| 1. BackgroundIntegrated Traditional Chinese and Western medicine combined minimally invasive treatment of hallux valgus deformity has many good points such as simple operation, the patient less pain, fewer complications, and efficacy to determine and so on. More than 30 years after two generations of continuous improvement, innovation and development, it has formed a standardized system for the diagnosis and treatment. At present this method has been treated more than 2 million cases of hallux valgus patients, the excellent rate reaches to 98.5%. The main technique points of the method are 1) the application minimally invasive techniques in Traditional Chinese Medicine foot and ankle surgery.2) An oblique osteotomy is used at the first metatarsal head and neck to correct the deformity.3) Chinese bone-setting techniques to correct deformities and joint dislocation and 4) based on a small plywood and paper pad clip principles and the "muscle bundle bone" theory, a "8"-shaped bandage fixed osteotomy end. Abandon the Western tradition methods such as plate and screws internal fixation and plaster external fixation. Patients are able to weight-bearing after operation. As soon as this method has been made, some Western orthopedics experts questioned it. It was believed by modern medicine that the healing of osteotomy need for stability between the sides of osteotomy. In order to achieve optimal healing, the sides of osteotomy must remain relatively stable after reset. When the human body in the weight-bearing the feet load increased, especially in the first metatarsal. Some orthopedic surgeons believe that the osteotomy is not fixed in this part will affect the stability of osteotomy-side. The osteotomy may appear delayed healing or even nonunion. Nevertheless the fact is Integrated Traditional Chinese and Western medicine treatment of hallux valgus method, through 30 years of clinical applications, the phenomenon of osteotomy non-union does not occur. Moreover the patients with metastatic metatarsalgia postoperative are also less. How to analyze the science mechanism of Integrated Traditional Chinese and Western medicine treatment of hallux valgus, to study the mechanism of Integrated Traditional Chinese and Western medicine treatment of hallux valgus from the biomechanics, to confirm the scientific content of the small plywood and paper pad clip principles and the "muscle bundle bone" theory would have great significance for the development of Chinese medicine orthopedic treatment to bone fractures theory.Where the osteotomy was performed at the 1st metatarsal bone of the hallux valgus? Which angle of osteotomy is the most scientific? Wether or not the "8 "-shaped bandage for non-invasive biological fixation after the osteotomy according to the small plywood and paper pad clip principles and the "muscle bundle bone" theory is stable? What the effects to the biomechanics of forefoot effects after the 1st metatarsal osteotomy healed? These issues still need to do in-depth studies to answer. So, it is necessary to study the mechanism of Integrated Traditional Chinese and Western medicine treatment of hallux valgus. Finite element analysis provides a useful tool for studying normal and pathological state of foot biomechanics. It enables us to have a fully understand the stress distribution of foot under different conditions, as well as the impact of various therapeutic measures on the foot. At present, the reports on finite element analysis of hallux valgus foot are very few. There is no related research on the site the first metatarsal osteotomy, the stability of osteotomy and the biomechanical changes in the foot after the osteotomy healing. The purpose of this study is to establish finite element model of the hallux valgus foot including bone, part of the tendon and intrinsic muscles, to analyze the effects on the osteotomy side and forefoot stress change of Integrated Traditional Chinese and Western medicine treatment of hallux valgus osteotomy site selection and fixation methods. The study results will improve understanding of the treatment of hallux valgus. It will have a far-reaching impact in improving and perfecting Integrated Traditional Chinese and Western medicine treatment of hallux valgus. The research methods for the modernization of traditional Chinese medicine orthopedic research opened a new way. 2. PurposesTo Study of Integrated Traditional Chinese and Western medicine Treatment of hallux valgus osteotomy surgery site, osteotomy angle, biological fixation and postoperative biomechanical mechanism of plantar stress to explain the mechanism of this therapy, further confirm the scientific.3. Contents of study3.1 The establishment of finite element model of hallux valgus foot3.1.1 Materials and methods3.1.1.1 Measurement of material parameters of foot-related organizationsA left calf-foot of fresh specimen of a 45-year-old woman was acquired. The flexor hallux longus muscle and it's tendon, internal and external side head of flexor hallux brevis, musculus extensor hallux longus and it's tendon, cross-head and oblique head of musculus adductor hallux, musculus abductor hallux were thumb abductor were dissected. And all the musles and tedon were made into samples. In order to removing the load creep deformation of the samples they were pre-loaded and stretched before testing. Repeated measurements for each sample 4 times, loading rate set 0.0835cm/min. Collection intensity limit, the maximum load load-displacement