Factors predisposing to periprosthetic fracture after hip arthroplasty: a case (n = 31)-control study.

We compared retrospectively 31 patients with a periprosthetic fracture to 31 patients in a control group. The Finnish Arthroplasty Register was used to count all periprosthetic fractures treated by revision arthroplasty in Finland and in Tampere University Hospital district during the years 1990-1999. We used the date of the previous operation to find the control group patients operated on at the same time in the same hospital district.