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. No other selection or matching criteria were used. The type of prosthesis, complications, age, BMI, cementation and primary diagnosis were compared. We found that patients who had a fracture as the primary diagnosis ran a 4.4 (95%CI = 1.4-14) times higher risk of periprosthetic fracture than those operated on for other reasons.