Derek Donegan, Michael Huo, Michael Leslie
Spontaneous fractures result from osteolysis or pathologic etiologies remote from the index arthroplasty. They can be classified as Della Valle IV.
These are from insufficiency fractures.
Further information about Della Valle classification can be found in the publication: Della Valle CJ, Momberger NG, Paprosky WG. Periprosthetic fractures of the acetabulum associated with a total hip arthroplasty. Instr Course Lect. 2003;52:281–290.