Biomechanical Analysis on NiTi Memory Alloy Stent for Lumbar Interbody Fusion / 医用生物力学

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.

Theoretical Verification of Dynamic Lumbar Interspinous Process Stabilization Device with Memory Alloys / 中国医疗器械杂志

To find an effective method of minimally invasive treatment combining prevention and assistance in the middle zone of conservative treatment and fusion surgery for lumbar degenerative diseases, through the clinical effect observation and the advantage and disadvantage comparison of several commonly used lumbar interspinous dynamic stabilization systems, by analyzing the physiological structure, biomechanics and relevant data of lumbar interspinous processes, based on fully understanding of memory alloy materials, a new dynamic lumbar interspinous fixation device with a memory alloy material has been independently designed and researched, which can not only reconstruct the normal biomechanical characteristics of the lumbar spine and satisfy the normal activities of the human spine, but also avoid damage to the original structure and reduce the incidence of postoperative complications. In addition, the device can be used to optimize the current therapeutic methods. According to our research, the dynamic lumbar interspinous process stabilization device with a memory alloy has theoretically achieved satisfactory results, which can be used to overcome the shortcomings of the existing technology and is superior to the current several dynamic lumbar interspinous process stabilization systems.

Finite Element Analysis of Lumbar Interbody Fusion with Stent-Bone Granule-Absorbable Bone Cement / 医用生物力学

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.

Biomechanical Properties of the Modified Memory Alloy Internal Fixator for Separation of Pubic Symphysis / 医用生物力学

Objective To investigate biomechanical characteristics of the modified memory alloy internal fixator for separation of pubic symphysis. Methods The model of pubic symphysis separation injury was established based on 10 pelvic specimens. The control group was fixed with the dynamic compression plate after reduction, and the experimental group was fixed with the modified memory alloy internal fixator for separation of pubic symphysis after reduction. The biomechanical stability for two kinds of internal fixation was compared. Results There were no loosening and fracture of internal fixation in both groups. The displacement of pubic symphysis in horizontal, anterio-posterior and vertical direction in the experimental group was obviously reduced compared with the control group (P＜0.05). Conclusions Compared with the dynamic compression plate, the modified memory alloy internal fixator for separation of pubic symphysis shows better resistance to the tensile force against horizontal and anterio-posterior direction, as well as better resistance to the vertical shear force.

Nitinol memory alloy two foot fixator with autologous cancellous bone grafting for old scaphoid fracture and nonunion / 中国修复重建外科杂志

Objective: To summarize the effectiveness of nitinol memory alloy two foot fixator with autologous cancellous bone grafting in treating old scaphoid fracture and nonunion. Methods: Between January 2013 and January 2017, 11 patients of old scaphoid fracture and nonunion were treated with nitinol memory alloy two foot fixator and autologous cancellous bone grafting. All patients were male with an average age of 26.1 years (range, 18-42 years). The fractures were caused by sport in 3 cases, falling in 7 cases, and a crashing object in 1 case. The interval between injury and operation was 6-18 months (mean, 8.9 months). Postoperative outcome measures included operation time, fracture healing time, grip strength, range of motion (ROM) of flexion, extension, ulnar deviation, and radial deviation, Mayo score, visual analogue scale (VAS) score, and the Disabilities of the Arm, Shoulder, and Hand (DASH) score. Results: The operation time was 35-63 minutes (mean, 48 minutes). All incisions had primary healing with no infection and loosening or breakage of internal fixator. All patients were followed up 12-30 months (mean, 20.7 months). X-ray films showed that fracture healing was achieved in all patients with an average time of 15 weeks (range, 12-25 weeks). All internal fixators were removed after 10-12 months of operation (mean, 11.2 months). At last follow-up, the grip strength, ROMs of flexion, ulnar deviation, and radial deviation were superior to those before operation ( P<0.05), no significant difference was found in ROM of extension between pre- and post-operation ( t=0.229, P=0.824). There were significant differences in above indexes between affected and normal sides ( P<0.05). At last follow-up, the Mayo, VAS, DASH scores were also significantly superior to those before operation ( P<0.05). Conclusion: For the old scaphoid fracture and nonunion, Ni-Ti arched shape-memory alloy fixator and autologous cancellous bone grafting can obtain good effectiveness, which is an effective treatment.

