Abstract:Abstract： Objective To study the influence from different placement angles of acetabular component on inner and outer stress distributions of periacetabulum in acetabular reconstruction of total hip arthroplasty (THA), so as to explore proper orientation for improving stability of acetabular component after THA. Methods Based on model with inhomogeneous material property assignment, nine THA models with acetabular component at different anteversion angles(15°, 20°, 25°) and abduction angles(40°, 45°, 50°) as well as one normal hip model were constructed. The maximal hip contact force in phase of single leg stance during normal gait cycle was chosen as the loading condition. In addition, according to the qualitative and quantitative principle, inner and outer stress distributions on 9 THA models were analyzed and compared with the normal hip model as control. Results When abduction angle of acetabular component was the nearest to anatomic angle (19° anteversion, 46° abduction) of acetabulum, the phenomenon of stress shielding on periacetabulum was the most obvious. When abduction angle of acetabular component was placed at 45° and anteversion angle changed from 15° to 25°, no significant influence was exerted on the whole stress distributions of THA models. Meanwhile, when anteversion angle of acetabular component was 15°, the THA model had good stability in stress distributions, and the phenomenon of stress shielding on cortical and cancellous bone was obviously improved. Conclusions For patients who have normal anatomic acetabulum and need to be treated with THA, the abduction angle of acetabular component should be placed at 45°, as that of normal acetabulum; the anteversion angle should be 5° smaller than that of normal acetabulum and between 15° and 20°.

Abstract:Objective To construct 3D finite element model of the thoracolumbar spinal cord, and study the mechanism of spinal cord injury caused by burst fracture through biomechanical experiments. Methods The compression simulation on burst fracture was performed using finite element technology, and the results were verified by comparing the tested models with the in vivo and in vitro experimental results. Results The strain distribution in white matter of the spinal cord was higher than that in grey matter at the initial stage of burst fracture. As the displacement of bony fragments increased, the strain distribution in grey matter increased subsequently. But when the displacement of bony fragments finally reached the maximum, the strain in white matter was higher than that in grey matter. Conclusions Traumatic severity of the spinal cord during burst fracture is dependent on the posterior encroachment, and the traumatic procedure order for ventral horn (motor function) or dorsal horn (sensory function) of cord tissue also plays an important role in the evaluation. In clinical practice, the patient’s condition can be evaluated more accurately by assessing severity of the spinal motor and sensory functions. Further understanding on strain distribution in the spinal cord during the injury may inspire new strategies for treating or preventing spinal cord injury.

Abstract:Objective To evaluate the influence of Circle of Willis on intravascular hypothermia. Methods A patient-specific model of the Circle of Willis was constructed based on the CT images and the in vitro perfusion experiment with cold water for 20 ℃ was performed. The water was injected from right intracarotid artery (ICA) to the area of middle cerebral artery (MCA) at the flow rate of 30 mL/min and made the cooling period last 15 min. The cooling and rewarming characteristics in the phantom and fluid around MCA were investigated using thermocouples arranged at 27 and 1 spatial locations. The areas distributed with cold water were further visualized using the dyed solution. Results The cold water from right ICA was mainly distributed to right anterior cerebral artery (ACA), MCA, and posterior communicating artery (PCoA), while only a little part of the water could possibly pass through anterior communicating artery (ACoA) to the left ACA. The nearer the locations to the area with cold water, the faster cooling down and also faster temperature recovery rate would be obtained. Moreover, the phantom temperature distributions were asymmetric around MCA due to the complicated bifurcation structures in this area. Conclusions This physical model is useful for investigating the influence of vasculature on endovascular hypothermia and applicable in designing patient-specific hypothermia therapy.

Abstract:Objective To study the hemodynamic characteristics after vascular drug eluting stent (DES) implantation, so as to provide theoretical guidance for clinical application of DES as well as improving the design of DES. Methods The geometry models of vascular lesions implanted with DES were constructed to numerically analyze drug concentration and wall shear stress (WSS) distributions in vessel by computational fluid dynamics (CFD) method. The results were compared with flow characteristics of the model with bare metal stent (BMS) implantation. Results Low WSS accompanied by high drug concentration would occur during blood flow in some areas after DES implantation, and vice versa. The presence of DES significantly reduced appearing such areas as either with low WSS only or with low drug concentration only. Theoretically, DES had more advantages than BMS at the stage of drug release. Conclusions DES could dramatically reduce the ratio of in-stent restenosis. Understanding the regular pattern of blood flow field distributions after DES implantation in detail will be beneficial to improve the design of DES, and further advance the overall performance of the stent, which can provide the theoretical basis for clinical research.

