removed and the intervertebral disc prosthesis is instead placed between the vertebral bodies. There it is anchored by metal extensions in accordance with its prosthetic design. Thanks to its special structure, the intervertebral disc prosthesis can follow the movements of the spine. Intervertebral disc prostheses are available for the cervical and lumbar spine. Both times the operation is done from the front, not from the back.
The possibility of installing an intervertebral disc prosthesis represents a major step in spinal surgery.
Intervertebral disc prostheses have only been implanted in large numbers for a few years. Around 11,000 intervertebral disc prostheses have been implanted worldwide, and the trend is clearly increasing. In comparison, around 180,000 knee and hip prostheses are implanted annually in Germany alone. The experience with intervertebral disc prostheses is therefore still relatively young. Much is still unknown regarding the long-term prognosis of an intervertebral disc prosthesis. Nevertheless, the first short to medium-term results after intervertebral disc prosthesis implantation are very encouraging, which is why a significant increase in the number of implantations is expected in the future.
Structure of an intervertebral disc prosthesis
An intervertebral disc prosthesis consists of two cobalt-chrome-molybdenum metal plates. The metal surface is coated with titanium or hydroxyapatite. The rough surface finish and the coating of the metal plates enable the prosthesis to grow well to the adjacent vertebral bodies. In order to ensure immediate stability after implantation, an intervertebral disc prosthesis has type-dependent metal projections, whereby the intervertebral disc prosthesis is attached to the adjacent vertebral body (primary stability) and prevents displacement until the final bony growth.
In order to be able to follow the movements of the spine, an intervertebral disc prosthesis has a core made of plastic (polyethylene) or metal lying between the metal plates. In the case of lateral inclination as well as forward and backward bending, the spinal column movements take place via the axes of this intervertebral disc core.
Indication for intervertebral disc prosthesis
Unless it is an emergency, the entire spectrum of conservative therapy for the herniated disc should be used before any surgical measure.
The optimal time for an intervertebral disc prosthesis implantation can also be missed if, due to intervertebral disc degeneration (decrease in height, loss of water in the intervertebral disc), greater spinal instability and subsequent degeneration of other vertebral structures have developed (e.g. the small vertebral joints).
A distinction must be made between the indication for the implantation of a disc prosthesis on the cervical and lumbar spine.
The classic indication for the implantation of a intervertebral disc prosthesis is the intervertebral disc-related, monosegmental back pain as a result of intervertebral disc wear (discopathy). Monosegmental means that only one intervertebral disc is diseased and needs to be replaced. Intervertebral disc-related means that the intervertebral disc itself is the cause of the back pain and there is no herniated disc or other wear-related changes in the spine.
In the meantime, however, 2-3 intervertebral disc segments are also being replaced at the same time, even if adjacent intervertebral discs are diseased and have their share in back pain. Good diagnostics are important in this regard, because not every intervertebral disc wear requires treatment. Only those intervertebral discs with disease-worthy are replaced.
Postnucleotomy syndrome, in the sense of persistent, intervertebral disc-related pain after a herniated disc has been removed, can also be an indication for the implantation of an intervertebral disc prosthesis.
While the acute herniated disc in the area of the lumbar spine is a contraindication to the implantation of a spinal disc prosthesis and is removed by microsurgery in the classic way (microdiskectomy), the herniated disc is increasingly treated with the intervertebral disc prosthesis. The sole removal of the herniated disc is not possible in the area of the cervical spine, because removal of the herniated disc from behind, as is common with the lumbar spine, is technically very difficult and dangerous from an anatomical point of view. Previously, herniated discs of the cervical spine were operated on from the front, the affected intervertebral disc together with the incident was removed and the adjacent vertebral bodies were fused, i.e. the spine was stiffened in this section.
Contraindications for intervertebral disc prosthesis
The implantation of an intervertebral disc prosthesis is not a panacea for the elimination of back pain.
On the contrary, most degenerative diseases of the spine are a contraindication to the implantation of an intervertebral disc prosthesis.
The reason is very simple: The implantation of an intervertebral disc prosthesis only removes the back pain that is caused by the diseased intervertebral disc itself. For this reason, it is a prerequisite for an intervertebral disc prosthesis that no other wear-related diseases of the spine may exist, which could be the cause or a cause of the back pain. In these cases, other surgical procedures are used. Otherwise, the surgery, which is not exactly small and cheap, cannot be successful and the pain before the operation will remain almost unchanged or even worsened afterwards.
