What is the blood supply to the femur in children?

Blood Supply of the Femur in Children

The femoral head in children receives its primary blood supply from the medial femoral circumflex artery (MFCA), specifically through its deep branch, which provides the dominant vascular supply via posterior superior and posterior inferior nutrient arteries. 1, 2

Primary Arterial Supply

The blood supply to the pediatric femoral head comes from three main sources:

• Deep branch of the MFCA: This is the most critical vessel, providing the primary blood supply to the femoral head 1, 2, 3
• Posterior inferior nutrient artery: Also originates from the MFCA and contributes to femoral head perfusion 2, 3
• Piriformis branch of the inferior gluteal artery: Provides an important anastomotic contribution 2, 3

Anatomical Course and Surgical Relevance

The deep branch of the MFCA follows a consistent extracapsular course:

• It crosses posterior to the obturator externus tendon at the level marked by a trochanteric branch at the proximal border of quadratus femoris 1
• It then travels anterior to the conjoint tendon of gemellus inferior, obturator internus, and gemellus superior 1
• The vessel perforates the joint capsule at the level of gemellus superior before entering its intracapsular segment 1
• Within the capsule, it runs along the posterosuperior aspect of the femoral neck, dividing into 2-4 subsynovial retinacular vessels 1

Critical surgical consideration: The obturator externus muscle protects the deep branch of the MFCA from disruption during hip dislocation, even after complete circumferential capsulotomy 1. Division of the short external rotators in posterior approaches can damage this vessel and cause avascular necrosis.

Age-Related Vascular Patterns

The vascular anatomy changes significantly with age:

• Newborn to 2 years: A greater number of ascending cervical arteries cross the anterior and medial surfaces of the mid-neck 4
• 3 to 10 years: Fewer ascending cervical arteries are present, which may be relevant to the etiology of Legg-Perthes disease 4
• Throughout childhood: The epiphyseal plate constitutes an absolute barrier to blood flow between the epiphysis and metaphysis in nearly all cases (122 of 124 specimens examined) 4

Vascular Anastomoses

Two important anastomotic rings exist:

• Extracapsular ring: Formed by the medial and lateral femoral circumflex arteries 4
• Subsynovial intra-articular ring: Located at the articular cartilage-neck junction 4

The intra-articular rings are more frequently discontinuous in males than females, which may have clinical implications for perfusion patterns 4.

Clinical Implications for Vascular Compromise

After hip trauma or dislocation, blood flow assessment is critical:

• CT angiography can effectively visualize the three main arteries supplying the femoral head 3
• A patent, contrast-enhanced deep branch of the MFCA after hip reduction suggests preserved blood flow 5
• Absence of blood flow in all three main arteries is strongly associated with development of avascular necrosis 5
• The diameter of the deep branch may increase after fracture/dislocation, possibly representing a compensatory response 5

Important caveat: The artery of the ligamentum teres provides minimal contribution to femoral head vascularity in children and shows no significant variation with age, sex, or race 4.