Articular collapse and surgical frequency in corticosteroid-associated osteonecrosis of the femoral head and the knee: An MRI-based prospective study

Background: The purpose of this magnetic resonance imaging (MRI)-based prospective study was to clarify the frequency of articular collapse in, and to define the frequency with which surgical interventions are performed for, osteonecrosis of the femoral head and the knee. Methods: MRI screening for osteonecrosis of the femoral head and the knee was prospectively performed within 1 year after corticosteroid administration. Those patients with osteonecrosis were conservatively followed with MRI to detect articular collapse by bone marrow edema. Several surgical interventions were considered after articular collapse. The frequencies of collapse and of surgical intervention were compared using the Kaplan-Meier method and the log-rank test. Results: Of 1,239 joints (623 hips and 616 knees) surveyed in the study, osteonecrosis was identified in 370 (191 hips and 179 knees) by MRI. Thus, the incidence of osteonecrosis was 30 % (31 % in hip and 29 % in knee). Of 155 hips and 154 knees followed for more than 2 years, the frequency of articular collapse was significantly higher in osteonecrosis of the femoral head than in osteonecrosis of the knee (p < 0.05, 38 % [59 hips] versus 5 % [7 knees]). After articular collapse, surgery was performed significantly more often for osteonecrosis of the femoral head than for osteonecrosis of the knee (p = 0.024, 63 % [37 femoral heads] versus 29 % [2 knees]). Conclusions: Osteonecrosis of the femoral head can result in clinically more severe sequelae than osteonecrosis of the knee, and surgery is more often performed for osteonecrosis of the femoral head.