Menu Close

M6 Disc Replacement Advantages

No Implant related failures and very low surgical complications.

We are often asked about failures and complications involving Disc Replacement Surgery and the implants we use.

We have some good news!

"No implant-associated failure or complication was found in any case involving the M6 Disc Implant."
Dr. Karsten Ritter-Lang - Special Clinic for Orthopedics

Less Complications and Revisions After M6 Disc Replacement

There is no medical surgery that can be done without complications or side effects. Therefore, the objective consideration of occurring complications is imperative.

Artificial Disc Replacement surgery of the lumbar spine is dependent on the availability of surgeons with appropriate experience and knowledge of the surgical approach required. Unfortunately, very few surgeons worldwide have the required experience in the field of surgical access to the spine. In addition, experience in determining the appropriate intervention, surgery, or implant also plays a significant role. If the procedure is not routinely performed, experience in making these determinations is also lacking.

In the case of complications, the question always arises as to what caused the problems.  Is the error to be found in the diagnosis and indication of what surgery is appropriate? Was the choice of suitable interventions, surgeries, or implants faulty or influenced by limited device availability or insurance limitations? Was the surgery performed without error, in accordance with current scientific standards?

All these questions require thorough consideration in every medical field, including the field of inter-vertebral disc prosthetics, also known as Artificial Disc Replacement.
Artificial Disc Replacement has been in use for over 40 years, and was originally developed in Germany.

Overall German Results

In Germany, all medical procedures performed in licensed hospitals are centrally recorded statistically, and both the diagnoses and the procedures are tracked via coding systems (ICD and OPS).

From these data, which are collected and published by the Federal Statistical Office, it can be determined that approximately 6000 operations with artificial disc replacement (disc endoprosthesis) are performed in Germany per year. Any revisions are also recorded using special OPS codes and this rate is approximately 5% per year for Disc Replacement surgery.

Disc Replacement vs Spinal Fusion Surgery

For comparison, the revision rate for spinal fusion surgery is on average about twice as high as that for Disc Replacement.

In the scientific literature, the complication and revision rates for Artificial Disc Replacement and Spinal Fusion Surgery, respectively, are as follows:

Peri- and Postoperative Complications
Artificial Disc Replacement 2-8%
Spinal Fusion Surgery  4-18%

Revision Surgery Rates
Artificial Disc Replacement 2-4%
Spinal Fusion Surgery 3-12%

These figures show a clear superiority of Artificial Disc Replacement as compared to Spinal Fusion Surgery.

Special Clinic for Orthopedics Results

An analysis of cases between 2014 and 2022, Special Clinic for Orthopedics

The following statistics are based on cases at the Special Clinic for Orthopedics from 2014 to 2022, and thus represent approximately 20% of the cases provided by our team over the past 20 years. In total, the number of patients we cared for is much higher and is likely to approximate 10,000 cases. Thus, further workup will continue, but is time-consuming given the large number.

Between 2014 and 2022, we provided disc replacement implants to 2614 patients in the cervical and lumbar spine, and we fused 2417 patients during the same period. Pre-operations and revisions were performed on 1643 patients. This means that minus our own revisions, every third patient who reached the clinic had already been pre-operated on.

In this paper, I would like to focus on the patients who underwent Artificial Disc Replacement surgery and try to determine the root cause of any complications or revisions.

In the context of the 2614 patients treated with Artificial Disc Replacement, we had 169 patients with revision operations after Artificial Disc Replacement in the same period.  This means that the revision rate is 2.75%. In relation to the number of implanted devices (4265), the revision rate is 1.69%.

But what were the reasons for the revisions? Here, of course, several considerations must be made:

  1. Patients who were fitted by us or elsewhere prior to revision
  2. Analysis of the reasons for revision
  3. Analysis of the implant types involved.

Only this overall view can help us to recognize certain patterns and this in turn is helpful to avoid errors in the future.

