Submitted on August 25, 2003
Accepted on December 15, 2003
Fluorescent microsphere method is suitable for chronic bone blood flow measurement-- A long-term study after meniscectomy in rabbits
Hermann Anetzberger*, Eckart Thein, Gudrun Loeffler, and Konrad Messmer
* To whom correspondence should be addressed. E-mail: Hermann.Anetzberger{at}helios.med.uni-muenchen.de.
The fluorescent microsphere (FM) method is considered a reliable technique to determine regional bone blood flow (RBBF) in acute experiments. In this study, we verified the accuracy and validity of this technique for measurement of RBBF in a long-term experiment and examined RBBF after meniscectomy. 24 anesthetized female New Zealand rabbits (3 groups, each n = 8) received consecutive left ventricular injections of FM in defined time intervals after meniscectomy: Group 1 from preoperatively to 3 wks postoperatively, group 2 from 3 wks to 7 wks, and group 3 from 7 wks to 11 wks postoperatively. To test the precision of the FM-method, two FM-species were injected simultaneously at the first and last measurement. After the experiment both humeri, femora, tibiae and reference organs (kidney, lung, brain) were removed and dissected according to standardized protocols. Fluorescence was determined in each reference blood and tissue sample and blood flow values were calculated. Blood flow in kidney, lung, and brain revealed no significant difference between right and left side and remained unchanged during the observation period, thus excluding errors due to shunting and dislodging of spheres in our experiments. Comparison of relative bone blood flow values obtained by simultaneously injected FM showed an excellent correlation at the first and last injection, indicating valid RBBF measurements in long-term experiment. We found a significant increase in RBBF 3 wks after meniscectomy in the right tibial condyles compared to the non-operated left side. Similar changes were found in the femoral condyles. RBBF in other regions of tibia, femur and humerus revealed no significant differences between right and left-sided bone samples of the same region. Our results demonstrate that the FM method is valid for measuring RBBF also in long-term experiments. In addition, we were able to demonstrate that meniscectomy leads to an increase in RBBF in the tibial condyles at a very early stage. This increase might be caused by stress-induced alterations of the subchondral bone.
