Advantages of DCE-MRI in assessing blood supply and the role of magnesium screws in promoting angiogenesis
necrotic, hypertrophy, femoral osteonecrosis, occlusion of blood vessels, non-traumatic osteonecrosis
GROUP B, VASCULARIZATION, OSTEONECROSIS, NECROTIC, HYPERTROPHY, NEOVASCULARIZATION, PATHOGENESIS
The pathogenesis of non-traumatic osteonecrosis remains unknown; however, alterations in intramedullary circulation are known to play a role. Narrowing or occlusion of blood vessels within the femoral head is a direct cause of non-traumatic femoral osteonecrosis. For example, in patients with hormone-induced osteonecrosis, glucocorticoids can cause adipocyte hypertrophy, which leads to the compression of venous sinuses and reduced blood flow to the femoral head [Dynamic Enhanced MRI (DCE-MRI) is a minimally invasive technique for assessing the perfusion status of a lesion. This technique reflects the distribution of microvasculature and capillary perfusion and is used to assess local tissue viability and function, allowing for a more specific assessment of the perfusion status of tissues and organs. Since conventional X-ray, CT and MRI cannot assess blood supply, and DSA (digital silhouette angiography) is more invasive (patients need to be hospitalised for follow-up examinations), the use of DCE-MRI (which allows follow-up examinations to be done on an outpatient basis without the need for hospitalisation) to assess the blood supply to the femoral head has significant advantages [In this study, we delineated regions of interest (ROI) in the necrotic, repaired, and greater trochanteric regions and created time-intensity (TIC) curves. We analysed the results of the DCE-MRI images and time-intensity (TIC) curves for the three groups of patients in the following three ways.The preoperative DCE-MRI images and TIC curves showed that the microcirculatory perfusion in the repair-responsive zone was significantly higher than that in the greater trochanter in the three groups of patients, reflecting enhanced blood flow velocity, capillary density and permeability in the repair-responsive zone compared to the normal bone marrow, and this enhancement may be related to the massive formation of neovascularization in the repair area. In contrast, microcirculatory perfusion in the necrotic area was lower than that in the greater trochanter, reflecting a decrease in blood flow velocity, capillary density and permeability in the necrotic area compared to the normal bone marrow, and a disruption of normal microcirculation in the bone.The postoperative DCE-MRI images and TIC curves showed that the microcirculatory perfusion in the repair-responsive area was lower in the three groups compared to the preoperative period, while the microcirculatory perfusion in the necrotic area was higher and closer to the normal microcirculatory perfusion in the greater trochanter. This suggests that the iliac flap transfer with vascular tip improves the blood supply to the necrotic area of the femoral head and regulates the abnormal hyperperfusion in the repaired area.Comparison of preoperative and postoperative DCE-MRI images and TIC curves between the three groups revealed that more neovascularization was observed around the implantation area in the existing cases in the group using the biodegradable magnesium nail after surgery and that the TIC pattern in the necrotic and repaired areas was more normalized in this group of patients than in the control groups (Group B and C). Thus, (we hypothesize) the use of biodegradable magnesium nails for fixation of bone flaps improves microcirculation and enhances vascularization of the reconstructed femoral head, and also provides new clinical data to support the pro-angiogenic effect of biodegradable magnesium nails.