A comparison of magnetic resonance imaging to bone scintigraphy in early traumatic ischemia of the femoral head

In adult rabbits, a unilateral subcapital osteotomy of the femoral neck was performed to induce avascularity. One half of the osteotomy sites were fixed with a magnetic resonance imaging (MRI) compatible absorbable pin and the other osteotomies had no fixation. The femoral heads were studied at three, five, and 12 days with roentgenographs, bone scintigraphy, and MRI, and MRI only at four weeks and six weeks after osteotomy. Histologic studies were performed after imaging to evaluate the viability of the femoral heads. At three, five, and 12 days after osteotomy, bone scintigraphy showed a decrease in uptake of radioisotope in the region of the femoral head on the operated side relative to the acetabulum and greater trochanter in 17 of 18 rabbits. A comparison of the surgically treated hip to the normal hip in fixed and unfixed osteotomies showed no change in the signal behavior of T1- or T2-weighted images in all rabbits Days 3, 5, and 12 (n = 18) after operation. The rabbit femoral heads with fixation of the osteotomy 28 days after operation showed a decrease in signal intensity in the subcapital region of the femoral head. Six weeks after operation, the fixed femoral head shows a loss of signal in a portion of the femoral head near the osteotomy. The MRI signal intensity appears to increase in the unfixed femoral heads six weeks after operation.