Anatomic and Patient Risk Factors for Postoperative Periprosthetic Hip Fractures: A Case-Control Study

Background Periprosthetic fracture remains a major source of reoperation following total hip arthroplasty (THA). Within 90 days of surgery, fractures may occur spontaneously or with minor injury and are therefore more likely related to patient factors including anatomic variation. Methods From 2008 to 2018, 16,254 primary THAs were performed at our institution; of those, 48 were revised for periprosthetic fracture within 90 days of surgery. A control group of 193 patients undergoing THA for hip osteoarthritis (OA) was randomly selected from the source population. We excluded patients with genetic bone disease and THA performed for hip fracture. We used logistic regression to analyze associations between patient factors (demographics, anatomical factors, comorbidities, surgical technique, and implants) and odds of 90-day periprosthetic fracture. Results Increased age was significantly associated with fracture (P = .002), as was female gender (P = .046). After adjusting for age and gender, absence of contralateral OA was associated with increased odds of fracture relative to patients with contralateral OA (odds ratio [OR] 3.85, 95% confidence interval [CI] 1.60-9.29), as was having a contralateral THA in place (OR 3.70, 95% CI 1.59-8.60). The neck-shaft angle, femoral offset, and the Dorr classification were not associated with increased odds of fracture. Additionally, the distance from the tip of the trochanter to the top of the femoral head was associated with increased odds of fracture per half centimeter (OR 1.48, 95% CI 1.14-1.93). Conclusion Risk of early postoperative periprosthetic fracture following THA is increased with age, female gender, and increasing distance from the greater trochanter to the top of the femoral head; and decreased in the setting of contralateral hip OA. The trochanter-head distance correlation with periprosthetic hip fracture indicates that the preoperative anatomy may influence PPF, particularly regarding how that anatomy is reconstructed.