Purpose: The gravity of osteonecrosis in patients with sickle cell anaemia is well known, but the spontaneous course of grade I and II necrosis is not. The first MRI studies performed in these patients were made in 1985. This study compared the spontaneous course in 45 cases of grade I and II necrosis diagnosed between 1985 and 1990 with that in 43 cases of hip necrosis with the same grades I and II diagnosed between 1990 and 1995 in adult patients with sickle cell anaemia treated by medullary drilling with autologous bone marrow grafts.

Material and methods: The 45 cases of necrosis followed were diagnosed between 1985 and 1990. These patients did not undergo conservative treatment until the sphericity of the femoral head was lost. They were followed clinically and radiographically up through 2000. The second group of 43 cases of hip necrosis were diagnosed between 1990 and 1995. These patients were treated by meduallary drilling with an autologous bone marrow graft. The bone marrow as harvested from the iliac crests, concentrated and reinjected in the osteonecrotic area. The patients were followed clinically and radiographically until 2000. All patients had an x-ray of the hip (AP and lateral views) at last follow-up. As the follow-up was different for the two groups, comparisons were made using the survival curves; all patients were followed for at least five years.

Results: In group I where the clinical course was spontaneous, the spherical shape of the head was lost in 100% of the patients at five years (30% at one year, 60% at two years and 100% at five years), leading to surgery for 80%, usually with prosthesis implantation. In group II where the patients were treated by drilling and autologous bone marrow transplantation, two patients (5%) lost femoral head sphericity at five years. Ten percent of the patients (4 patients) had lost the femoral head sphericity at the current mean follow-up of eight years (minimum five, maximum ten) and required reoperation for prosthesis implantation. MRI and CT imaging in the non-reoperated patients demonstrated a spherical head and remodelling or disappearance of the osteonecrosis at five years.

Discussion and conclusion: The spontaneous course of necrosis in adults with sickle cell anaemia is unfavourable after five years. This spontaneous course can be modified (at least the rate of progression) by drilling associated with autologous bone marrow transplantation, if it is performed early enough.