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Natural Language Processing and Large Language Model-Based Automated AO/OTA Classification of Proximal Femoral Fractures: A MIMIC-IV Retrospective Study

Jin Y, Fan Z, Yan X, Li J, Wu Z, Zhang Y

2026

Abstract

Abstract Background Accurate AO/OTA classification of proximal femoral fractures is a critical step in surgical decision-making and prognostic evaluation; however, the complexity of the classification system and the heterogeneity of terminology in radiology reports pose significant challenges for large-scale, standardized application of the classification. In recent years, with the advancement of AI technologies, large language models (LLMs) equipped with retrieval-augmented generation (RAG) capabilities have offered new possibilities for automatically extracting fracture classification information from unstructured radiology reports. Methods This study conducted a retrospective analysis of 23,179 radiology reports from the MIMIC-IV database. Through a multi-stage annotation process involving independent labeling by two orthopedic surgeons and adjudication by a senior expert, a total of 157 acute cases of AO/OTA type 31A (intertrochanteric fractures) and type 31B (femoral neck fractures) were ultimately included. We evaluated three experimental models: zero‑shot prompting, few‑shot learning (5 examples per class), and RAG‑augmented prompting (incorporating a structured AO classification knowledge base). Classification performance was assessed using accuracy, F1‑score, and confusion matrices. All type 31C (femoral head fractures) cases underwent expert re‑adjudication to evaluate annotation quality. Results The RAG‑LLM framework achieved an accuracy of 94.29% (F1 = 94.29%) in…

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