701404 - Outcomes with Porous PEEK Interbody Cages for Anterior Cervical Discectomy and Fusion at Three or More Levels

Background
Compared to one- or two-level procedures, anterior cervical discectomy and fusion (ACDF) at three or more levels remains uniquely challenging, particularly with regards to reported high pseudarthrosis rates (14.3%-45.8%) and implant-related complications. Porous surface polyether-ether-ketone (PEEK) interbody cages have recently been introduced for ACDF, however, minimal data exist about the efficacy of these implants in ACDF procedures at three or more levels.

Purpose:
The present study aimed to assess the initial clinical and radiographic outcomes of porous PEEK devices for ACDF at three or more levels.

Study Design/Setting:
Multi-center retrospective cohort study

Eligible population:
Patients who underwent primary ACDF for degenerative cervical disc disease at three or more levels with porous PEEK cages between January 2016 and October 2018 by three fellowship-trained spine surgeons at three separate institutions were included in the study.

Length of Follow-up:
Mean: 12.5 months (Min: 6 months, Max: 33 months)

Patient accountability:
39 available for study, 0 excluded, 39 final

Outcome Measures:
Preoperative and final postoperative clinical outcome scores including Visual Analog Scale (VAS) Neck pain, VAS Arm pain, Neck Disability Index (NDI) were collected. Preoperative, immediate postoperative, and final neutral lateral radiographs were assessed to measure C2-C7 lordosis, cervical sagittal vertical axis (SVA), fusion segment lordosis, T1 slope, lordosis proximal/distal to fusion segment, and disc height. Rates of pseudarthrosis (lack of bony bridging or segment motion on flexion/extension) and cage subsidence ≤2mm were also assessed on postoperative radiographs by two reviewers.

Methods
Preoperative and postoperative clinical outcomes and radiographic measures were compared using paired t-tests. Statistical significance was set at p<0.05.

Results
A total of 39 patients who underwent ACDF at three or more levels with porous PEEK cages were included (24 [61.5%] were three-level, 14 [35.9%] were four-level, and one [2.6%] was five levels). Mean age was 59.7 ± 9.0 years, mean body mass index was 31.0 kg/m2, 56.4% of patients were female, and 25.8% had a smoking history.

Two patients had cage subsidence of 2mm (5.1%) and one patient had pseudarthrosis (2.6%). The patient who had pseudarthrosis was a smoker and was the only patient who underwent a reoperation (2.6%). The pseudarthrosis rate amongst smokers was 12.5%. When comparing radiographic measurements (Table 1), there was a significant increase in preoperative-postoperative and preoperative-final overall cervical lordosis (Pre-Post p<0.001, Pre-Final p<0.001), SVA (Pre-Post p=0.002, Pre-Final p=0.018), fusion segment lordosis (Pre-Post p<0.001, Pre-Final p<0.001), T1 slope (Pre-Post p=0.031, Pre-Final p=0.030) and disc height (Pre-Post p=0.004, Pre-Final p=0.010). Clinical outcomes (Table 2) showed significant improvement from the preoperative visit to final postoperative follow-up (NDI p<0.001, VAS Neck p<0.001, VAS Arm p<0.001).

Conclusion:
The present study is the first to assess porous PEEK cages for ACDF procedures at three or more levels and supports that these devices are a clinically viable alternative for achieving successful outcomes. High rates of fusion (97.4%) were observed in this challenging patient cohort, which compares favorably with previously published rates of fusion in ACDF at 3 or more levels (54.2%-85.7%).