Fracture line distribution in femoral head fractures: a complement to Pipkin, Brumback, and AO/OTA classifications

Purpose This study aimed to explore the fracture line distribution and validate fracture classifications of Femoral head fractures (FHFs). Materials and methods A total of 209 FHFs were reviewed retrospectively. Subjects were classified by associated injuries and commonly used fracture classifications (Pipkin, Brumback, and AO/OTA), and the universality degree of classifications was evaluated. The fracture line directions were determined in the coronal and axial CT planes. 3D mapping analysis of fracture lines was performed separately by each group. 3D maps were employed to analyze the discrimination degree of inter-subtype classifications and create a new classification. The subjects were subsequently reclassified. Correlations between classifications were analyzed to determine the matching degree of the three classifications. Results The universality degrees were 98.6% (pipkin), 44.5% (Brumback), and 94.3% (AO/OTA). The cases of (100%) Brumback and (98.5%) AO/OTA can be classified by Pipkin. The mean angles of fracture lines to the coronal and axial axis of primary compressive trabeculae were 20.25° and 54.56°. The discrimination degrees of inter-subtype of classifications were 0 (Pipkin), 60% (Brumback), and 33% (AO/OTA). A new classification with three regions and five types was created on 3D maps. Pipkin and AO/OTA matched one region, while Brumback matched two regions. Conclusions There were three distributed fracture regions in FHFs that mismatched Pipkin, Brumback, and AO/OTA classifications. The new classification, based on morphometric features of FHFs, could compensate for the shortcomings of commonly used classifications, improving their applicability in treating FHFs.