Traumatic hangman's fracture after cervical disk arthroplasty with device in-tact: A case report and literature review

BACKGROUND CONTEXT: Cervical disk arthroplasty (CDA) has been demonstrated to be a safe and effective method to treat myelopathy with the added benefit of preserving neck mobility compared to anterior cervical discectomy and fusion (ACDF). Few studies describe complications of trauma after CDA, and to our knowledge this is the only study describing a grossly intact artificial cervical disk (ACD) without extrusion after high energy trauma. Based on our case and a review of literature, we hypothesize that, given adequate osseous integration (OI), CDA may be a safe intervention despite their risk for higher energy trauma. PURPOSE: To present a rare case of high-energy trauma after CDA resulting in a Hangman's fracture and grossly in-tact ACD and to engage a biomechanical discussion of trauma after CDA and ACDF utilizing a literature review. STUDY DESIGN/SETTING: Case-report with literature review and discussion PATIENT SAMPLE: Electronic medical record data OUTCOME MEASURES: Computed Tomography, Magnetic Resonance Imaging, and X-Ray physiologic measures METHODS: We report the case of a 44-year-old woman who received a C5-C6 level CDA with a (Synthes Prodisc-C©, Synthes Spine Company, L.P., West Chester, PA) and was subsequently involved in a high-speed motorcycle accident one-and-a-half years later resulting in a Hangman's fracture. RESULTS: Radiographic evidence after the motorcycle wreck demonstrated a minimally displaced Hangman's fracture at the C2 vertebrae through the pedicles on both sides, partially involving the transverse foramina with approximately 5 mm of displacement. The ACD at C5-C6 was grossly intact and no malalignment was noted. Three years later the patient elected to have an ACDF due to recurrence of facet pain that appeared by way of selective medial branch block injections to originate posteriorly in the facets of C5-6. A literature review revealed reports of trauma induced adjacent disk herniation, metallosis, and implant extrusion after CDA. No accounts of intact hardware, or concomitant Hangman's fracture after CDA were found following high-energy trauma. CONCLUSIONS: Our case reveals the first reported occurrence of a traumatic Hangman's fracture with intact fusion hardware after CDA. We hypothesize that the preserved mobility in the affected spinal level after the CDA exerted a protective effect compared to an ACDF following the high-speed trauma, particularly on the adjacent segments. This case and included literature review, reveal the need for future research efforts to guide decision making in whether ACDF or CDA is superior in younger patients at higher risk for trauma.