The following errors could be systematically identified:
- Hematoma early/postoperatively
- subsidence
- migration
- Root irritation early
- Early complication SPL
- Paresis early
- early infection
- Defect of the implant
- low grade infection
- Spondylolisthesis aquisata
- osteolysis
- Stick-slip friction
- hypermobility
- instability
- Rotational Slippage
- loosening
- persistent stenosis
- Late acute infection

Here again, a distinction must be made between early and late complications. The early complications were postoperative hematoma, nerve root irritation, and paresis, followed by subsidence, migration, and the early complication spondylolisthesis aquisata as immediate postoperative instability. Only one early infection was noted.

Late complications were implant defects and low grade infections followed by spondylolisthesis aquisata, osteolysis of unclear cause, stick-slip friction, hypermobility, instability, rotational slippage, loosening, persistent stenosis and, in distinction from low grade infections, acute late infection.

If the reasons for revision are further differentiated, it becomes apparent that, as a rule, early complications are not implant-associated.

In the case of late complications, there are clear indications of implant-associated and non-implant-associated complications.

Implant Defects
All cases of implant defects are exclusive to Cadisk-C and -L, which has been withdrawn from the market.

Low-grade Infections
If bacteria enter the bloodstream (hematogenous infection pathway), bacterial colonization of an implant surface is possible. Spinal infections often require long-term intravenous antibiotic or antifungal therapy and can equate to extended hospitalization time for the patient. Immobilization may be recommended when there is significant pain or the potential for spine instability. If the patient is neurologically and the spinal column is structurally stable, antibiotic treatment should be administered after the organism causing the infection is properly identified. Patients generally undergo antimicrobial therapy for a minimum of six to eight weeks. The type of medication is determined on a case-by-case basis depending on the patient’s specific circumstances, including his or her age.  Nevertheless, the numbers are in the absolute per mille range.

We have seen osteolyses of unclear cause exclusively in ESP-L implants usually occurring 4-5 years after implantation and again leading to increasing complaints. The reason for their occurrence is unclear, but it must be assumed that they only occur with one type of prosthesis, so that there is a clear implant association here.

The same applies to the stick slip friction. We have observed this effect exclusively with the Triadyme implants. The spherical design of the surface can lead to overloading of the articulating surfaces with perceptible crepitation during rotational movements of the head.

Subsidence, in turn, affects different types of implants and is not causally implant-associated; rather, due to the force distribution occurring immediately after surgery, occasional weakening of the cover plate of the caudal vertebra occurs with sinking of the implant.

In the migrations that have occurred, the L5/S1 segments are usually affected. In this case, it is not the implant that is the cause, but rather the implantation technique.

The complex of hypermobility, instability and rotational slippage can essentially be summarized as increasing instability of the affected segment, which the implant must follow due to its design. Intervertebral disc implants are not designed to compensate for segmental instabilities that occur, which is why primary implantation is contraindicated in cases of known instability. However, it cannot be ruled out that instabilities may develop over time even in supplied segments, which then overtax the lying implant.

The situation is similar with spondylolisthesis aquisata; this pathology is already known to occur after fusion surgery. The present cases almost exclusively involve the L5/S1 segment and almost without exception the M6-L. Since the prosthesis, in contrast to classical ball and socket prostheses, has all the movement qualities of a normal healthy intervertebral disc, the possibility of translation is given and thus the implant will passively follow a sliding of the respective cranial vertebra and thus be damaged.

Persistent stenoses are the result of insufficient primary decompression or arise on the basis of secondary hypersostotic bone formation postoperatively. In either case, they are not implant associated.

Acute late infections must be distinguished from low grade infections. These arise as acute, clinically imposing infections with accompanying abscess formation and are also known from other areas of orthopedic surgery. As with low grade infections, the pathway of origin is also hematogenous. Again, there is no implant-associated origin.


In our experience no implant-associated complication was found in any case involving the M6 Artificial Disc Replacement implant.

During the same period, a total of 4265 disc replacement implants were implanted in the cervical and lumbar spine in 2614 patients. Related to these numbers, 72 revision surgeries were necessary for various reasons. Thus, the number of necessary revisions is 2.75% in relation to the number of patients and 1.69% in relation to the number of implants.

Overall, our revision rate is thus about half of the German average. Only 0.38% of the revisions were implant associated and did not involve the M6 Disc. All other revisions showed no implant associated causes.

Dr. Karsten Ritter-Lang - Special Clinic for Orthopedics