MRI of the cartilaginous epiphysis of the femoral head in the piglet hip after ischemic damage

MRI of the cartilaginous epiphysis (CE) of piglet femoral head was performe d after ischemic damage to study the changes in the CE found on MRI and to correlate these changes with histologic findings. Avascular necrosis of the femoral head was induced with a suture ligature in nine piglets; one pigle t was killed postoperatively on day 3 and on weeks 1, 2, 3, 4, 6, 7, and 8 (two piglets were killed on week 3), MRI of the ischemic and contralateral nonischemic hip joints were obtained with a 60-mm field of view (low resolu tion MRI). Biopsy cores of the femoral heads were imaged with a 15-mm held of view (high resolution MRI) and correlated with histologic sections. The CE for all operated hips, except for the 3-day postoperative specimen, show ed evidence of ischemic changes on histologic assessment; the severity of d amage increased with time, The MRI appearance of ischemic and nonischemic C E was clearly different by 2 weeks after the operation, No trilaminar signa l pattern was evident in the high resolution Ta-weighted (T2W) imaging of t he ischemic CE from 2 weeks after the operation, In the 3- to 8-week postop erative specimens, focal areas of low signal intensity on high resolution T 1-weighted (T1W) and T2W imaging corresponded to the areas of chondronecros is found on histologic assessment. The regions of high signal intensity on T2W imaging corresponded to the areas of chondrocyte clusters with increase d safranin-O staining. High resolution MRI can demonstrate changes in the C E associated with ischemic injury and may have a role in the assessment of the CE and its development after ischemic injury.