Impact of Femoral Morphology and Stem Design on Intraoperative Periprosthetic Femoral Fractures in Cementless Total Hip Arthroplasty

Background: Intraoperative periprosthetic femoral fractures (IPFF) represent a concerning and often under-recognized complication in total hip arthroplasty (THA). Although several risk factors have been reported, their association with specific femoral morphology and stem geometry has not been fully addressed. This study aimed to identify the incidence and risk factors for IPFF in THA using cementless tapered stems. Methods: A retrospective review was conducted on 3137 primary THAs (2622 patients) performed with cementless tapered stems at a single institution between February 2011 and August 2018. Femoral morphology was classified according to the Dorr types; A (1425 hips, 45.4%), B (1542, 49.2%), and C (170, 5.4%). Femoral stems were categorized as flat, rectangular, or quadrangular tapered designs. The occurrence of IPFF was identified through surgical records and postoperative radiographs. Multivariate regression analysis was performed to identify independent risk factors for IPFF. The mean age at THA was 55 years (range, 15–96), and 52.9% of the patients were women. Results: The overall incidence of IPFF was 2.2% (69 hips). Non-displaced cracks in the proximal metaphysis (58 hips, 84.1%) were the most common type of fracture. The incidence of IPFF was significantly higher in Dorr type A (3.0%) and type C (4.7%) femurs compared with type B (1.2%) femurs. Multivariate regression revealed that female sex (odds ratio [OR], 1.752; p = 0.032) and Dorr type A (OR, 2.898; p < 0.001) and type C (OR, 4.530; p < 0.001) were significantly associated with IPFF. Additionally, the use of quadrangular tapered stems was associated with a higher risk compared with flat tapered stems (OR, 7.382; p < 0.001). Conclusions: Dorr type A and C femurs, along with female sex and the use of quadrangular tapered stems, were significant risk factors for IPFF. Our findings suggest that preoperative consideration of individual femoral morphology and careful selection of stem design are essential to mitigate the risk of IPFF in THA using cementless tapered stems.