691 - Porous Silicon Nitride Spacers versus PEEK Cages with Autograft: 12 Mo...

General Session: Innovative Technologies

Presented by: M. Arts - View Audio/Video Presentation (Members Only)

Author(s):

M. Arts(1), J. Wolfs(1), T. Corbin(2)

(1) Medical Center Haaglanden, Neurosurgery, Den Haag, Netherlands
(2) University of Minnesota, Clinical Outcomes Research Center, Maple Grove, MN, United States

Abstract

Purpose: Polyetheretherketone (PEEK) plastic is a common material used in medical devices for interbody fusion. Silicon nitride (Si3N4) is an alternative to PEEK, with desirable bone compatibility and imaging characteristics. Silicon nitride can be manufactured in solid and/or a porous form with osteoconductive properties. It is currently unknown how a silicon nitride spacer with the graft hole filled with porous silicon nitride performs clinically. The objective of the study was to compare clinical outcomes of two test groups at 12 months: PEEK cage filled with autograft versus silicon nitride spacer (with a porous center but without any graft material) in an ACDF procedure with no supplemental anterior fixation.

Methods: Surgical procedures were performed in a single center in the Netherlands by two neurosurgeons Patients were selected if they had radicular and/or medullary symptoms at a single level and no confounding comorbidities or problems that would prevent them from completing the trial. The primary outcome measure was the Neck Disability Index, which was used to calculate sample size and assess noninferiority. Secondary measures included SF-36, arm and neck VAS, and patient and surgeon assessment of recovery. Patients were recruited and randomized into two groups on a 1:1 allocation. All outcomes measures were collected at 3, 6, 12 and 24 months. A sample size of 92 patients was calculated to be sufficient to test noninferiority between the groups. Patients and research nurses were blinded to group through at least the 12 month follow-up visit. The first data analysis was conducted when all patients reached the 12 month time point.

Results: Analysis was performed on 96 patients through 12 months. There were no differences in operative statistics or length of stay. There was no statistical or clinically significant difference in NDI scores between the groups (p=0.23). Noninferiority was confirmed. There were also no significant differences in SF-36 (p=0.61) and VAS outcomes (p=0.11) at 12 months or in adverse events. One patient in each group had a reoperation due to symptomatic subsidence. One PEEK patient died of unrelated causes but was a clinical and fusion success at the time of death. Five (5) silicon nitride and four (4) PEEK patients had new symptoms develop at an adjacent level and were treated with ACDF procedures. There were no implant failures in either group. Fusion rate and mean rotation on flexion-extension were similar (p=0.25) for the two groups, with no statistical difference at any time point. Surgeons found no statistical difference in migration or subsidence on x-ray or CT.

Conclusions: At 12 month follow-up, porous silicon nitride can promote interbody fusion in ACDF at rates similar to those achieved with bone autograft. Composite silicon nitride spacers with a porous core had nearly identical outcomes when compared to PEEK cages filled with locally-harvested autograft. These observations are consistent with previous data showing silicon nitride cages having high reliability, with no cage failures during insertion or in-situ. Thus this data further validates the use of silicon nitride as a biomaterial in cervical fusion.