Periprosthetic fractures of the femur in primary total hip arthroplasty: a New Zealand Joint Registry analysis

Background: Periprosthetic femoral fractures around total hip arthroplasty (THA) are increasing annually, and are a major cause for revision surgery in the New Zealand Joint Registry (NZJR). The aim of this study was to determine the timing and risk factors for periprosthetic femoral fractures in THA requiring revision surgery in the NZJR.

Methods: All patients with a primary THA who sustained a periprosthetic femoral fracture requiring revision THA recorded in the NZJR were reviewed to determine age, gender, body mass index, American Society of Anesthesiologists (ASA) rating and femoral stem fixation (cemented or uncemented). Revision rates were calculated per 100 component years (cy), and risk factors determined in the first 90 days, and beyond.

Results: Between 1999 and 2017, there were 713 revision THA for periprosthetic femoral fractures. Early revision THA was significantly associated with ASA score and body mass index ≥40. There was no gender difference (P = 0.274). The revision rate in uncemented femoral stems (1.12/100 cy) was significantly higher (p < 0.001) than cemented stems (0.16/100 cy). After 90 days, the revision rate was significantly higher with increasing age (P < 0.001), males (P < 0.001) and higher ASA score (P < 0.001). The difference between cemented (0.07/100 cy) and uncemented (0.05/100 cy) stems did not reach statistical significance (P = 0.108).

Conclusion: The rate of revision THA for periprosthetic femoral fracture is higher in uncemented femoral stems in the first 90 days, and is significantly associated with ASA score and morbid obesity. After 90 days, the rate is lower for uncemented femoral stems, but did not reach statistical significance.