Examination of the osteoconductive, antibiofilm & biomechanical properties of a PEEK-ZEOLITE composite biomaterial for intervertebral spine fusion surgery

S. Sankar, D.W. Johns, J.J. Crudden
Difusion Technology Inc.,
United States

Keywords: PEEK, zeolite, spine, antibiofilm,osteoconductive,biomaterial,interbody cages

Summary:

Introduction: Polyether ether ketone (PEEK), a common spine biomaterial demonstrates intrinsic inertness and hydrophobic properties, thereby resulting in an inherent susceptibility to bacterial infections and reduced fusion capacity within the intervertebral space due to fibrous encapsulation.ZFUZE TM & CleanFuzeTM (CF), are two bioactive PEEK- zeolite(aluminosilicate) composite biomaterials with the latter containing silver; and are known to have osteoblast stimulative and infection resistive effects due to ceramic zeolite particles and silver ions respectively.Thse composite PEEK biomaterials can also be loaded with various cations ,including silver ions, due to these microporous zeolites which confer unique properties to an orthopedic biomaterial. Aim: To validate the biomaterial's twin aims of osteoconduction/osteointegration and prevention of biofilm;which is associated with implant associated infections in load bearing applications; while possessing adequate biomechanical properties to act as a structural construct. Methods: a) Study of the osteointegrative and osteoconductive aims were completed via invitro cell culture assays, a rabbit femoral critical defect model and the finished intended use of the device was analysed via an ovine cervical spine fusion model. b) The antimicrobial/antibiofilm properties were studied via co-culture osteoblast-bacterial assays,a modified biofilm Bioreactor assay & in a rabbit spine infection model c) The biomechanical requirements of the interbody device to serve as a permanent structural scaffold for spine fusion were evaluated via static and dynamic biomechanical parameters in torsion,compression,subsidence and expulsion. Results: 1. Micro-CT and Histological analysis of peek-zeolite (ZFuzeTM) composites in a rabbit model demonstrates : a)Increased bone-implant contact & apposition-suggesting improved osseointegration relative to tradtional PEEK implants. b) Greater bone in growth into the inner diameter of the dumbbell shaped implant relative to traditional PEEK implants. 2. Invitro cell assys prove that these composites possess attractive osteoblast,prliferation,differentiation and mineralization characteristics relative to predicate PEEK materials. 3. ASTM F2077-11 testing of PEEK-Zeolite demonstrates improved static &dynamic biomechanics relative to PEEK predicate cages for vertebral body replacement and interbody fusion 4. Ovinecervical spine fusion study revealed that PEEK-Zeolite interbody devices show increased fusion mass and improved bone-implant interface compared to predicate PEEK devices. 5. Imaging shows increased radiolucency relative to PEEK due to zeolite resulting in attractive imaging properties 6.PEEK-Silver zeolite(CF) composites are strongly antimicrobial invitro, while PEEK is very susceptible to infection. 7.PEEK-Silver zeolite(CF) composites show increased osteoblast proliferation in vitro compared to PEEK in both a sterile and infected setting. 8. PEEK-Silver Zeolites(CF) are effective in preventing biofilm formation while PEEK is highly vulnerable. 9. PEEK Silver zeolite(CF) exhibits normal wound healing characteristics while PEEK shows suppurative inflammation and degenerative changes consistent with active infection in an invivo spine infection model Conclusion: These novel PEEK-Zeolite composites would provide for an alternative implant material in spine with favourable osteointegrative and antibiofilm properties while improving upon the handling, imaging and modulus benefits of PEEK.