By Mark Jenkins, D.O.
Osteonecrosis of the hip (ON), also known as Avascular Necrosis and Aseptic Necrosis, is a significant condition that affects young adults usually between the ages of 20-40 years old. The natural progression of the disease is eventual collapse of the ball of the hip with resultant end-staged arthritis, pain, and loss of function. The prevalence of this disease is not known, but around 10,000-20,000 new cases are diagnosed each year. Bilateral disease ranges from 20-80 percent in different studies, and reported even higher in cases caused by steroid use.
ON is considered by many to be caused by interosseous hypertension (high pressure inside the bone) followed by venous stasis (sluggish blood flow), edema, cell death, scar formation then infarction (little to no blood flow). The hip is more vulnerable to ON than other areas due to the fact that the arterial blood flow comes from the thigh area and travels up the hip to form a ring of vessels. The number one traumatic cause is a displaced fracture of the neck of the hip. The main non-traumatic causes are alcohol abuse, cortico-steroid use, Sickle Cell Disease, and idiopathic (unknown cause).
The diagnosis of ON is based on the patient’s history, physical exam, and imaging studies. Blood lab work is usually normal except in cases of Sickle Cell Disease. The patient’s history is usually one of groin pain, decreased Range of Motion (ROM), and a limp. There may be no symptoms in the early development of the disease. Regular X-rays may also be normal early in the disease process. Later, the X-rays can show cyst under the bone, and an increased white appearance to the ball of the hip. The physical exam generally shows decreased ROM, groin pain with forced internal rotation. Bone scans can show changes in the ball before regular X-rays but are very non-specific for ON. Magnetic resonance imaging (MRI) is the study of choice to diagnose if regular X-rays are normal.
The treatment of ON is based on the stage of the condition when identified, and the amount of involvement of the ball of the hip. Early stages can be treated by a core decompression. This is simply drilling holes into the dead bone of the hip to decrease the pressure, and hopefully stimulate new blood vessels to grow. A vascularized bone graft can also be done in early cases to improve blood flow except in cases of Sickle Cell Disease. Good to excellent results only occur in around 17-40 percent of the cases treated with the above two procedures. The treatment for more advanced cases with collapse and end-stage arthritis is a total hip replacement, which has good reported outcomes.
ON of the hip is a devastating problem that is best treated early, but is often not found until it is more advanced. Recognizing the more common causes and a thorough exam by your physician offers the best chance of making the diagnosis early and preventing later collapse of the hip.
For more information on osteonecrosis of the hip or other orthopedic issues, Dr. Jenkins may be reached at Chatham Orthopædics, 4425 Paulsen Street, Savannah, GA 31405 or you may call him at (912) 355-6615