Figure 2 shows a hypertrophic nonunion of the clavicle fracture. The process of fracture healing usually takes place over a 6-week period and is typically completed by 3 to 4 months. The size and location of the fracture usually determines the healing time; smaller bones in the hand may take 4 to 6 weeks to heal while a femoral shaft fracture may take up to 3 months.1

The evidence of fracture union is determined by the presence of a bridging callus on imaging and full weight bearing of the involved extremity without pain. An injury with a persistent fracture line and pain with weight bearing for a period of 9 months and does not show progression of healing on imaging for 3 months is considered a nonunion fracture.1,2

There are 2 types of nonunion fractures: hypervascular and avascular. In hypervascular nonunions, blood supply flows to the ends of the fracture fragments and there is usually some degree of bridging callus. These types of nonunions will show vascularity of the fragments on bone scan. However, hypervascular nonunions never fully heal as a result of motion through the fracture site.2 Hypervascular nonunions can have hypertrophic fracture ends rich with callus that are often called “elephant foot” nonunions (as illustrated in this case). Oligotrophic nonunions also have vascular fracture ends but have little to no callus formation.1-3

For avascular nonunion fractures, the ends of the fracture fragments have no circulation and no potential to heal. Avascular nonunions have persistent fractures lines without any bridging callus. A pseudarthrosis occurs when a hypervascular nonunion forms a false joint as fracture motion tricks the body into thinking the fracture is a joint. A pseudarthrosis may be hypertrophic or oligotrophic in appearance but often has no pain with weight-bearing activities. A pseudarthrosis may also present with new-onset pain and swelling ≥12 months after a clavicle fracture. A joint capsule may be identified during operative inspection of a pseudarthrosis nonunion.2,3

Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.


1. Frölke JP, Patka P. Definition and classification of fracture non-unions. Injury. 2007;38 Suppl 2:S19-S22.  

2. Cunningham BP, Brazina S, Morshed S, Miclau T. Fracture healing: a review of clinical imaging and laboratory diagnostic optionsInjury. 2017;48 Suppl 1:S69-S75. 

3. Aiyer A. Nonunion. OrthoBullets website. Updated November 11, 2019. Accessed August 3, 2020.  

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