1. Surgical & Orthopaedic Research Laboratories, University of New South Wales, Sydney, Australia PEEK/Ti combined cages: A systematic review of radiological and clinical outcomes in spinal fusion and preclinical evaluation Y. Assem, M. Pelletier, W. Walsh, K. Phan, R. Mobbs Neurospine Clinic, Prince of Wales Hospital

2. Declaration of Interest I declare that in the past three years I have: held shares in: none received royalties from: none done consulting work for: none given paid presentations for: none received institutional support from: none Signed: Yusuf Assem

3. Spinal interbody fusion is rapidly evolving with advancements in the domains of: Graft substitution Approach variation Implant design Material selection Biomaterial surface optimization. Introduction

4. Radiographic solid fusion = Successful ALIF Polyetheretherketone (PEEK)  Similar elastic modulus to human cortical bone and with radiolucent properties Treated Titanium (Ti)  Osseointegration capacity Ti/PEEK Goal - Optimal environment to promote arthrodesis

6. Solid fusion at 3 months postop. White arrow demonstrating incorporation of allograft/BMA at graft/endplate junction. Grey arrow demonstrating no halo/lucency at Titanium/bone junction (incorporation).

7. Method Methods: Systematic search  Medline, Embase and Cochrane. Key search terms – “spinal fusion”, “PEEK”, “titanium”, “cage”. Inclusion criteria Human clinical trials Ti/PEEK “combined” cages All surgical approaches/degenerative pathologies

8. The novelty of this intervention translates into a paucity of clinical trials. Albeit the results of the seven clinical studies that met the criteria for inclusion are promising. Results

9. Randomized Control Trials Retrospective Cohort Studies Prospective Cohort Studies

10. All studies reported rate of fusion as a primary outcome. Improved fusion in the Ti/PEEK cohort (1 and 5 - NS) Identical fusion (91.7%) (2) Excellent fusion (96%, 100% and 94%) Ti/PEEK (4, 6 and 7)

11. Ti coating did not negatively affect PEEK subsidence (NS) TrialSubsidence 3Ti/PEEK cohort reduced subsidence (1.57mm) compared to the PEEK cohort (1.76mm) - 18 months 5Full Ti coating resulted in less subsidence than partial coating (1.52 mm to 1.57 mm), although slightly more than uncoated PEEK (1.38mm) 6Only Ti/PEEK implants in 18 patients - 0% subsidence

13. Conclusions Clinical studies at this early stage demonstrate that Ti/PEEK implants are Safe Efficacious Exhibiting similar fusion rates and clinical outcomes compared to the current standard PEEK.

14. There are no significant differences in radiographic fusion of Ti/PEEK NS This Ti/PEEK combination is promising However not all Ti/PEEK combinations are equal Further clinical trials are needed to substantiate differences and establish Ti/PEEK cages as a mainstay of clinical practice.

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