Prospective, Randomized, Blinded Clinical Trial Comparing PEEK and Allograft Spacers in Patients Undergoing Anterior Cervical Discectomy and Fusion Surgeries

Alan T. Villavicencio, MD; E. Lee Nelson, MD; Sharad Rajpal, MD; Kara Beasley, DO; Sigita Burneikiene, MD


Spine. 2022;47(15):1043-1054. 

In This Article

Abstract and Introduction


Study Design: Prospective, randomized, blinded clinical trial.

Objective: To examine clinical and radiological outcomes in patients undergoing anterior cervical discectomy and fusion (ACDF) surgeries randomized to receive either polyether-ether-ketone (PEEK) or structural bone allografts.

Summary of Background Data: The biomechanical qualities as well as osteoconductive, osteogenic, and osteoinductive properties of various graft materials have been previously evaluated. There remain questions, however, as to whether there are any clinical and/or radiographic outcome differences in the selection of interbody graft types for ACDF.

Methods: Patients undergoing one- to three-level ACDF with single anterior plate fixation were randomized (1:1 ratio) to receive either cortical allograft or PEEK interbody spacers. Radiographic and clinical outcomes were assessed at 3, 6, 12, and 24 months with an additional postoperative radiographic assessment.

Results: A total of 120 patients were enrolled and randomized. Comparing clinical outcomes, no differences in arm or neck pain scores were noted; however, there was a statistically significant (≤0.041) improvement in SF-36 PCS scores for the allograft group at all follow-up time points and a tendency toward lower disability scores. Overall, evidence of radiographic fusion was achieved in 87 (91.6%) patients: five (10.2%) and three (6.5%) patients had pseudoarthrosis (P = 0.72) in the PEEK and allograft groups, respectively. At 24 months' follow-up time, any cervical or segmental alignment restoration achieved with surgery was lost and no statistically significant changes were detected when all levels of surgery were included. Likewise, there were no statistically significant differences between the groups for anterior or posterior body height measurements at the 24 months' follow-up. Approximately 20% of patients had anterior and posterior subsidence, all grade 0 regardless of the group assignment.

Conclusion: Comparable radiographic outcomes were observed for patients undergoing one- to three-level PEEK versus allograft-assisted ACDF surgeries. Although MCID comparisons suggest that allograft and PEEK-treated patients have similar clinical outcomes, testing that incorporates the magnitude of the change suggests that there may be a statistically significant greater magnitude of improvement for the allograft group patients, but further studies with a larger sample size would be helpful to determine if a true effect exists.


Anterior cervical discectomy and fusion (ACDF) is one of the most commonly performed spinal operations. There is ongoing debate among surgeons which interbody graft material provides better clinical and radiographic outcomes. In a cross-sectional survey published by Yoon et al in 2017,[1] the majority of surgeons believe that graft selection affects fusion rates (89%) and time to fusion (86%), and the most commonly used structural graft was polyether-ether-ketone (PEEK) (84%) out of all cages (64%) used worldwide, followed by autograft iliac crest tricortical bone (20%), and allograft (8%). Interesting geographical differences were noted, with North American surgeons utilizing mostly composite allografts (49%) versus PEEK cages (45%–66%) in other regions. Furthermore, autograft tricortical iliac crest graft was chosen as the criterion standard for ACDF by 60% of surgeons, followed by PEEK cage (22%) and allograft (8%). It is unclear whether such disparities are driven by perceived effectiveness, individual preferences, or reimbursement mechanisms.[2]

Besides extensively discussed individual biomechanical and histological qualities and advantages of graft materials at the microscopic level that define the osteoconductive, osteogenic, and osteoinductive properties,[3–8] the question remains whether there are any clinical and/or radiographic outcome differences in the selection of interbody grafts for ACDF. There are no prospective, randomized clinical trials comparing allograft and (PEEK) clinical and radiological outcomes reported to date.[9,10]

The primary objective of this study was to perform a prospective, randomized clinical trial and examine clinical and radiological outcomes in patients undergoing ACDF surgeries randomized to receive either PEEK or structural bone allografts.