all authors were involved in drafting the article or revising it critically for important intellectual content , and all authors approved the final version for publication .
dr . fukui had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis .
acquisition of data : fukui . analysis and interpretation of data : fukui , kaneuji , matsumoto .
 highlightsit is important to accurately diagnose the status of idiopathic osteonecrosis of the femoral head and to consider another possible pathogenesis when a patient with idiopathic osteonecrosis of the femoral head has hip pain even without femoral - head collapse.ignored or misdiagnosed concomitant femoroacetabular impingement in a patient with idiopathic osteonecrosis of the femoral head might leads to poor outcomes of surgical treatments such as bipolar hemiarthroplasty or osteotomies.in a patient with idiopathic osteonecrosis of the femoral head , it should be paid attention if concomitant femoroacetabular impingement exists or not . 
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