DUAL-ENERGY X-RAY ABSORPTIOMETRY IN OSTEONECROSIS OF THE FEMORAL-HEAD

Osteonecrosis of the hip classically produces a heterogeneous density in the femoral head, although the bone marrow ischemia extends down to the femoral neck and trochanters. Also, bone insufficiency fractures due to diffuse bone loss have been implicated in the genesis of osteon ecrosis. Objectives. To use dual-energy X-ray absorptiometry to quanti fy the bone changes produced by osteonecrosis of the hip and to compar e bone mineral density values in patients with osteonecrosis of the hi p and in controls. Methods. Bone mineral density was measured at the f emoral neck (total femoral neck, Ward's triangle, and trochanter), fem oral head and lumbar spine using dual-energy X-ray absorptiometry (DPX , L Lunar) in 22 patients with osteonecrosis of the hip and in 22 age- and sex-matched controls. Results. In the patients with osteonecrosis, bone mineral density on the affected side was higher than on the oppo site side at the femoral head (+18%), femoral neck (+7%), and Ward's t riangle (+6%) and lower at the trochanter (-4%). These differences wer e most marked at the more advanced end of the osteonecrosis spectrum. As compared to age-specific normative values, the osteonecrosis patien ts had moderately decreased bone mineral density values at the lumbar spine (-0.53+/-1.1 SD or -6+/-1.5%) and at the femoral neck on the nor mal side (-0.9+/-1.4 SD or 12+/-1.8%). As compared to the controls, bo ne mineral density was significantly decreased at Ward's triangle (-25 %; P: 0.04) and nonsignificantly decreased at the lumbar spine (-4.7%; P: 0.15) and at the femoral neck (-15%; P: 0.09).