Clinical application of nitinol memory alloy two foot fixator combined with Kirschner wire in treatment of trans-scaphoid perilunate dislocation / 中国修复重建外科杂志

Objective: To evaluate the effectiveness of nitinol memory alloy two foot fixator combined with Kirschner wire in the treatment of trans-scaphoid perilunate dislocation. Methods: Between September 2011 and October 2018, 17 patients with trans-scaphoid perilunate dislocation were treated with nitinol memory alloy two foot fixator and Kirschner wire. There were 12 males and 5 females, with an average age of 32.6 years (range, 23-52 years). The disease duration was 8 hours to 9 days, with an average of 6.5 days. The causes of injury included 6 cases of falling injury, 4 cases of traffic accident injury, 3 cases of stress injury of wrist caused by sports, 2 cases of violent injury of wrist caused by machine impact, 1 case of military training injury, and 1 case of other injury. One case was complicated with nerve injury. According to Herbert's classification, all the fractures were type B4. At 1 week before operation, 3 months, 6 months after operation and last follow-up, the wrist function was evaluated according to the Krimmer scale score. Results: All the 17 patients were followed up 10.5-48 months, with an average of 18.6 months. There was no loosening or infection of the internal fixator, no necrosis of the scaphoid and lunate. The periosteal dislocations of the patients were well reduced and the scaphoid fractures all healed. The healing time was 4-18 months, with an average of 11.3 months. The Krimmer wrist scores were 37.5±4.4, 61.3±7.2, 83.3±9.3, 87.3±8.2 at 1 week before operation, 3 months, 6 months after operation and last follow-up, respectively. The Krimmer wrist score at each time point after operation was significantly improved when compared with that before operation ( P0.05). At last follow-up, the Krimmer wrist function was excellent in 13 cases, good in 2 cases, fair in 1 case, poor in 1 case, and the excellent and good rate was 88.23%. Conclusion: Nitinol memory alloy two foot fixator combined with Kirschner wire in the treatment of trans-scaphoid periosteal dislocation has definite effectiveness, simple operation, and good recovery of wrist function after operation.

Shape memory alloy actuation of non-bonded piezo sensor configuration for bone diagnosis and impedance based analysis

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.

Biomechanical comparison of three kinds of fixation instruments for calcaneal osteotomy / 中国修复重建外科杂志

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.

Biomechanical study of nickel-titanium three-dimensional memory alloy mesh and autologous bone in treatment of canine tibial plateau collapse fracture / 中国修复重建外科杂志

Objective: To evaluate the biomechanical effect of a nickel-titanium (Ni-Ti) three-dimensional memory alloy mesh in treating a canine tibial plateau collapse fracture model and to lay a foundation for further experiments in vivo. Methods: Sixteen tibial plateau specimens of 8 adult Beagle dogs were harvested. Twelve specimens were taken to prepare canine tibial plateau collapse fracture models (Schatzker type Ⅲ) and randomly divided into groups A, B, and C, with 4 specimens in each group. Four normal tibia specimens were used as blank control group (group D). In groups A and B, the bone defects were repaired with Ni-Ti three-dimensional shape memory alloy mesh combined with autologous bone and simple autologous bone respectively, and fixed with the lateral plate and screw. In group C, the bone defect was directly fixed with the lateral plate and screw. By using a biomechanical tester, a progressive load (0-1 700 N) was loaded vertically above the femoral condyle. The maximum failure load was recorded and the stiffness was calculated according to the load-displacement curve. Results: The maximum failure loads in groups A, B, C, and D were (1 624.72±7.02), (1 506.57±3.37), (1 102.00±1.83), and (1 767.64±24.56) N, respectively; and the stiffnesses were (129.72±20.83), (96.54±27.05), (74.96±17.70), and (169.01±35.62) N/mm, respectively. The maximum failure load and stiffness in group A were significantly higher than those in groups B and C, but which were significantly lower than those in group D ( P<0.05). Conclusion: Ni-Ti three-dimensional memory alloy mesh combined with autologous bone can repair the Schatzker type Ⅲ tibial plateau collapse fracture, which has better biomechanical properties than simple autologous bone grafting.

Biomechanical study on nickel-titanium three-dimensional memory alloy mesh combined with autologous bone for living model of canine tibial plateau collapse fracture / 中国修复重建外科杂志

Objective: To evaluate the effect of nickel-titanium three-dimensional memory alloy mesh combined with autologous bone for living model of canine tibial plateau collapse fracture by biomechanical testing. Methods: Sixteen healthy 12-month-old Beagle dogs were randomly divided into 4 group, 4 dogs in each group. The dogs were used to establish the tibial plateau collapse fracture model in groups A, B, and C. Then, the nickel-titanium three-dimensional memory alloy mesh combined with autologous bone (the fibula cortical bone particles), the artificial bone (nano-hydroxyapatite), and autologous fibula cortical bone particles were implanted to repair the bone defects within 4 hours after modeling in groups A, B, and C, respectively; and the plate and screws were fixed outside the bone defects. The dogs were not treated in group D, as normal control. At 5 months after operation, all animals were sacrificed and the tibial specimens were harvested and observed visually. The destructive axial compression experiments were carried out by the biomechanical testing machine. The displacement and the maximum failure load were recorded and the axial stiffness was calculated. Results: All animals stayed alive after operation, and all incisions healed. After 1-3 days of operation, the animals could stand and move, and no obvious limb deformity was found. The articular surfaces of the tibial plateau specimens were completely smooth at 5 months after operation. No obvious articular surface collapse was observed. The displacement and maximum failure load of specimens in groups A and D were significantly higher than those in groups B and C ( P0.05). Conclusion: The nickel-titanium three-dimensional memory alloy mesh combined with autologous bone for subarticular bone defect of tibial plateau in dogs has good biomechanical properties at 5 months after operation, and has better axial stiffness when compared with the artificial bone and autologous bone graft.