- Acute herniated disc of the lumbar spine (disproportionate operation)
- Osteoporosis (risk of the intervertebral disc collapsing into the adjacent vertebral body)
- Older age (usually additional wear on other vertebral structures, often poor bone quality)
- Vertebral body gliding (spondylolisthesis (cause of pain is not treated))
- Wear of the vertebral joints (spondylarthrosis (cause of pain is not treated))
- Spinal canal tightness (spinal stenosis (cause of pain is not treated))
Advantages of the intervertebral disc prosthesis
Until recently, the classic surgical procedure for back pain caused by intervertebral discs (no herniated disc!), As in the case of an acute herniated disc of the cervical spine, was stiffening of the spine with removal of the intervertebral disc and fusion of the vertebral bodies. It is an established procedure with good operational results.
A major disadvantage of this surgical procedure, especially in the area of the lumbar spine, is the greater trauma compared to the implantation of intervertebral disc prostheses, since the operation is performed on the back through the muscles and ligaments of the spine. This results in a longer recovery time (rehabilitation) for the patient compared to an intervertebral disc prosthesis implantation.
The greatest advantage of the intervertebral disc prosthesis is the preservation of the natural mobility of the spine. For the following reason: A stiffening operation on the spine disrupts the natural transmission of force at the spine and the intervertebral discs that border on the stiffened spine section are overloaded. This can result in renewed back pain due to premature wear and tear (connection degeneration). Studies on the cervical spine showed that intervertebral discs in the immediate vicinity of a vertebral body fusion are stressed by an average of 73% more than usual.
By moving the intervertebral disc prosthesis naturally, all spinal column sections are to be stressed and there is no connection degeneration of the neighboring segments. Long-term studies on this are still missing.
Nevertheless, the mobility of the intervertebral disc prostheses is at least given and after at least 1 year is on average 8 ° for the segment L5 / S1 and 10 ° for the segment L4 / 5. To what extent this mobility can be maintained over the years is not yet certain.
The most important thing in preparation for the operation of the intervertebral disc prosthesis is the correct indication.
In addition to the physical examination, this mainly requires imaging examination methods.
A disease of the intervertebral disc can be diagnosed on X-ray images. The intervertebral disc itself cannot be seen on an X-ray, but a reduced vertebral body distance between two adjacent vertebral bodies indicates a height-reduced and therefore diseased intervertebral disc (chondrosis). Cover and base plate irregularities as well as bone densification of the neighboring vertebral bodies indicate the involvement of the vertebral bodies in the disease process (osteochondrosis).
The x-ray also provides evidence of a reduced bone density or of instability among the vertebral bodies. A vertebral body offset can be seen on the lateral x-ray images. Sometimes, however, x-ray functional images (x-ray images with maximum forward and backward bends) are necessary to demonstrate vertebral body displacement and thus instability. As already mentioned, severe instability or osteoporosis is a contraindication to the implantation of a disc prosthesis.
MRI (magnetic resonance imaging) of the cervical spine and lumbar spine
Magnetic resonance imaging of the cervical spine or the lumbar spine is indispensable in the diagnosis of diseases of the spine. In contrast to the X-ray, the intervertebral disc itself, but also all other important structures of the spine, can be assessed. A disease of the vertebral body joints (spondyloarthritis) is recognized as well as a narrowing of the vertebral canal (spinal stenosis). Both diseases are contraindications to the implantation of a disc prosthesis.
The MRI of the lumbar spine / cervical spine (magnetic resonance imaging) is therefore the best imaging method for the diagnosis of spinal disorders. However, what MRI (magnetic resonance imaging) cannot achieve is to establish a relationship between the image findings (e.g. a diseased intervertebral disc) and the complaints of a patient.
This means that a diseased intervertebral disc can be the reason for back pain, but it does not have to be. On the contrary, most patients with wear-related changes in the intervertebral discs are symptom-free.
In order to reliably diagnose intervertebral disc disease as a pain trigger, another examination method can be used, discography.
A discography represents a small surgical procedure that is performed only under local anesthetic. It is a diagnostic procedure that relies on the patient's cooperation.
A contrast medium is injected into the intervertebral disc with a thin needle and an X-ray is then taken. In this way, the intervertebral disc tissue can be imaged precisely and damage can be made visible. Above all, however, the injection serves to secure the diagnosis if there is suspicion of a disc-related (discogenic) back pain.
