Experimental Study On Treatment Of ANFH In Beagle Within The Titanium Alloy Femoral Head Interior Supporting System

Objective:The object of this study was to use a titanium alloy femoral head interior supporting system in the treatment of ANFH (Avascular Necrosis of Femoral Head) in beagle model which was made by the liquid nitrogen that had been improved. Imaging and histology were used to observation the repair process, and the maximum compressive strength and the average elastic modulus of the subchondral bone in the femoral head were measure, to provide a theoretical basis for treatment ANFH by interior supporting system.Methods:1. establish the beagles femoral head osteonecrosis models. The femoral head osteonecrosis models on random side are established in twenty-six healthy adult beagle using liquid nitrogen that had been improved. Firstly, exposure the rear hip joint capsule through posterolateral approach,"T" shape incision joint capsule, cut off the round ligament of the femoral head, make the hip subluxation. Using liquid nitrogen freezing femoral head with sterile funnel. The radiological and histology examination are made at the two months after liquid nitrogen frozen, two random selected beagle dogs were sacrificed to text and verify the succeed of ANFH animal models. 2. The research about titanium alloy femoral head interior supporting system used in treatment of beagle femoral head osteonecrosis models. The femoral head osteonecrosis models on random side are established in twenty-six adult beagles using liquid nitrogen. Except two randomly selected beagles that are killed, the rest (24beagles) are randomly classified into two groups after models which have been made2months. Group A acted as femoral head osteonecrosis model control, which were used to get primary information of necrosis of femoral head and as a test for animal models. Group B are carried out titanium alloy femoral head interior surpporting system implantation after core decompression. The healthy side of two groups is treated as normal control group. The radiological, histology examination and biomechanics examination are made in6beagles of each group at3,6months after the interior surpporting system implantation. Double sample T-test was used in statistical analysised.Results:1. Two months post-surgery, X-ray examination can see density of the femoral head becomes irregular, mild cystic changes and local bone sclerosis are in the pedal area of femoral head, and slightly collapse in femoral head was seen. MRI scans Avascular femoral head demonstrated joint effusion; dotted, linear or flaky intermediate signal on T1WI; dotted, linear or flaky high signal on T2WI. The histological examination shows cartilage surface becomes rough and thinning, or partial loss. Trabecular bone becomes rarefaction, thinning, fractured. Diffuse presence of empty lacunae is seen. Intramedullary hematopoietic cells significantly reduced, showing tiny intravascular thrombosis.2. After femoral head interior supporting system was implanted1) three months after implanted:(1) X-ray examination and CT scan have shown bone repair effect in Group A is significantly worse than group B. Irregular contour of the femoral head, flat collapse, uneven density, and fracture cracks can be seen at the weight-bearing area of the femoral head, and the articular surface is not smooth, joint space slightly narrow, trabecular texture is not normal for group A. The operated lateral femoral head shape is regular, cystic low-density areas are weakening、disappeared or restore to normal density, no obvious collapse of the femoral head was seen for group B.(2) biomechanics examination:The maximum compressive strength of femoral head subchondral bone in two groups and the contralateral are respectively (49.38±2.37and91.30±2.21),(81.78±2.36and91.16±2.32)Mpa; and average elastic modulus are respectively (78.86±2.24and153.42±3.36),(139.90±3.49and151.96±3.75)MPa. The maximum compressive strength and average elastic modulus of femoral head subchondral bone in the group A and group B are significantly different from the contralateral (P<0.05), and between groupA and group B, the difference has statistical significantly (P<0.05). (3)HE stain for the bony tissue:The percentage of empty lacunae count in two groups and the contralateral are respectively (22.44±1.34and11.52±1.29),(15.44±1.47and12.54±1.61)%; The blood vessels counting are respectively (21.20±1.79and43.40±3.05),(33.00±2.55and46.20±3.35). The percentage of empty lacunae count and blood vessels counting of the group A and group B are significantly different from the contralateral (P<0.05), and between groupA and group B, the difference has statistical significantly (P<0.05).(4)Immunohistochemisty stain for the bony tissue:Buffy represents positive result. The data from immunohistochemistry are quantitied by MIAS(Micro Imagery Analysis System) analysis Program. The gray scale of BMP-2in two groups and the contralateral are respectively (189.90±12.90and100.34±6.56),(134.80±11.00and105.16±6.43); while the gray scale of bFGF are respectively(192.90±11.50and112.86±7.59),(139.70±9.43and115.18±7.22). The BMP-2and bFGF of the group A and group B are significantly different from the contralateral (P<0.05), and between group A and group B, the difference has statistical significantly (P<0.05).2) six months after implantation:(1)X-ray examination and CT scan have shown completely collapsed of the femoral head for group A, the operated lateral femoral head is substantially normal femoral head for group B. Biomechanics examination:the maximum compressive strength of femoral head subchondral bone in two groups and the contralateral are respectively (53.44±2.45and91.50±2.02),(88.78±2.45and91.94±2.99) Mpa; and average elastic modulus are respectively (84.66±3.03and154.30±3.46),(153.74±3.20and155.98±3.55)MPa. The maximum compressive strength and average elastic modulus of femoral head subchondral bone in group A is significantly different from the contralateral(P<0.05); but group B is not significantly different from the contralateral (P>0.05); and there is significantly difference between group A and group B (P<0.05).(3)HE stain for the bony tissue:The percentage of empty lacunae count in two groups and the contralateral are respectively (19.58±1.41and12.42±1.40),(12.46±1.51and11.48±1.54)%。; The blood vessels counting are respectively (27.00±2.12and42.40±3.78),(43.00±3.54and44.80±3.56). The percentage of empty lacunae count and blood vessels counting in group A is significantly different from the contralateral (P<0.05); group B is not significantly different from the contralateral (P>0.05), but there is significantly difference between group A and group B (P<0.05).(4)Immunohistochemisty stain for the bony tissue:The gray scale of BMP-2in two groups and the contralateral are respectively (161.90±12.10and98.22±6.33),(110.04±8.60and102.28±7.79); while the gray scale of bFGF are respectively(157.20±10.10and113.68±6.93),(124.92±7.55and116.26±6.30). BMP-2and bFGF of group A is significantly different from the contralateral (P<0.05); group B is not significantly different from the contralateral (P>0.05), but there is significantly difference between group A and group B (P<0.05).Conclusion:1. We successfully produced avascular necrosis of the femoral head in adult beagle by liquid nitrogen freezing that have been improved. The mortality of this method formation is low, the way that is simple and the repeatable is high. For the traumatic is smaller, it does not damage the stability of hip. This animal models can be used to explore clinical treatment of femoral head necrosis in the experimental study, and provide the ideal animal model for our subsequent studies at the same time.2. The treatment of ANFH in beagle with titanium alloy femoral head interior supporting system after core decompression is effective, which can effectively promote the repairment of necrotic area and improve the anti-collapse biomechanical property of the femoral head, enhance the speed of new bone formation, necrosis reparation of the femoral head. Three months after surgery, the indicators of titanium alloy femoral head interior supporting system group is better than that of the necrosis in the control group, but worse than normal contralateral side. Six months after surgery the indicators of this group is obviously better than the necrosis control group, and there is no significant difference between this group and normal contralateral group. The titanium alloy femoral head interior supporting system can provides a new way for treatment of ANFH.