Abstract:Objective To study the biomechanical effects of 3 different retention methods (clasp, attachment or zygomatic implants) on repairing unilateral maxillary defects by using 3D finite element analysis method. Methods The maxillary unilateral defect model was reconstructed by the medical image processing software Mimics. The prosthesis was generated by mirroring technology. After processing, the finite element model of maxillary model by the three different retention methods was established to simulate stress distributions of maxilla during occlusion. Results Compared with the other methods, by using zygomatic implant retention method, stresses on affected and unaffected palate were the largest as 7.399 and 4.864 MPa, respectively, while those on affected and unaffected maxilla were the smallest as 10.46 and 10.86 MPa, respectively. Stress on zygomatic implant itself was 15.25 MPa, which was also the smallest. Conclusions Different retention methods had an obvious impact on unilateral maxillary defect restoration. The clasp and attachment retention methods could share the stress on palate by carrying bracket. The zygomatic implant retention method could also share the stress on maxilla by passing the stress to the zygoma.

Abstract:Objective In order to analyze and evaluate the feasibility and effectiveness of induction scheme for bodily movement of incisor in children, the size, orientation and position of the force on tooth surface were estimated and analyzed. Methods The orthodontic jaw from a child was scanned to establish the 3D solid model including mandibular incisor, periodontal ligament and alveolar. Initial strain distributions on outer surface of the periodontal ligament were calculated by software Abaqus, and then the positive strain as the stimulation of the tooth movement was used to simulate the inducted effects from the inducer which was changed twice in succession. Results The rate of orthodontic tooth movement was about 0.27 mm per week, and the total displacement during an induction period was about 1 mm per month, showing it was in accordance with the real inducted effects in clinic. Conclusions The present study proved the feasibility of induction scheme for bodily movement of incisor in children and provided reference for formulation and optimization of induction scheme in clinic.

Abstract:Objective To analyze patterns of functional bundles in anterior and posterior cruciate ligaments during knee joint movement, so as to provide important references for studying injury mechanism of cruciate ligaments and implant reconstruction. Methods Five healthy knee cadavers were elaborately dissected to expose insertions of functional bundles in anterior and posterior ligaments on both the femur and tibia. CT scans and 3D finite element reconstruction with Mimics and ANSYS were conducted at 0°, 30°,60°, 90°, and 120° flexion angle of the knee joint. The center points of insertions and parallel sections of functional bundles defined by the software ANSYS and CATIA were connected to the centerlines, and at five different knee flexion angles, the lengths of centerlines, defined as the bundle lengths, were measured. Results The length of anterior medial bundle (AMB) of anterior cruciate ligament (ACL) increased gradually as the flexion angle grew from 0° to 90°, but slightly decreased at 120° flexion angle; whereas the length of posterior lateral bundle (PLB) of ACL decreased as flexion angle went from 0° to 90° and slightly increased at 120° flexion angle. In posterior cruciate ligament (PCL), both anterior lateral bundle (ALB) and posterior medial bundle (PMB) extended in length as the flexion angle went from 0° to 120°. The change of ACL and PCL bundle’s length was statistically significant (P<0.05). Conclusions ACL bundles functioned in a reciprocal manner and PCL bundles functioned in a complementary manner during knee flexion. Through establishing the finite element model of functional bundles in cruciate ligaments, the actual length of cruciate ligaments could be reflected, which provided a reasonable method for studying the changes of actual length of functional bundles in cruciate ligaments during knee flexion.

Abstract:Objective To obtain the multi-axis load histories on physiological coordinate of the pilot when performing Herbst maneuver by flight simulation, and make analysis on the obtained typical data. Methods The 3D geometrical model of the aircraft was established in CAD software based on design parameters of the fourth-generation aircraft, 6 key motion parameters of mass center were obtained by flight simulation, and 3D human body model was developed according to anthropometric measurement data of Chinese male pilot; based on the location of cabin and seat in the aircraft, the assembly model with both the aircraft and human body was established and the multi-axis load histories at different locations of human body under Herbst maneuver were obtained through kinematics analysis of the human-aircraft system. An analytic case of Herbst maneuver at altitude of 3 km and flight velocity of 90 m/s was carried out. Results The load histories at chest, foot and head of human body were basically coincided, but Gy histories between the chest and hand were different; the Gy peak value of hand was about 1.6 g; under the multi-axis loads, the +Gx peak value was about 3.0 g, being the maximum. Conclusions The load histories of aircraft mass center cannot be used as those of human body because it may have some deviation, and the Gy histories for hand cannot be replaced by load histories of other locations on human body when they are used for analysis on effects of multi axis load on operating behaviors of the aircraft.

