BASIC SCIENCE & PATHOLOGY

SUBCHONDRAL INSUFFICIENCY FRACTURE IS AN ETIOLOGY OF SPONTANEOUS OSTEONECROSIS OF THE KNEE

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: The clinical characteristics of spontaneous osteonecrosis of the knee are similar to those of subchondral insufficiency fracture.

Materials and Methods: We have re-evaluated 24 surgical specimens clinicopathologically, which had had both a clinical and pathological diagnosis of spontaneous osteonecrosis of the knee.

Results: Five cases (3 males and 2 females, over 59 years of age) were re-interpreted as subchondral insufficiency fracture of the medial femoral condyle, where no evidence of antecedent osteonecrosis was present. There were 10 causes where a subchondral fracture and small areas of bone necrosis were observed. However, the area of necrosis was present only between the fracture line and the articular surface. In another 9 cases the lesion was detached from the condyle.

Discussion and Conclusion: Our clinicopathological findings suggest that the primary event in spontaneous osteonecrosis of the knee is a subchondral insufficiency fracture of the medial femoral condyle.