1. University of Tsukuba College of Medicine, School of Medicine and Health Sciences, , Tsukuba, Ibaraki, Japan
2. University of Tsukuba Department of Orthopaedic Surgery, Faculty of Medicine, , Tsukuba, Ibaraki, Japan
3. University of Tsukuba Department of Diagnostic Pathology, Faculty of Medicine, , Tsukuba, Ibaraki, Japan
4. Kyushu University Department of Anatomic Pathology, Graduate School of Medical Sciences, , Fukuoka, Fukuoka, Japan