Table 1.

Classification of non-union fractures adapted from Panagiotis et al. 2005 [5]

Classification	Description/pathology
Hypertrophic (hypervascular, viable, vital)	Inadequate immobilisation, yet adequate blood supply. In radiographs, callus formation is decreased with an elephant-foot or horseshoe configuration observed.
Atrophic (avascular, non-viable, avital)	Poorly vascularised non-union, resulting in poor potential for forming bone cells and, therefore, delayed healing. There is little callus formation around the fibrous tissue–filled fracture gap.
Oligotrophic	The body can initiate a healing response but is unable to complete the fracture formed between the two ends of the bone.
Septic	A bacterial infection impedes the healing process. Typical bacterial strains that inflict non-union sites include coagulase negative Staphylococcus spp. and Propionibacterium spp.
Pseudoarthrosis	Persistent motion at fracture site causes formation of false joint (joint that develops at the site of a fracture), often producing synovial fluid.