Although non-unions being one of the most common complication after long-bone fracture fixation, the definition of this entity remains controversial and varies widely among authors. A clear definition is crucial, not only for the evaluation of published research data but also for the establishment of uniform treatment concepts. The aim of this systematic review was to identify the definitions and different criteria used in the scientific literature to describe non-unions after long bone fractures.
A comprehensive literature search was performed in PubMed, Cochrane Library, Web of Science, and Embase. according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Prospective therapeutic and diagnostic clinical studies in which adult long-bone fracture non-unions were investigated as main subject were included in this analysis.
One hundred fifty-two studies investigating 6432 long-bone non-unions met inclusion criteria for this analysis. In total 49% (75/152) of included studies did not define non-union at all, even though non-union was their main study subject. A definition of non-union on either clinical, radiologic or time criteria could be found in 51% (77/152) of the included studies. Non-union was defined based on time criteria in 83% (64/77), on radiographic criteria in 65% (50/77), and on clinical criteria in 43% (33/77). A combination of clinical, radiologic and time criteria for definition was only found in 35% (27/77) of all the included studies that defined non-union. The time point when authors defined an unhealed fracture as a nonunion showed a considerable heterogeneity, ranging from four to 24 months.
In the current orthopaedic trauma literature, we found a lack of consensus with regard to the definition of long bones non-unions. Therefore, a standardized definition of non-union remains unclear. Without valid and reliable definition criteria of non-unions, the establishment of standardized diagnostic and treatment algorithms as well as the comparison of studies remain difficult. The lack of a clear definition emphasizes the need for consensus-based definition of fracture non-unions based on clinical, radiographic and time criteria.