A 68-year-old postmenopausal woman with a history of osteoporosis slips on a wet floor and falls directly onto her right hip. X-rays show a fracture of the femoral neck with the fracture line extending completely across the bone, separating the femoral head from the rest of the femur. The fracture surfaces appear relatively smooth without fragmentation. On closer inspection, the fracture line is noted to be at approximately 30° to the horizontal. Which classification best describes this fracture?

Explanation

## Femoral Neck Fracture Classification ### Clinical Scenario Analysis The key radiological findings are: - Complete fracture across the femoral neck - Fracture line at approximately 30° to the horizontal - Smooth fracture surfaces without fragmentation - No impaction or overlap of fragments ### Fracture Line Orientation and Classification | Fracture Type | Angle to Long Axis | Fracture Line Appearance | Mechanism | Comminution | | --- | --- | --- | --- | --- | | **Transverse** | 90° (perpendicular) | Straight across, horizontal | Direct blow perpendicular to bone | Minimal | | **Oblique** | 30–60° | Diagonal across bone | Shear + compression forces | Minimal to moderate | | **Comminuted** | Variable | Multiple fragments | High-energy trauma | Extensive | | **Impacted** | Variable | Fragments driven together | Compression force | Fragments overlap/telescope | ### Why This Is an Oblique Fracture **Key Point:** The fracture line at 30° to the horizontal defines an oblique fracture. This angle is the hallmark of oblique fractures and distinguishes them from transverse (90°) fractures. **High-Yield:** Oblique fractures of the femoral neck carry clinical significance: 1. **Vascular compromise risk** — the oblique orientation may disrupt the blood supply to the femoral head more severely than transverse fractures 2. **Displacement tendency** — oblique fractures are more prone to displacement due to muscle pull and gravity 3. **Healing potential** — oblique fractures have a larger surface area for healing compared to transverse fractures, which may theoretically improve union rates, but displacement risk is higher **Clinical Pearl:** In femoral neck fractures, the Pauwels classification uses the angle of the fracture line to the horizontal: - **Pauwels Type I:** < 30° (more horizontal, more stable) - **Pauwels Type II:** 30–50° (intermediate) - **Pauwels Type III:** > 50° (more vertical, less stable, higher nonunion risk) This patient's 30° fracture is at the borderline between Type I and Type II, indicating moderate instability. **Mnemonic — Fracture Line Angles:** - **T**ransverse = 90° (perpendicular) - **O**blique = 30–60° (diagonal) - **V**ertical = approaching 90° (in context of femoral neck, high Pauwels angle) **Warning:** Do not confuse oblique with transverse simply because the fracture appears "relatively smooth." The angle of the fracture line, not the smoothness of the surface, determines the classification. A smooth surface just indicates low-energy trauma without comminution.