Analysis Of Human Femoral Curvature And Biomechanical And Clinical Study Of Compression Fixation For Distal Femoral Fractures

Femur is the longest and strongest long bone in human body,which is about 1/4 of the human height.The shape of human femur is not straight,and its curvature and angle are of individual differences.Even after adulthood,the curvature and angle of human femur will change with aging,which is regular.However,few studies concerned the parameters of femoral curvature in Chinese people.More importantly,regarding the treatment of femoral fractures,the application of conventional fixators usually cannot fully adapt to the personalized femoral curvature and angle.The incidence of postoperative internal fixation failure,nonunion and malunion caused by local stress shielding remains high.In view of the above problems,we have systematically studied the dynamic deformation of bones in various parts of the human body,and put forward the law of bone dynamic deformation.In order to identify the age-related changes of femoral curvature and the related factors,and to provide data to design the femoral internal fixation of Chinese people.The purpose of this study was to investigate the sagittal femoral bowing(s FBA),the coronal femoral bowing angle(c FBA),the sagittal femoral cortical index(s FCI)and the coronal femoral cortical index(c FCI)of Chinese from the mature stage to the elderly stage.Whether the four morphological parameters are related to age and whether FCI is related to s FBA and c FBA are two practical problems.Distal femoral fractures(DFFs)are a kind of uncommon but severe fractures because about half of DFFs are associated with intra-articular fractures of the knee.Type C DFFs is a complex complete intra-articular fracture.The coronal width by internal fixation for the DFFs is an important factor affecting the long-term curative effect of knee.At present,femoral intercondylar width cannot be accurately reduced by the minimally invasive reduction technology.Bilateral locking compression plate(LCP)fixation is one of the common methods for the treatment of type C DFFs.However,the compression effect of locking screws or lag screws cannot fully restore the width between the medial and lateral condyles of the distal femur.In order to solve the above problem,we invented a slot-designed compression bolt(SCB).In order to further clarify the internal fixation effect of the SCB for the treatment of type C DFFs,our study first compared the biomechanical stability of the different reduction degrees fixed by SCB for DFFs,and then compared the biomechanical characteristics between SCB and ordinary locking screws for the treatment of DFFs.Surgical site infection(SSI)is a major challenge for most orthopedic and trauma surgeons after the clinical treatment of distal femoral fractures.To provide data support for the prevention and monitoring of postoperative infection after distal femoral fractures.We prospectively studied the epidemiology and related risk factors of the SSI after open reduction and internal fixation of distal femoral fractures.Part One Age-related dynamic deformation of the femoral shaft and associated osteoporotic factors: a retrospective study in Chinese adultsObjective: The purpose of this study was to determine whether morphological parameters of the femoral shaft are in age-related deformation and identify correlations between parameters of femoral cortical thickness and femoral shaft bowing.Methods: 120 patients(mean 50 years,range 18?104 year)who had received standard long-standing anteroposterior and femoral lateral radiographs from October 2016 to October 2019 were included in this retrospective study.The sagittal femoral bowing angle(s FBA),sagittal femoral cortical index(s FCI),coronal femoral bowing angle(c FBA)and coronal femoral cortical index(c FCI)were measured by two orthopaedists separately.All the participants' demographic data,including age,sex,body laterality,height,and weight,were collected.The Student's t-test,Mann–Whitney U test,two-way ANOVA,Pearson correlation and multiple linear regression were used in the statistical analysis.Results: The mean age of the male and female participants was46.95±15.25 and 52.22±15.61 years,respectively.Two-way ANOVA revealed that females had a significantly lower s FCI than males at the right side(P<0.05).There were no significant interactions between sex or body laterality and the s FBA,c FBA,s FCI and c FCI groups(P>0.05).Pearson correlation revealed that s FCI was strongly correlated with s FBA(r=-0.535,P<0.05)and c FBA(r=-0.535,P<0.05).Multiple linear regression analysis demonstrated that both age(?=0.304 and 0.308 respectively)and s FCI(?=-0.322 and-0.414respectively)were two independent predictors associated with s FBA and c FBA respectively.Conclusions: The femoral shaft bowing of the Chinese population were positively correlated with ageing,whereas the sagittal femoral cortical thickness negatively correlated with ageing.A high FBA occurred in femoral shafts with a low s FCI,which revealed that femoral shaft bowing was associated with femoral cortical thickness.During femur-related surgery in older patients,more attention should be paid to these femoral morphological changes.Part Two The comparation on the biomechanical stability from different degree of reduction after internal fixation by the slotdesigned compression bolt for distal femoral fracturesObjective: To compare the biomechanical stability from different degree reduction after internal fixation by the slot-designed compression bolt for distal femoral fractures.Methods:1.Thirty-six adult male knee specimens treated with formalin were used to make the C1 fracture model of distal femur.When the separated displacement of distal femoral fractures was 0 mm,1 mm,2 mm and 3 mm,the slot-designed compression bolts were used to assist bilateral locking compression plate for internal fixation.The axial ballast test,horizontal torsion test and cyclic axial load test were performed on the four groups of fracture models.2.The range of pressure load of biomechanical machine was from 100 to1000 N,the axial displacement of each group was recorded when the axial ballast load was 400 N,700n,1000N;the torsional stiffness of each group was calculated when the horizontal torsion was 5;the axial displacement of each group wasfinally recorded