The diagnostic value of buttressing of the femoral neck

The skeletal system can react to disease in limited ways and it is therefore not surprising that different pathologic conditions may to some extent exhibit similar radiologic features. Certain combinations of findings are more likely to occur in some diseases than others. One may speak of the “predictive” value of various radiologic features relative to the clinical condition being considered. Buttressing of the medial aspect of the femoral neck is much more common in some diseases of the hip than others. Figures 1 to 4 illustrate the roentgenographic findings in the hip in four joint diseases. Buttressing of the femoral neck is present in Figures 1 and 2, but absent in Figures 3 and 4. In addition there are other radiologic features that are important considerations in the differential diagnosis. The four diseases represented are: ischemic osteonecrosis, rheumatoid arthritis, ankylosing spondylitis, and osteoarthritis. Can you match these diseases with the figures? The answer may be found at the end of the article. Buttressing, or subperiosteal bone apposition, of the femoral neck is frequent in osteoarthritis and ischemic necrosis of the femoral head. It was evident radiologically in 33 of 73 consecutive patients with idiopathic osteoarthritis ( 1 ) and in 24 of 32 hips in which