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Objective To evaluate biomechanical properties of the nickel-titanium (NiTi) memory alloy stent and its in vitro biomechanical properties for lumbar interbody fusion. Methods The mechanical properties of the NiTi memory alloy stent were tested on mechanical testing machine. Moreover, lumbar interbody fusion was simulated on fresh lumbar specimens, and biomechanical properties of the NiTi memory alloy stent with matching bone graft for used for lumbar interbody fusion were analyzed and compared with the traditional box-shape cage. Results The maximum compressive strength of the NiTi memory alloy stent was ( 12 964 ± 962) N. The maximum deformation within the effective range of memory characteristics was (4. 68±0. 03) mm. The recovery rate of the NiTi memory alloy stent was up to 99. 86% . Compared with the intact lumbar model, the stability of the operative segment after the simulated lumbar interbody fusion using NiTi memory alloy stent alone was increased in the direction of anterior flexion, posterior extension, lateral flexion and rotation, which was equivalent to the box shape cage group (P>0. 05). After the combined use of autogenous bone granule and absorbable bone cement the ROM of the operative segment was further reduced (P0. 05). The pull-out strength of the NiTi memory alloy stent with matching bone graft group was significantly stronger than that of the box-shape cage group (P<0. 05). Conclusions The NiTi memory alloy stent in this study was designed with a matched bone granule-absorbable bone cement graft,which provided a new idea for the further optimization and development of lumbar interbody fusion. With excellent support and deformation properties, this NiTi memory alloy stent is biomechanical equivalent to the traditional box shape cage for lumbar interbody fusion, and can greatly improve the stability of surgical segment and the pull-out strength of implants after the combined use of autogenous bone granule and absorbable bone cement.
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Objective To evaluate the biomechanical properties of lumbar interbody fusion with NiTi memory alloy stent-autogenous bone granule-absorbable bone cement. Methods The normal L3-5 segment finite element model (M0), L4-5 intervertebral fusion model with box fusion cage (M1), L4-5 intervertebral fusion model with NiTi memory alloy stent (M2) and L4-5 interbody fusion model with bone granule-absorbable bone cement for casting bone graft (M3) were constructed, respectively. The models were applied with mechanical loading to analyze the mechanical stability and the peak stress of L4 interior endplate. Results The range of motion (ROM) of L4-5 segment in M1 and M2 models was significantly lower than that of M0 model under flexion, extension, lateral flexion and axial rotation. In M3 model, the stability of the surgical segment was further improved and the peak stress of L4 interior endplate was much smaller than that of M1 and M2 models. Conclusions NiTi memory alloy stent and traditional box fusion cage have biomechanical equivalence when used alone in lumbar interbody fusion, and application of bone granule-absorbable bone cement for casting bone graft can further improve the stability and reduce the stress of endplate.
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In the recent years, there has been a growing interest in research community towards the application of smart materials for bio-medical structural health monitoring. Amongst the smart materials, directly bonded piezo sensors (DBPS), based on the electro-mechanical impedance (EMI) technique, have been successfully employed for the above purpose. The principle behind the EMI technique is that high frequency excitations (typically > 30 kHz) generated by a surface bonded PZT patch are used to detect changes in structural drive point impedance caused by cracks or any other type of damage. Bone healing and damage have been shown to be successfully monitored using the DBPS. However, in most of the diagnostic cases of live human and animal subjects, directly bonding a PZT patch is always an irritant or hazard for a live subject. To circumvent direct bonding, the authors have developed and experimentally demonstrated a non-bonded piezo sensor (NBPS) configuration as a good alternative to DBPS while maintaining the effectiveness of measurement well within discernible limits. This paper presents further improvement in the NBPS configuration aiming at autonomous operation of the gripping mechanism using shape memory alloy (SMA) wires. The experiments are performed on replicas of femur bone in healthy and osteoporosis state. This paper shows the effective use of SMA clamping for bone identification and its damage assessment in comparison to earlier mechanical gripping using jubilee clamps. This paper also covers impedance based identification applied to SMA and clamp based NBPS configurations. In place of raw admittance signatures, effective drive point impedance is utilized for the purpose of bone diagnostics which provides a more realistic assessment of the condition of bone.
