A 72-year-old woman with osteoporosis presents to the emergency department after a fall at home. An AP hip X-ray is obtained. On examination of the radiograph, the structure marked **D** (Shenton line) appears disrupted, with loss of the normal continuous arc. Which of the following hip fracture patterns is MOST consistent with this radiographic finding and carries the HIGHEST risk of avascular necrosis of the femoral head?

Explanation

## Why Subcapital intracapsular fracture with displacement (Garden III–IV) is right Disruption of Shenton line is a highly sensitive screening sign for hip pathology, particularly fractures involving the femoral neck and proximal femur. Intracapsular fractures (especially subcapital variants) disrupt the medial femoral neck contour, breaking the normal continuous arc formed by the medial femoral neck and superior margin of the obturator foramen. Displaced intracapsular fractures (Garden III–IV) carry the highest risk of avascular necrosis (~30%) because the fracture line disrupts the blood supply to the femoral head, which is primarily supplied by lateral epiphyseal vessels arising from the medial and lateral femoral circumflex arteries. The more displaced the fracture, the greater the vascular compromise and AVN risk. This is the classic "hip fracture" pattern in elderly osteoporotic patients and represents the most serious prognostic scenario requiring urgent reduction and fixation or arthroplasty. ## Why each distractor is wrong - **Intertrochanteric fracture (between greater and lesser trochanters)**: While intertrochanteric fractures are the most common extracapsular hip fractures and may disrupt Shenton line, they do NOT disrupt the blood supply to the femoral head (which lies proximal to the fracture line). AVN risk is low (~5%), making this a lower-risk pattern than displaced intracapsular fractures. - **Subtrochanteric fracture (5 cm distal to lesser trochanter)**: Subtrochanteric fractures are extracapsular and located well distal to the femoral head blood supply. Although they may show Shenton line disruption, AVN risk is minimal because the femoral head vasculature remains intact. These fractures are managed primarily for mechanical stability, not AVN prevention. - **Stress fracture of the femoral neck without displacement**: Undisplaced stress fractures or impacted fractures (Garden I–II) maintain femoral head blood supply and carry minimal AVN risk (<5%). While they may show subtle Shenton line changes, they do not carry the high AVN risk of displaced intracapsular fractures and are typically managed conservatively or with cannulated screw fixation to preserve the native femoral head. **High-Yield:** Disruption of Shenton line + displaced intracapsular fracture = highest AVN risk (~30%); always assess Shenton line as a quick screening tool for hip fracture severity on every AP hip X-ray. [cite: Apley 10e; Gray's Anatomy 42e Ch 80]