[The core decompression of the femoral head for stage I idiopathic osteonecrosis]

The osteonecrosis of the femoral head is a progressive multi-etiological disease ; its primum movens is circulatory and the pathophysiology is still unexplained. Ficat and Arlet classified this disease into 5 stages from 0 to IV. The progression from one stage to another is inevitable if surgical treatment is not performed early. The MRI is currently the investigation of choice in detecting infraradiological stage I necrosis. The core decompression as proposed by Ficat and Arlet allows to excise the necrotic zone, confirm the histological diagnosis, decompress the intramedullary increased pressure and favor the neovascularization of the femoral head. The aim of this study is to present the mid-term results of the core decompression in a series of 17 hips in 16 patients with an average age of 46 years that were operated upon in stage I idiopathic necrosis of the femoral head, 4 to 6 weeks after the symptoms appeared. The MRI demonstrated the zone of necrosis in 16 hips. The histological examination confirmed the diagnosis of necrosis in 16 hips including the one which was negative on MRI. The Merle d'Aubigné hip score was used for the clinical evaluation and showed to be less than 15 in all hips preoperatively. This score improved to 18 (full value) after a mean follow-up of 8 years, ranging from 3 to 13 years. The X-rays of the operated hips remained normal at the final follow-up in all cases. The very high percentage (100%) of recovery and healing in stage I femoral head necrosis in this series may be explained by the absence of obvious etiological factors (idiopathic necrosis) and moreover by the short delay between the onset of the symptoms and the operative treatment. We believe that the MRI is the examination of choice that should be done early in patients with a painful hip and normal X-rays and that core decompression performed soon is an excellent procedure to treat stage I idiopathic necrosis of the femoral head.