Periprosthetic femoral fracture within two years after total hip replacement: analysis of 437,629 operations in the nordic arthroplasty register association database.

BACKGROUND: We used the Nordic Arthroplasty Register Association database to evaluate whether age, sex, preoperative diagnosis, fixation, and implant design influence the risk of revision arthroplasty due to periprosthetic fracture within two years from operation of a primary total hip replacement.

METHODS: Included in the study were 325,730 cemented femoral stems and 111,899 uncemented femoral stems inserted from 1995 to 2009. Seven frequently used stems (two cemented stems [Exeter and Lubinus SP II] and five uncemented stems [Bi-Metric, Corail, CLS Spotorno, ABG I, and ABG II]) were specifically studied.

RESULTS: The incidence of revision at two years was low: 0.47% for uncemented stems and 0.07% for cemented stems. Uncemented stems were much more likely to have this complication (relative risk, 8.72 [95% confidence interval, 7.37 to 10.32]; p < 0.0005). Age had no consistent influence on the risk for revision of cemented stems, but revision in the uncemented group increased with increasing age. A cemented stem was associated with a higher risk in male patients compared with female patients (hazard ratio, 1.95 [95% confidence interval, 1.51 to 2.53]; p < 0.0005), whereas an uncemented stem was associated with a reduced risk in male patients compared with female patients (hazard ratio, 0.74 [95% confidence interval, 0.62 to 0.89]; p = 0.001). The risk for revision due to early periprosthetic fracture increased during the 2003 to 2009 period compared with the 1995 to 2002 period both before and after adjustment for demographic factors and fixation (relative risk, 1.44 [95% confidence interval, 1.18 to 1.69]; p < 0.0005). The hazard ratio for the Exeter stem was about five times higher than that for the Lubinus SP II stem (hazard ratio, 5.03 [95% confidence interval, 3.29 to 7.70]; p < 0.0005). Of the five uncemented stems, the ABG II stem showed an increased hazard ratio of 1.63 (95% confidence interval, 1.16 to 2.28) (p = 0.005), whereas the Corail stem showed a decreased hazard ratio of 0.47 (95% confidence interval, 0.34 to 0.65) (p < 0.0005) compared with the reference Bi-Metric design.

CONCLUSIONS: The shape and surface finish of the femoral stem and its fixation could be related to the increased risk of some prosthetic designs. Even if the incidence of early periprosthetic fracture in general is low and other reasons for revision must be considered, specific attention should be given to the choice of fixation and stem design in risk groups.

LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.