Avascular necrosis of the hip in children with sickle cell disease and high Hb F: Magnetic resonance imaging findings and influence of alpha-thalassemia trait

Avascular necrosis (AVN) of the hip is a common cause of morbidity in sickl e cell disease (SCD). its prevalence increases with age and predisposing fa ctors include coexistent alpha -thalassemia trait, frequent vaso-occlusive crisis and a high hematocrit (Hct). SCD is relatively mild among Kuwaiti pa tients because of their elevated Hb F levels, but a subset exists with seve re recurrent vasoocclusive crises. We carried out a prospective magnetic re sonance imaging (MRI) study of the hip in a group of patients being followe d in the Pediatric Hematology clinics of Al-Mubarak and Al-Amiri Hospitals. The association of AVN with age, frequency of hospitalization, alpha -thal trait, steady-state Hb, Het, Hb F, WBC and platelet counts was investigate d. MRI was carried out with a 1.5-tesla GE unit with a super-conducting mag net. Thirty patients (19 males, 11 females) (23 SS and 7 S beta Thal) were studied. Their ages ranged from 6 to 17 years, with a mean of 9.8 +/- 3.5 y ears, and Hb F from 11 to 35% with a mean of 22.8 +/- 5.7%. Among the SS pa tients, 11 (47.8%) had coexistent a-thal trait (-3.7-kb deletion). A total of 8 (26.7%) patients (6 SS and 2 S beta Thal) had varying degrees of osteo necrosis of the hip. Four (36.4%) of the 11 SS patients with alpha -thal tr ait and 2 (16.7%) of those without alpha -thal trait had osteonecrosis. Thi s difference is, however, not statistically significant (chi (2) = 0.3, P = 0.5). While there was also no significant difference in the mean age and h ematological parameters (Hb, Hct, Hb F, WBC, platelets), the SS patients wi th osteonecrosis had a significantly higher number of hospitalizations for vasoocclusive crisis in the preceding 3 years than those without osteonecro sis. Copyright (C) 2001 S. Karger AG, Basel.