1998, 13(4):193-199. DOI: 10.3871/j.1004-7220.1998.4.199.
Abstract:Objective: To study the mechanical degradation characteristic of carbon fiber reinforced polyester(CFR/PE), polysulfone (CFR/PSF) and polyetheretherketone (CFR/PEEK) in. physiologicalenvironment. Methods : Compressive strength and modulus of three samples were tested fbllowingconditioning in physiological saline at 37℃, 65℃ and 95℃ for time periods from 0 to 256 days. Drysamples were used as controls. The percentage value of degradation of compressive strength andmodulus of each of the materials were calculated and compared. Results :No significant loss incompressive strength and modulus values of CFR/PEEK of the saline-saturated or dry controlsamples as a function of conditioning time or temperature. However, the compressive strength andmodulus of CFR/PE and CFR/PSF were significantly decreased as long as saline saturate. Thecompressive property value of CFR/PE and CFR/PSF are corelative to both time and temperature.Conclusionf There is satisfactory biomechanical stability of CFR/PEEK in physiologicalenvironment. It must be taken into consideration of materials' mechanical degradation propertieswhen CFR/PE and CFR/PSF be used in vivo as implants.
1998, 13(4):200-203. DOI: 10.3871/j.1004-7220.1998.4.203.
Abstract:This experiment is using a method of photoelastic stress analysis to analyse tibia- astragalusload bearing region, size and tibia - astragalus joint contact stress distribution situation when theankle joint at different nexangle. The results show: when the flex angle is at 7° the contact streedistiribution is largest and the press stress is the smallest with even disribution if the angle enlangto over 19°, the contact stress distribution area will be decreased and press stress will be increased.When the flex angle is over 43°, the contest stress distribution area will be decreasd significantlywhile the press stress will be increased. Basing on these propositionwe we understand, in view ofstress, when one wears high heel shoes, the best flex angle is 0°19°, If the flex is over 43°,theankle joint tends to get tatigue injury.
1998, 13(4):204-207. DOI: 10.3871/j.1004-7220.1998.4.207.
Abstract:For analysing the sole pressure distribution in the congenital dislocation of hip jont, we employedthe sole- pressure-distribution-video-image- system designed by the authors to messure thedynamic sole pressure in bilateral feet standing phase of a gait of the 7 patients with unilateralcongenital dislocation of the hip. By auto-pairing-control and statistical student's T testing, theresults showed: there are significant difference (p<0.05), in time, sole pressure, sole-pressure-timeintegrals in standing phase in diseased limb compared with the normal limb. The differences areclosely related to the pathophysiologic changes of the congenital dislocated hip joint. Due to theshortage of the limb and the dysfunction of the musculus gluteus medius caused by the dislocatedhip joint, the diseased limb compensate to and pathologically reach a new balanced state with thecontralateral normal one. By assessing the sole pressure, more knowledge of the congenitaldislocation of hip joint will be obtained to be a quantified index for assessing and evaluating theeffect of operation at the aspect of biomechanics.
1998, 13(4):208-214. DOI: 10.3871/j.1004-7220.1998.4.214.
Abstract:Seven fresh corpse knee joint were used to simulate excessive lateral patellar tilt by tighting thelateral patellar retinaculum, then the sagittal patellar osteotomy was performed at four differentosteotomy angles. The load was 200N. The contact area and pressure was measured at normalstatus, patellar tilting, 5 degree, 10 degree, 15 degree, 20 degree of osteotomy angle using Fujipressure sensitive film. The patellar tilt angle was gauged on patellar axial film of 45 degree of kneeflexion.The results showed that the contact area and pressure decreased in medial patellar surface,and increased in lateral patellar surface while patel1ar tilt occured. This alteration was mostprominent at 30 degree of knee flexion. After patellar sagittal osteotomy,the contact pressuredistribution of patellar tilt was improved markedly at more than 10 degree of sagittal patellarosteotomy angle. The 15 degree of osteotomy angle was the best to improve the distribution ofcontact pressue while patellar tilt existed. The results offered a reliable evidence for application ofsagittal patellar osteotomy and the selection of osteotomy angle.
1998, 13(4):215-221. DOI: 10.3871/j.1004-7220.1998.4.221.
Abstract:Using biomechanical experimental technics, Was analysed Cause of disease mechanism ofbiomechanim for unstable pelvic fracture, 6 specimens of human pelvic taken from fresh cadavers ofbrain injure after sudden death wasused in this study. To approach the biomechanical properties ofpelvis in normal Chinese adult, After appropriate management of the specimen, the loads in thesimulated test (stand position, side compression position,the ins and outs position) are 500N, 1000N.With strain electric measuring apparatus, the distribution of main stress and main strain, and theirdirection angles, ultimate load and shape of unstable pelvic were acquired. So the type of pelvicfracture and cause of disease mechanism for unstable pelvic fracture should be very complicated.Biomechanical parameters were provided the theoretical in c1inical application of differentinterfixation for vertically unstable pelvic fracture.
