Head of femur

The head of femur, situated at the upper end of the femur, assumes a rounded shape. It’s orientation is directed medially and upwards, and it forms the hip joint by articulating with the acetabulum of the pelvic bone.

Within the head, there exists a roughened pit-like depression known as the fovea, which serves as an attachment point for the ligament of the head of femur, also referred to as the ligamentum teres. The basal end of this ligament is affixed to the margins of the acetabular notch. Notably, the ligament the passage of arterial twigs originating from the posterior division of the obturator artery and the ascending cervical branch of the medial circumflex femoral artery. These arterial twigs (a.k.a. medial epiphyseal arteries) traverse the acetabular notch in conjunction with the ligamentum teres, ultimately reaching the medial portion of the head of femur.

Contrasting the smaller medial segment, the larger lateral part of the head of femur receives its blood supply from the lateral epiphyseal arteries. To better comprehend the blood supply dynamics, it is important to note the presence of an extracapsular arterial ring encircling the proximal region of the femoral neck. This arterial ring is formed by the medial and lateral circumflex femoral arteries. From this arterial ring, ascending cervical branches emanate, coursing medially along the femoral neck. Consequently, they pass beneath the synovial membrane and assume the designation of retinacular arteries, contributing to the formation of a sub-synovial intracapsular arterial ring. It is from this intracapsular ring that the lateral epiphyseal arteries arise, providing vascular nourishment to the lateral aspect of the head of femur.

It is important to note that an intracapsular fracture of the femoral neck can potentially disrupt the retinacular arterial supply to the head of femur, resulting in avascular necrosis of the head.