Introduction

The femoral artery is the continuation of the external iliac artery below the level of the inguinal ligament and serves as the primary blood supply to the lower limb. The deep femoral artery is the main branch of the common femoral artery. The largest branches of the deep femoral artery are the medial femoral circumflex artery and the lateral femoral circumflex artery. The medial femoral circumflex artery is anatomically posteromedial, while the lateral femoral circumflex artery is posterolateral as they branch from the deep femoral artery.[1][2] The lateral femoral circumflex artery supplies blood to the femoral head and neck, greater trochanter, vastus lateralis, and the knee.[2]

The lateral femoral circumflex artery is clinically significant because it can suffer an injury during surgical procedures in the area around the hip joint. It is also useful as a vascular graft for coronary artery bypass graft surgery and other vascular graft surgeries.

Structure and Function

The primary blood supply to the lower limb is via the femoral artery. The deep femoral artery is the main blood supplier to the thigh. The medial circumflex artery and the lateral circumflex artery are the main branches of the deep femoral artery. The medial circumflex artery supplies the hip joint, while the lateral circumflex artery supplies the soft tissues surrounding the hip joint.[3]

Distal to its branching point, the lateral femoral circumflex artery courses laterally between the divisions of the femoral nerve. It then travels inferiorly into the septum between the sartorius and rectus femoris muscles, where it further divides into the ascending, transverse, and descending lateral femoral circumflex arteries.[4][5][6]

Ascending Branch

Approximately 11 cm distal to the anterior superior iliac spine, the ascending branch of the lateral femoral circumflex artery bifurcates into muscular and capsular branches. These branches supply the femoral neck at the level of the intertrochanteric line, the anterior hip capsule, and the anterior portion of the femoral neck.[7]

The ascending branch of the lateral femoral circumflex artery supplies approximately 18% of the blood supply to the femoral head with a higher percentage of the vascularity being within the anterior portion of the femoral head.[7]

One anatomical study found that while the medial femoral circumflex artery dominates the majority of the blood supply to the femoral neck, about one-third of the femoral neck gets supplied by the lateral femoral circumflex artery. In the same study, researchers determined that the lateral femoral circumflex artery largely supplies the anteroinferior femoral neck.[7] 

Descending Branch

Distal to its branch point, the descending branch of the lateral femoral circumflex artery courses down medial to the vastus lateralis muscle.[4][5] Lateral branches from the descending lateral femoral circumflex artery either perforate the vastus lateralis or travel within the muscular septum until they reach the skin overlying the anterolateral thigh. Medial branches from the descending lateral femoral circumflex artery course medially beneath the rectus femoris and supply the rectus femoris and the skin overlying the anteromedial thigh.[4] 

Embryology

The changes in blood supply to the femoral head throughout development has been described previously by Ogden.[8] He explained that the proximal femur and cartilaginous epiphysis is initially equally supplied by the lateral and medial femoral circumflex vessels. The lateral femoral circumflex supplies the anterior half of the femoral head and the epiphysis and the medial femoral circumflex supplies the posterior half of the femoral head during the first few years of life. As time progresses, the lateral femoral circumflex system regresses to supply the junction between the anterior femoral neck and the metaphysis. Meanwhile, the medial circumflex system continues to develop and expand to supply the growing femoral neck to become the dominant blood supplier of the femoral head. Because of this shift of blood supply of the femoral head and neck during development, the anterolateral portion of the capital femoral epiphysis is at an increased risk of vascular compromise.[7][8]

Physiologic Variants

There have been many studies examining the variations in the branching patterns of the femoral vessels. In most people, the lateral femoral circumflex artery (LFCA) branches from the deep femoral artery just superior to the origin of the medial femoral circumflex artery (MFCA). In some cases, the lateral femoral circumflex artery and the medial circumflex artery branch from the deep femoral artery at the same level. The lateral femoral circumflex artery may also directly branch from the femoral artery both above and below the level where the deep femoral artery branches from the femoral artery.[1]

An article by Tomaszewski, Vikse, et al.,[9] classified the branching patterns of the lateral femoral circumflex artery relative to the rest of the femoral artery branches:

• Type 1 (normal): LFCA branches from the deep femoral artery superior to the origin of the MFCA
• Type 2: The LFCA branches from the common femoral artery above the origin of the deep femoral artery
• Type 3: The LFCA branches from the common femoral artery at the level of the origin of the deep femoral artery
• Type 4: The LFCA branches from the superficial femoral artery
• Type 5: The lateral ascending and lateral descending branches of the LFCA individually branch from either the common femoral artery, deep femoral artery or superficial femoral artery and do not originate from a common branch (i.e., LFCA). 

These types have also been reported in other anatomic studies as well.[3]

One study also reported that the diameter of the femoral vessels was greater in males than in females.[1]

Prakash et al. hypothesized that the anatomical variations of the femoral artery branches exist because of an evolutionary shift in the origin of the deep femoral artery. The deep femoral artery used to be a branch of the internal iliac artery, and over the course of evolution, now branches from the femoral artery.[10]

Surgical Considerations

The lateral femoral circumflex artery and its many anatomical variants are important to keep mind when approaching the hip for surgical intervention. Procedures such as total arthroplasty of the hip, trochanteric/intertrochanteric osteotomies, hip arthroscopy, and injections to the hip joint may put the artery at risk.[1] Surgeons must be cautious during surgeries on or around the femoral head to avoid injury to the lateral and medial femoral circumflex arteries. Injuries to these vessels may cause avascular necrosis of the femoral head.

The branches of the lateral circumflex femoral artery course along the anterior femoral neck and are at risk of injury during surgery of the femoral neck.[7]

The lateral circumflex femoral artery can also suffer damage during vascular interventional procedures such as catheterization, stenting, embolectomy, angiography, and angioplasty.[1][6]

The lateral circumflex artery has also been used for bypass grafting in the heart, brain, and neck.

Clinical Significance

The lateral femoral circumflex artery supplies blood to the head and neck of the femur. Damage to the artery itself or injury of the hip joint may compromise the blood supply to the joint and lead to ischemia and necrosis of the supplied bone and soft tissues.[1]

Recent studies have suggested that the lateral femoral circumflex artery contributes to the blood supply of the anteroinferior femoral neck. Hence, femoral neck fractures may damage the terminal branches of the lateral femoral circumflex, compromising the blood supply to the femur and surrounding soft tissues.[7] There have been reported cases of pseudoaneurysms of the deep femoral artery and the left and right femoral circumflex arteries in patients with intertrochanteric hip fractures.[11]

The lateral femoral circumflex artery may be at risk during intramuscular injections of the anterior thigh as well as ultrasound-guided hip joint injections.[12][13]

The lateral circumflex femoral artery along with its septocutaneous branches and musculocutaneous perforators are the main blood supply of anterolateral thigh flaps, a soft-tissue flap used in reconstructive surgeries.[4][5]

Surgeons can use the descending branch of the lateral femoral circumflex artery in bypass grafting and vascular reconstructions. It also has utility in posterior inferior cerebellar artery revascularization,[14] and oropharyngeal reconstructions.