Risk of Intraoperative Periprosthetic Femoral Fracture According to Cementless Femoral Stem Geometry: A Cohort Study Based on the Radaelli Classification.

Background Intraoperative periprosthetic femoral fracture is an uncommon but clinically significant complication of total hip arthroplasty (THA) that may compromise implant stability and increase the risk of early revision surgery. Several patient- and surgery-related factors have been associated with its occurrence, including bone quality, femoral morphology, and implant design. Cementless femoral stems have been associated with a higher incidence of intraoperative fractures compared with cemented fixation due to the need to achieve press-fit stability and increased implant-bone contact during implantation. Recently, a classification system proposed by Radaelli and colleagues categorized cementless femoral stems according to geometry, length, and modularity, allowing a standardized comparison between implant designs. However, limited evidence exists evaluating the association between femoral stem geometry according to this classification and the risk of intraoperative periprosthetic fracture. Methods A retrospective cohort study was conducted, including patients who underwent primary THA with an uncemented femoral component between January 2019 and March 2025 at a tertiary care hospital in Mexico City. Patients were identified through the institutional surgical database using the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) procedural codes. Demographic, clinical, radiographic, and surgical variables were collected from electronic medical records. Femoral stem geometry was classified according to the Radaelli classification. The primary outcome was the occurrence of intraoperative femoral periprosthetic fracture. Statistical analysis included descriptive statistics, group comparisons, and logistic regression to evaluate associations between stem geometry and fracture risk. Results A total of 1,384 patients undergoing primary THA with an uncemented femoral stem were included. Fifty intraoperative femoral periprosthetic fractures were identified, corresponding to an incidence of 3.6%, which falls within the range reported in previous studies. The most frequently used femoral stem geometries were short fit-and-fill stems (455, 32.9%), flat wedge stems (396, 28.7%), and quadrangular wedge stems (188, 13.6%). Flat wedge stems accounted for the highest proportion of fractures (17, 34%), followed by short fit-and-fill stems (10, 20%). Logistic regression analysis demonstrated no statistically significant association between most stem geometries and fracture risk. The only geometry associated with increased risk was C2 fit-and-fill stems (OR 22.29; 95% CI 1.34-371.82); however, this finding was based on a very small sample size. Conclusion No statistically significant association was identified between most femoral stem geometries according to the Radaelli classification and fracture risk. Flat wedge stems accounted for the highest proportion of fractures in this series, although without demonstrating an independent statistical association.