title: A unified theory of bone healing and nonunion: BHN theory.
abstract: This article presents a unified clinical theory that links established facts about the physiology of bone and homeostasis, with those involved in the healing of fractures and the development of nonunion. The key to this theory is the concept that the tissue that forms in and around a fracture should be considered a specific functional entity. This 'bone-healing unit' produces a physiological response to its biological and mechanical environment, which leads to the normal healing of bone. This tissue responds to mechanical forces and functions according to Wolff's law, Perren's strain theory and Frost's concept of the "mechanostat". In response to the local mechanical environment, the bone-healing unit normally changes with time, producing different tissues that can tolerate various levels of strain. The normal result is the formation of bone that bridges the fracture - healing by callus. Nonunion occurs when the bone-healing unit fails either due to mechanical or biological problems or a combination of both. In clinical practice, the majority of nonunions are due to mechanical problems with instability, resulting in too much strain at the fracture site. In most nonunions, there is an intact bone-healing unit. We suggest that this maintains its biological potential to heal, but fails to function due to the mechanical conditions. The theory predicts the healing pattern of multifragmentary fractures and the observed morphological characteristics of different nonunions. It suggests that the majority of nonunions will heal if the correct mechanical environment is produced by surgery, without the need for biological adjuncts such as autologous bone graft. Cite this article: Bone Joint J 2016;98-B:884-91.
authors.affiliation: Ashford and St Peter's Hospitals NHS Foundation Trust, Guildford Road, Chertsey, Surrey KT160PZ, UK.
authors.forename: D S
authors.initials: DS
authors.lastname: Elliott
authors.affiliation: Ashford and St Peter's Hospitals NHS Foundation Trust, Guildford Road, Chertsey, Surrey KT160PZ, UK.
authors.forename: K J H
authors.initials: KJ
authors.lastname: Newman
authors.affiliation: Nottingham University Hospitals NHS Trust, Nottingham NG7 2UH, UK.
authors.forename: D P
authors.initials: DP
authors.lastname: Forward
authors.affiliation: Nottingham University Hospitals NHS Trust, Nottingham NG7 2UH, UK.
authors.forename: D M
authors.initials: DM
authors.lastname: Hahn
authors.affiliation: Nottingham University Hospitals NHS Trust, Nottingham NG7 2UH, UK.
authors.forename: B
authors.initials: B
authors.lastname: Ollivere
authors.affiliation: University of Sao Paulo, Rua Dr. Ovidio Pires de Campos, 333, Sao Paulo, Brazil.
authors.forename: K
authors.initials: K
authors.lastname: Kojima
authors.affiliation: John Radcliffe Hospital, Oxford, OX3 9DU, UK.
authors.forename: R
authors.initials: R
authors.lastname: Handley
authors.affiliation: Basingstoke and Northamptonshire Hospital, RG24 9NA, UK.
authors.forename: N D
authors.initials: ND
authors.lastname: Rossiter
authors.affiliation: Beth Israel Hospital, Boston, Massachusetts, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Wixted
authors.affiliation: Massachusetts General Hospital, Boston, Massachusetts, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Smith
authors.affiliation: Nottingham University Hospitals NHS Trust, Nottingham NG7 2UH, UK.
authors.forename: C G
authors.initials: CG
authors.lastname: Moran
mesh_terms: D001842:Bone and Bones / Q000502:physiology; D005593:Fracture Fixation, Internal; D017102:Fracture Healing / Q000502:physiology*; D050723:Fractures, Bone / Q000503:physiopathology / Q000601:surgery*; D005599:Fractures, Ununited / Q000503:physiopathology* / Q000601:surgery; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D018889:Ilizarov Technique; D013314:Stress, Mechanical
keywords: Bone healing; Nonunion; Strain