1998, 13(4):222-226. DOI: 10.3871/j.1004-7220.1998.04.226.
Abstract:Objective: To make biomechanical study on our newly develeped composite fixture- external fixatorand 3 compress perews for fem ornal neck fracture. Methods f Seven cadaveric hip joints were used inbiomechanical investigation. First. some data of normal hip joints were recorded, then, thespecimens were divided into two groups and control osteomy was performed to the model of thefYacture of femoral neck. The tested group was fixed by the composite fixture and control group wasfixed by only three compress screws, Results: the distribution of stress, strain, displacement,rotation and ultimate strength were recorded, the results of the composite fixture were found to bestronger thnn that of the control group. Conclusionf the stab1ility effect of the composite Iixture isbetter than that of the screws.
1998, 13(4):227-232. DOI: 10.3871/j.1004-7220.1998.4.232.
Abstract:In this study, femurs from 7 cadavers were fractured and then immobilized with wave plates andcommon compressive plates respectively. Comparisons wtre made on biomechanical properties ofthese two types of plates by means of axial compression, three-point bending and twisting test.Results of the studys showed that the wave plates are significantly different from the commoncompressive ones (P<0.01) in that the strength and rigidity of the wave plates are respectively 32%and 33% greater. Experiments proved that the stress resistance rate of the wave plates is 32.5% lessthan that of the common compressive plates,which contributes to the improvement of the stressconditions for bone remodelling and quickens the growth of the callus, the wave plates arepreferable to the common compressive plates, and hence it is in accord with the principle ofbiomechanics to adopt the wave plates. Wave plates were used in treating 147 patients with fractureof the femoral shaft. After 324 months of follow-up, the rate of excellent recovery turned out to be95.8%,indicating that the application of wave plates is a desirab1e method of internal fixation totreat fracture of the femoral shaft, and therefore deserves further popularization in clinical practice.
1998, 13(4):233-237. DOI: 10.3871/j.1004-7220.1998.4.237.
Abstract:In this study 32 cases of osteoporosis with intertrochanter fracture were divided into two groupsaccording to whether or not an effective stress stimulation applied on the fracture portion afteroperation. Bone cancellous specimens were taken for scanning electron microscopy. Results showed:at two weeks after fracture, the process of callus formation were similar in the two groups; but inthe remodeling stage, in the stress stimulated fracture group, collagen fibers formed well along thelong axis of trafg thin, perforaed and disconnected. The surface of cavity is smooth and few collagenfibers formed. The study indicated that in addition to good relocation and rigid fixation andeffective stress stimulation in the remodeling stage of fracture healing are essential to the treatmentof osteoporotic fracture.
1998, 13(4):243-247. DOI: 10.3871/j.1004-7220.1998.4.247.
Abstract:In this paper, we introduce a development of clinical L steel plate since 1994 year, which useddevice for the interfixation of unstability fracture 60 cases in the intertrochanteric hipfractures.Sixty cases were treated in this manner, a long-term follow-up 25 months in average revealedoverall excellent results. Bone union was obtained in 8.9 weeks with satisfaxtory function of thelimbs in all patiebts. We examined the effect of the L steel plate on strain and displacent in theproximal femur, using eight cadaver femora instrumented with six strain gauges along the medialand lateral cortices. Before and after experimentally created two-part and four-part fractures. Strainpatterns and screw motion were compaerd. With previously obtained values for a sliding hip screwdevice. the biomechanical characteristics of the two devices were loaded to 1800N.Experimentalresults showed, the L steel plate appear to offer distinct biomechanical adventage over the SHS inthe treatment of unstable intertrochanteric fractures.
1998, 13(4):248-282. DOI: 10.3871/j.1004-7220.1998.4.282.
Abstract:Under a reasonable predigesting of spinal column, Based on anatomy and biologic mechanics, thispaper proposes a mechanical model about the stability of spinal column keeping perpendicularity.Thereafter, we discuss the function and expression of subsystems of spinal column in detail. By anexample of computing simulation, the rationality of model is indicated. And then, combining themodel and a large number of cases, we analyze the reason that induces the difficulty of restorationin the case that the Centrum is extruded, and the problem that exists in traditional therapeutics. Inthe end, we reveal that it is necessary to make the spasmodic muscle recovered in order to make theCentrum restored.
1998, 13(4):253-257. DOI: 10.3871/j.1004-7220.1998.4.257.
Abstract:This paper discussed the several factor of the influenced stability of the fracture, gave the limit loadand permissoble load on fixed stability, and compared with the experiment, the formal in theconvenient in the personal computer.