The injection of the contrast medium leads to an increase in pressure in the intervertebral disc space, which leads to a provocation of pain. When injecting, the patient should feel exactly the pain he is familiar with and should also express this to the doctor.
If this is the case, one speaks of a positive distension test. If no pain is provoked, the distension test is negative and the cause of the back pain remains unclear at first. An intervertebral disc prosthesis implantation will then be avoided.
Intervertebral disc prostheses are operated from the front (neck or abdomen), regardless of whether they are on the cervical or lumbar spine.
Various surgical steps must be carried out as part of an intervertebral disc prosthesis implantation. Since not every operation follows the same scheme, the key and most important steps for a prosthetic disc implantation are outlined below. The individual steps mentioned below neither claim to be complete nor are they listed in strict chronological order.
They are only intended to show which steps are generally to be expected in any case. The actual operation time is between 90 and 120 minutes. However, since there are always individual differences, deviations both upwards and downwards are quite possible.
- General anesthesia of the patient
- Position the patient supine
- Skin disinfection and sterile covering
- Approximately 8 cm long longitudinal or transverse skin incision, depending on the height of the intervertebral disc to be operated on
- Splitting of the abdominal muscles
- Retroperitoneal access through the psoas muscle
- Identification of the height of the intervertebral discs while protecting the large abdominal vessels and sensitive nerve plexuses (superior hypogastric plexus)
- Clear the intervertebral disc compartment from the front
- Refresh the vertebral base and cover plates
- Spreading (distraction) of the intervertebral disc space
- Insertion of the intervertebral disc prosthesis in the correct position under X-ray control (central in the view from the front, relatively far back in the view from the side)
- Inserting wound hoses (drainage)
- Skin suture
Intervertebral disc prosthesis cervical spine
Degenerative (wear-related) diseases of the cervical spine are becoming increasingly common. On the one hand, they occur as part of a natural aging process, but can also result from trauma or from factors such as long working hours on the computer and lack of exercise.
Such degeneration of the intervertebral discs (the cartilaginous parts between the 7 cervical vertebrae) can lead to pronounced complaints, including pain and numbness in the shoulder and neck area, which can radiate either high into the head or up to the arm and even the hands. As this greatly reduces the quality of life of those affected, they often consult a doctor with a request for quick help.
The first thing that is usually attempted is conservative therapy, which often does not have a satisfactory effect. While stiffening of the spine (spondylodesis) was previously recommended in such cases, today one tends to use an intervertebral disc prosthesis. Compared to the surgical stiffening of the spine, the insertion of an intervertebral disc prosthesis is the safer procedure for the patient.
In order to protect the spinal cord, surgical access is always from the front during a disc prosthesis operation using a 3 to 4 cm long skin incision.
The procedure usually takes about 1 to 2 hours and is performed under general anesthesia.
The desired intervertebral disc is first removed through the incision (discectomy). The space that has now been freed up is filled up by an implant, the intervertebral disc prosthesis.
This prosthesis usually consists of two metal plates, between which there is a layer of plastic. This means that the implant can on the one hand grow well and firmly with the surrounding structures and on the other hand can withstand the extensive movements in the area of the cervical spine. Since the thickness of the prosthesis is aligned with that of the intervertebral disc and has a certain deformability, the mobility of the neck should be almost as natural after the operation as before the illness.
If everything goes without complications, the patient can usually leave the hospital on the second day after the operation. First, he then has to wear a neck brace for about 6 weeks in order not to endanger the healing process. At the end of this time at the latest, everything should have healed well and the affected person can return to their normal everyday and professional life, but this is often also possible while wearing the cervical collar.
The insertion of a spinal disc prosthesis in symptomatic diseases of the cervical spine has been considered the treatment of first choice for some years because it is associated with a very high success rate (approximately 90%) and has a very low risk of complications. Advantages over other possible procedures are also the preservation of the natural range of movement of the neck and especially the rapid rehabilitation through the option of direct mobilization.
Intervertebral disc prosthesis of the lumbar spine
Degenerative (wear-related) diseases of the lumbar spine are becoming increasingly common.
On the one hand, they occur as part of a natural aging process, but they can also result from trauma or from factors such as long working hours on the computer, obesity and lack of exercise.
Such degeneration of the intervertebral discs (the cartilaginous parts between the 5 lumbar vertebrae) can lead to pronounced symptoms, including pain and numbness in the back, which can radiate to the hip and sometimes even to the legs.
