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OBJECTIVE@#To study the self-tapping performance test method of self-tapping bone screws based on the YY/T 1505 standard.@*METHODS@#With reference to the method of YY/T 1505, various factors affecting the self-tapping force test was optimised, and the self-tapping force judgment method was improved.@*RESULTS@#The experimental results showed that the self-tapping force obtained by the improved self-tapping force judgment method has good repeatability and high stability of the experimental data. At the same time, the test results of other influencing factors indicated that the manufacturer should fully consider the test material and the size of the pre-drilled hole.@*CONCLUSIONS@#An improved method for judging the self-tapping force is helpful for the repeatability and stability of the test data. This study has certain significance referring to the self-tapping performance test of self-tapping bone screws.
Subject(s)
Biomechanical Phenomena , Bone ScrewsABSTRACT
Objective To make finite element analysis and compressive performance test on three-dimensional (3D) printed personalized poly-ether-ether-ketone (PEEK) condyle prosthesis, so as to analyze stress distribution characteristics and mechanical properties of the prosthesis, and to evaluate its clinical value and prospect. Methods The finite element models of PEEK condyle prosthesis, mandible and fixation screw were established by software such as CBCT, Mimics, Geomagic Studio, SolidWorks and ANSYS Workbench. The maximum mastication force was applied, and the maximum stress of the condyle prosthesis and screw, as well as the stress and strain of the mandible were recorded. In order to simulate the actual clinical situation, a special fixture was designed to test compression performance of the condyle prosthesis prepared by the fused deposition modeling (FDM) and selective laser sintering (SLS) at the rate of 1 mm/min. Results The peak stress of the PEEK condyle prosthesis was 10.733 MPa, which was located at the back of the condyle neck. The peak stress of 5 fixing screws was 9.707 5 MPa, which appeared on the 2# and 5# screws near the trailing edge of the mandibular ascending branch. The peak stress of both the prosthesis and the screw was smaller than its yield strength. The maximum pressure of the condyle prosthesis prepared by FDM and SLS was (3 814.7±442.6) N and (1 193.970±260.350) N, respectively. Compared with the SLS preparation, the FDM prepared prosthesis not only had higher compression strength but also better toughness. Conclusions The 3D printed personalized PEEK condyle prosthesis shows uniform stress distributions and good mechanical properties, which can provide the theoretical basis for PEEK as reconstruction material for repairing temporomandibular joint.
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Objective To evaluate biomechanical strength of locking compression plate (LCP) for fixation of periprosthetic proximal femur fractures (PPFF). Methods Eight matched pairs of Vancouver type B1 adult cadaveric PPFF specimens were fixed with the LCP and the inverted distal femoral less invasive stabilization system (LISS), respectively. Four bicortical locking screws (LCP group) and four unicortical locking screws were used to the length of prosthesis stem, and four double cortical locking screws were used to fix the distal end of the fracture in two groups, the distance from the locking screws to the fracture were also equal. The maximum bending load, maximum bending displacement, bending stiffness, maximum torque, maximum torsional angle and torsional stiffness of two groups in four-point bending test and torsion test were compared and analyzed. Results The maximum bending load, maximum bending displacement and bending stiffness of LCP group were all larger than those of LISS group, but the difference was not statistically significant (P>0.05). The maximum torque, maximum torsional angle and torsional stiffness of LCP group were obviously larger than those of LISS group，and there was a statistical difference between two groups (P<0.05). Conclusions The stiffness of anti-torsion with LCP is significantly better than that with LISS. Consequently, LCP has better biomechanical stability for PPFF.
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experimental test for mechanical properties of a vascular stent is a main method to evaluate its effectiveness and safety, which is of great significance to the clinical applications. In this study, a comparative study of planar, V-groove and radial compression methods for the radial support property test were performed, and the effects of compression rate and circumferential position on the test results were conducted. Based on the three-point bending method, the influences of compression rate and circumferential position on flexibility were also explored. And then a best test proposal was selected to evaluate the radial support property and flexibility of the three self-designed stents and the comparative biodegradable vascular stent (BVS) (BVS1.1, Abbott Vascular, USA) with different outside diameters of 1.4 mm, 1.7 mm and 2.4 mm. The results show that the developing trends of the compression load with the compression displacement measured by the three radial support property test methods are the same, but normalized radial force values are quite different. The planar compression method is more suitable for comparing the radial support properties of stents with different diameters and structures. Compression rate has no obvious effect on the testing results of both the radial support property and flexibility. Compression circumferential position has a great impact on testing radial support property with the planar or V-groove compression methods and testing flexibility with three-point bending method. The radial support properties of all the three self-designed stents are improved at a certain degree compared to that of the BVS stent. The study has better guide significance and reference value for testing mechanical properties of vascular stents.