Abstract:Objective To provide a quantitative analysis tool by building a mathematical model of seasickness habituation to make adaptive training plans scientifically for anti-seasickness purpose. Methods Based on the regular pattern of seasickness habituation, an exponential model of motion sickness incidence (MSI) was established to extract such seasickness habituation parameters as anti-motion sickness incidence (AMSI) and anti-motion sickness rate (μ) through making the seasickness habituation data fitting into the corresponding training, and the effects of AMSI and μ on MSI was also simulated. Results The data from two marine adaptive trainings were well fitted with the MSI model, and the fitting results of AMSI and μ were 0.87 and 0.048 for intermittent training, or 0.81 and 0.34 for continuous training. Effects of seasickness habituation training would be enhanced by increasing the value of AMSI and μ. Conclusions The present model of MSI is suitable for evaluating the effect of training on anti-seasickness and making the optimal strategy for such seasickness habituation training.

Abstract:Objective To study the control problem in dynamic foot biomechanical simulator and propose a complete multi-axis control algorithm which could be more competitive than that of current gait simulators in aspects as simulations in degree-of-freedom (DOF), velocity, precision, weight-bearing and trial efficiency. Methods A novel custom-made foot and ankle biomechanical simulator was developed to simulate both motion and force characteristics in a stance phase with 5 DOF. A model of the simulator was built in Matlab based on gait analysis and reasonable simplification. Iteration learning control (ILC) was proposed to control multi-axis forces and was verified in Simulink. Finally, the control strategy was validated in the simulation platform with a prosthetic foot. Results The novel simulator could complete the motion and force loading process within 5 seconds in one stance after 4-5 iterations. All 3D ground reaction forces (Fz, Fy and Fx) had high verified repeatability. The tracking curves of Fz and Fy with 50% of real body weight could converge to the target ones with root mean square (RMS) error of 20 N and 8 N using ILC, respectively, which was smaller than 10% of simulated loads. Conclusions The proposed control strategy greatly improved intelligence of the simulator and provided a good foundation to further improve the simulation speed and accuracy. The development of the simulator is of great significance to the cadaveric experiments on foot and ankle biomechanics.

Abstract:Objective To obtain kinematic and kinetic parameters of the ankle joint from young man with ankle lateral collateral ligament (LCL) injury during walking, and to investigate the biomechanical characteristics of gaits by these ankle-injured patients. Methods Qualysis MCU500 3D image capture system and Kistler 3D force platform were used to test synchronously the gait of 15 patients with LCL injury and 15 healthy young men. Results For patients with LCL injury, the vertical component of ground reaction force (GRF) changed smoothly, and the posterior anterior component of GRF and the medial-lateral component of GRF were larger than that of healthy young men during anterior-middle support phase and during 60% anterior support phase, respectively. The moment of ankle joint plantar flexion in patients with LCL injury and in healthy young men was similar. The largest ecstrophy and extorsion moment of the ankle joint was found at the injured side of patients with LCL injury, with the largest output power in the sound limb of them. Conclusions The stability of the ankle joint in patient with LCL injury was decreased, with abnormal gait appeared during walking. The sound limb had to compensate the injured limb to reduce the load on the injured limb by switching quickly to the phase of vertical support at the moment of heel-striking. This study provides theoretical references for both the prevention and treatment of ankle joint injury in clinic and rehabilitation training.

