The laser speckle method is a new form of tissue flowmetry that can analyze the interference pattern that appears when tissue is illuminated with a laser beam. During surgery for 100 cases of osteonecrosis of the femoral head, we measured the blood flow within the subchondral bone using this method. We compared the flow maps (two-dimensional distribution of the microcirculation) obtained this way with the necrotic area estimated by the preoperative magnetic resonance images and with the collapse seen during surgery. The laser specklc method was able to distinguish between the ischemic areas and the normal areas in 92 femoral heads, including five hips for which neither the magnctic resonance images nor the collapse observed during surgery demonstrated a distinct margin surrounding the necrotic area. We concluded that the laser speckle method is useful for defining the margin around a necrotic area.
In the treatment of osteonecrosis of the femoral head, a transtrochanteric rotational osteotomy is designed to prevent the progressive collapse of the articular surface (17)(18)(19)(20). In this procedure, the femoral head is rotated around the neck axis; thus, the necrotic focus can be rotated away from the weight-bearing area and the weight-bearing force is transferred to the intact articular surface. The outcome of a rotational osteotomy chiefly depends on the ratio of the transposed intact articular surface to the acetabular weightbearing surface after the procedure; it is especially successful when the intact articular surface area occupies more than one-third of the femoral head. When the lesions extend over two-thirds but less than fourfifths of the femoral head, a rotational osteotomy with intentional varus positioning may be indicated. Thus, in determining the indication for a rotational osteotomy, identifying the full extent of the lesion is important to achieve good results.
Currently, the location and extent of necrosis of the femoral head are identified with plain radiographs, tomographs, computerized tomographs, and magnetic resonance imaging. Magnetic resonance imaging is the