Subject(s)
Absorbable Implants , Mechanical Phenomena , Polymers , Prosthesis Design , Stents , Stress, MechanicalABSTRACT
In the research of artificial joint biomechanics, it is a common method in the world to evaluate the biomechanical properties of the implanted fixtures through experiments . The domestic research started late, and the corresponding testing methods were lacking. There is still no unified standard. In this paper, a complete hardware test system was designed and built around the existing mechanical testing machine, including:binocular vision catcher, torque bearing clamp, film pressure sensor and so on. The system can accurately measure the relative motion angle value, external torque value, and inter pressure value of each joint. It has some reference significance for the forming and standardization of the artificial joints' evaluation system.
Subject(s)
Biomechanical Phenomena , Joint Prosthesis , Motion , Pressure , TorqueABSTRACT
OBJECTIVE: To explore the efficacy and safety of the axial load mechanical testing for removing external fixator. METHODS: Between January 2014 and August 2015, 27 patients with tibia and fibula fractures caused by trauma underwent an external fixation. Of 27 patients, 21 were male and 6 were female with the average age of 45 years (range, 19-63 years), including 7 cases of closed fracture and 20 cases of open fracture. X-ray film results showed spiral unstable fracture in 4 cases and comminuted unstable fracture in 23 cases. All patients underwent an external fixation. Bone nonunion occurred in 3 cases because of infection, and bone nonunion combined with bone defect occurred in 1 case, who received tibial osteotomy lengthening surgery. When X-ray film showed continuity high density callus formation at fracture site, axial load mechanical test was performed. If the axial load ratio of external fixator was less than 10%, the external fixator was removed. RESULTS: At 21-85 weeks after external fixation (mean, 44 weeks), axial load mechanical test was performed. The results showed that the axial load ratio of external fixation was less than 10% in 26 cases, and the external fixator was removed; at 6 weeks after removal of external fixator, the patients could endure full load and return to work, without re-fracture. The axial load ratio was 14% in 1 case at 85 weeks, and the X-ray film result showed that fracture did not completely heal with angular deformity; re-fracture occurred after removing external fixator, and intramedullary fixation was used. CONCLUSIONS: External fixator axial load mechanical testing may objectively reveal and quantitatively evaluate fracture healing, so it is safe and reliable to use for guiding the external fixator removal.
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OBJETIVO: Analisar as características morfométricas e mecânicas dos músculos sóleo e gastrocnêmio após imobilização na posição de encurtamento. MÉTODO: 20 ratos Wistar (250 ± 20g) foram distribuídos igualmente em grupos imobilizado e controle. A imobilização foi realizada no membro posterior esquerdo por meio de órtese de resina acrílica, com a articulação do tornozelo em flexão plantar máxima. Após 7 dias da imobilização, a massa muscular, número e comprimento de sarcômeros em série, área das fibras musculares, densidade de área de tecido conjuntivo intramuscular e força máxima de ruptura do tríceps sural foram avaliados. Os dados foram analisados pela ANOVA e teste de Tukey (p< 0,05). RESULTADOS: O músculo sóleo imobilizado apresentou alterações em todas as variáveis morfométricas analisadas, enquanto que, no músculo gastrocnêmio, algumas adaptações não foram observadas. Na análise do ensaio de tração, o grupo imobilizado apresentou redução de 20 por cento na força máxima de ruptura muscular. CONCLUSÃO: Os resultados deste estudo revelaram que curto período de imobilização promove alterações nos parâmetros morfométricos das fibras musculares, com repercussões na mecânica muscular. Tais resultados permitem sugerir a necessidade da reabilitação em músculos submetidos à imobilização, mesmo a curto prazo, para que a mesma possibilite o retorno precoce das características musculares normais.
