Surgical Anatomy of the Hip Joint

Abstract

The hip joint is the largest ball-and-socket joint in the human body. It consists of the femoral head and the acetabulum. Connecting the pelvis and the lower limb, the hip joint is the pivot of the transmission of body weight from the trunk to the lower limbs; it also has very important roles in retaining balance, supporting the weight of the upper body and walking. The cuplike acetabulum forms at the union of three pelvic bones---the ilium, pubis, and ischium, with the prominent rim augmented by the ring-shaped fibrocartilaginous lip, the acetabular labrum, which extends the joint beyond the equator and makes the joint stable as well as flexible at the same time. The joint capsule is tough and tight, with multiple ligaments around it. Iliofemoral ligament, the strongest one among these ligaments, lies in front of the joint capsule, also known as the Y ligament or Bigelow ligament. This ligament can limit hyperextension of the hip joint, strengthen the joint capsule, and help to maintain the upright posture. There is a 1.2-cm-long V-shaped ligament between the deep acetabulum and the femoral head. It is called the femoral head ligament, which contains vessels to nourish femoral head. The femoral head is hemispherical, and the femoral head is oriented medially and anteriorly. In the center of the femoral head, there is a fossa, where the femoral head ligament attaches, and the rest is the articular surface, covered by a lubricated layer called hyaline cartilage. The cup-shaped acetabulum and the spherical femoral head make the joint congruent. The hip movements have three mutually perpendicular main axes, all of which pass through the center of the femoral head, resulting in three degrees of freedom and three pair of principal directions: flexion and extension; lateral rotation and medial rotation; and abduction and adduction (Fig. 1.1).