Introduction: There has been increasing attention on cervical arthroplasty as an alternative to arthrodesis as a way to preserve motion, reduce adjacent level degeneration, avoid reoperation, and improve patient-reported outcome. There are three types of cervical artificial discs on the market: constrained, semi-constrained, and unconstrained. There is no federally funded in vivo study that directly compares different cervical artificial discs.
Methods: We performed cervical arthroplasty at C3/4 level in 14 healthy female adult Alpine goats. Five goats received Bryan (Medtronic) (constrained disc); five goats received ProDisc-C (DePuy Synthes Johnson&Johnson) (semi-constrained); and four goats received Mobi-C (LDR Biomet Zimmer) (unconstrained). These goats were monitored in a unit for six months with regular cervical spine radiographs.
Results: All 14 goats tolerated the surgery well. All had satisfactory placement of hardware. No migration of implant occurred in the Bryan and ProDisc-C groups. 100% migration rate (4/4) was observed with Mobi-C within the first week, requiring implant removal and arthrodesis with an interbody and anterior plating. Heterotopic ossification was observed at six months in 40% of goats with Bryan (2/5). Partial heterotopic ossification (with motion preservation) was seen in 20% of goats with ProDisc-C (1/5). Cervical motion was ultimately preserved at six months in no goats with Mobi-C (due to fusion), 60% of goats with Bryan, and 100% of goats with ProDisc-C.
Conclusions: Unconstrained cervical artificial discs are prone to anterior migration. Constrained discs are more likely to develop heterotopic ossification than semi-constrained discs. Semi-constrained discs are most likely to preserve motion.
Patient Care: By helping clinicians choose which cervical artificial disc is safe and effective.
Learning Objectives: 1) Recognize different designs of cervical artificial discs
2) Discuss potential complications of cervical arthroplasty
3) Identify the most likely cervical artificial disc design to maintain motion