APPROACHES TO STUDY OF ISCHEMIA IN BONE

Ischemic osteonecrosis is a complication of certain traumatic and a nu mber of idiopathic conditions. The course of the disease may result in collapse of the convex member of a joint and osteoarthritis, often re quiring arthroplasty. Increasing incidence in young adults poses a cha llenge for development of long-term joint prostheses. Current status o f research into the disease is discussed and three new models using in travital microscopy described. The first, an arterial occlusion (AO) m odel, creates ischemia by occluding the common iliac artery exclusivel y, avoiding direct trauma on other tissues in the limb. The second, a total occlusion (TO) model utilizes classical tourniquet occlusion of the thigh vessels. The third, a venous occlusion (VO) model, is also a tourniquet procedure but it blocks occlusion of the femoral artery wi th a protective sheath. Preliminary results from AO and TO studies are reported which show that reperfusion injury is detectible after ische mia doses as short as 4 h. This complication was confirmed by observat ion of leukocyte adherence, secondary ischemia, and abnormal vessel le akage. Also, a new quantitation of osteonecrosis is introduced whereby fluorescently-tagged dead osteocytes and computer-based image process ing provide values for an ''osteonccrosis index.'' Viewing of all vasc ular events is made possible by intravital microscopy through a bone c hamber window implanted in rabbit tibias. It is proposed that such chr onic visual techniques allow quantitation of events leading to osteone crosis as well as the revascularization, resorption and hone appositio n of creeping substitution which characterizes postischemia recovery. (C) 1998 John Wiley & Sons, Inc.