Comparisons between bone biopsies before and after transplantation will be assessed by paired t-test (if comparing scores) or by paired McNemar's test (after switching scores into categorical variables). Multivariable analysis adjusted for age, gender, diabetes, immunosuppressive regiments and/or its cumulative doses, and renal function will be performed to identify independent risk factors for the disease type and severity. In females, menopause will be considered as an effect modifier of bone volume.