title: The relationship between interfragmentary movement and cell differentiation in early fracture healing under locking plate fixation.
abstract: Interfragmentary movement (IFM) at the fracture site plays an important role in fracture healing, particularly during its early stage, via influencing the mechanical microenvironment of mesenchymal stem cells within the fracture callus. However, the effect of changes in IFM resulting from the changes in the configuration of locking plate fixation on cell differentiation has not yet been fully understood. In this study, mechanical experiments on surrogate tibia specimens, manufactured from specially formulated polyurethane, were conducted to investigate changes in IFM of fractures under various locking plate fixation configurations and loading magnitudes. The effect of the observed IFM on callus cell differentiation was then further studied using computational simulation. We found that during the early stage, cell differentiation in the fracture callus is highly influenced by fracture gap size and IFM, which in turn, is highly sensitive to locking plate fixation configuration. The computational model predicted that a small gap size (e.g. 1 mm) under a relatively flexible configuration of locking plate fixation (larger bone-plate distances and working lengths) could experience excessive strain and fluid flow within the fracture site, resulting in excessive fibrous tissue differentiation and delayed healing. By contrast, a relatively flexible configuration of locking plate fixation was predicted to improve cartilaginous callus formation and bone healing for a relatively larger gap size (e.g. 3 mm). If further confirmed by animal and human studies, the research outcome of this paper may have implications for orthopaedic surgeons in optimising the application of locking plate fixations for fractures in clinical practice.
authors.affiliation: Department of Infrastructure Engineering, The University of Melbourne, Parkville, VIC, 3010, Australia. s.miramini@unimelb.edu.au.
authors.forename: Saeed
authors.identifier: http://orcid.org/0000-0001-6943-7444
authors.initials: S
authors.lastname: Miramini
authors.affiliation: Department of Infrastructure Engineering, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors.forename: Lihai
authors.initials: L
authors.lastname: Zhang
authors.affiliation: The Epworth Hospital, Richmond, VIC, 3121, Australia.
authors.forename: Martin
authors.initials: M
authors.lastname: Richardson
authors.affiliation: Department of Infrastructure Engineering, The University of Melbourne, Parkville, VIC, 3010, Australia.
authors.forename: Priyan
authors.initials: P
authors.lastname: Mendis
authors.affiliation: Biomedical Engineering and Medical Physics, Queensland University of Technology, Brisbane, QLD, 4001, Australia.
authors.forename: Adekunle
authors.initials: A
authors.lastname: Oloyede
authors.affiliation: Department of Medicine, Monash University, Clayton, VIC, 3168, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Ebeling
mesh_terms: D001860:Bone Plates; D002454:Cell Differentiation; D003198:Computer Simulation; D005592:Fracture Fixation; D017102:Fracture Healing; D006801:Humans; D008422:Materials Testing; D009068:Movement
keywords: Computational simulation; Fracture healing; Locking plate fixation; Mechanical testing; Mesenchymal stem cell differentiation; Osteoporosis