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Animals , Humans , Alloys , Constriction , Diagnosis , Electric Impedance , Femur , Hand Strength , Memory , OsteoporosisABSTRACT
Objective: To compare the biomechanical characteristics of self-made nickel-titanium shape memory alloy stepped plate with calcaneal plate and cannulated compression screws in fixing calcaneal osteotomy.
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Objective To evaluate the influence from deformation history of arch-wires on its orthodontic force. MethodsA finite element model including brackets and arch-wires in free status was built, and the position of brackets under clinical condition was obtained through laser scanning on the plaster dental model. Based on the finite element method, the brackets were moved to the clinical position through two different movement pathways, using a thermal-mechanical shape-memory-alloy model of arch-wires. The orthodontic force obtained from the two pathways were then compared and analyzed. Results The relative differences in the orthodontic force obtained from the two pathways were significant, with a range from 0.3 to 8.0. The influence of deformation pathway on the orthodontic force was reduced if the arch-wire was first overloaded and then unloaded to the clinical condition，but reduction of the orthodontic force varied at different positions of arch-wires, and the relative differences might increase at certain positions. Conclusions The deformation history of arch-wires has some direct relation with the orthodontic force produced on the NiTi shape-memory-alloy, and the evaluation on the orthodontic force should trace its deformation history.
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BACKGROUND: The incidence of distal femur fracture in the elderly has been increasing recently, and commonly occurs with osteoporosis. Retrograde intramedullary nailing has been considered a good surgical option for distal femur fracture. The purpose of the present study was to present our surgical results with retrograde intramedullary nailing for distal femur fractures with osteoporosis. METHODS: Thirteen patients diagnosed with extra-articular distal femur fracture and osteoporosis and managed with retrograde intramedullary nailing were retrospectively reviewed. Cement augmentation was used in four patients, shape memory alloy was used in eight patients and both were used in one patient. All patients were followed up for more than 2 years. Radiologic alignments. were scored and Tegner and the Lysholm activity score was used for a functional assessment. RESULTS: The average time to clinical union was 13 weeks (range, 10 to 15 weeks). In 12 of our cases, the total alignment scores were excellent. At the last follow-up, the mean range of motion was 116degrees (range, 110degrees to 125degrees). The average functional score at postoperative 1 year was 2.6 (range, 1 to 5). CONCLUSIONS: Retrograde intramedullary nailing is a good surgical option for distal femur fracture with osteoporosis. Cement augmentation and shape memory alloy can also be used for added mechanical stability. This surgical technique is very useful for distal femur fracture with osteoporosis as it promotes fracture healing and early rehabilitation.
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Aged , Aged, 80 and over , Female , Humans , Male , Alloys , Bone Cements , Femoral Fractures/pathology , Femur/pathology , Fracture Fixation, Intramedullary/instrumentation , Osteoporosis, Postmenopausal/pathology , Osteoporotic Fractures/pathology , Range of Motion, Articular , Retrospective Studies , Treatment OutcomeABSTRACT
Objective To explore the effect of persistent stress on the ultrastructure of cancellous bone in the process of fracture healing.Method A transverse osteotomy on both sides of the femoral tuberositas was performed in 20 adult dogs. One side was fixed with a self-designed tuberositas memofy-pressure connector (TMC) which was made of NiTi shape memory alloy, and the other with compressive steel-wire (SW) cerclage.Five animals in each group were sacrificed at 2, 4, 8, 12 weeks after operation and observed under transmission electron microscope.Results The fracture healing was accelerated in the TMC group.The osteoblasts, chondroblasts and collagen fibers at the fracture sites showed significantly different morphology between the 2 groups at every observation time.Most cells and collagen fibers in the TMC group grew along the same direction as the stress, but those in the SW group grew in disorder.Both the number and functional activity of the osteoblasts and chondroblasts were higher in the TMC group than in the SW group.Conclusion Persistent stress can enhance healing and bone reconstruction following a cancellous bone fracture.
