1224 Clinical and Radiographic Results From a Prospective Randomized FDA IDE Trial Comparing 3-level ACDF to Circumferential Fusion

INTRODUCTION: Pseudarthrosis is a well-documented risk following ACDF, particularly when treating multiple levels. Including posterior supplemental fixation and fusion (circumferential cervical fusion, CCF) with lateral mass screws and rods decreases the risk of pseudoarthrosis, but introduces the burden of a second open surgery. METHODS: Subjects were randomized 1:1 to ACDF or CCF. All had symptoms resulting from degenerative discs at 3 levels. The primary endpoint was fusion at 12 months. The secondary endpoint was a composite safety outcome assessed at 24 months and was dependent on fusion, improvement in NDI, absence of surgical revision, and maintenance/improvement in neurological status. Fusion was assessed by an independent imaging lab with success defined as all treated segments exhibiting a range of motion <2 with evidence of bridging bone across the interbody space. RESULTS: At the time of this interim analysis, 202 subjects (58±9 years, 59% female) contributed to 12-month outcomes and 116 subjects (58±10 years, 57% female) to 24-month outcomes. At 12 months, CCF had a higher percentage of subjects with successful fusion when compared to ACDF (CCF=61.0%, ACDF=16.7%, p<0.001). At 24 months, CCF exhibited higher rates of composite safety success when compared to ACDF (CCF=50.8%, ACDF=22.8%, p=0.002). Observed differences in composite safety success at 24 months were largely driven by differences in fusion success (CCF=74.6%, ACDF=33.3%, p<0.001) and incidence of subsequent surgical intervention (CCF=1.7%, ACDF=22.8%, p=0.002). CONCLUSIONS: Subjects treated with CCF had superior radiographic and safety outcomes when compared to ACDF only. The observed rate of revision in the ACDF only group suggests the risk of symptomatic pseudoarthrosis in 3-level treatment may be greater than what is currently reported.