The Experimental Study On The Treatment Efficacy Of Femoral Head Osteonecrosis By A Titanium Alloy Type Of Femoral Head Interior Surpporting System Implantation And Core Depression With Bone Graft

Objective:To explore the establishment of the beagle dogs femoral-head osteonecrosis animal models by improved liquid nitrogen freezing method, at the same time,to provide animal models for subsequent experimental study. Also our research is to explorea new way of treatment femoral-head osteonecrosis by a titanium alloy type of femoral head interior surpporting system implanting into the dogs femoral-head osteonecrosis models after core depression and finally observing the radiological, the biomechanics and histology results.Methods:Unilateral femroal head osteonecrosis was induced in28healthy adult beagle dogs using liquid nitrogen freezing(15.09±0.14Kg;24.17±0.26months.At the first month、the second month post-sugery, two beagle dogs once were randomly choosed to perform radiological and histological examination and osteonecrosis was observed.The rest24begale dogs were randomly divided into2groups: group A conducted free fibular graft implantation and core depression, group B conducted a titanium alloy type of femoral head interior surpporting system implantation and core depression. The health side of the two groups is treated as self-control. The radiological and biomechanics examination and histology examination are made at3、6months after the treatment.Results:At the first month, X-ray shows mild cystic changes was seen in the femoral head, MRI scans demonstrated joint effusion, dotted intermediate or high signal.At the second month, X-ray examinations see shape and density of the femoral head becomes irregular, cystic changes worsening and local bone seleros is in the subchondral area of the femoral head, MRI scans Avascular femoral head demonstrated joint effusion, linear or flaky intermediate or high signal.The histology examination shows trabecular bone becomes rarefaction, thinning, fractured. Diffuse presence of empty lacunae is seen. Intramedullary hematopoietic cells significantly reduced, showing tiny intravascular thrombosis at the first and second month. Avascular necrosis of the femoral head was observed.3months after the treatment, X-ray and CT show the operated lateral femoral head shape recovery, the femoral head was seen almost as the normal side for both group A and B.Fibula column shadow is still visible for group A. Macro Biomechanics examination:the maximum compressive strength of femoral head subchondral bone in two groups and the contralateral side are respectively (73.58＋2.21and92.10＋1.92)、(81.78±2.36and91.16±2.32)Mpa;and average elastic modulus are respectively (131.56±3.08and153.98±3.60),(139.90±3.49and151.96±3.75)MPa. The maximum compressive strength and average elastic modulus of femoral head subchondral bone in group A and group B are significantly different from the contralateral side(P<0.05),and between group A and group B,the difference has statistical significance (P<0.05). Nano-micromechanics examinations:elastic modulus of femoral head subchondral bone in two groups and the contralateral side are respectively(8.847±0.653and12.160±1.258),(9.763±0.745and12.456±1.420)GPa, and hardness are respectively (0.277±0.023and0.355±0.011)、(0.302±0.031and0.359±0.015)GPa. The elastic modulus and hardness of femoral head subchondral bone in group A and group B are significantly different from the contralateral side(P<0.05),and between group A and group B,the difference has statistical significance (P<0.05).The histology examination shows:In group A and group B empty lacunaes decreasing, empty lacunaes、Pyknosis,karyolysis,and karyorrhexis were partly observed. The percentage of trabecular bone area fraction in two groups and the contralateral side are respectively (35.40±1.66and39.41±1.32)、(36.92±1.17and39.27±1.18)%; and the vessel area fraction are respectively (16.15±1.09and19.51±0.98)、(17.42±1.89and19.41±1.21)%. The percentage of trabecular bone area fraction and the vessel area fraction in group A and group B are significantly different from the contralateral side(P<0.05), and between group A and group B, the difference has statistical significance (P<0.05). The gray scale of VEGF in two groups and the contralateral side are respectively (153.39±13.85and115.48±9.74)、(138.01±12.39and112.51±8.35); and Bcl-2are respectively (142.13±12.87and105.46±6.48)、(129.06±12.77and103.61±5.26).The gray scale of VEGF and Bcl-2in group A and group B are significantly different from the contralateral side (P<0.05),and between group A and group B,the difference has statistical significance (P<0.05).6months after the treatment, X-ray and CT show the operated femoral head was seen as the normal side for both group A and B.Fibula column shadow is still visible for group B.Macro Biomechanics examination:the maximum compressive strength of femoral head subchondral bone in two groups and the contralateral side are respectively (87.94±2.31and90.96±2.07)、(88.78±2.45and91.94±2.99)Mpa;and average elastic modulus are respectively(149.74±3.16and154.10±3.47)、(153.74±3.20and155.98±3.55)MPa. The maximum compressive strength and average elastic modulus of femoral head subchondral bone in group A and group B are with no significantly different from the contralateral side(P>0.05),and between group A and group B,the difference has no statistical significance (P>0.05).Nano-micromechanics examinations:elastic modulus of femoral head subchondral bone in two groups and the contralateral side are respectively(11.378±0.935and12.568±0.880)、(11.730±0.750and 12.346±0.625)GPa, and hardness are respectively (0.338±0.016and0.356±0.015)、(0.344±0.018and0.358±0.013)GPa. The elastic modulus and hardness of femoral head subchondral bone in group A and group B are with no significantly different from the contralateral side(P>0.05), and between group A and group B,the difference has no statistical significance (P>0.05).The histology examination shows:almost normal appearance observed in group A and group B.The percentage of trabecular bone area fraction in two groups and the contralateral side are respectively(37.78±1.56and39.33±1.92)%、(38.14±1.41and39.56±1.71)%;and the vessel area fraction are respectively (18.54±1.23and19.46±1.35)％、(18.70±1.31and19.54±1.25)%.The percentage of trabecular bone area fraction and the vessel area fraction in group A and group B are with no significantly different from the contralateral side(P>0.05),and between group A and group B,the difference has no statistical significance (P>0.05).The gray scale of VEGF in two groups and the contralateral side are respectively(130.34±15.82and116.56±11.45、(128.39±12.72and115.50±10.74);and Bcl-2are respectively (117.52±14.60and102.53±4.28)、(116.58±12.64and103.59±5.63).The gray scale of VEGF and Bcl-2in group A and group B are with no significantly different from the contralateral side (P>0.05),and between group A and group B,the difference has no statistical significance (P>0.05). Conclusions:We successfully produced avascular necrosis of the femoral head in adult beagle dogs by improved liquid nitrogen freezing method. The way that is simple,convenient and the traumatic is smaller because it protect the stability of the hip.This method has high success rate, high survival rate of animals and less complications.It can provide animal models for experimental study on the treatment efficacy of adult femoral head avascular osteonecrosis.The way of treatment of femoral head osteonecrosis by a titanium alloy type of femoral head interior surpporting system and core depression can effectively restore and maintain the biomechanical properties of femoral head, promote angiogenesis in order to facilitate the repairmenr of bone necrotic area, inhibit apoptosis of bone cells to prevent collapse of the femoral head. It is expected to provide a new treatment for the preservation of the femoral head.