Comparison of dynamic cervical implant versus anterior cervical discectomy and fusion for the treatment of single-level cervical degenerative disc disease: A five-year follow-up

Objective: To compare clinical and radiographic outcomes of dynamic cervical implant(DCI) with anterior cervical discectomy and fusion(ACDF) in the treatment of single-level cervical degenerative disc disease (CDDD) 5 years after surgery. Patients and methods: Forty-three patients with DCI were matched one-to-one with patients with ACDF based on age, gender, and operative segment in this retrospective study. All patients had been followed up for more than 5 years. Radiological assessments included heterotopic ossification(HO), adjacent segment degeneration (ASD), intervertebral height (IH), range of motion (ROM) at C2-7, the implanted level and adjacent levels. Clinical parameters included Visual Analogue Scale (VAS), Japanese Orthopedic Association (JOA) scores, Neck Disability Index (NDI) and Short Form-36 scores(SF-36). Patients were also asked to rate their postoperative satisfaction at final follow-up. Results: The postoperative ROM of C2-7 and ROM at the implanted level in the DCI group were higher than those in the ACDF group. The ROM at the implanted level in the DCI group was maintained at 2 years postoperatively but decreased at final follow-up (10.7 degrees vs 4.5 degrees). The rate of HO in the DCI group was 46.5% (20/43). The rate of ASD was comparable between the two groups (16.3% vs 20.9%). The JOA, VAS, NDI, and SF-36 scores were comparable between two groups and improved postoperatively. However, the proportion of patients who reported their level of satisfaction as being very satisfied, or somewhat satisfied was larger in the ACDF group than that in the DCI group (95.3% vs 79.1%). Conclusions: DCI resulted in better ROM of C2-7 and the implanted level than ACDF did. The clinical outcomes were similar between two groups. However, the ROM at the implanted level decreased at final follow-up in the DCI group, which may contribute to patient dissatisfaction. The long-term outcomes were not that satisfactory especially due to the deviation from its original intention as a non-fusion technique. As such, we have not used DCI in the past 2 years.