OBJECTIVE: to analyze the morphometric and mechanical characteristics of the soleus and gastrocnemius muscles after immobilization in a shortened position. METHODS: 20 Wistar rats (250 ± 20g) were divided equally into immobilized and control groups. The left hind limb was immobilized by means of an acrylic resin orthosis, with the ankle joint at maximum plantar flexion. After seven days of immobilization, the muscle mass, number and length of sarcomeres in series, muscle fiber cross-sectional area, density of the intramuscular connective tissue area and tensile strength of the triceps surae muscle were evaluated. The data were analyzed by the ANOVA and Tukey tests (p< 0.05). RESULTS: The immobilized soleus muscle presented changes in all the morphometric variables analyzed, while some of these changes were not observed in the gastrocnemius muscle. Analysis of the traction test showed that the immobilized group presented a 20 percent decrease in the maximum tensile muscle strength. CONCLUSION: The results from this study showed that short-term immobilization causes changes to the morphometric parameters of the muscle fibers, with repercussions on muscle mechanics. These results suggest the need for rehabilitation of muscles subjected to immobilization, even if only for a short period, in order to achieve early recovery of normal muscle characteristics.
Subject(s)
Rats , Animals , Immobilization , Muscle, Skeletal , Rats, WistarABSTRACT
Objective: To study the relationship between the depth and width of cavity design and to analyze the tendency of breaking load in preparations. Methods:Plaster models of mandibular first molar were prepared and magnified by 150%. Cavity on occlusal surface was designed and prepared in a cylinder shape with the depth(mm) of 3.0,4.5 and 6.0,and diameter(mm) of 3.0,4.5 and 6.0,respectively. 8 cavity samples were prepared for each design. The breaking load of the tooth models before and after restoration with self-curing resin was measured by Instron tester.Mechanical model static load test and two variable regression analysis were applied to study the mechanical property of the cavity design. Results:Before restoration, with the increase of depth and diameter, the incidence rate of tooth fracture increased. The width was the main factor. After restoration, the load was undertaken by restoration directly, and could be transfered to tooth and periodontal tissue through restoration uniformly. When the diameter of the cavity increased, the diameter of restoration also increased, and thus decreased the load on local structure of the tooth. With two-regression analysis, the regression equation and regression curve were obtained. Conclusion: The fracture of tooth before and after restoration is related to the diameter and depth of cavity design in cylinder shape. The regression equations of changing tendency of breaking load (Y) in preparation caused by the change of depth(X 1) and diameter(X 2) of cavity obtained by two-regression analysis are presented as follows: Before restoration: Y=1593.317-51.178 X 1-79.489X 2.After restoration:Y=1802.928 -192.461X 1+225.128X 2.
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Objective To prospectively assess the predictive power of centralization phenomenon in the curative effect of automated PLD.Methods The survey population was consisted of 109 patients with inclusion heraiation demonstrated by CT/MRI,74 men and 35 women with average age of 43.1 years(17～75 years). All were complained of low back pain,with varying degrees of lower extremity pain and altered sensation, lasting for more than 2 months;including one symptomatic disc in 99 patients and two symptomatic discs in 10 patients.Patients were undergone dynamic mechanical spinal test and reported whether the test would aggravate their pain.The assessment included forward flexion,extension,rotation of the trunk to the right and left, rotation to the left with fight extension,rotation to the fight with left extension,and whether straight leg raising in the supine position would aggravate back pain or leg pain.Symptom resposes were categorized into three groups:centralization group(CG),partial-centralization group(PCG)and noncentralization group(NCG). Centralization of pain is the progressive retreat of the most distal extent of the referred or radicular pain toward or to the lumbar midline.Noncentralization of pain is the peripheralization of pain in one or more directions, and no change in the distal-most pain location or intensity.All patients received a single therapy with PLD. Results A follow-up of 109 patients for 3 to 6 months,including 46 cases with 24 as exellent and 22 as good reaching 100% of excellent good rate in CG by MacNab standards;43 cases with 5 as exellent,29 as good,9 as fair and poor,with total effective rate of 79.1% in PCG.Twenty cases of NCG symptoms showed no improvement and therefore surgery was considered.Conclusions Centralization phenomenon occurrence during initial mechanical evaluation is a very accurate predictor for successful PLD outcome.Nonoccurrence of centralization would accurately predict poor PLD outcome and thus helpful as early predictor of the need for surgical treatment.