curve and other data. The load-displacement curve was transformed into force-deformation curve. The force divided by the cross sectional area, the displacement divided by specimen length, and the stress-strain curve was acquired. Fit the line segment of the curve and obtain the elastic modulus (E).3.1.1.2 Image data acquisition and storageA young women volunteer with hallux valgus was selected, aged 28 years old, height 168 cm, weight 62 kg. The HAV angle was 24°, IM angle was13°of her right foot. There no other foot deformity, no metatarsalgia under the metatarsal head, no history of foot surgery and trauma, no other foot deformity caused by other system diseases. Using spiral CT to scan the affected foot, slice thickness lmm, interval 1mm, scanned from toe to heel, which obtained 512×512 pixel CT image 542 pages. The pictures were outputted and storage in DCIOM format. 3.1.1.3 The establishment of finite element model of hallux valgusUsing the relative software to segment foot CT image and extract the contour data, to distinguish soft tissue, bone cortex, medullar cavity of the boundaries, and access to the edge of bone contour vector data. According to free-form surface entity modeling rule, to reconstruct surface of foot bone, obtain three-dimensional solid model of foot bone and assemble. In order to simplify the model reduce calculating amount, the model only took into account bone, cartilage, tendon, foot intrinsic muscles four kinds of organizational materials. Three-dimensional model of the foot was entered the finite element software ANSYS12.0, to definite material properties and assign material parameters, to carry out meshing, obtain finite element model.3.1.1.4 Load and boundary constraints of modelSimulated the foot force conditions of a 62kg person standing balance in feet., and the 1st metatarsal stress distribution and variation when the heel in lift, toe dorsiflexion 30°and 70°. Set foot pressure, plantar tendon force and the foot friction was load. The interaction between the the surface of support structure and the plantar surface is defined as contact. The friction coefficient is 0.6. According the principle of loading and ground reaction force equivalent exchange, through the support structure surface a concentration force was exerted up to the pressure center. The upper surface of the talus was fully bound. The ankle joint is considered in the middle position.3.1.1.5 Foot scan plantar pressure test of hallux valgusA Foot scan USB21 meter flat plantar pressure measurement system was used, which produced by Belgian RSscan company. The same patient was tested. According to the patient body weight adjust the force plate before the test. The static and dynamic loading situations of foot were measured respectively. The static pressure (P) and the maximum dynamic pressure (MP) were observed in six regions of foot. Compare the measured value and finite element analysis results, to find the relationship between them and test the reliability of finite element model.3.1.2 Resultsi. By measuring and calculating 9 samples data were obtained, including:length, width, thickness, cross-sectional area, maximum load, ultimate strength and elastic modulus. Providerelative precise material parameters for the foot finite element model construct,ii. Established 7 three-dimensional finite element modeles of the hallux valgus foot standing and gait cycle standing phase with different positions (0°,30°,45°and 70°). The bone, cartilage, tendon, intrinsic muscles and skin of the Modeles were reconstruced, which include 67,239 nodes,69,189 units.iii. Compared the static plantar stress between finite element model and Foot scan foot force plate the two stress concentration was broadly consistent. Pressure values in the parts of the 2nd,3rd,5th metatarsal head were very close. Compared the maximum stress conversion value of Finite element in sole, which simulated a gait cycle with the maximum stress value of Foot scan force plate measured in corresponding parts, the trend of the maximum pressure was similar.3.1.3 ConclusionsFinite element models of hallux valgus were established in this study, including bone, tendon, intrinsic muscles, and skin and so on. Parts of the material parameters were measured and some relevant data were obtained. The reliability of the finite element model was tested by Foot scan force plate. The results proved finite element models reliable and they basically reflected the actual situation of hallux valgus.3.2 The finite element analysis on the osteotomy end stability of 1st metatarsal in different directions osteotomy3.2.1 Materials and methods3.2.1.1 Research MaterialsEstablished finite element osteotomy models of hallux valgus and 7 kinds of working conditions were simulated which the osteotomy line and 1st metatarsal axis were angulated in 30°,45°,60°,75°,90°,105°,120°in sagittal plane.3.2.1.2 Test MethodsSimulated a body weight 62kg hallux valgus patient who suffered from 1st metatarsal osteotomy stood toe plantar flexion as far as possible the osteotomy end conditions of the stress and displacement in different angle osteotomy. Set the proximal osteotomy end the fixed end and distal end the free end. Set the ends filled with granulation tissue.The constraints of other parts were similar with the former. One foot was beared about 310N weight load. Considered the effects of the flexor hallux longus muscle and flexor hallux brevis muscle only on the osteotomy end. Muscle strength was expressed with