Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Vascularity of the Proximal Femur and Femoral Head

Core Takeaways

Primary Blood Supply: The medial femoral circumflex artery (MFCA) provides the dominant arterial perfusion to the femoral head.
Mechanism of Ischemia: Trauma, high-energy fractures, and joint dislocations compromise the terminal retinacular branches of the MFCA, leading directly to avascular necrosis (AVN).
Iatrogenic Risk: Femoral shaft fracture fixation in young patients carries a specific risk of femoral head AVN if the deep branch of the MFCA is injured during proximal nail entry.

Dominant Inflow: The medial femoral circumflex artery originates from the deep femoral artery (profunda femoris) or directly from the common femoral artery.
Course and Trajectory: The vessel wraps posteriorly around the femoral neck beneath the iliopsoas and obturator externus muscle systems.
Terminal Perfusion: Terminal ascending branches penetrate the posterosuperior and posteroinferior retinaculum of the capsule to supply the weight-bearing articular dome of the femoral head.

Traumatic Disruption:
- Intracapsular Femoral Neck Fractures: Shear and displace terminal retinacular vessels running along the femoral neck cortex.
- Posterior Hip Dislocations: Stretch, compress, or tear the ascending cervical branches and deep terminal divisions of the MFCA.
Clinical Result: Rapid cellular hypoxia of osteocytes in the subchondral bone, leading to subchondral collapse, cartilage fragmentation, and secondary degenerative arthrosis.

Clinical Context	Injured Vessel Division	Mechanism of Vascular Insult	Primary Clinical Consequence
Traumatic Fractures / Dislocations	Terminal ascending retinacular branches	Direct mechanical transection or severe stretch by displaced bone fragments	Acute loss of femoral head perfusion and subsequent avascular necrosis
Femoral Shaft Fixation (Young Patients)	Deep branch of the medial femoral circumflex artery	Iatrogenic trauma during starting point placement (piriformis fossa or trochanteric entry) for intramedullary nailing	Iatrogenic avascular necrosis of the femoral head in an otherwise uninjured proximal joint

Intramedullary Nail Entry Caution: When preparing an entry portal for an antegrade femoral nail, precise trajectory is critical to protect the deep branch of the MFCA near the trochanteric fossa.
Time-Sensitive Reduction: Traumatic hip dislocations and displaced intracapsular femoral neck fractures represent orthopedic emergencies requiring urgent anatomical reduction to relieve tension on remaining retinacular vessels.