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Objective Clutching internal fixtor (CIF) loose and the fixed part weakly heal up are often found in orthopedic clinic.In the present paper, biomechanics methods were used to try to explain and analyze these issues, provide a helpful suggestion for the application of CIF in clinic. Method Commercial finite element method(FEM) Program ANSYS was applied to set up the Finite Element Models of orthopedic CIF and bone tissue to analyze and evaluate the biomechanical performances of the Ni Ti shape memory alloy CIF. Results There is an interaction force between embracing force of CIF and resistant force of bone tissue during the orthopedic clinical treatment. The embracing force along two semi-circular arms of CIF is increasing from the open position and reached the maximum value at the open symmetry position where the deformation of the bone occurre. Conclusion It is the key to choose the force loading position during the practical treatment, as the concentration force is the main force when there is an interactive force between the bone and the CIF.
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Objective To compare the clinical outcome of shape memory alloy (SMA) embra-cing fixator and reconstruction plate fixation in treatment of displaced or comminuted midshaft clavicle fractures. Methods There were 65 patients with displaced or comminuted midshaft clavicle fractures surgically treated with either a SMA embracing fixator or a reconstruction plate. The patients were divided into two groups according to fixation methods, ie, SMA embracing fixator group (30 patients at average age of 28.1 years) and reconstruction plate group (35 patients at average age of 26.1 years). All pa-tients were followed up for mean 12 months and shoulder function was evaluated using shoulder score. Results Compared with reconstruction plate group, SMA embracing fixator had shorter operation time, smaller wound incision and less loss blood (all P < 0.05). However, there was no statistical difference in aspects of hospital stay, cost, JOA shoulder score and bone union rate between two groups (all P > 0.05). Conclusion The internal fixation with SMA embracing fixator is better than reconstruction plate fixation in treatment of midshaft clavicle fractures.
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Objective Clutching internal fixtor(CIF)loose and the fixed part weakly heal up are often found in orthopedic clinic.In the present paper,biomechanics methods were used to try to explain and analyze these issues,providing a helpful suggestion for the application of CIF in clinic.Method Commerical finite element models(FEM)Program ANSYS was applied to set up the finite element models of orthopedic CIF and bone tissue to analyze and evaluate the biomechanical performances of the NiTi shape memory alloy CIF.Results There is an interaction force between embracing force of CIF and resistant force of bone tissue during the orthopedic clinical treatment.The embracing force along two semi-circular arms of CIF is increasing from the open position and reached the maximum value at the open symmetry position where the deformation of the bone occurred.Conclusion It is the key to choose the force loading position during the practical treatment,as the concentration force is the main force when there is an interactive force between the bone and the CIF.
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Objective Clutching internal fixtor(CIF)loose and the fixed part weakly heal up are often found in orthopedic clinic.In the present paper,biomechanics methods were used to try to explain and analyze these issues,providing a helpful suggestion for the application of CIF in clinic.Method Commerical finite element models(FEM)Program ANSYS was applied to set up the finite element models of orthopedic CIF and bone tissue to analyze and evaluate the biomechanical performances of the NiTi shape memory alloy CIF.Results There is an interaction force between embracing force of CIF and resistant force of bone tissue during the orthopedic clinical treatment.The embracing force along two semi-circular arms of CIF is increasing from the open position and reached the maximum value at the open symmetry position where the deformation of the bone occurred.Conclusion It is the key to choose the force loading position during the practical treatment,as the concentration force is the main force when there is an interactive force between the bone and the CIF.
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Objective Clutching internal fixtor(CIF)loose and the fixed part weakly heal up are often found in orthopedic clinic.In the present paper,biomechanics methods were used to try to explain and analyze these issues,providing a helpful suggestion for the application of CIF in clinic.Method Commerical finite element models(FEM)Program ANSYS was applied to set up the finite element models of orthopedic CIF and bone tissue to analyze and evaluate the biomechanical performances of the NiTi shape memory alloy CIF.Results There is an interaction force between embracing force of CIF and resistant force of bone tissue during the orthopedic clinical treatment.The embracing force along two semi-circular arms of CIF is increasing from the open position and reached the maximum value at the open symmetry position where the deformation of the bone occurred.Conclusion It is the key to choose the force loading position during the practical treatment,as the concentration force is the main force when there is an interactive force between the bone and the CIF.
