Experimental Study On Effect After PMMA Injected In Normal Rabbit Femoral Head

Objective:To investigate histological features of femoral head which polymethyl methacrylate(PMMA,bone cement)be injected into by experimental study on animals. To observe the effect on normal femoral head tissue after the operation which injection into femoral head and after that bone cement be injected into the femoral head. To explore the safety and feasibility of treatment FicatⅡ,Ⅲnecrosis of the femoral head within the bone cement injection.Methods:1.The preparation of the group and experimental animals:Breed all animals of prepare for operation a week early to keeping them to adapt to the environment and make sure all animals disease-free. All animals don't take water and food,and their hair of bilateral inguinal be removed a day before the operation. 35 purebred Chinese white rabbits were divided randomly into A, B groups. Group A as blank control group contained 5 rabbits. Group B contained 30 rabbits, and the left femoral head be injected PMMA (the experimental group),and the right femoral head be only punctured (negative control group). Killed every 10 rabbits in group B four weeks, eight weeks and twelve weeks after the operation. 2.Operation method: bilateral femoral head of Group B will be operated.Supine position, 40mg/kg of sodium pentothal to intraperitoneal injection of anesthesia.Conventional disinfection, ventri-lateral incision of the hip, the lateral femoral artery access, separate iliopsoas, and exposed the junction of femoral head and neck, not cut round ligament, not hip dislocation, and protect the surrounding tissue, hammer pin for lumbar puncture into the head and neck junction of the femoral head. At this point suture incisions of negative control group. Bone cement be concocted, its liquid and solid compared to 3:2, and its characters such as "thin paste" shape, and be injected into the femoral head of the experimental group through the lumbar pin. The time of injection is about 60-90 seconds. Suture the incisions. 3. method of perfuse by ink and collect femoral head specimens:Femoral head of group A be perfused by ink and collected directiy. Every 10 Femoral head of group B be perfused by ink and collected four weeks, eight weeks and twelve weeks after the operation. All animals don't take water and food, and their hair of abdomen be removed a day before operation. 100 ml zhonghua ink, and 3 g gelatin be heated together by water, make gelatin dissolved in the ink. First heparin injected through rabbit ears margin intravenous(2.5-3.0 mg/200-300g). Supine position, 40mg/kg of sodium pentothal to intraperitoneal injection of anesthesia. Conventional disinfection. Median abdominal incision, draw the small intestine, revealed the abdominal aorta and inferior vena cava, insert polyethylene pipe containing heparin. Lavage by saline, the inferior vena cava intubation first outflow in the red blood, and that can be stopped when the color be pink. Perfusion with ink don't stop until the color of animals'eyes, tongue, limbs and tail be black. Animals are died, and whose bilateral femoral head be cut for specimens. 4.HE dyeing: Cut the femoral neck at the basement which be preserved in 10% formalin, marked,and put them in 8% formic acid solution for three times to demineralized, it need two weeks. Dewatering. Transparent. Steeping wax.. Repair the specimen. slice 5μm. Waterbath. Stretched preparation. Bake slice. H.E dyeing: Fuse wax. Hydration with alcohol. Dyeing with Urolen Blue. Acidation. Return orchid. Dyeing with eosin. Hydration with alcohol again. Transparent. Mounting with resin. 5. Histology observation : Observe the bone cement-bone tissue structure in femoral head by microscope after polymethyl methacrylate(bone cement)be injected into femoral head. Count the number of osteoblast;osteoclast;empty bone lacuna and micrangium in 10 low-power field on every specimen's slice. 6. Statistical analysis:Statistical analysis by SPSS12.0. All data be expressed by mean±standard deviation( x±s ) , and be treatment by one-way ANOVA and compare between every group. Results: Observation of bone cement: All the femoral head is round and smooth, without stripping and articular cartilage degeneration. Bone cement embedded between trabecular at the section of femoral neck. By X-ray: The femoral head of the control group is round, no significant changes in density, trabecular bone is normal. The femoral head of experimental group is round, density has increased, but uniform, the trabecular bone structure is integrity. Through the microscope, we can see achromophil uniform material between the trabecular bone, which looks like stripe because of be cut. There is no normal bone structure in it. It is the bone cement which be injected into the femoral head. Bone cement infiltrate along the cavitas medullaris, and occupied the space of them after be injected. Bone cement and normal trabecular bone become chimerism. Within the observation of bone tissue in femoral head: Bone cement occupied the space of the cavitas medullaris after be injected. There appears destruction at the edge of the trabecular bone which contact with the bone cement four weeks after the operation. The number of osteoclasts increased, the bone repair process started at the same time, the number of osteoblasts also increased, a new osteoid appears. But inside the trabecular bone and the trabecular bone which little contact with bone cement, the structure is integrity, and bone lacuna is not empty. The number of micrangium in cavitas medullaris decrease for close to bone cement. The destruction at the edge of the trabecular bone is still exist eight weeks after the operation. The number of osteoclasts still increased, the bone repair process also strengthened at the same time, the number of osteoblasts also increased, inside the trabecular bone and the trabecular bone which little contact with bone cement, the structure is still integrity, and bone lacuna is still not empty. The number of micrangium started to rise. The destruction at the edge of the trabecular bone is significantly reduced twelve weeks after the operation. The number of osteoclasts decreased significantly over the previous two groups, but the bone repair process continue to strengthen, the bone repair process, the number of osteoblasts markedly increased inside the trabecular bone and the trabecular bone which little contact with bone cement, the structure is still integrity, and bone lacuna is still not empty. The number of micrangium in cavitas medullaris markedly increase. Between the control group and the blank control group, the morphology of femoral cartilage surface and the structure of the trabecular bone are same. We can't see the change of the number of osteoclast, osteoblast and microvascular in the control group four, eight and twelve weeks after operation. Statistical analysis: The number of empty bone lacuna in the blank control group, the negative control group and the experimental group compared no difference (P> 0.05). The number of osteoblasts in the experimental group and the blank control group, the negative control group compared more difference(P<0.05), but the number of osteoblasts in the blank control group and the negative control group compared no difference(P>0.05). The number of osteoclasts in the four weeks, eight weeks experimental group and the blank control group, the negative control group, twelve weeks experimental group compared more difference (P<0.05). But the number of osteoclasts in the blank control group, the negative control group, twelve weeks experimental group compared no difference(P>0.05). The number of micrangium in the experimental group and the blank control group, the negative control group compared more difference (P<0.05), but the number of micrangium in the blank control group and the negative control group compared no difference(P>0.05).Conclusions:1.Bone cement infiltrate along the cavitas medullaris, and occupied the space of them after be injected. Bone cement and normal trabecular bone become chimerism. Ultimately, the coexistence of the bone cement and the trabecular bone is formed.2. The operation which pin into femoral head has no effect on the femoral head. It is a safe, effective and minimally invasive surgical method.3. Due to chemical and thermal burns, bone cement causes a certain amount of damage to the trabecular bone and marrow cavity surface of the femoral head at the beginning after it is injected into the femoral head, and result in reducing the number of microvessels, and affected the blood supply of the femoral head, but can't directly kill bone cell inside the trabecular bone. With the extension of time, the damage caused by bone cement is repaired, the number of microvascular recovery, the blood supply of the femoral head have been resumed.