load. That was about 319N. Muscle load wre supposed parallel with the 1st metatarsal long axis. The friction coefficient in osteotomy faces was set to 0.6.3.2.1.3 Observation ProjectObserved the maximum Von Mises stress and the total value of the displacement in osteotomy ends of the seven kinds of conditions under the same load conditions, and compared.3.2.2 Resultsi. The total displacement of osteotomy end diminished gradually from 30°, reched to the minimum at 60°, and then gradually increased. The displacement increased significantly as osteotomy angle exceeds 90°. The maximum displacement occurred at 120°, which was 0.6486mm; the minimum displacement occurs at 60°, which was 0.2833mm.ii. The Von Mises stress of the osteotomy end gradually increased from 30°, reached to the first peak at 75°, and then flattened and reduced gradually. The stress increased rapidly at 105°. The maximum stress occurred at 120°, which was 0.986Mpa; the minimum stress occurred at 30°, which was 0.212Mpa.3.2.3 ConclusionsThrough simulation and calculation to the osteotomy in different angles of 1st metatarsal in the sagittal plane by finite element model it had found the osteotomy end was the most stable at about 60°. Only Maintain osteotomy line direction from the dorsal distal to plantar proximal lateral in the sagittal plane could the osteotomy ends maintain stability. According to factors that influencing the osteotomy stability, the best osteotomy angle in the sagittal plane should adjust appropriately according to the patients different situations. Osteotomy should not be taken fixed angle.3.3 The finite element analysis on the fixed action of Integrated Traditional Chinese and Western medicine treatment of hallux valgus external fixation methods in 1st metatarsal osteotomy end3.3.1 Materials and methods3.3.1.1 Research MaterialsEstablished finite element model of hallux valgus with osteotomy at 1st metatarsal neck. The osteotomy line was angled with the vertical of 1st metatarsal axis into 10°in the sagittal plane, with the vertical of 1st metatarsal axis into 15°in the horizontal plane. Simulated standing conditions with a pad in 1st toe web and "8"-shaped bandage fixation. The material properties and material parameters of parts of the Model could be found in the first two parts.3.3.1.2 Test MethodsSimulated a body weight 62kg hallux valgus patient who suffered from 1st metatarsal osteotomy and fixation stood toe plantar flexion as far as possible the osteotomy end conditions of the stress and displacement. Set the proximal osteotomy end the fixed end and distal end the free end. Set the ends filled with granulation tissue.The constraints of other parts were similar with the former. The force of the sub-toe pad and the "8"-shaped bandage external fixation was 24.84N by the experimental measurement. It cuold be divided into two powers; one was vertical with hallux the other parallel with 1st metatarsal. They were expressed with load in analysis. Other load and settings were same as the previous model.3.3.13 Observation ProjectObserved the maximum Von Mises stress and the total value of the displacement in osteotomy end and the displacements of X, Y, Z axises.3.3.2 Resultsi. Displacement of the osteotomy end:it was 0.261mm in X axis,0.078mm in Y axis,-0.167mm in Z axis. The total displacement in osteotomy end was 0.293mm. The main displacement occurred in X axis. The other two were very small.ii. The Von Mises stress of the osteotomy end was 0.712Mpa. The stress was mainly located in the lateral edge of the osteotomy end.3.3.3 ConclusionsThrough simulation and calculation to the "8"-shaped bandage external fixation of Integrated Traditional Chinese and Western medicine treatment of hallux valgus it had found the fixation can effectively reduce the displacement of the osteotomy end. The stress was moderate. It could promote osteotomy to healing in an approach of endochondral ossification.4. SummaryThe study analyzed the choice of osteotomy angles and effects of the fixation methods on the stability and healing of osteotomy by finite element in Integrated Traditional Chinese and Western medicine treatment of hallux valgus. It explained how to determin the osteotomy angles from the biomechanical viewpoint. It analyzed the mechanism of sub-toe pad and "8"-shaped bandage external fixation. At the same time a deep study had done on the role of "muscle bundle bone" theory in the treatment of hallux valgus. The understandings of the mechanism in Integrated Traditional Chinese and Western medicine treatment of hallux valgus were deepened and improved, and confirmed its scientific content. It will have a far-reaching impact on the constant improvement and development of the theories and methods in Integrated Traditional Chinese and Western medicine treatment of hallux valgus.5. Innovationsi. The establishment of dimensional finite element model on hallux valgus osteotomy in different directions, and "8 "-shaped bandage external fixation open up a new way for evaluation of hallux valgus surgical methods and prognosis of the feasibility.ii. The finite element analyses were performed on stress and displacement of osteotomy ends by simulating osteotomy and fixation methods of Integrated Traditional Chinese and Western medicine treatment of hallux valgus, and proved the scientificity of Integrated Traditional Chinese and Western medicine treatment of hallux valgus from the biomechanical mechanisms.
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