As we grow, the internal bone structure of the hip ball or femoral head becomes larger and becomes the main foundation to maintain the spherical shape. This also explains why older children have a worse prognosis than very young children. First, a small child’s hip ball (femoral head) can be 50% cartilage and 50% bone so, a child relies less on the internal bone structure to maintain the round shape of the head as compared to an adolescent or adult whose femoral head is 90% bone and only 10% cartilage. There are several reasons why younger children can experience hip avascular necrosis and heal with minimal long-term problems. (*Female patients enter the extremely poor prognostic age group >10 years.) Why do younger patients have a better prognosis with hip AVN? The following is a list of age groups and prognosis from hip AVN with no aggressive treatment: In the adolescent age group, the most common causes of AVN are corticosteroids, sickle cell disease, slipped capital femoral epiphysis, and idiopathic (meaning that it occurs spontaneously with cause unknown) it is termed Perthes disease – extreme late onset. Once a young person reaches an age above 10 years for females and 12 years for males, then AVN of the hips take on an entirely different clinical course and a worse prognosis. The typical age group for Perthes disease is between 4-6 years of age. However, in young people who have not reached final growth or skeletal maturity, the most common cause of hip AVN is unknown and called Legg-Calve-Perthes disease, which is more commonly referred to as Perthes disease. Adult hip AVN can be caused by the use of chronic or high dose corticosteroids, alcoholism, sickle cell disease, trauma, work environments that expose the person to extreme barometric pressures, (e.g., Caisson’s disease), hyperlipidemia (increased blood lipid / fat levels), Gaucher disease and pancreatitis. The age of the affected person plays a critical role in the typical cause of the avascular necrosis and the prognosis of recovery. There are many causes of avascular necrosis of the femoral head. What causes avascular necrosis of the hip? This mismatch in joint shape leads to pain, irritation of the joint, loss of motion and function and eventual joint degeneration or arthritis. After the femoral head or joint has lost its original shape, then the joint does not fit together properly this is called a loss of joint congruency. Once the foundation’s stability is lost, then the entire structure can shift, break, collapse and lose the original shape of the structure. This can be compared to the settling or collapse of a foundation of a house or building. This causes weakness in the area of the AVN with eventual bony collapse and loss of strength and shape. Once the bone has died, there is a gradual process of bone breakdown and absorption by the body to repair the area. Reduction or restriction of blood (also known as ischemia) is more common in certain bones due to the underlying anatomy such areas include the femoral head, which is more predisposed to avascular necrosis. Healthy bone requires a continuous blood supply, just like other tissues and organs. Although bones appear to be a static frame for the body, the skeletal system is very biologically dynamic and full of ever-changing tissue. Without a blood supply, the bone cells die, and the surrounding bone loses its normal living environment. It is almost exclusively used in the pediatric population to assess for slipped upper femoral epiphysis (SUFE) and Perthes disease.Share Tweet Email Print What is avascular necrosis (AVN) of the hip?Īvascular necrosis (AVN) of the hip, also referred to as osteonecrosis or aseptic necrosis, is a condition where the blood supply to the ball of the hip joint (femoral head) is lost, causing the bone to die. bilateral examination allows for better visualization of the hip joints and femoral neck.lataral projection to aid and diagnose femoroacetabular impingement (FAI) due to its increased sensitivity for detecting femoral head-neck asphericity.the ideal projection for bilateral hip or femur trauma.lateral projection demonstrating the neck of the femur without movement of the either limb.can only be conducted on unilateral hip trauma.lateral projection demonstrating the neck of the femur without movement of the affected limb.standard rolled lateral view demonstrating the femoral neck and acetabular rim can only be performed on non-trauma patients.often only performed in follow up studies.demonstrates the hip joint in the AP plane, with the limb internally rotated so the neck of the femur is in profile.Hip radiographs are performed for a variety of indications including 1-3: The series is requested for a myriad of reasons from trauma to atraumatic hip pain. The hip series is comprised of an anteroposterior (AP) and lateral radiograph of the hip joint.
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