A prospective randomized controlled multicentre study of ProDisc–C vs anterior cervical discectomy and fusion for treatment of symptomatic cervical disc disease in Asian population: a 4-year outcome.

Introduction
The current standard surgical treatment option managing symptomatic cervical disc disease(SCDD) is anterior cervical discectomy and fusion(ACDF). Even though ACDF results in high clinical success and low complications, it could lead to hypermobility and increased intradiscal pressure at adjacent levels secondary to rigid immobilization at fused vertebral levels, resulting in adjacent disc degeneration. ProDisc–C is a cervical total disc replacement (TDR) designed to potentially preserve the motion at involved cervical vertebral segment, while reducing pain and neurological symptoms. Currently, literatures comparing ProDisc–C versus ACDF in Asian population is limited. It was noted that race is an important component that influences complication rate, length of hospital stay and mortality after cervical spine procedures.

Objective/Aim
To evaluate safety, efficacy, and the overall success of ProDisc-C versus ACDF at 48-months post-surgery in Asian patients in treating single-level symptomatic cervical disc disease(SCDD).

Methods
This multicentre, prospective, randomized controlled trial was conducted with patients with single-level SCDD involving C3-C7-vertebral segments. The patients were randomized into group-A treated with ProDisc-C and group-B with ACDF(treated with standalone cage with bone autograft) at 2:1 ratio. 120 patients consisting of 80 patients in group-A (ProDisc-C) and 40 in group-B (ACDF) were enrolled. Assessments conducted at baseline, 6-weeks, and 3-, 6-, 12-, 18-, 24-, 36- and 48-months post-surgery and annually till 84 months. The overall success at 48-months was composed of: (1)>20% improvement in neck disability index (NDI); (2)neurological success (maintained/improved); (3)absence of secondary surgery at index level; and (4)absence of device-related adverse events.

Results
Of 120 patients, 76-patients in group-A and 37-patients in group-B were treated as per protocol (PP). Overall success in PP last observation carried forward analysis was 79% in group-A and 75.7% in group-B at 48-months(p=0.0122), demonstrating non-inferiority of ProDisc-C to ACDF. Additionally, ProDisc-C demonstrated non-inferiority to ACDF at 18-months(81.6% vs 83.8%, p=0.0398) and at 36-months(80.3 vs 78.4, p=0.0156). Both groups had similar results in (i)NDI success(97.2% in group-A vs 100% in group-B), (ii)neurological success(83.3% in group-A vs 87.5% in group-B), (iii)absence of secondary surgery at index level(97.2% in group-A vs 100% in group-B) and (iv)absence of device-related adverse events(97.2% in group-A vs 193.75% in group-B) at 48-months(pp). Both groups had similar secondary outcomes(VAS-pain scores&SF-36). However, the range of motion was preserved in group-A and was significantly reduced in group-B at 48-months.

Conclusion
The use of ProDisc-C is feasible, safe, and effective for treatment of SCDD in Asian population. ProDisc-C demonstrated non-inferiority to ACDF in overall success at 18, 36 and 48-months. Both groups had similar secondary outcomes, future large-scale studies focusing on Asian population are required to establish clear non-inferiority of ProDisc-C to ACDF in terms the secondary outcomes in addition to overall success.