when the cyclic axial load was 100-400 N,100-700 N and 100-1000 N.Each model was measured 10 times for a test.3.The Shapiro Wilk test was used to determine whether the data was conformed to normal distribution.For data conforming to normal distribution and variance uniformity,the mean ± standard deviation(x ± s)was used.The one-way ANOVA was performed to compare the four groups,and Tukey test was used for the comparison between the two groups.Results: In the axial ballast test,there was no significant difference of the axial displacement between the 0 mm group and the 1 mm group.The axial displacement of the groups with 2 mm and 3 mm reduction gap was significantly higher than that of the groups with 0 mm and 1 mm.In the horizontal torsion test,with the increase of the reduction gap,the torsional stiffness of the system gradually decreased when the reduction gap was 5°clockwise,and the torsional stiffness differences between the each of the reduction groups were statistically significant.During the cyclic axial load test,there was no significant difference in the cyclic axial displacement between the 0 mm and the 1 mm group at the levels of 100-400,100-700 and100-1000 N.The cyclic axial displacements of the groups with 2 mm and 3mm reduction gaps under three loads were significantly higher than those of the groups with 0 mm and 1 mm.Conclusions: The reduction gap between the distal femur fracture blocks affected the biomechanical stability around the distal femur.The increase of the reduction gap will result in the decrease of the vertical stiffness and torsional stiffness of the bilateral locking compression plate assisted by slot-designed compression bolts for internal fixation.Anatomical reduction of distal femur fracture was the best way to recovery of physiological state.When the displacement gap of the fracture was 0-1mm,strong internal fixation could keep stable.However,the displacement gap over 2mm would make the significantly decreased system stiffness of the distal femur with internal fixation.Part Three Comparative study on biomechanical characterist-ics and stability of slot-designed compression bolt and locking screw for the treatment of distal femoral fracturesObjective: To compare the biomechanical characteristics and stability of slot-designed compression bolt and locking screw for the treatment of distal femoral fractures.Methods:1.Thirty-six adult male femoral specimens were used to make C1 distal femoral fracture models.According to the random number table,the fracture models were divided into two groups: the bilateral locking compression plate combined with locking screw group and the bilateral locking compression plate combined with slot-designed compression bolt group.The vertical ballast test,horizontal torsion test and cyclic axial load test were carried out.2.The range of pressure load of biomechanical machine was from 0 to1000 N.The axial displacement of the two groups was recorded when the axial ballast load was 400,600,800 and 1000N;the torsional stiffness of the two groups was tested when the horizontal torsion was 5°;the axial displacement of the two groups was recorded when the cyclic axial load was 100-400,100-600,100-800 and 100-1000 N.Each specimen was measured 10 times for each test.3.The Shapiro Wilk test was used to determine whether the data was normal distribution.For the data in line with normal distribution and homogeneity of variance,One-way ANOVA was used for the comparison of the four groups,and Tukey test was used for the comparison of each two groups.Results: In the axial load test,when the axial load was 400 N,there was no significant difference of the axial stiffness between the slot-designed compression bolt group and the locking screw group(P > 0.05).When the axial load increased to 600,800 and 1000 N,the axial stiffness of the slot-designed compression bolt group was significantly higher than that of the locking screw group.In the horizontal torsion load test of 5° clockwise,there was no significant difference in the torsional stiffness between the slot-designed compression bolt group and the locking screw group.In the cyclic axial load test,the compression displacement of the slot-designed compression bolt group was significantly lower than that of the locking screw group at the levels of 100-400,100-600,100-800 and 100-1000 N cycles.Conclusions: Compared with locking screw,the slot-designed compression bolt assisted bilateral locking compression plate fixation of distal femoral fractures was more axially stable,and had higher system stiffness.The slot-designed compression bolt had the advantages for minimally invasive operation and intra-articular compression.Part Four Incidence and predictors of surgical site infection after distal femur fractures treated by open reduction and internal fixation: a prospective single-center studyObjective: There remain limited data on the epidemiological characteristics and related predictors of surgical site infection(SSI)after open reduction and internal fixation(ORIF)for distal femur fractures(DFFs).We designed this single-centre prospective study to explore and forecast these clinical problems.Methods: From October 2014 to December 2018,364 patients with DFFs were treated with ORIF and followed for complete data within one year.Receiver operating characteristic(ROC)analyses,univariate Chi-square analyses,and multiple logistic regression analyses were used to screen the adjusted predictors of SSI.Results: The incidence of SSI was 6.0%(22/364): 2.4%(9/364)for superficial SSIs and 3.6%(13/364)for deep SSIs.Staphylococcus aureus(methicillin-resistant S.aureus in 2 cases)was the most common pathogenic bacteria(36.8%,7/19).In multivariate analysis,parameters independently associated with SSI were: Open fracture(OR: 7.3,P = 0.003),drain use(OR:4.1,P = 0.037),and incision cleanliness(OR: 3.5,P = 0.002).An albumin/globulin(A/G)level ? 1.35(OR: 0.2,P = 0.042)was an adjusted protective factor for SSI.Conclusions: The SSI after ORIF affected approximately one in 15 patients with DFFs.The open fracture,drain use,high grade of intraoperative incision cleanliness,and preoperative A/G levels lower than 1.35 were significantly related to increasing the risk of post-operative SSI after DFFs.We recommended that more attentions should be paid to these risk factors during hospitalization.