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

Introduction: 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. Methods: 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. Results: 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%). Conclusions: 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.