Radiological evaluations
femoral head necrosis, ONFH, oedema, necrotic
COLLAPSE, OEDEMA, NECROTIC

X-ray: X-ray(orthopantomogram and frog-mogram) was taken on 1, 3, 6 months after surgery to assess the preoperative morphological location of necrotic areas, postoperative morphology, progression of ONFH and the amount of gas production of the magnesium screws.CT: The femoral head was evaluated by CT coronal measurements on postoperative day 1, 3 and 6 months postoperatively. CT was used to evaluate specifically the postoperative iliac bone graft position, the loosening of the magnesium screw, the amount of gas production, the growth and fusion of the bone graft with the surrounding normal tissue, and the collapse of the femoral head.DCE-MRI: All MRI experiments were performed using a 3.0 T MRI (SIGNA Architect) with a air coil. The "double line sign" of femoral head necrosis was selected as the boundary according to the T2-weighted MRI image, with the necrotic zone on the medial side and the repair response zone between the "double lines". Coronal DISCO (Differential Sub-sampling with Cartesian Ordering) imaging was performed with a field of view of 36 × 36 cm, covering the area of entire pelvis and proximal femur. The other scan parameters included a repetition time = 4.2 ms, echotime = 1.5 ms, a flip angle = 12°, a slice thickness = 1.0 mm, and a matrix size = 360 × 360. Before DISCO imaging, gadoteric acid meglumine salt (0.4 mL/kg) was injected as the contrast agent at a rate of 3 mL/s. Coronal DISCO imaging with a total 15 arterial phases was performed 10 s after the onset of contrast agent administration. Each single-period scan took 12.7 s; therefore, the total scan time was 192 s. Datum was processed using GE's Geniq software. Regions of interest (ROI) were plotted in necrotic area, the repaired area, and the greater trochanter, and time-signal intensity curves (TIC) were obtained and classified for all pixel points within the region of interest. The area under the curve (IAUGC), peak contrast-enhanced signal (CER), maximum slope of the curve (MaxSlope), volume shift constant (Ktrans), volume rate constant (Kep), and extracellular interstitial volume fraction outside the vessel (Ve) were calculated. IAUGC reflects whole blood flow, CER reflects capillary density, MaxSlope reflects blood flow velocity, and Ktrans and Kep reflect nutrient flow. Ktrans and Kep reflect nutrient exchange capacity, and Ve reflects tissue oedema. The reconstruction and recovery of blood supply of the femoral head were evaluated and the microenviromental blood supply changes were observed.A senior radiologist with at least 5 years of clinical experience first independently reviews all of the patient's pre- and post-operative imaging data. Subsequently, the radiologist conducts radiological evaluations together with one orthopedist and one chief orthopedic physician, to ensure accuracy and consistency in the interpretation of the imaging data.