Effect Of HBO Therapy On Proximal Femur Of Femoral Head Necrosis Induced By Steroid

The treatment of avascular necrosis of femoral head is challenging, because it often occurs in young, active patients. For young people, avascular necrosis of femoral head is often associated with steroid. When femoral head necrosis induced by steroid developed to Ficat III and IV stage, total hip arthroplasty may be the most effective treatment. While the bone quality of patients taking steroid is poor, especially in those young, active patients. Now, integration of bone and porous implant come into a focus of research.Hyperbaric Oxygen used in clinic become more wide, for example, it can promote the healing course. If it can be used to promote the integration of bone and porous implant is steal unknown.Objective1. To evaluate the effects of different dosages of dexamethasone on proximal femurs in a rat model by histology, expression of BMP-2 and its receptor, apoptosis.2. To evaluate the effects of different courses of hyperbaric oxygen (HBO) therapy on proximal femur after short period of high dosage of glucocorticoid application in rat model by assessing histology, expression of BMP-2 and its receptor.3. To disgust the early effect of HBO therapy on bone ingrowth in porous implant in a rabbit model of avascular necrosis of femoral head induced by dexamethasone.Methods:1. Ninety-six male rats of 5-month old were divided into 4 groups: control group (Group C), 5mg/kg group (Group L), 10mg/kg (Group M), 15mg/kg (Group H), drugs were administered twice a week by intramuscular injection. Observe the changes of histology, expression of BMP-2 and its receptor and apoptosis of proximal femurs.2. Ninety 4-month-old Wister male rats were administered high dosage of dexamethasone for 6 weeks, and then they were divided into 3 groups: Control Group (Group A), One-course Group (Group B), Three -course Group (Group C). At time of 4, 8, 12 weeks after treatment of HBO therapy, histology, expression of BMP-2 and its receptor (BMP-Râ… ) of the upper 1/3 of femur were assessed respectively.3. Thirty-two 4 month old New Zealand rabbit were injected with dexamethason intramuscularly for 8 weeks. After the model of necrosis of femoral head established, they were divided into 4 groups randomly, they were control group (Group C), HBO group (Group H), rhBMP-2 group (Group B) and HBO plus rhBMP-2 or union group (Group U), each goup had 8 rabbits. The femurs of rabbits in Group C and H were implanted with bare porous implants; while the femurs of rabbits in Group U and B were implanted with implants compounded with rhBMP-2. Group C and B were under no any interference; Group H and U were treated 30 minutes with HBO each day for 20 days. All groups gain roentgenology films at 4, 8 and 12 weeks postoperative. All rabbits were killed at 12 weeks, in 7 days and 3 days before they were killed, they were injected with tetracycline intramuscularly. All samples of right femurs were used for hard tissue slices, while all samples of left femurs were used for biomechanics test. Results1. Area ratio of bone trabeculae and medullary cavity, area ratio of cortical bone and medullary cavity, contents of BMP-Râ… reduced with time and increased dosages in experimental groups, all of them are lower than that of Group C. The number of empty bone lacunae and the number of apoptosis cells have a trend of increasing with time and increased dosages. Average percentage of dyed areas and average optical density of BMP-2 in Group L are markedly higher than that of Group C at 2 weeks and then decreased, by the 8th week they are significantly lower than that of Group C. While Average percentage of dyed areas and average optical density of BMP-2 in Group M and H are at approximately the normal level at 2 weeks. They decreased gradually at 4, 6 and 8 weeks to a lower level.2. The vessel numbers of cavity in Group C and D are larger than that of Group A and bone trabeculae and cortical bone of Group C and D are thicker than those of Group A. The relations of three groups with regard to area ratio of bone trabeculae and medullary cavity (TCR), area ratio of cortical bone and medullary cavity (CCR), average percentage of dyed areas (DAP) and average optical density (OD) of BMP-2 and contents of BMP-Râ… (BRC) of proximal femurs are Group C> Group B> Group A, differences are significant (p<0.01). TCR, CCR, DAP, OD, BRC in Group A show a trend of decreasing, while there are no significant differences between 3 phases (p>0.05). TCR, CCR, DAP, OD, BRC in Group B and C show trends of increasing, there are significant differences on the contents of BMP-Râ… between 3 phases (p<0.01); there are significant differences between 4- and 8-week and 4- and 12-week about the rest indexes (p<0.01), while there is no significant difference between 8- and 12-week (p>0.05). As to the empty rate of bone lacunae (ER), there is significant difference between three Groups (p<0.01). The ER in Group A has a trend of increasing with time, however, there is no significant difference between phases (p>0.05); the ER in Group B and C have trends of decreasing, there are significant differences between 4- and 8-week and 4- and 12-week (p<0.01 both), while there is no significant difference between 8- and 12-week (p>0.05).3. In histology, we find that the situation of new bone formation and contact of bone and implants in Group C and B are similar, there is few new bone on the surface of implants and there is no new bone within porous implants. The new bone on the surface of implants in Group H is greater than that in Group C and B, and there is much new bone formation within porous implants in Group H. The surface of implants in Group U is all covered by new bone, but new bone in porous implants is fewer than that of Group H. The outcome of fluorescence test is that there is few fluorescence areas around and within porous implants, and fluorescence band is dim. The fluorescence band around implants in Group B is similar to that of group C, while there is no fluorescence band in porous implants, there are all dark areas within implants under scope. All spaces around and within implants are filled with bright fluorescence band. Spaces around implants in Group U are also filled with bright fluorescence band, however, though porous spaces are filled with fluorescence band , it's dimmer than that of Group H. The result of pull out test show that anti- shearing force in Group H and U is greater than that in Group C and B, the differences are significant (p<0.05). Anti- shearing force in Group U is little greater than that in Group H, there is no difference between the two groups (P>0.05). Anti- shearing force in Group B is greater than that in Group C, the difference is significant (p<0.05).Conclusions1. High dosages of dexamethasone can damage the quality of proximal femur; the higher the dosages of dexamethasone are administered and the longer the administering time lasts, the poorer of the proximal femur will be.2. After administered glucocorticoid for a short term, pathological changes are still maintained and have trends of increasing in early stage. HBO can reverse these changes. The outcome of 3-course HBO therapy is better than that of 1-course therapy.3. HBO therapy can improve integration rate of bone and implant, promote new bone ingrowth into porous implant, enhance the integration strength of bone and implant. HBO and rhBMOP-2 have cooperative effect, but the carrier of rhBMP-2 can prevent bone ingrowth into implant.