LONG-TERM EFFECTS OF CORE DECOMPRESSION BY DRILLING - DEMONSTRATION OF BONE HEALING AND VESSEL INGROWTH IN AN ANIMAL STUDY

Avascular necrosis of the femoral head is associated with bone marrow hyperpression. Although core decompression by drilling is an accepted treatment regimen, until today no experimental results exist concernin g the physiological effects of this procedure. Published clinical data are controversial. In an animal study marrow decompression was carrie d out by drilling of both hips in 18 healthy male sheep. In the right hip of each animal a resorbable stent was implanted in order to prolon g the duration of core decompression. Over a time period of 24 weeks t he effects were studied by measurement of the intraosseous pressure, b y the plastination method and by morphological examination with light and electron microscopy. Bone drilling is a procedure of high short-ti me efficacy in decompressing the bone marrow. But decompression lasts only for a short time period. Three weeks postoperatively the drill ch annel is sealed by hematoma and fibrous tissue in both hips (with/with out stent) and no significant decompressive effect is measured. Ingrow th of vessels along the drill channel is found in all hips after a tim e period of 3 weeks. These vessels originate from the periosteum as we ll as from the bone marrow and form temporary anastomoses between the periostal-diaphyseal-metaphyseal and the epiphyseal-physeal circulator y system. In conclusion, for the first time an anastomosis induced by drilling between both circulatory systems of bone is demonstrated and the importance of the periosteum is confirmed. The time of decreased c ore pressure induced by drilling is too short for substitution of a ne crotic area and could be the explanation of the inferior clinical resu lts of the procedure.