Review Question - QID 4399

The clinical presentation and images are most consistent with left hip osteonecrosis as a result of coagulation and vascular occlusion caused by sickle cell anemia.

Sickle cell disease is a genetic disorder of hemoglobin synthesis characterized by 2 abnormal hemoglobin S alleles. Under low oxygen conditions the affected blood cells become "sickle shaped" and unable to pass through vessels. This results in vascular occlusion that may have a variety of clinical consequences depending on the body part affected.

Hernigou et al. review the natural history of symptomatic osteonecrosis in adults with sickle cell disease. Once symptomatic , osteonecrosis of the hip in sickle cell disease has a high likelihood of progressing and leading to femoral head collapse. Deterioration can be rapid and in most patients operative intervention is necessary to prevent further collapse or alleviate intractable pain.

Mont et al. performed a literature review on the natural history of untreated asymptomatic osteonecrosis of the femoral head. Their findings supported that asymptomatic osteonecrosis had a high prevalence of progression to symptomatic femoral head collapse. Small, medially located lesions had a low rate of progression, while medium to large sized osteonecrotic lesions did progress in a substantial number of patients. They recommended consideration of joint-preserving surgical treatment in asymptomatic patients with a medium-sized or large, laterally located lesion.

Figure A shows an AP pelvis with left hip osteonecrosis. Figure B shows a T2 coronal MRI with left hip osteonecrosis. Illustration A shows an example of a hemoglobin molecule which has become "sickle shaped," and as a result is unable to pass through vessels efficiently.

Incorrect Answers:
Answer 2: Progressive slippage of the physis though the hypertrophic zone describes slipped capital femoral epiphysis.
Answer 3: These radiographs are most consistent with osteonecrosis of the femoral head. There is an increased incidence of Salmonella osteomyelitis in patient with Sickle Cell disease, but Staphylococcus aureus is still the most common organism.
Answer 4: Accumulation of glycosaminoglycan breakdown products describes lysosomal disorders.
Answer 5: COL5A1 or COL5A2 mutation describes the mutation of Ehlers Danlos syndrome.