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[Objective]To evaluate the biomechanical features of Ni-Ti shape memory alloy stemless femoral prosthesis.[Method]Using CT(computer tomography) scanning photographs of adult femur,three-dimensional model of the femur was built by CAD(computer aided design) software.Based on the the structure of femoral model,shape memory alloy stemless femoral prosthesis was designed.Three-dimensional finite element model was created for the normal femur,Ni-Ti shape memory alloy stemless femoral prosthesis,and traditional stemmed hip prosthesis.Under static loads and walking loads,the Von Mises stress distributions of each model were analyzed and compared.[Result]The stress distribution of shape memory alloy stemless femoral prosthesis was not obviously different from normal femur,stemless femoral prosthesis's proximal femoral stress was close to that of normal femoral model but significantly higher than traditional stemmed hip prosthesis.Von Mises stress of memory alloy claws was distributed evenly,and the Max was only 13.23Mpa,there was no stress concentration.[Conclusion](1) Ni-Ti shape memory alloy stemless femoral prosthesis has great biomechanical properties,may reduce the stress-shieding effect of the proximal femur.The fixed method that use memory alloy claws can make prosthesis fixed firmly to the bone and reduce stress concentration.
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Objective To establish a three-dimensional finite element model and make mechanical analysis of "V"-type atlantoaxial reduction and internal fixation. Methods According to "V"-type atlantoaxial and internal fixation,based on screw-type Ⅱ design parameters,and using Pro/E 2001 and MSC.Patran 2005 software,we set up a finite element model and calculated the region containing the node scope of the force as the sites binding and 100N mechanics adding. Results The model looked realistic,geometric similarity.The deformation stress field mainly concentrated in the reset device V-tip arm bending and stability.The strength of its maximum stress was 4.78MPa,and the scope had 2794 nodes.V-type wing of the acute angle point of convergence of the premises to bear the stress intensity followed.It was 0.31MPa,and the scope had 1953 nodes.V-type wing by the end of edge was the smallest for the 1.22?10-3MPa,and there was the scope of 1730 nodes. Ⅱ-shaped fixed nail stress concentrated at the central parts of tooth and the art on both sides of teeth,with maximum stress intensity of 1.68?10-2MPa,and there was the scope of 1146 nodes. Conclusion The reduction and fixation devices to load at the time of recovery deformation forces and mechanical characteristics adapted to Ni-Ti shape memory alloy material functions and super-elasticity completely,which meets the clinical needs.
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[Objective]To discuss the failure and countermeasure of Ni-Ti shape memory alloy fixer for treatment of limb fracture.[Method]A retrospective survey was performed in 259 cases with fracture treated by Ni-Ti shape memory alloy fixer.Eight cases of the fixer had been ruptured,risen,loosen after operation.[Result]The failure case of Ni-Ti shape memory alloy fixer for treatment of limb fracture were 8 case in 259 case.There were one case of ulna and two cases of femur fracture had be ruptured after the first operation,healing up after the second operation.The fixer has been risen of shoulder bone and femur fracture in each one and two cases of clavicle,the fracture has be malformation concrescence.One case of patella fracture was loosn after concrescence.[Conclusion]The requisite for Ni-Ti shape memory alloy fixer is needed for treatment of limb fracture,the right operation's condition,the best type and length are selected for different part,the convalescent exercise is regnired after operation to avoid failure of treatment.
