| Objective：1.Comparing the cross-sectional morphological differences with differentregions of rib level and different rib level of region, and to further clarify themechanical characteristics.2.Comparing the mechanical characteristics with different regions ofsame rib level and different ribs levels of section, a clearer understanding ofthe ribs mechanics distribution, and to forecast the rib fractures prone areas.3.After rib fractures, two internal fixation methods made the mechanicaltest respectively and compared the differences between them.Methods：1. Six (M) adult cadavers thorax specimens numbered. The ribs weredivided into three regions by37.5%,62.5%along its axial direction from ribnodules (0%) to the CJJ point(100%). Ribs were Cut off at the midpoint of therib length, anterior specimen used for measuring the mechanical test of formerregion; posterior specimen used for measuring the mechanical test of latterregion; the length of each rib was300mm. Rib specimens contained ribmidpoint were dissected to use for measuring the mechanical test of latterregion.4th,6th,8th ribs were dissected from the left and right corpse thorax,left ribs used for determining the mechanical test of former and latter region.Right ribs used for lateral region. Rib specimens numbered respectively,achieved a total of54segments of rib fragments.2. Rib fragments were placed on the electronic universal mechanicaltester, Span is set to100mm, load speed is set to2.5mm/min.Three-pointbending test was made between different level and region of the ribs until thespecimen destruction, recorded load and the maximum load when displacement were2,4,6,8,10,15,20mm, described and recorded in the load-deformation curve.3.Damage specimens after test were total of18segments,6segments of4th rib,6segments of6th rib,6segments of8th rib, Damage specimens weredivided into A,B groups, fixed with the fixed plates and titanium clips clawbone plate respectively, made the three-point bending test until the specimenyield and recorded relevant data on the same loading conditions.4. rib cross sections were removed with rongeur from the full-length25%,50%,75%three point (damage point) in ribs respectively about1cm thatdistricted from rib nodules (0%) to CJJ point (100%) were used for research,to measure the cross sectional high H, breadth B; former, posteri, the upperand lower cortical thickness T, cross-sectional area of total,cortex andmedulla. The elastic modulus,stiffness, bone stress, bone strain werecalculated according to the geometric and mechanical indicators.Results：1Mechanical test data of the normal rib1.1Different region with respect to rib level: For the maximum load,theformer region of4th rib were found to vary significantly than lateral andposterior region (P1=0.004, P3=0.000), there were no significant differencesbetween lateral and posterior region (P2=0.192) and the maximum load had aminimum value of78.24±3.99N; There were significant difference betweenlateral and posterior region (P2=0.006),The maximum stress of lateral regionhad a minimum value of27.46±3.99MPa. Maximum load and stiffnesswere significant difference among former and lateral, latter region(P<0.05),the minimum value of Maximum load and stiffness value were91.08±8.27N,0.56±0.14Nm2,respectively. Maximum load, Maximum stress, Modulus ofelasticity, stiffness on the fromer region of8th rib had a minimum value thanlateral,latter region, the difference was statistically significant(P<0.05).1.2Different rib levels with respect to region: Former region of8th rib hadthe lowest value of maximum load,modulus of elasticity than4th and6th ribs,the difference was statistically significant(F=16.035, P=0.001). The maximum load on lateral region of4th rib were found to vary significantly than6th and8th ribs(F=24.06, P=0.000) and had the lowest value of97.63±12.69N; themaximum stress value of6th rib existed significant differences than4th,8thribs (P1=0.004, P2=0.001), maximum stress value of6th rib had a maximumvalue0f37.85±6.66N. The maximum load, stiffness values of6th rib inlateral region respectively had the largest value of155.01±22.90N,1.21±0.17Nm2; Mechanical indicators were no significantly differencebetween4th and8th rib(P>0.05).2Geometrical test data of the normal rib2.1Different rib levels with respect to region:4th,6th,8th rib, the height ofcross section was the largest value at50%,and the Width was the largest valueat25%; upper, lower, inner and outer cortical thickness had increasing trendfrom75%-25%; the total cross-sectional area of75%,50%,25%keptconsistency. since the cortical cross-sectional area tended to increase from75%-25%. Medulla sectional area had decreasing trend from75%-25%.2.2Different region with respect to rib level: For the side of75%,50%and25%,the width of cross section had the largest value in the6th rib, the heightof cross section had increasing trend by the4th to8th rib; for the side of50%and25%,8th rib was significantly thinner than4th,6th rib at the upper andlower side of cortical thickness;4th rib were thinner than6th,8th ribs at theinner side cortex thickness. For the side of75%, there were no significantdifferences(P>0.05) at the upper and lower side of cortical thickness and varysignificantly(P<0.05) at the inner and outer side of cortical thickness amongthe4th,6th,8th rib. Cortical cross-sectional area had decreasing trend whilemedulla cross-sectional area had increasing trend; Total cross-sectional areabetween the4th and6th ribs at75%was significantly difference(P1=0.009);Medulla cross-sectional area had no significant difference6th rib issignificantly greater than4th,8th ribs at the medulla sectional area of25%,50%.3Test date of internal fixed group: For the maximum load and peakdeformation: Two ribs groups before fixed were found to vary no significantly (P>0.05) in the4th,6th,8th ribs; the claw plants groups before fixed and afterfixed had significantly differences(P<0.05) between4th,8th rib.In the6th rib,two groups had no significant difference(P=0.116,P=0.119).The rib boneplants groups before fixed and after fixed had significantly differences(P<0.05)between4th,8th ribs; there were no statistical difference in the4thrib(t=0.031,t=0.201). Two fixed groups had no significant difference in the4th,6th,8th(t>0.05).Conclusions：1.Differences of rib level or region, resulted in different geometricmorphometric data, and a certain regularity exists during the distribution.2.Differences of rib level or region,resulted in different mechanical date.Former region was more susceptible to break than lateral, posterior region;8thrib was easier to break with respect to4th,6th rib.3.Titanium clips fixed Plates and Claw shaped bone plate, two methodsfixed fracture ribs had no significant differences. |
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