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Objective: The exact relationship among atypical periprosthetic femoral fractures (APFFs), typical periprosthetic femoral fractures (PFFs), and atypical femur fractures (AFFs) remains unclear. This study aimed to investigate the prevalence of APFFs among PFFs and to identify the clinical characteristics, management, and prognosis that distinguish APFFs from typical PFFs and AFFs to further determine the relationship among these three fracture types. Methods: In this retrospective study, we reviewed the clinical data of 117 consecutive patients who had PFFs after hip arthroplasty between January 2012 and December 2022 and further classified them into an APFF group and a typical PFF group according to the revised ASBMR diagnostic criteria for AFF. Moreover, patients who had subtrochanteric or femoral shaft fractures in the same period and met the diagnostic criteria for AFF were recruited and classified into the AFF group. Demographic information, minor features of AFF, comorbidities, history of medication usage, management, and complications were collected and compared among patients with typical PFFs, APFFs, and AFFs. Results: Eleven PFFs were identified as APFFs, and the prevalence of APFFs among PFFs was 9.4%. Significant differences were found in generalized increase in cortical thickness (p = 0.019), prodromal symptoms (p < 0.001), and the incidence of bilateral fractures (p = 0.010) among the groups, where the incidences of these minor features in the APFF group and the AFF group were higher than those in the typical PFF group. Of note, the duration of fracture healing of APFFs was significantly longer than that of typical PFFs and AFFs (p < 0.001 and p = 0.004, respectively). In addition, the APFF group and the AFF group had higher proportions of patients with rheumatoid arthritis (p = 0.004 and p = 0.027, respectively), bisphosphonate (BP) usage (p = 0.026 and p < 0.001, respectively), and longer duration of BP usage (p = 0.003 and p = 0.007, respectively) than the typical PFF group. Furthermore, significant differences were found in management (p < 0.001) and complication rate (p = 0.020) among the groups, and the rate of complications in the APFF group and the AFF group was higher than that in the typical PFF group. Conclusions: APFFs not only fulfilled the mandatory and major diagnostic criteria for AFF but also had many clinical characteristics, management and prognosis distinguishing them from typical PFFs but resembling AFFs; hence, the diagnostic criteria for AFF might be revised to incorporate APFF as a distinct subtype of the condition. [ABSTRACT FROM AUTHOR]

Objective: It is unclear whether less acetabular coverage is associated with the failure of core decompression (CD) for osteonecrosis of the femoral head (ONFH). This study aimed to investigate the clinical outcomes of CD for ONFH with small‐ or medium‐sized pre‐collapse lesions, and determine what factors, especially acetabular anatomical parameters, predict the failure of CD. Methods: Between January 2010 and December 2022, we retrospectively reviewed 269 consecutive CDs in 188 patients diagnosed with ONFH with small‐ or medium‐sized pre‐collapse lesions. The Kaplan–Meier method was used to evaluate the survival rate of CD for ONFH with progression of collapse or conversion to total hip arthroplasty (THA) as the endpoint. Univariate and multivariate logistic regression analyses were conducted to identify the potential risk factors for the failure of CD. Receiver operating characteristic (ROC) curve analysis was further performed with conversion to THA as the endpoint to determine the predictive value of these factors. Results: The overall 5‐year survival rate of CD for ONFH with small‐ or medium‐sized pre‐collapse lesions was 74.3% (95% confidence interval (CI) 69.0%–81.1%) with progression of collapse as the endpoint and 83.9% (95% CI 79.3%–88.7%) with conversion to THA as the endpoint. Univariate logistic regression analysis showed that bilateral affected hips was significantly associated with progression of collapse, and center‐edge angle (CEA), sharp angle, acetabular head index (AHI), as well as acetabular depth ratio (ADR) were significantly associated with both progression of collapse and conversion to THA. Multivariate logistic regression analysis further indicated that CEA and AHI were independent risk factors for both progression of collapse and conversion to THA. ROC curve analysis with conversion to THA as the endpoint revealed that the cutoff values for CEA and AHI were 26.8° (sensitivity = 74.4%, specificity = 78.6%, area under the curve (AUC) = 0.809) and 79.8 (sensitivity = 78.4%, specificity = 73.8%, AUC = 0.818), respectively. Conclusions: CD showed satisfactory clinical outcomes for ONFH with small‐ or medium‐sized pre‐collapse lesions where less acetabular coverage with a CEA < 26.8° or AHI < 79.8 was identified as an independent risk factor for the failure of CD. [ABSTRACT FROM AUTHOR]