Which is larger and more important, the medial circumflex (MCA) artery or the lateral circumflex (LCA) artery of the hip?

Medial vs Lateral Circumflex Artery of the Hip: Comparative Anatomy and Clinical Importance

The medial femoral circumflex artery (MFCA) is both larger and significantly more important than the lateral femoral circumflex artery (LFCA), as it provides the dominant blood supply to the femoral head and neck, contributing approximately 82% of the vascularity to the femoral head compared to only 18% from the LFCA 1.

Anatomical Size and Distribution

Primary Blood Supply Dominance

• The MFCA is the most significant blood vessel supplying the hip joint and serves as the main artery supplying the femoral head through its deep branch 2, 3.
• Quantitative MRI studies demonstrate that the MFCA contributes 82% of the vascularity to the femoral head, while the LFCA contributes only 18% 1.
• For the femoral neck, the MFCA provides 67% of the blood supply compared to 33% from the LFCA 1.

Regional Vascular Territories

• The MFCA supplies the femoral head primarily via posterior superior nutrient arteries and the posterior inferior nutrient artery 3.
• The LFCA does have a notable contribution to the anteroinferior aspect of the femoral neck, supplying approximately 48% of this specific region 1.
• The MFCA also provides blood supply to the adductor muscles and hip joint in addition to the femoral head 4.

Clinical Significance and Surgical Implications

Risk of Avascular Necrosis

• Damage to the MFCA during surgical procedures can result in femoral head necrosis due to its dominant role in femoral head perfusion 4.
• The deep branch of the MFCA is particularly at risk during surgical approaches to the hip joint 2.
• After hip dislocation, the MFCA's integrity is critical for maintaining femoral head vascularity 3.

Anatomical Variations

• The MFCA originates from the deep femoral artery (DFA) in 50% of cases, but has an atypical origin from the common femoral artery (CFA) in 31% of cases 2.
• In 67.2% of cases, the MFCA originates from the profunda femoris artery, while in 32.8% it originates directly from the femoral artery 5.
• Rare variations include suprainguinal origin from the external iliac artery in common trunk with the inferior epigastric artery 4.

Important Anastomoses

• The most important anastomosis for the MFCA is with the inferior gluteal artery via the piriformis branch, which may provide collateral blood supply to the femoral head 3.

Common Pitfalls and Clinical Considerations

• Surgical Planning: Failure to identify MFCA anatomy preoperatively can lead to inadvertent vessel injury during hip approaches, resulting in devastating avascular necrosis of the femoral head 4, 3.
• Anatomical Variability: The high frequency of anatomical variations (up to 50% of cases have non-standard origins) necessitates careful preoperative imaging to identify vessel origins 2, 5.
• Regional Considerations: While the LFCA is less important overall, surgeons must recognize its significant contribution to the anteroinferior femoral neck when planning anterior surgical approaches 1.