A biomimetic gradient porous cage with a micro-structure for enhancing mechanical properties and accelerating osseointegration in spinal fusion

Objectives:Spinal fusion is a widely employed treatment of patients with degenerative disc disease,in which a cage is used to replace the disc for spinal fusion.But it often fails for insufficient mechanical strength and poor osseointegration.Here,we designed a polyether-ether-ketone(PEEK)/tantalum(Ta)composite cage with a biomimetic gradient porous micro-structure,simultaneously enhancing mechanical properties and accelerating osseointegration in spinal fusion.Materials and methods:In the study,based on the mechanical performances of PEEK and osteogenic potential of Ta,and the three-dimensional(3D)structures of cuttlebone and vertebra,the cages were respectively 3D printed by pure PEEK,PEEK with 5 wt%Ta(PEEK/Ta-5),PEEK with 10 wt%Ta(PEEK/Ta-10)and PEEK with 15 wt%Ta(PEEK/Ta-15),then verifiedin vitroand in sheep cervical fusion model systematically.Results:Vertebral Gyroid structure PEEK/Ta-15 cage exhibited superior mechanical properties than Cuttlebone-like structure PEEK/Ta-15 cage,closer to the cervical vertebra.Furthermore,PEEK/Ta-15 cage with higher Ta microparticles in PEEK provided a biomimetic gradient porous micro-structure with higher surface energy,guiding cell biological behavior,promoting new bone penetration,and accelerating osseointegrationin vivo.Conclusion:In conclusion,the study designed a biomimetic gradient porous cage with a micro-structure for enhancing mechanical properties,accelerating osseointegration and forming an anatomical lock in the fusion segment through composites,mechanical efficiency,surface extension,and pores.

Pedicle Subtraction Osteotomy with a Cage Prevents Sagittal Translation in the Correction of Kyphosis in Ankylosing Spondylitis

Background： Sagittal translation （ST） is an accidental event that surgeons commonly encounter during a spinal osteotomy in the correction of kyphosis in ankylosing spondylitis （AS）. However, there is a paucity of effective techniques to prevent ST. The purpose of this study was to propose a pedicle subtraction osteotomy （PSO） with a cage as a method to prevent ST and to explore the efficacy and feasibility of this method in the treatment of kyphosis in AS. Methods： We retrospectively reviewed 89 consecutive patients with AS kyphosis who underwent a PSO （Group B, 46 patients） or a PSO with a cage （Group A, 43 patients） from February 2009 to December 2013. Pre- and post-operative radiographic results were reviewed. ST and complications were analyzed in both groups. Clinical assessment was performed using the Scoliosis Research Society-22 （SRS-22） outcomes metric. The patients were followed up for at least 2 years. Results： Group A achieved the same re-alignment of the kyphotic spine as Group B. Two （4.7%） of the 43 patients in Group A and 14 （30.4%） of the 46 patients in Group B had intraoperative ST （2＂2 = 10.020, P = 0.002）. Significant differences were identified between the two groups in the height change of the osteotomized column. SRS-22 scores improved significantly in both groups. Seven patients experienced neurologic complications （1 in Group A and 6 in Group B）. Eight patients had cerebrospinal fluid leakage （2 in Group A and 6 in Group B）. Conclusion： PSO with a cage significantly avoided ST during the osteotomy procedure and might represent a new, safe, and feasible choice tbr treating patients with AS kyphosis.