As this greatly reduces the quality of life of those affected, they often consult a doctor with a request for quick help. The first thing that is usually attempted is conservative therapy, which often does not have a satisfactory effect. While stiffening of the spine (spondylodesis) was previously recommended in such cases, today one tends to use an intervertebral disc prosthesis.
Compared to the surgical stiffening of the spine, the insertion of a spinal disc prosthesis is the safer procedure for the patient.
In order to protect the spinal cord, the surgical access during an intervertebral disc prosthesis operation takes place with the help of a 5 to 8 cm long skin incision on the lower abdomen. The procedure usually takes about 1 to 2 hours and is performed under general anesthesia.
The desired intervertebral disc is first removed through the incision (discectomy). The space that has now been freed up is filled up by an implant, the intervertebral disc prosthesis.
This prosthesis usually consists of two metal plates, between which there is a layer of plastic. This is so that the implant can on the one hand grow well and firmly with the surrounding structures and on the other hand can withstand the extensive movements in the area of the lumbar spine.
Since the thickness of the prosthesis is aligned with that of the intervertebral disc and has a certain deformability, the mobility of the lower back should be able to run almost as naturally after the operation as before the illness.
If everything goes without complications, the patient can usually leave the hospital on the second day after the operation. First of all he has to wear a soft bandage (for about 6 weeks) in order not to endanger the healing process. At the end of this time at the latest, everything should have healed well and the affected person can return to their normal everyday and professional life, although this is often also possible while wearing the bandage.
Only with practicing particularly stressful sports should you wait a little longer, if possible, cycling or swimming are not a problem. To ensure an optimal course, it is advisable to integrate physiotherapy into the long-term treatment.
The insertion of a spinal disc prosthesis in symptomatic diseases of the lumbar spine has been regarded as the treatment of choice for several years because it is associated with a very high success rate (approximately 90%) and has a very low risk of complications. Advantages compared to other possible procedures are also the preservation of the natural range of movement of the lumbar spine and especially the rapid rehabilitation through the option of direct mobilization.
Complications arising from the anterior approach can be distinguished from those caused by the implant.
Overall, serious complications when implanting a disc prosthesis are rare.
Access-related complication opportunities
- Lumbar spine: scar fracture, abdominal wall fracture, peritoneal injuries, intestinal injuries, bladder injuries, intestinal paralysis, ureter injury, retrograde ejaculation disorder, vascular injuries, nerve root irritation
- Cervical spine: vascular injuries, nerve injuries, temporary or permanent hoarseness
- General complications: infection, wound healing disorder, thrombosis, pulmonary embolism, etc.
- Implant migration, sinking in, contortion of the plastic core, plastic abrasion (wear)
Post-operative follow-up treatment is unlikely to be carried out immediately in any hospital. On the one hand, this is related to the experience of the surgeon, on the other hand, individual peculiarities during the operation are taken into account in the aftercare plan (e.g. operation of several intervertebral disc prostheses, intervertebral disc height, complications, etc.). The surgeon should always determine the aftercare individually.
Without being able to go into details, the following applies to many patients after uncomplicated, monosegmental implantation of an intervertebral disc prosthesis:
- Getting up on the 1st postoperative day.
- Removal of wound tubes on the 2nd postoperative day.
- Physiotherapy (static abdominal and back muscle training).
- Possibly. Prescription of a lightweight orthopedic bodice.
- Learning back-friendly everyday behavior.
- Discharge after approx. 1 week or after threading on the 11th or 12th postop. Day.
- Sitting at home for longer than 1 hour at a time should be avoided.
- No lifting or heavy carrying in the first 6 weeks.
- Implementation of a rehabilitation measure from the 6th postoperative week.
- Ability to work between the 6th and 12th postoperative week.
- Swimming and cycling from the 4th-6th postop. Week.
- Highly stressful back sports (e.g. tennis, skiing, etc.) only from 6 months postop.
- X-ray control after about 6 weeks.
As already mentioned, modern intervertebral disc prostheses are only implanted to a significant extent (for 4-5 years). Therefore, there are no long-term studies on the durability of these prostheses. It has also not yet been proven that the intervertebral disc prosthesis prevents connection degeneration of the neighboring segments.
The short to medium-term results after implantation of the intervertebral disc are good to very good. In most studies, the good to very good results are over 90%. At 4%, revision surgery is less common worldwide than with vertebral body fusion (approx. 10%).