Incidence of osteonecrosis and insufficiency fracture of the hip and knee joints based on MRI in 300 renal transplant patients

The purpose of this study was to investigate the incidence of necrosis and insufficiency fracture of the hip and knee using magnetic resonance imaging (MRI) in renal transplant patients. We examined 300 consecutive renal transplant patients using MRI of the hips and knees (T1-weighted coronal MRI) preoperatively and at 3 and 6？months postoperatively. Oblique axial-plane T1-weighted MRI and short-tau inversion-recovery T2-weighted MRI were performed parallel to the femoral neck when distinguishing the osteonecrosis of the femoral head (ONFH) from subchondral insufficiency fracture (SIF) of the femoral head was difficult. ONFH was observed in 3 hips (3 cases, 1.0%). Osteonecrosis of the knee was observed in 2 knees (1 case, 0.3%). SIF of the femoral head was observed in 5 hips (3 cases, 1.0%). Bilateral simultaneous onset of SIF of the femoral head was observed in 2 cases (0.7%). Insufficiency fracture of the knee was observed in 2 knees (1 case, 0.3%). When it was difficult to distinguish ONFH from SIF of the femoral head, oblique axial-plane T1-weighted MRI and the short-tau inversion-recovery T2-weighted MRI parallel to the femoral neck were useful to establish the correct diagnosis