Heterotopic ossification, osteolysis and implant failure following cervical total disc replacement with the M6-C™ artificial disc

• Published in: European spine journal 2024-03, Vol.33 (3), p.1292-1299
• Main Authors: Häckel, Sonja, Gaff, Jessica, Pabbruwe, Moreica, Celenza, Alana, Kern, Michael, Taylor, Paul, Miles, Andrew, Cunningham, Greg
• Format: Article
• Language: English
• Subjects: Bone implants; Computed tomography; Medicine; Medicine & Public Health; Neurosurgery; Original Article; Ossification (ectopic); Osteolysis; Pain; Patients; Risk factors; Surgical Orthopedics; Transplants & implants
• ISSN: 0940-6719; 1432-0932
• DOI: 10.1007/s00586-024-08129-5

Introduction A recent study reported a 34% mid-term revision rate after M6-C™ cervical total disc replacement (CTDR) for wear-related osteolysis. Here, we aim to investigate the prevalence, risk factors, and radiographic characteristics of periprosthetic bony changes and implant failure of the M6-C™ artificial disc. Methods We retrospectively analysed radiographic (conventional X-ray, CT scan) and clinical outcomes (EQ-5D-5L, Neck Disability Index (NDI), and Visual Analog Scale (VAS) for neck and arm pain) data collected during routine follow-up of patients who underwent CTDR with the M6-C™ between 2011 and 2015. Results In total, 85 patients underwent CTDR with the M6-C™. Follow-up data were available for 43 patients (54% female, mean age 44 years) with 50 implants and a mean follow-up of 8.1 years (6.5–11 years). Implant failure with the presence of severe osteolysis was identified in 5 (12%) patients who were all male ( p  = 0.016) and implanted at the C5/6 level ( p  = 0.11). All failed implants required revision surgery. The overall prevalence of osteolysis was 44% (22/50 implants) and 34% (17/50 implants) for significant heterotopic ossification. Patients with high-grade osteolysis showed higher VAS arm pain ( p  = 0.05) and lower EQ-5D-VAS health VAS ( p  = 0.03). Conclusion We report a lower reoperation rate for failed M6-C™ implants than previously published, but confirmed that osteolysis and heterotopic ossification are common following CTDR with the M6-C™ and may be asymptomatic. Therefore, we strongly recommend ongoing clinical and radiographic monitoring after CTDR with the M6-C™, particularly for male patients implanted at the C5/6 level.