To evaluate the effectiveness of core decompression according to anatomic location and extent of necrotic portion.

The authors reviewed 28 hips with a mean follow-up of 36 months. Cases were classified according to Steinberg, Ficat, Ohzono, Kerboul index, Koo's index, and lateral head index. Failure was defined radiographically as depression of the femoral head compared with the previous one , and clinically HHS lesser than 80.

Radiographically, success rates were 15.8% (3/19) in Steinberg IIC, 15.8% (3/19) in Ficat IIA, 26.3% (5/19) in Ohzono 1C, 28.6% (6/21) in Kerboul index greater than 250, 30.4% (7/23) in Koo's index greater than 40, and 15% (3/20) in lateral head index smaller than 12%. Clinically, success rates were 26.3% (5/19) in Steinberg IIC, 26.3% (5/19) in Ficat IIA, 36.8% (7/19) in Ohzono 1C, 38.1% (8/21) in Kerboul index greater than 250, 39.1% (9/14) in Koo's index greater than 40, and 25% (5/20) in lateral head index smaller than 12%.

Core decompression was ineffective in preventing the collapse of the femoral head for the lesions with diffuse involvement and located laterally at weight- bearing portion, even though in the early stage of osteonecrosis, there was no collapse of the femoral head.