This paper corrects a decades-long mistranslation of Pauwels' 1935 biomechanical classification of femoral neck fractures. It traces how misreading of figure captions in the original German text led to systematically wrong angle thresholds in English-language references. The correct boundaries are: Degree I <30°, Degree II 30–50°, Degree III ≥50°.
If you trained from Rockwood and Green or any major English-language trauma text, you likely learned that Pauwels Degree III starts at 70°. That is wrong.
The correct Degree II/III boundary is 50°. When you encounter a femoral neck fracture with a fracture line between 50° and 70°, it is a Pauwels Degree III fracture — not Degree II. With dominant shearing stress and a varus Kipp moment driving displacement.
In current practice, Garden's classification has replaced Pauwels for predicting AVN risk and guiding fixation vs. Arthroplasty decisions. The AVN data confirm why: Pauwels Degree I carries a 53% AVN rate vs. 0% for Degree III, the inverse of what the mechanical model would imply.
Where Pauwels still matters: if you are planning a valgus intertrochanteric osteotomy for a femoral neck malunion, the classification directly informs your corrective angle. That is the one context where knowing the correct thresholds changes your preoperative plan.
This paper corrects a decades-long mistranslation of Pauwels' 1935 biomechanical classification of femoral neck fractures. It traces how misreading of figure captions in the original German text led to systematically wrong angle thresholds in English-language references. The correct boundaries are: Degree I <30°, Degree II 30–50°, Degree III ≥50°.
If you trained from Rockwood and Green or any major English-language trauma text, you likely learned that Pauwels Degree III starts at 70°. That is wrong.
The correct Degree II/III boundary is 50°. When you encounter a femoral neck fracture with a fracture line between 50° and 70°, it is a Pauwels Degree III fracture — not Degree II. With dominant shearing stress and a varus Kipp moment driving displacement.
In current practice, Garden's classification has replaced Pauwels for predicting AVN risk and guiding fixation vs. Arthroplasty decisions. The AVN data confirm why: Pauwels Degree I carries a 53% AVN rate vs. 0% for Degree III, the inverse of what the mechanical model would imply.
Where Pauwels still matters: if you are planning a valgus intertrochanteric osteotomy for a femoral neck malunion, the classification directly informs your corrective angle. That is the one context where knowing the correct thresholds changes your preoperative plan.