| The femoral head is at the top of the femur and hip acetabular component, Hip is the ball joints, because the ball joint structure has the inherent stability, Hip femoral head is to maintain stability of the structure is under load and transfer hub. Femoral Head mainly composited by the cartilage, bone and dense cancellous bone, Cancellous bone is in the largest proportion, femoral head necrosis is normal seen in clinical. Femoral head necrosis of the femoral head will be so incompatible with the acetabulum, not sliding parallel to the surface along the surface or not to cut, femoral cartilage, the bone of cancellous bone and compression by the abnormal separation, disrupted the normal femoral head The stress distribution. Not by the normal femoral head of the cancellous bone trabeculae arrangement changed, its mechanical properties will also change, understand the normal and pathological femoral head viscoelastic rheological properties of artificial joints and new materials research, on the design of a new artificial joints is important.Given the author of the femoral head in normal and pathological stress relaxation, creep experimental study of normal and pathological viscoelastic properties of the femoral head comparison. The purpose of this study is to study the artificial joint materials for the design of artificial joints viscoelastic theoretical basis. Femoral head necrosis of the femoral head on the mechanical properties of viscoelastic effects, this study has not yet reported in the literature. First, stress relaxation methods and process(1) Materials1.1By normal laboratory specimens from eight normal people died of acute head trauma fresh male body, aged 19-28 years old, osteonecrosis of the femoral head were eight specimens were male, aged 58-70 years old. Normal group after the death of the deceased were 1-2 hours of anatomy remove the femoral head. Pathological specimens from older artificial joint replacement femoral head necrosis. Normal and pathological specimens removed after the group with normal saline soaked gauze wrapped, packed in sealed plastic bags placed in the preservation of water -20℃. In the experiment were removed after the thaw at room temperature in abeyance.(2) Measurement of samplesUniversal microscope to measure the height and diameter of specimens, specimens height of 34.2-42.6 mm, a diameter of 31.6-40.2 mm.(3) Experimental Equipmenta.Shimadzu AG-10TA control electronic universal testing machine. Load transfer through the load cell and strain through machines contingency unit transmission, the end of the experiment after the computer automatically output stress relaxation, creep data and curves. Control plane with the stress and strain rate and increased stress or strain to maintain constant functions.b.JXD-2 reading microscope(4) Statistical MethodsStress relaxation group and the experimental data normalized stress relaxation function of the computer data to mean±standard deviation, and statistical comparison of the experimental data with a linear regression analysis of the methods of regression analysis, that the regression coefficient c, d and a, b value.SPSS11.0 the data were statistically analyzed using information technology to the mean±standard deviation( x±S), a randomized design of single-factor analysis of variance (ANOVA), a method of matching DunnextT3 inspection, testing significantly in the level of P <0.05 or P <0.01.(5) The results of stress-relaxation groupa.Each group of samples compression stress relaxation From the normal group, the eight group pathological specimens compression stress relaxation experiments. The original sample size will be entered into the computer in the control machine. Bone flexibility mainly from entropy change, which does not exist only state with such organizations will be loading, unloading cycles change, it is necessary to repeatedly to achieve stable condition. The experimental damage to the greatest stress for the stress less than 30 percent of specimens repeatedly increase, unloading 20, pre-treatment experimentã€24-30】.The testing machine with adjustable temperature environment ranged in -35-250℃, the experimental simulation normal question, in 36.5±0.5℃under the temperature field. Specimens will be placed in the PH value of 7.4 saline bath, neutral position (vertical) slot on the test machine saline table. The experiment on the normal group, pathological group of eight femoral head specimens were 50% / min response rate of increase of strain imposed on the sample. When the normal response to 0.8707 percent, pathological strain group reached 0.646 percent, the normal stress reached 0.352 MPa, pathological stress group reached 0.352 MPa at the constant strain and stress with time change continually declined. Computer Program set from time t (0) began collecting data. S acquisition of a 0.6 per data collected 10 times every 10 S after a data acquisition, data acquisition 50; data were collected 100, 7200 S lasted. To set time, the printer automatically print out experimental data and curves.Second, creep equations and experimental process(1) MaterialsExperimental stress relaxation and creep experiments are non-destructive experiments done stress relaxation experiments were done 24 hours after the resumption of creep experiments, the femoral head to the normal and pathological specimens eight creep experiments. Creep test equipment, sample measurements, data processing, sample pre-treatment methods, and stress relaxation of the same.(2) the sample group and the experimental results of compression creep In this experiment, 0.5 GPa / min rate of increase the stress imposed on the samples often stress, when normal group reached 0.335 MPa stress, strain reached 0.625 percent, pathological group reached 0.336 MPa stress, strain to reach 0.296% at constant stress and strain with the Time change has been rising. To set the time automatically after the computer experimental data and output curves.Third, stress relaxation test resultsThe experimental results show that stress relaxation, whether normal or pathological initial group of 600 S greater stress relaxation, stress after the slow decline to 7200 when the S curve basic balance, stress relaxation curve is the relationship between the number change. 7200 S normal longitudinal stress relaxation is 0.209MPa, 7200 S pathological group longitudinal stress relaxation is 0.15MPa, 7200S normal stress relaxation was significantly higher than that of 7200S pathological group of stress relaxation (P <0.05). Forth, creep experimental resultsThe experimental results show that creep, whether normal or pathological initial group of 600 S creep larger changes, contingency rise slowly, reaching 7200 S curve, the basic balance creep, creep curve is a change in the index. Longitudinal normal creep volume for 7200S is 0.664%, pathological group of vertical creep 7200S is 0.392% for the normal group S creep in 7200 was significantly larger than morbid group (P <0.05).The initial contingency of the sick group creep experimental is 0.336%, is significantly less than the normal control group of initial response (P <0.05)... |
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