A 72-year-old man presents with a fall at home and acute left hip pain. AP pelvis X-ray shows a displaced intracapsular femoral neck fracture (Garden III). The structure marked **A** (femoral head within the acetabulum) is at risk of a serious complication due to disruption of its blood supply. Which of the following best explains the mechanism of this complication and the most appropriate surgical management?

Explanation

## Why option 1 is correct In adults, the femoral head (structure **A**) receives its primary blood supply from the medial circumflex femoral artery (a branch of the profunda femoris), which delivers blood via retinacular vessels coursing along the femoral neck in an inferior-to-superior direction. Displaced intracapsular femoral neck fractures (Garden III/IV) disrupt these critical retinacular vessels, interrupting the blood supply to the femoral head and resulting in avascular necrosis (AVN) in 20–30% of cases. In a physiologically older patient with lower pre-fracture mobility and shorter life expectancy, hemiarthroplasty is the preferred surgical option because it restores hip function while avoiding the higher operative burden and revision risk of total hip replacement. This aligns with current orthopedic guidelines (Apley 10e; Gray's Anatomy 42e Ch 80). ## Why each distractor is wrong - **Option 2**: While the artery of the ligamentum teres (artery of the round ligament) does contribute to femoral head blood supply, it is SECONDARY and minor in adults—significant only in children. It cannot be the primary mechanism of AVN in this case. Additionally, total hip replacement is not the only option; hemiarthroplasty is equally valid and often preferred in older patients. - **Option 3**: The lateral circumflex femoral artery supplies the femoral neck and intertrochanteric region, not the femoral head. Disruption of the lateral circumflex is not the mechanism of femoral head AVN. Furthermore, dynamic hip screw fixation is used for extracapsular (intertrochanteric) fractures, which do NOT compromise femoral head blood supply. - **Option 4**: The obturator artery does not supply the femoral head; it supplies the medial thigh and obturator muscles. Cannulated screw fixation is appropriate for undisplaced intracapsular fractures (Garden I/II), not displaced fractures, because fixation alone cannot restore blood supply once retinacular vessels are disrupted. **High-Yield:** Displaced intracapsular femoral neck fractures → retinacular vessel disruption → AVN risk → hemiarthroplasty in older patients, THR in younger active patients; extracapsular fractures spare the femoral head blood supply. [cite: Apley 10e; Gray's Anatomy 42e Ch 80]