Posterior intraprosthetic dislocation of cervical arthroplasty: illustrative case.

BACKGROUND: Cervical disc herniation is a common condition usually treated with anterior cervical discectomy and fusion (ACDF) or, more recently, with cervical disc arthroplasty (CDA). Both treatments offer similar clinical results. However, CDA has been found to offer fewer medium- to long-term complications as well as potential reduction of long-term adjacent disc degeneration. OBSERVATIONS: A 40-year-old man was treated with cervical discectomy and arthroplasty due to a C6-C7 disc herniation with left C7 radiculopathy. After the treatment, his postoperative follow-up appointments were uneventful for 9 months. However, after 9 months, he reported cervical pain and a right C7 radiculopathy after neck extension. Imaging confirmed a posterior intraprosthetic dislocation, the first case reported to date. The patient was received emergency surgery under neuromonitoring, and the prosthesis was replaced by an ACDF and anterior plate. The insert presented a rupture of the anterior horn. The patient presented no preoperative or postoperative neurological deficit, and his follow-up review revealed no issues. LESSONS: Posterior intraprosthetic dislocation is an extremely rare complication. It may occur with Mobi-C cervical arthroplasty in the case of rupture and oxidation of the polyethylene insert. Spine surgeons should be aware of this potential major complication.