Nonunion and pseudarthrosis of fracture healing. A histopathologic study of 95 human specimens.

Forty-one human tissue specimens from fracture nonunions in extraarticular locations demonstrated a spectrum of clefts at the site of nonunion ranging from tiny microscopic spaces within the soft tissue of the nonunion to dominant clefts that completely separated the ends of the fracture. These latter specimens were examples of frank pseudarthrosis. The soft tissues lining the large clefts were often considerably eroded. Pseudarthrosis of fracture healing may be a late manifestation of more mobile nonunions that progressively tear apart. Fifty-four additional nonunion or pseudarthrosis specimens from former intraarticular fractures demonstrated the same sequence of changes occurring in 24 of the cases. However, 30 of the intraarticular fractures demonstrated no tissues of a fibrous nonunion, which could indicate that in such locations pseudarthrosis may exist from the date of the original fracture.