ABSTRACT
Objective To compare the stress and its distribution between our self-designed new assembly of locking compression plate (NALCP) of low elastic modulus versus conventional locking compression plate (LCP) in fixation of femoral comminuted fractures.Methods Six pairs of cadaveric femur were used to create models of middle femoral comminuted fracture.The femoral fracture models were fixated respectively by NALCP of Ti2448 with low elastic modulus (E =30 Gpa) (NALCP group) and conventional LCP of Ti-6Al-4V with high elastic modulus (E =110 Gpa) (LCP group).Axial and torsion loads were applied on the models in the 2 groups to simulate those on one leg when a person slowly walks.The relative maximum displacements on the X,Y and Z axes of fracture fragments,and the maximum and average strains of the plate were recorded in the 2 groups.Nephograms of strain distribution were made for the 2 groups.The results of fatigue test under axial loads were recorded for NALCP group.Results Both the axial and torsion loading tests showed significantly larger principal and average strains in NACLP group than in LCP group (P ＜ 0.05).However,there were no significant differences between the 2 groups in the relative maximum displacements of fracture fragments on X,Y or Z axis (P ＞ 0.05).The plate strain nephograms for the 2 groups showed consistent strain distributions.The plates in NALCP group survived 1,000,000 fatigue tests under axial loads,without any deformation,loosening or breakage.Conclusion As our NALCP of low elastic modulus may be better in stress transmission and distribution,it can effectively reduce the effect of stress-shielding and promote bone healing.
ABSTRACT
Objective To compare the biomechanical characteristics of new assembly of locking compression plate (NALCP) and locking compression plate (LCP) in internal fixation of femoral shaft comminuted fractures.Methods The preparation of a femoral shaft wedge fracture model (AO type 32-C2.1),six pairs of (12) femoral specimens were collected and divided into two groups randomly,with six in each group.The Group A was made up of the new assembly of locking compression plate fixation model (NALCP),and Group B the locking compression plate fixation model (LCP).The biomechanical properties of steel plates in two groups were tested by axial loading and torsional loading tests.The relative maximum displacement of fracture blocks in two groups on the X,Y and Z axes (the coronal axis was set as X axis,through the medial and lateral femur;the transverse axis was set as Z axis,through the femoral intercondylar fossa,perpendicular to the X axis;the sagittal axis was set as Y axis,perpendicular to the X and Z axis),the maximum strain,and the average strain of the steel plate were recorded.Strain distribution nephogram was produced,and the axial loading fatigue test results of Group A were recorded.Results Axial loading test:the relative maximum displacement of fracture in Group A on X,Y and Z axis were smaller than those in Group B (P ＜0.05 or 0.01);the main strain of Group A was greater than that of Group B (P ＜0.01);there was no significant difference in the average strain between Group A and Group B (P ＞ 0.05).Torsional loading test:The relative maximum displacement of fracture in Group A on X and Z axis was smaller than that of Group B (P ＜ 0.01);there was no statistically significant difference between the two groups on the Y axis (P ＞ 0.05);the main strain of plate in Group A was greater than that in Group B (P ＜ 0.01);there was no statistically significant difference in the average strain between Group A and Group B (P ＞ 0.05).There was no obvious difference in strain distribution between the two groups.In Group A,the fatigue test of axial cyclic loading was performed for 1 million times,and the NALCP was intact without deformation,loosening,or rupture.Conclusion NALCP can provide strong mechanical stability for comminuted femoral fracture.The design of bridge steel plate is reasonable,which can effectively avoid stress concentration,reduce the stress shielding of steel plate,and facilitate bone healing.