At the recently concluded International Society for the Advancement of Spine Surgery (ISASS) annual meeting one of the speakers, Dr. Scott Blumenthal from the Texas Back Institute (TBI), presented evidence of late cervical disc arthroplasty failure due to infection and osteolysis.

Osteolysis is essentially the reverse of ossification where bone is actively resorbed by osteoclasts. It most often refers to a pathological process where articulating surfaces of a motion preserving implant create microscopic particles which in turn stimulate an inflammatory response, an immunological response or changes in the bone's structural load. In these five case reports, Dr. Blumenthal reported one case in which histology suggested a wear particulate stimulated reaction.

Dr. Scott Blumenthal—who performed the first total disc replacement in the United States, has published several landmark papers on total disc replacement (TDR) and is Clinical Assistant Professor of Orthopedic Surgery at the University of Texas Southwestern Medical School—reported that five patients had had their infected cervical total discs removed due to osteolysis. Four of those cases involved the M6-C prosthesis (manufacturer Orthofix) and one involved the Prestige LP (manufacturer Medtronic Spine).

On average, these cervical disc implants failed three years after surgery (range: 24-54 months). According to Dr. Blumenthal, the patients reported good symptomatic relief following initial TDR implantation. Over the ensuing several months, however, these five patients gradually developed neck and/or arm pain.

In every case, the TBI surgeons found bony osteolysis of the vertebral body endplates contacting the prosthesis and that osteolysis was visible on plain radiographs. The TBI team then used a CT scan to evaluate the extent of bone loss.

Notably, the research team also identified C. acnes culture in every case and treated each patient with IV antibiotics for six weeks.

The study was supported by the Center for Disc Replacement at TBI, and two other internationally renowned disc arthroplasty practitioners and researchers also contributed:

Orthofix’s Welcomes Dr. Blumenthal’s Study

Orthofix, the manufacturer of the M6-C™ cervical disc and headquartered in Lewisville, Texas (about 4 miles from TBI), welcomed Dr. Blumenthal’s data collection and documentation for his ISASS presentation. As the company explained to OTW: “Orthofix welcomes the review of safety and efficacy data for artificial cervical discs and believes all manufacturers should be working in collaboration with the surgeon community to ensure this product class and disc arthroplasty in general is well understood. The 55,000 M6-C artificial discs implanted over the past 15 years provides significant real world evidence that we continually monitor.”

“Implant failures are not unique to any particular device and present various clinical and radiographic evidence. The cases presented in the TBI abstract summarize analyses from two M6-C patients in the investigational device exemption (IDE) study, two M6-C patients outside the study and one competitive product patient who developed an osteolytic reaction after total disc replacement, at a single center, which required reoperation. C. acnes was identified from operative culture in all cases.”

Other ISASS Cervical Disc Reports

All total disc replacement implants currently on the market came through the rigorous premarket approval (PMA) process of regulatory approval. It’s the most difficult, clinical study centric, expensive and time consuming gauntlet for bringing a medical device to market.

Specifically, as regards Orthofix’s M6-C cervical disc replacement, that means there is a significant body of clinically relevant evidence exists about the implant.

The M6-C disc has actually been available to spine surgeons outside the U.S. since 2006. More than 55,000 M6-C discs have been implanted in more than 20 countries and there is upwards of 10 years patient experience for about 8,000 cases (more than seven years for about 15,000 patients and more than five years of data for about 25,000 patients).

Dr. Frank Phillips, Professor of Orthopedic Surgery at Rush University Medical Center and an investigator in the original M6-C FDA approved study (as was TBI), also presented data about the M6-C at the ISASS annual meeting.

Dr. Phillips presented midterm study results and reported, “Patients treated with the M6-C artificial cervical disc continue to have statistically significant benefits at three and four years as measured by the Visual Analog Scale (VAS) scores as compared to anterior cervical discectomy and fusion (ACDF) patients”.  Specifically, Dr. Phillips reported, in part:

The FDA approved study for the M6-C was a prospective, non-randomized, concurrently controlled trial at 23 sites in the U.S. The study collected data on safety and effectiveness of the M6-C for treatment of single-level symptomatic cervical radiculopathy with or without compression. Similar data was also collected for patients treated for the same condition using ACDF.

The overall success rate for the M6-C for the protocol-specified primary endpoint was 86.8% at 24 months versus 79.3% in the control group. The data demonstrated that the M6-C was not inferior to ACDF and on February 2019, the FDA approved it for sale in the United States. Orthofix is currently engaged in its U.S. investigational device exemption (IDE) 10-year post approval study and will continue to report longer term data as it is collected.

What Happened to the Patients With Osteolytic TDR Implants

One piece of good news from the TBI experience is that, despite the extensive bony resorption accompanying the M6-C and Prestige osteolysis, only one of the five patients required a total corpectomy and reconstruction with a cage (which was the patient who’d received a 2-level Prestige LP).

The other four cases, all M6-C, had their implants removed and were treated with an ACDF procedure and an anterior plate with good clinical outcomes.

As we stated above, the TBI team discovered C. acnes from operative culture in all the cases. The team was able to get pathology results for two patients. In one case the results were consistent with acute infection and in the second case the results were more consistent with chronic wear particle-mediated inflammation.

Clinically, all the patients reported good clinical outcomes following their revision surgery with, as Dr. Blumenthal reported, resolution of each patient’s pre-revision pain and neurologic symptoms.

According to Dr. Blumenthal: “The true etiology of these late cases of post-TDR osteolysis and their impact on the overall safety of the prostheses involved remain unclear.”

“Further study is needed to quantify the rates of late osteolysis in different prostheses designs, and more detailed pathological analysis may differentiate infectious from wear-mediated osteolytic reactions.”

“It remains unclear whether the reported cases of late osteolysis following cervical TDR stem from infection with C. acnes causing gradual bony resorption, or if the primary pathology is that of an osteolytic foreign body mediated reaction to wear debris, with possible secondary colonization. These cases of late osteolysis along with others reported in the literature are concerning and spine surgeons should be aware of the possibility of this occurrence and address it with patients.”

Dr. Blumenthal and the TBI team is now reviewing data from other M6-C and Prestige patients to determine if this experience was an outlier or an early sign of something more serious.

Orthofix is assisting TBI telling OTW: “TBI was a site in the Orthofix M6-C IDE study, and we are in the midst of our post approval study, so we are still engaged with TBI and their patients. We are leveraging their experience in spine arthroplasty, our IDE data and our real world evidence to continually monitor artificial disc performance and ensure good patient outcomes.”

I just got my prestige cervical disk replacement at C4-5 that was installed in 2007 then taken out due to a complete failure of the product. It was metal on metal in my neck. The Dr that did the extraction said was it is like a bomb went off in my neck. I was one of the 1st people to receive this surgery. I had multiple scans done from CT with contrast and without, also 2 myelogram procedures which I elected for because I was in so much pain. I started having pain 6 months to 1yr after surgery. The pain got worse every yr. I went to a mental hospital 2 times for depression dealing with the pain. I had to endure 8+ years of immense pain. Lost loved one’s childhood friends due to the pain medication I was given. I’m 1yr out of the extraction of the Implant and got a fusion in the area. I literally got shorter when the Implant failed. I’ve read multiple articles about this and seen only 5-6 cases that were close to my situation. My story has to be recorded in the medical records. Thank you Jason Rousse

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