Revisiting Pauwels' classification of femoral neck fractures.

Pauwels' femoral neck fracture classification is based on the biomechanical principle that shear stress and varus force increase along more vertically oriented fractures, resulting in higher risk of fracture displacement and ultimately nonunion. This principle continues to guide construct selection for femoral neck fracture internal fixation and is the foundation for treating non-union with valgus osteotomy. However, with poor inter- and intra-rater reliability, dated treatment recommendations, and unreliable prognostic value, the Pauwels classification cannot be directly applied in its entirety to the management of femoral neck fractures in modern practice.