BASIC SCIENCE & PATHOLOGY

SUBCHONDRAL INSUFFICIENCY FRACTURE OF THE FEMORAL HEAD - A DIFFERENTIAL DIAGNOSIS IN OSTEONECROSIS

Takuaki Yamamoto, M.D.*, Yukihide Iwamoto, M.D., Peter G. Bullough, M.D.*
Department of Orthopaedic Surgery, Kyushu University, Fukuoka, JAPAN Department of Orthopaedic Pathology, Hospital for Special Surgery, New York, USA*

Introduction: Subchondral insufficiency fracture of the femoral head (SIP) is a recently proposed concept, which needs to be differentiated from osteonecrosis.

Materials and Methods: A retrospective review of 464 removed femoral heads (from 419 patients) with both radiologic and histologic evidence of subchondral collapse was performed.

Results: Ten cases previously diagnosed as osteonecrosis were histopathologically reinterpreted as SIP. All these cases were osteopenic females over 65 years old. Radiologically, a subchondral collapse was noted mainly in the superolateral segment of the femoral head. MRI, available in 3 cases, showed a diffuse low intensity on Tl and high intensity on T2. Bone scintigram, available in 4 cases, showed increased uptake in the femoral head. Histopathologically, fracture callus and granulation tissue were found beneath the subchondral bone end plate. There was no evidence of osteonecrosis.

Discussion and Conclusions: SIF should be included in the differential diagnosis of acute onset of coxarthrosis in the elderly.