Intraoperative Bone Blood Flow Measurement in Patients with Femoral Head Osteonecrosis

Abstract

Osteonecrosis of the femoral head is generally considered to be related to ischemia of bone [1]. This has been difficult to demonstrate definitively due to the lack of a direct method for measuring bone blood flow [4]. Laser Doppler flowmetry (LDF) measures at capillary level blood cell motion [2]. The light from a 2-mW He-Ne laser source is conducted down optical fibers to the tissue of interest. In bone, the light penetrates to a depth of 4 mm and effectively evaluates the bone circulation at 2.1–2.5 mm. The moving blood cells strike the light, producing an energy shift that is proportional to the velocity and concentration of the moving blood cells. The Doppler-shifted light is conducted by two afferent optical fibers to photodetectors. The output signal, blood cell flux, is expressed in millivolt units. Because we had previously been able to confirm the utility of LDF in the study of bone blood flow experimentally, we wished to apply the technique to the study of the pathogenesis of femoral head osteonecrosis in patients in various stages of the disease [2].