Performed titanium locking plate versus nickel-titanium memory alloy embracing fixator in the treatment of multiple rib fractures / 中国胸心血管外科临床杂志

@#Objective     To compare clinical outcomes between the performed titanium locking plate and nickel-titanium memory alloy embracing fixator for the treatment of multiple rib fractures, and to select a better internal fixator for multiple rib fractures. Methods     A total of 206 consecutive patients with multiple rib fractures were admitted to Department of Cardiothoracic Surgery in Beijing Luhe Hospital of Capital Medical University from October 2011 to September 2016. According to different treatment strategies, the patients were divided into 2 groups: a performed titanium locking plate group (a titanium plate group, n=105) and a nickel-titanium memory alloy embracing fixator group (an embracing fixator group, n=101). There were 82 males and 23 females with a mean age of 46.5±9.7 years ranging from 23 to 65 years in the titanium plate group, and 83 males and 18 females with a mean age of 44.7±10.3 years ranging from 19 to 63 years in the embracing fixator group. The preoperative data, curative outcomes, visual analogue scale (VAS) and postoperative complications were compared between the two groups. Results     There was no statistical difference in the preoperative data between the two groups, and all patients successfully completed the operation. Compared with the embracing fixator group, the incision length and operation time were shorter, intraoperative bleeding and VAS score were less, and curative outcome was better in the titanium plate group. Conclusion     The performed titanium locking plate has a great advantage in the clinic, which can be preferred.

Rib's strapping-traction technology combined with memory-alloy ribs embracing fixator for multiple rib fractures under video-assisted thoracoscope / 中华创伤杂志

Objective To investigate the clinical efficacy of rib's strapping-traction technology using absorbable implants combined with memory-alloy ribs embracing fixator in treating multiple rib fractures under video-assisted thoracoscope.Methods A retrospective case control study was performed to analyze 178 patients with multiple rib fractures treated from January 2015 to June 2017.According to the operation method,all patients were divided into observation group (91 patients) and control group (87 patients).The observation group including 59 males and 32 females aged (39.7 ± 7.8)years adopted internal fixation by rib's strapping-traction technology using absorbable implants combined with memory alloy ribs embracing fixator under video-assisted thoracoscopic surgery.The control group including 56 males and 31 females aged (40.2 ± 6.9) years adopted internal fixation by conventional rib's clamping-traction technology using towel forcep combined with memory-alloy ribs embracing fixator under video-assisted thoracoscopic surgery.The incision length,single rib internal fixation time,number of internal fixation rib fractures,visual analogue scale (VAS) score on postoperative 1 d,postoperative chest drainage,postoperative hospital stay,and postoperative fracture healing were compared between the two groups.Results All patients were followed up for 3-30 months (mean,16.7 months).All operations were successful,with no case of thoracotomy.The observation group had shorter incision length [(4.3 ± 1.2) cm vs.(6.2 ± 1.7) cm] and single rib internal fixation time [(10.3±2.9)min vs.(14.1 ±2.3)min] than the control group (P＜0.05).There were no significant differences (P ＞ 0.05) between the two groups in number of internal fixation rib fractures [(5.7±.3.6) vs.(5.9±3.3)],postoperative chest drainage [(668.3 ±131.4)ml vs.(703.7±116.2)ml],postoperative hospital stay [(6.4 ± 1.8) d vs.(6.8 ± 1.7) d],the VAS score on postoperative 1 d [0-3 point,62％ vs.61％;4-6 point,38％ vs.39％],postoperative osteophyte formation rate [postoperative 1 month,97％ vs.95％;postoperative 3 months,100％ vs.100％].Stable chest walls and thoracic deformity recovery were seen in all patients,with no significant complications occurred.Conclusion Rib's strapping-traction technology using absorbable implants combined with memory-alloy ribs embracing fixator under video-assisted thoracoscope is convenient and has exact efficacy for multiple rib fractures,with advantage of shorter incision length and operation time over conventional thoracoscopic surgery,and thus is worthy of clinical application.

