Thousands of UK patients may face complex surgery to remove a spinal implant now linked to progressive bone loss, after the device was withdrawn from sale and an urgent recall was issued for X-ray monitoring. The M6-C artificial cervical disc, manufactured by Orthofix, was designed as a motion-preserving alternative to spinal fusion, but has been associated with osteolysis – a condition in which bone tissue is destroyed and reabsorbed by the body around the implant. Orthofix announced the discontinuation of the M6-C and its lumbar counterpart, the M6-L, in February 2025 as part of a strategic shift.
What is osteolysis?
Osteolysis is a progressive and potentially devastating complication. Studies suggest that polyethylene wear debris from the M6-C implant is a significant factor driving the bone destruction. Some research has also identified a delayed allergic reaction to polycarbonate urethane (PCU) as a possible cause. The resulting bone loss can compromise the stability of the device, leading to implant loosening, spinal instability, nerve root or spinal cord compression, chronic pain, and neurological deficits including paralysis. In addition, patients may develop heterotopic ossification (abnormal bone growth), severe infection, abscess formation, and dysphagia (difficulty swallowing) due to compressive masses anterior to the disc.
Evidence of the scale of the problem is mounting. A US MAUDE database study published in 2025 found that the M6-C accounted for 138 reported osteolysis events and showed the highest reported rate of osteolysis – 36.2% – among commonly used cervical disc replacements. A study in the European Spine Journal reported that up to 34% of patients who underwent M6-C disc replacement developed severe osteolysis requiring revision surgery and spinal fusion. Another study (Häckel et al., 2024) recorded a 10% failure rate due to osteolysis and implant failure. Research by Clohisy and colleagues in 2023 indicated an overall prevalence of osteolysis at 44% and significant heterotopic ossification at 34%. A 2022 study by Scott-Young et al. reported a 34% mid-term revision rate for wear-related osteolysis. Literature suggests that revision surgery is often required between five and eight years post-implantation, meaning mandatory monitoring may be needed for at least a decade.
Regulatory action has been slow to catch up. Australian regulators issued a hazard alert over bone loss linked to the M6-C disc as early as 2020. In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) did not issue a Device Safety Information notice (DSI/2026/001) until January 2026, following an assessment of emerging evidence and adverse incident reports. The MHRA found that there had been a delay in the manufacturer’s communication of the risks of osteolysis to users and patients in the UK. Updated warnings regarding osteolysis were introduced internationally as early as 2020, but UK updates to the Instructions For Use followed later in 2023, and a formal Field Safety Notice was not issued to UK users until August 2025. The MHRA has now mandated the active identification and recall of patients with the M6-C device, along with mandatory ongoing annual radiological monitoring – X-rays – for all patients, even those who remain asymptomatic. The British Association of Spinal Surgeons has issued guidance requiring all patients with an M6-C implant to remain on active monitoring.
Patient experiences and legal action
Sophia Harrison, 52, from East Grinstead, East Sussex, had the M6-C implant fitted in 2019. Two years later she developed pins and needles in her hands and noticed a lump in her throat that affected her voice and swallowing. She did not initially connect the two symptoms. After receiving a letter from the MHRA, she underwent a CT scan which detected osteolysis and also revealed a large mass – a 10cm abscess. “My doctor said he nearly fell off his chair looking at the results as the infection continued to grow despite being drained,” Ms Harrison said. “I can feel it growing again by the day and I’ve now been told they may have to take out two further discs along with the implant and insert a metal rod.” She described the prospect of such surgery as “daunting”.
“I’m speaking out as I want to raise awareness and tell people who have this implant to have a scan as soon as they can so that they can avoid what is happening to me,” she said. “You may not even be aware you have an associated infection or other symptoms. I feel for all of the surgeons who are having to clear up the mess of the previous doctors who inserted these implants into patients.” Ms Harrison expressed anger at the delay in disclosure: “I am so angry that we weren’t told about the faults of the disc that leads to bones disintegrating. It’s absolutely despicable as the manufacturer would have known about this so why has it taken so long? If I had known earlier, the infection would have been caught and I would not be facing what has now become such complex and daunting surgeries on my spine.”
Law firm Penningtons Manches Cooper has been contacted by at least 10 people who have had the M6-C implant and is now exploring whether a legal claim is possible against the manufacturer. Lyndsey Skibinski, a specialist medical negligence solicitor at the firm who is advising Ms Harrison and leading the investigation, said: “This is a potentially huge public health issue with thousands of patients affected. Most of the people approaching us have had the implant in place for between eight and nine years but it is crucial that anyone who has this implant gets a scan to identify any problems and continues with recommended annual monitoring. Many will need complex surgery to remove the implants which poses the risk of paralysis or long term chronic pain. We are currently investigating the legal options open to those we are advising to see how we can secure justice for the trauma and suffering they are experiencing and also to recover funding for future treatment and rehabilitation.” Another law firm, Leigh Day, is also investigating potential claims against Orthofix on behalf of affected patients.
Patients who have an M6-C implant are advised to seek a consultation with a spine surgeon if they experience any of the following: increasing neck pain; increasing arm pain radiating from the neck to the arm or hand; pins and needles in the hands or arm; clumsiness or weakness in the hands or arm; electric-type sensations into the arms or trunk on neck movements; increasing clumsiness and loss of balance in the legs; persistent or worsening neck pain; arm pain, numbness or weakness; neurological symptoms; reduced movement in the neck; or a sensation of device loosening or instability.
Dr Stephanie Millican, deputy director of benefit risk evaluation at the MHRA, said the regulator had started an investigation into the M6-C device following reports in early 2025. “The MHRA took these concerns seriously and found that there was a delay in the manufacturer’s communication of the risks of osteolysis to users and patients in the UK,” she said. “Patient safety is our top priority. We continuously monitor medical devices used in the UK to ensure they perform to the expected standards. The MHRA has advised healthcare professionals that patients implanted with the M6-C artificial cervical disc should be informed of the risks of osteolysis, receive annual routine monitoring and discuss the need for further investigation and continued follow-up. Patients who have an M6-C device implanted should expect to be contacted by their surgeon or implanting hospital. We encourage patients, carers and healthcare professionals to report any suspected side effects to the MHRA via the Yellow Card scheme.” The Yellow Card scheme is the MHRA’s system for collecting reports of adverse incidents involving medical devices; reports can be made online or by email to [email protected], but cannot be made by telephone.
Over 70,000 M6-C devices have been implanted worldwide in more than 20 countries. In Australia alone, 1,460 discs had been implanted by August 2021. In 2024, the M6-C and M6-L product lines generated global net sales of $23.4 million. The device was originally developed by Spinal Kinetics, which Orthofix acquired in 2018. Following the discontinuation, surgeons are migrating to alternative total disc systems, including the Prodisc-C Nova, Mobi-C, Simplify Cervical Disc, and numerous others. The MHRA has advised that patients with an M6-C implant should be contacted by their surgeon or implanting hospital for ongoing review.