Classification of femoral neck fractures according to pauwels: interpretation and confusion ——Reinterpretation: a simplified classification based on mechanical considerations

The Pauwels Classification of femoral neck fractures, initially published in 1935, is used world-wide. Unfortunately, modern textbooks give varying angle and anatomic specifications between the classified fracture grades. This inconsistency is perpetuated in the literature, so that it is difficult to compare conclusions made by different authors. Pauwels himself left room for interpretation. He published two studies, one in 1935 and one in 1973, each including 3 diagrams. The 1935 version cited an angle of 8° representing the vector of static forces acting on the femoral head. The 1973 diagrams, however, cited an angle of 16° to represent dynamic forces, without changing the angle from horizontal. This already complex scheme is complicated by the fact that it depends on other factors such as femoral neck shaft (CCD) angle, femoral neck and head diameter, and/or distance of the fracture from the center of the femoral head. The multitude of factors argues against a rigid classification based on fixed angles from horizontal. Pauwels himself did not establish fixed critical angles between the fracture grades. In his own explanation of the system, he placed more value on mechanical considerations such as compression stress, shear stress, tensile force, shearing force, and torque. We propose therefore a simplified version of the Pauwels Classification: Grade I for fractures impacted in valgus, Grade II for fractures without free torque, and Grade III for fractures with free torque.