Rare Posterior Dislocation of Mobi-C Cervical Disc: A Case Report and Surgical Resolution.

BACKGROUND Cervical disc prosthesis (CDP) is a well-established treatment for cervical degenerative disc disease. It provides motion preservation and decreases adjacent segment degeneration associated with ACDF. It is highly effective, with a low failure rate, but rare complications, including prosthesis migration, can occur. The posterior migration of a CDP is extremely rare, and only a few cases have been described in the literature. This report describes a unique case of posterior intraprosthetic dislocation of a Mobi-C prosthesis and adds valuable knowledge about this rare complication. CASE REPORT A 50-year-old female non-smoker underwent C6-C7 discectomy with implantation of the Mobi-C prosthesis for cervical disc herniation causing radicular pain and paresthesia. The initial postoperative results were good, with remission of neurological symptoms and no complications. However, after 2.5 years, she presented with neck pain and numbness of the right upper limb after routine physical activity. Imaging studies, including computed tomography (CT), revealed a posterior migration of the polyethylene insert with compression of the spinal cord. Revision surgery was undertaken comprising removal of the dislocated prosthesis and conversion to ACDF using the Anchor C system. Complete symptom resolution was achieved, and implants were properly aligned without complication in this procedure. CONCLUSIONS Posterior intraprosthetic dislocation of the Mobi-C prosthesis is an extremely rare complication. This case report with long-term follow-up shows ACDF is an effective method of salvage. Further investigation is necessary for understanding failure mechanisms, and development of CDP design is needed to avoid such complications.