title: Comparison of three calcium phosphate bone graft substitutes from biomechanical, histological, and crystallographic perspectives using a rat posterolateral lumbar fusion model.
abstract: This study evaluated the effectiveness of three calcium phosphate bone graft substitutes with different chemical compositions on spinal fusion using a rat posterolateral lumbar fusion model. Specifically, two recently developed non-dispersive tetracalcium phosphate/dicalcium phosphate anhydrous-based calcium phosphate cements (CPCs), namely a CPC consisting of equimolar amounts of the two compounds (nd-CPC) and a CPC consisting of a two-fold greater amount of dicalcium phosphate anhydrous (DCP-rich CPC), were compared with a commercial calcium phosphate bone graft (c-CPG) consisting of hydroxyapatite (60%) and β-tricalcium phosphate (40%). Single-level posterolateral lumbar fusion was performed at the L4-L5 vertebrae in fifteen adult rats (n=5 for each group). Spinal fusion was evaluated with radiographs, manual palpation, mechanical testing, micro-CT, and histology 8 weeks post-surgery. In particular, the crystallographic phases in the three substitutes were identified before and 8 weeks after their implantation. Manual palpation revealed stable constructs in nearly all of the spine specimens. The stiffness and bending load of fused spines in the two CPC groups were comparable to those in the c-CPG group. The radiographs specifically revealed implant resorption and bone remodeling in the DCP-rich CPC group. Analysis of 3D micro-CT images revealed that the bone volume ratio in the DCP-rich CPC group was significantly greater than those in the nd-CPC and c-CPG groups. Histology showed that the DCP-rich CPC group exhibited the highest degree of bone regeneration and osseointegration. Notably, DCP-rich CPC led to a pronounced phase transformation, generating the greatest amount of poorly crystalline apatite among the three groups, which together with adequate resorption may explain the aforementioned positive findings. We therefore conclude that of the bone graft substitutes considered, DCP-rich CPC has the greatest potential to be used in spinal fusion.
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, Tainan 701, Taiwan; Department of Orthopedics, Show-Chwan Memorial Hospital, Changhua 50544, Taiwan; Department of Orthopedic Surgery, Faculty of Medicine, National Yang-Ming University, Taipei 112, Taiwan.
authors.forename: Ming-Hsien
authors.initials: MH
authors.lastname: Hu
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, Tainan 701, Taiwan; Department of Orthopedics, Show-Chwan Memorial Hospital, Changhua 50544, Taiwan.
authors.forename: Pei-Yuan
authors.initials: PY
authors.lastname: Lee
authors.affiliation: Department of Fiber and Composite Materials, College of Engineering, Feng Chia University, Taichung 40724, Taiwan. Electronic address: wincheng0925@yahoo.com.tw.
authors.forename: Wen-Cheng
authors.initials: WC
authors.lastname: Chen
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, Tainan 701, Taiwan; Medical Device Innovation Center, National Cheng Kung University, Tainan 701, Taiwan. Electronic address: jjhu@mail.ncku.edu.tw.
authors.forename: Jin-Jia
authors.initials: JJ
authors.lastname: Hu
mesh_terms: D000818:Animals; D018786:Bone Substitutes / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D004195:Disease Models, Animal; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D019736:Prostheses and Implants; D051381:Rats; D017207:Rats, Sprague-Dawley; D013123:Spinal Fusion; D014057:Tomography, X-Ray Computed
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; C485817:beta-tricalcium phosphate; C485830:tetracalcium phosphate; C485829:calcium phosphate, dibasic, anhydrous
keywords: Bioresorption; Calcium phosphate cements; Histology; Posterolateral lumbar fusion; Spinal fusion; Surface treatment