title: A polycaprolactone-tricalcium phosphate composite scaffold as an autograft-free spinal fusion cage in a sheep model.
abstract: Titanium (Ti) based spinal fusion cages are frequently used in the clinics for the treatment of spinal degeneration and related diseases, however, their further clinical application is generally harassed by several drawbacks such as stress shielding, non-biodegradability and additional bone grafting procedure. Our earlier work has demonstrated the efficacy of a biodegradable macro-porous polycaprolactone-tricalcium phosphate (PCL-TCP) composite scaffold in promoting bony tissue ingrowth as well as its ability to sustain mechanical loads upon implantation into an orthotopic defect site. In this study, we investigated the use of PCL-TCP scaffold as an autograft-free spinal fusion cage in a preclinical sheep model over 12 months, and compared the fusion efficacy against Ti cages incorporated with autografts. Results showed that despite PCL-TCP scaffold as an autograft-free cage attaining a slower fusion rate at early stage (6 month), it achieved similar degree of spinal fusion efficacy as Ti cages aided with autograft at 12 month post-operation as evidenced by the radiographic and histological evaluation. PCL-TCP cages alone demonstrated better bone ingrowth with 2.6 fold higher bone/interspace ratio (B/I) and more homogeneous bone tissue distribution compared with that of the Ti cages (88.10  ±  3.63% vs. 33.74  ±  2.78%, p < 0.05) as seen from the histological and micro-CT analysis. Moreover, besides the bone tissue ingrowth, a quantitative approach was illustrated to accurately evaluate the osteointegration of fusion cage with surrounding bone tissue, and showed a 1.36 fold higher degree of osteointegration occurred in PCL-TCP cage group than Ti cage group (CS/PC: 79.31  ±  3.15% vs 58.44  ±  2.43%, p < 0.05). Furthermore, biomechanical analysis showed comparable mechanical strength of fused segments in both groups in terms of the range of motion and stiffness at 12 month (p > 0.05). The degradation profile of the PCL-TCP cages was noted to increase in tandem with new bone ingrowth into the pores, while maintaining good structural integrity necessary for supporting the spinal interbody segments. Therefore, with the better osteointegration, more bone tissue ingrowth as well as its favorable biodegradable and radiolucent properties, PCL-TCP cage has been demonstrated to be a promising candidate as an autograft-free fusion cage for clinical application.
authors.affiliation: Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China; Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Key Laboratory of Tissue Engineering, School of Medicine, Shanghai Jiao Tong University, Shanghai 200011, China; National Tissue Engineering Center of China, Shanghai 200241, China; No. 89 Hospital of PLA, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Zhi-gang
authors.initials: ZG
authors.lastname: Wu
authors.affiliation: Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Xiao-kang
authors.initials: XK
authors.lastname: Li
authors.affiliation: Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China. Electronic address: guozheng@fmmu.edu.cn.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Guo
authors.affiliation: Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Su-hua
authors.initials: SH
authors.lastname: Wu
authors.affiliation: Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Yong-quan
authors.initials: YQ
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.affiliation: Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637457, Singapore.
authors.forename: Swee-hin
authors.initials: SH
authors.lastname: Teoh
authors.affiliation: Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637457, Singapore.
authors.forename: Yu-chun
authors.initials: YC
authors.lastname: Liu
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Key Laboratory of Tissue Engineering, School of Medicine, Shanghai Jiao Tong University, Shanghai 200011, China; National Tissue Engineering Center of China, Shanghai 200241, China. Electronic address: mr.zhiyong@gmail.com.
authors.forename: Zhi-yong
authors.initials: ZY
authors.lastname: Zhang
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D064592:Autografts; D001846:Bone Development; D018786:Bone Substitutes / Q000737:chemistry*; D005260:Female; D011091:Polyesters / Q000737:chemistry*; D012756:Sheep; D013123:Spinal Fusion / Q000379:methods*; D054457:Tissue Scaffolds / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*
chemical_list: D018786:Bone Substitutes; D011091:Polyesters; C016240:polycaprolactone; D014025:Titanium
keywords: Biodegradable; Fusion cage; Polycaprolactone; Ti6Al4V; Tricalcium phosphate