Changes in intraosseous pressure and bone blood flow of the distal femoral shaft after femoral medullary canal blocking with bone cement / 中国组织工程研究

ABSTRACT

BACKGROUND: Implantation of artificial joint of bone cement can result in long-term blocking of recipient site medullary canal and blood vessel lesion, and lead to changes in intraosseous pressure and bone blood flow of distal femoral shaft.OBJECTIVE: To explore the changes in the intraosseous pressure and bone blood flow of distal femoral shaft after blockage of the proximal and middle femoral medullary canal by bone cement.DESIGN: Controlled observation.SETTING: People's Hospital of Guangxi Zhuang Autonomous Region.MATERIALS The experiment was performed at the Experimental Animal Center of Chongqing Medical University between July 2002 and April 2003. Thirty-two healthy adult New Zealand rabbits were selected and randomly divided into model group (n=24) and control group (n=8). Polymethyl methacrylate (PMMA) TJ bone cement was provided by Tianjin Synthetic Materials Research Institute.METHODS: The rabbit model was established by infusing femoral medullary canal of left side with PMMA. The lateral greater trochanter of anesthetized rabbits were resected below the third trochanter through spatium intermusculare by posterior lateral femur approach, but the neck of femur was remained to expose intertrochanteric fossa and entry of medullary canal following by intramedullary reaming to 1/2 length of femur. The wound was washed repeatedly to remove the destroyed myeioid tissues, and was dried with gauze. Bone cement was prepared by manually stirring powder with solution at a ratio of 21, until dough shape formed. A small piece of dough-shaped bone cement was filled in middle femoral stenosis as cavity blocker. Ten minutes later, the solidified bone cement was re-blended until dough shape and implanted into medullary canal fully. When the bone cement was completely solidified, the incision was sutured. The 24-modeled rabbits were randomly divided into 4 subgroups according to the following observation time points (n=6) postoperative 0 day (T0),4th week (T4), 8th week (T8) and 16th week (T16).MAIN OUTCOME MEASURES: ①Physiological pressure-measuring instrument was used to detect and compare the intraosseous pressure of bilateral distal femoral medullary canal of the model and control groups. ②Radionuclide bone imaging was used to detect and compare the dynamic and static images of bilateral distal femoral of the rabbit models at different time points.RESULTS: Thirty-two rabbits were all included in final analysis with no loss. ①There were no significant differences in the intraosseous pressure between the distal femurs in normal rabbits (P＞0.05); the pressure of the experimental side increased significantly compared with control side (P＜0.01). In model group, there were no significant differences in the intraosseous pressure between the control sides of rabbits at different time points (P＞0.05), but the experimental sides presented continuous high intraosseous pressure state. The pressure of T4 was higher than that of T16 (P＜0.05); there were no significant differences between any other two time points (P＞0.05). ②Compared with the dynamic and static images at different time-points, the counting of nuclide in the experimental sides was markedly lower than the control sides at T0 and T4 while higher at T8 and T16; the count reached the peak at T16. There were no significant differences in the nuclide counting ratio between T0 and T8, T0 and T16, T4 and T16, T8 and T16, T4 and T8, respectively except T0 and T4 (P＜0.05). The dynamic and static radionuclide bone imaging showed the same changes.CONCLUSION: The intraosseous and intramedullary blood circulation is severely damaged after blocking of the proximal and middle femoral medullary canal with bone cement, resulting in local alterations of hymodynamics, a series of changes in intraosseous pressure and bone blood flow in the distal femur, which causes continuous and a long-term high intraosseous pressure.