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[Objective]To evaluate the effect of continuous dynamic pressure stress on experimental humeral fracture healing and to explore the role of COX-2 /PGE2 /cAMP signaling pathway in healing promotion induced by the special biomechanical condition.[Method]A total of 120 New Zealand rabbits were divided randomly into three groups: Group A,unilateral humeral fracture was fixed with shape memory connector(SMC),producing axial continuous dynamic pressure stress on fracture gap.Group B,fixed with 4-hole DCP,and Group C,fixed with SMC and gavaged with aqueous suspensions of celecoxib(3 mg/kg/day) after fracture.COX-1 and COX-2 mRNA expressions in fracture gap were determined by real-time RT-PCR at 0,3,7,14,21,28 and 56 days after operation,as well as the contents of PGE2 and cAMP were measured by radioimmunoassay(RIA).Bone-specific alkaline phosphatase(B-ALP) activity was determined by measuring p-nitrophenol and osteocalcin concentrations were measured using enzyme-linked immunosorbent assay(ELISA) for serial collected blood samples.Callus specimens fixed by formalin were used for histopathological examination.[Result]The COX-2 mRNA levels normalized with GAPDH mRNA as well as the contents of PGE2 and cAMP showed significant difference along with the 56-day period and also between the two internal fixations.Histopathological observation and determination of serum biochemical markers of bone formation revealed that the endochondral bone formation and the callus remodelling took place earlier in Group A than in Group B.The accelerated healing process and increased serum values of the bone formation markers induced by continuous dynamic pressure stress of SMC were inhibited by celecoxib,a specific COX-2 inhibitor.[Conclusion]The persistent dynamic longitudinal pressure stress produced by SMC contributed to endochondral bone formation and callus remodelling,resulting in an acceleration of fracture healing,which was considered to be closely correlated with the COX-2/PGE2/cAMP signal transduction pathway.
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Nickel titanium shape memory alloys(NiTi-SMA) are thought to be the promising biomaterials of biological osteosynthesis(BO) with regard to biomedical applications. However, a critical concern is the release of harmful Ni ions from the implants into the living tissues. And little is known about the influences of surface modifications on the biocompatibility of these alloys. The emphasis was focused on the recent developments, the related questions, surface treatments, future directionsin.
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Objective To study the effect and indication of the shape memory alloy(SMA)embracing fixator for treatment of clavicular fracture.Methods Thirty-six cases with clavicular fr acture were treated with SMA embracing fixator,of which 33we re middle third fracture and 3were between middle and lateral fracture.Results Thirty-five cases were followed up f or an average of 16months(from 8to 20months)and the average clinical healing was 2.8months(between 2and 4months).The results were evaluated accordi ng to Han Pingliang' s criteria and showed that 22cases wa s excellent,and 11cases was good.The excellent and good rate was 94.3percent.Conclusion The internal fixation with SMA embra cing fixator is less traumatic,stab le,safly effective to treat clavicular fracture.It is recommendable for treatment of clavicu lar fracture located in the middle an d proximal.The SMA embracing fixator must be pru dently used when the fracture is in th e curvature of clavicle.
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Objective:To design a new elastic implant-distraction apparatus. Methods:The implant-distraction apparatus consists of tow units, a TiNi shape memory alloy spring and an implant, made of pure titanium TA2.Spring was put into the hollow implant.After horizontal osteotomy, the implant-distraction device was placed into the partial edentulous area of mandible of 6 dogs to distract the alveolar bone.Results: The apparatus was manufactured.It could implement continual autodistraction and kept stable in the in vivo experiment. 10 weeks after application of the apparatus the transport bone segment was vertically augmented by 4.7 mm on average.Conclusion: The implant-distraction device is functional in distraction osteogenesis.
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To evaluate initial experience with shape memory alloy stent as an alterative to colostomy in patients with intestinal obstruction by colorectal cancer, forty four patients diagnosed with acute and chronic colorectal obstructions from malignant causes were subjected to stent placement. Among them 41 patients achieved clinical decompression. Thirty three cases died within 51～720 days and the other 5 cases were still alive without intestinal obstruction for 1～8 months. Our conclusions are shape memory alloy stent may be useful in the management of terminal or high risk surgical patients for palliative purposes instead of colostomy. Palliative management by stent placement combined with chemotherapy and immunotherapy might prolong the survival time of these patients. Placement of stent for acute colorectal bowel obstructions facilitates preoperative bowel preparation for surgical resection and obviates the need for fecal diversion or on table lavage.