Clinical effect of cemented long stem prosthesis and memory alloy embracing fixator in the treatment of type B2 periprosthetic fractures / 中国综合临床

Objective To study the clinical effect of cemented long stem prosthesis and memory alloy embracing fixator in the treatment of type B2 periprosthetic fractures.Methods Fom April 2014 to April 2016,102 cases of peripheral B2 periprosthetic fractures patients were selected and randomly divided into bone cement long stem prosthesis revision surgery(group A) and revision of cemented long stem prosthesis combined with memory alloy embracing fixator(group B),each group with 51 cases.Clinical efficacy was evaluated according to Beals and Tower criteria,used Harris score to evaluate the hip the joint function,used the Visual Analogue Scale(VAS) score to evaluate the pain,after follow-up of 40 months,the clinical curative effect of 2 groups of patients,fracture healing time,complications and Harris score and VAS score were observed.Results The excellent rate of B group was significantly higher than that of A group,with statistical significance(90.2% vs.72.5%,χ2=5.239,P<0.05).Fracture healing time of group B was shorter than that of group A,with statistically significant ((10.2±2.5) weeks vs.(21.3±8.9) weeks,t=8.575,P<0.05).Harris the score of group B was higher than the group A,with statistically significant((89.9±13.5) points vs.(71.2±18.9) points,t=5.750,P<0.05).VAS score of group B was significantly lower than the group A,with statistically significant((1.23±0.25) points vs.(5.98±1.08) points,t=30.600,P<0.05).There were no complications such as infection,nonunion,loss of reduction and loosening of internal fixation in the 2 groups.Conclusion Revision of cemented long stem prosthesis combined with memory alloy embracing fixator is an ideal methods for the treatment of type B2 periprosthetic femoral fractures,which provides a good initial stability for fracture healing.

Biomechanical study of improved memory alloy embracing fixators in treatment of periprosthetic femoral fracture due to hip arthroplasty / 中华创伤杂志

Objective To study the mechanics of improved memory alloy fixators for salvage of periprosthetic femoral fracture (PFF) after hip arthroplasty in the elderly.Methods Thirty countrymen fresh cadaveric femurs with no pathological defect,fracture,deformity or tumor were randomly divided into experimental group and control group with 15 femurs in each according to the random number table.A model of Vancouver type B1 periprosthetic femoral fracture following hip arthroplasty was induced.The fracture was treated with modified memory alloy embracing fixators in experimental group;instead general memory alloy embracing fixators in control group.All specimens were tested biomechanically.Results Under the same mechanical loading,the two groups showed respective 30％ and 48％ maximum differences in stress value and displacement.Results in three-point bending test did not differ significantly between the two groups (P ＞ 0.05),but there were significant differences in axial compression and torsion test (P ＜ 0.05 or 0.01).Conclusion The improved memory alloy embracing fixators present better resistance to compression and torsion compared to the general fixators.

Clinical study of Ni-Ti shape memory alloy embracing fixator for multiple rib fractures / 临床外科杂志

Objective To summarize the experience of diagnosis,treatment and clinical effects of Ni-Ti shape memory alloy embracing fixator for severe chest trauma complicated with multiple rib frac-tures.Methods From January 2009 to June 2013,the clinical data of 148 cases with embracing fixator and 47 cases with non-internal fixation were retrospectively analyzed and compared.Results Internal fix-ation was superior to non-internal fixation in hospital stay,pain perception,mechanical ventilation time, pulmonary function recovery and complications(P<0.05).Conclusion Ni-Ti shape memory alloy em-bracing fixator is better than other conservative therapies in the treatment of multiple rib fractures and it's worthy of spreading.

Comparison of 60 multiple fractured ribs patients treated with surgical and non-surgical treatment / 安徽医科大学学报

To compare the effect of surgical and non-surgical treatment for multiple fractured ribs retrospectively, with 30 cases in each group. Patient's length of stay, visual analogue scale ( VAS) pain, independent ambulation time, cost of hospitalization, thoracoplasty degree and the lung ventilation function were evaluated. The results showed that VAS declined obviously in patients of surgical group, length of stay and independent ambulation time were shorter. Compared to the non-surgical group, the maximal voluntary ventilation increased significantly and ref-erral rib reduction was significantly better, but cost of the surgical group was higher. It's an effective treatment for using nickel titanium memory alloy embracing fixator in the treatment of multiple fractured rips, and is worthy of clinical application.

Influence from deformation history of NiTi shape-memory-alloy arch-wires on orthodontic force / 医用生物力学

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.

Retrograde Intramedullary Nailing for Distal Femur Fracture with Osteoporosis

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.

An ultrastructural observation of the effect of persistent stress on cancellous bone healing WAN / 中华创伤骨科杂志

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.

Three-dimensional finite element numerical analysis of the Ni Ti shape memory alloy clutching internal fixator / 医用生物力学

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.