Abstract:Objective To discuss the possibility for regeneration of knee joint with normal function under bionics biomechanical environment. Methods Seven normal rabbits with two metal frames respectively mounted on their femur and tibia of single (right) side leg by two threading pins of 1.5 mm diameter were used. Then the external artificial joints, containing two four-bar-linkage inside and outside of the knee to simulate motion trajectory of the joint in sagital plane were connected with the two preset fixed frames before osteotomy. The arthro-cartilage of the knee joint, crucial ligaments, semi-lunar fibro-cartilages, and partial under-cartilage-osseous intra articular capsule were cut off during osteotomy, with the patella, sesamoid bones remained intact. Insertion sites of muscle tendons were not invaded as far as possible, and capsules with ligaments outside were kept complete when the incision wound was closed by suture. The rabbits could move freely after osteotomy. The range of motion (ROM) of the knees in sagital plane and bony gap between the femur and tibia were measured by X-Ray films during the fracture healing after osteotomy. Results External artificial knee joints were successfully installed on right legs of 6 rabbits among the seven. The rabbits moved freely after osteotomy under the control of minimal invasive external artificial joint in bionics trajectory. The average angles between femoral shaft and tibial shaft at the 1st week after osteotomy were from (144.7±15.62)° in extremely flexed position to (44.2±25.77)° in extremely extended position, with ROM of (100.5±29.03)°. At the 12th week, the average angles were from (139.4 ± 12.92)° in extremely flexed position to (40.4±22.04)° in extremely extended position, with ROM of (99.0±23.39)°. No significant differences were displayed in flexed/extended position and ROM between the 1st and 12th week, with the bony gaps of the knees still existed but decreased significantly from (4.03±1.84) mm at the 1st week to (2.32±1.05) mm at the 12th week. In contrast, bony gaps of the opposite knees were not changed significantly, which were (1.27±0.22) mm on average. At the end of 16th week after osteotomy, the external artificial joints were removed. Newly born cartilage, with white color and smooth surface, were covered at lower end of the femur and upper end of the tibia. Typical trochlear surface appeared at the front side of regenerated cartilage corresponding to the posterior surface of the patella. And the regenerated fibro-bundle linkage similar with ligament, which started from bony structure of regenerated lower end of the femur and inserted into regenerated upper end of the tibia, was observed in each rabbit. At the 25th week, the average angles between femoral shaft and tibial shaft were from (148.3 ± 4.75)° in extremely flexed position to (48.30±17.57)° in extremely extended position, with ROM of (100.0±20.80)°. In the opposite (left) leg, the average angles between femoral shaft and tibial shaft were from (148.3±7.5)° in extremely flexed position to (21.6±9.09)° in extremely extended position, with ROM of (126.7±6.88)°, and the average bony gap of the knees after osteotomy was (1.4±0.59) mm, while that of the opposite (left) knees was (0.92±0.35) mm. Conclusions The external artificial joint with bionics trajectory could reserve the space for regeneration of rabbit knee joint by providing motion modeling environment, and proved the stress adaption during fracture healing. The present results indicated that regeneration of the knee joint after intra-capsular osteotomy in bionics biomechanical environment was possible.

Abstract:Objective To design a new correction device for elbow deformity with active orthopedic force based on Ilizarov technique, and discuss its curative effect on elbow orthotics in clinic. Methods A total of 44 patients with elbow joint dysfunction were randomly divided into treatment group (n=22) and control group (n=22), and treated with new deformity orthotic device and continuous positive motion, respectively. The functional recovery of the elbow joint for patients in two groups was evaluated after 3-month treatment. Results The range of motion (ROM) of elbow flexion-extension in treatment group was significantly larger than that in control group, and the effective rate for treatment group and control group was 90.91% and 81.82%, respectively. Conclusions The use of such correction device for elbow deformity showed good curative effect for treating elbow joint dysfunction, which is worth popularization and application in clinic．

Abstract:Invisible appliance technology is the latest product resulting from image processing, computer-aided design and rapid prototyping technology in the field of orthodontics, and its development conforms to people’s pursuit for clinical treatment with modern concept of being beautiful, comfortable and healthy. The invisible appliance technology now has been widely used for treating different types of clinical orthodontic malocclusions by doctors, but researches on its clinical efficacy, biological and biomechanical mechanism still show quite deficiency. In this paper, the progresses of biomechanical research on invisible appliance technology were reviewed with the purpose to provide theoretical references for the reasonable, scientific and effective application of invisible appliance technology in clinic.

Abstract:Virtual technology of cardiovascular interventional surgery can be used for surgical training, surgical navigation, surgical optimization and postoperative evaluation in cardiovascular interventional procedures. In this paper, the composition of virtual cardiovascular interventional operation system was introduced, and the research status of virtual cardiovascular interventional operation both at home and abroad was discussed, including detailed analysis on working principles of several representative products. Through the intensive study on force feedback used as the key techniques in virtual cardiovascular interventional surgery, the author investigated its future development as well as how to improve the training effect and success rate of cardiovascular interventional operation.