Pauwels Classification of Femoral Neck Fractures

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Pauwels divided femoral neck fractures into three types based on the inclination of the fracture line measured from the horizontal on a standard AP pelvic radiograph.

The femoral neck is loaded in compression during weight-bearing. A horizontal (low-angle) fracture is held together by axial compressive forces — the same force that drives healing. As the fracture line tilts toward vertical, an increasing component of the load becomes a shear force that slides the proximal fragment downward along the fracture plane.

• Type I (under 30 degrees): Compression across the fracture site exceeds shear. The bone surfaces are pressed together, which promotes stability and union. Standard fixation (cannulated screws or sliding hip screw) works reliably.
• Type II (30 to 50 degrees): Shear is significant. The fracture has a tendency to displace inferoposteriorly. Fixation must provide some shear resistance — parallel cannulated screws placed with a valgus orientation, or a sliding hip screw with a derotation screw.
• Type III (over 50 degrees): Shear dominates over compression. The proximal fragment tends to slide down and medially, causing varus collapse and screw cut-out. Standard parallel screws have a high failure rate. Fixation must actively resist shear: a valgus-angled blade plate, a dynamic hip screw with an anti-rotation screw, a cephalomedullary nail, or — in older patients — primary total hip arthroplasty.

• Inter-observer reliability is moderate at best. Multiple studies (including those by Beimers and colleagues) have shown that different surgeons measure the Pauwels angle differently on the same radiograph, and the same fracture can shift types with minor rotation of the hip or pelvis.
• The classification is purely biomechanical and does not account for patient age, bone quality, displacement, timing of surgery, or vascularity — all of which influence outcome as much as, or more than, the fracture angle alone.
• Garden and Garden-Pauwels hybrid systems exist. In practice, many surgeons consider displacement (Garden type) alongside the Pauwels angle. A Garden IV (fully displaced) Pauwels I fracture may carry a worse prognosis than a Garden I (undisplaced) Pauwels III fracture treated urgently.
• Modern fixation implants have narrowed the outcome gap between Pauwels types. Locking plates, angular-stable implants, and cephalomedullary nails provide shear resistance that older screw-only constructs could not, so the prognostic difference between Type II and Type III is less dramatic than in Pauwels' original series.
• CT is increasingly used to define the fracture geometry more precisely than plain radiographs, especially in vertically oriented fractures where surgical planning depends on the exact geometry.