The finite element analysis of a fractured tibia applied by composite bone plates considering contact conditions and time-varying properties of curing tissues

This paper addresses the use of composite bone plates in healing long-bone fractures such as transverse fractures of the tibia using finite element analysis, that takes into consideration contact conditions and material property variations of calluses in relation to the healing period. For the time-varying properties of calluses in relation to the healing period, stepwise material properties were imposed on the callus part based on the time elapsed, and the loading conditions were coupled with the callus properties based on the length of the healing period. The strain distributions at the fracture site were calculated according to the stacking sequence of the bone plate and healing time. The analysis results showed that composite bone plates with stacking sequences of [0]_12T for the Kevlar/BCP composites generated the most appropriate strain distributions at the fracture site during the early healing process.     

Analysis of dynamic strains in tibia during human locomotion based on flexible multibody approach integrated with magnetic resonance imaging technique

Bone is known to adapt to the prevalent strain environment while the variation in strains, e.g., due to mechanical loading, modulates bone remodeling, and modeling. Dynamic strains rather than static strains provide the primary stimulus of bone functional adaptation. The finite element method can be generally used for estimating bone strains, but it may be limited to the static analysis of bone strains since the dynamic analysis requires expensive computation. Direct in vivo strain measurement, in turn, is an invasive procedure, limited to certain superficial bone sites, and requires surgical implementation of strain gauges and thus involves risks (e.g., infection). Therefore, to overcome difficulties associated with the finite element method and the in vivo strain measurements, the flexible multibody simulation approach has been recently introduced as a feasible method to estimate dynamic bone strains during physical activity. The purpose of the present study is to further strengthen the idea of using the flexible multibody approach for the analysis of dynamic bone strains. Besides discussing the background theory, magnetic resonance imaging is integrated into the flexible multibody approach framework so that the actual bone geometry could be better accounted for and the accuracy of prediction improved.     

Injury tolerance of tibia for the car–pedestrian impact

Lower limbs are normally the first contacted body region during car–pedestrian accidents, and easily suffer serious injuries. The previous tibia bending tolerances for pedestrian safety were mainly developed from three-point bending tests on tibia mid-shaft. The tibia tolerances of other locations are still not investigated enough. In addition, tibia loading condition under the car–pedestrian impact should be explored to compare with the three-point bending. This work aims to investigate the injury tolerance of tibia fracture with combined experimental data and numerical simulation. Eleven new reported quasi-static bending tests of tibia mid-shaft, and additional eleven dynamic mid-shaft bending test results in the previous literature were used to define injury risk functions. Furthermore, to investigate the influence of tibia locations on bending tolerance, finite element simulations with lower limb model were implemented according to three-point bending and pedestrian impact conditions. The regressive curve of tibia bending tolerance was obtained from the simulations on the different impact locations, and indicated that tibia fracture tolerance could vary largely due to the impact locations for the car–pedestrian crash.     

126例胫腓骨骨折手术治疗临床体会

目的探讨126例胫腓骨骨折手术治疗的临床疗效。方法选取我院2008年6月至2009年6月我院收治的胫腓骨骨折患者126例,根据患者实际情况采取不同的手术方式,A组(46例)行外固定架手术,B组(38例)行加压钢板内固定手术,C组(42例)行带锁髓内钉固定手术,观察术后治疗效果。结果 3组术后疗效比较,A组优良率为87.0%,C组优良率为92.9%,2组显著高于B组71.1%,具有显著性意义,P<0.05;A组、C组愈合时间也明显短于B组,P<0.05,具有显著性差异。结论根据患者不同的损伤情况,应该采取不同的手术方式治疗胫腓骨骨折;手术固定方式应该首选带锁髓内钉固定和外固定支架固定。     

Safety assessment characteristics of pedestrian legform impactors in vehicle-front impact tests

This study investigated the characteristics of safety assessment results of front-area vehicle impact tests carried out using the Transport Research Laboratory (TRL) legform impactor and a flexible legform impactor (FLEX legform impactor). Different types of vehicles (sedan, sport utility vehicle, high-roof K-car, and light cargo van) were examined. The impact locations in the study were the center of the bumper and an extremely stiff structure of the bumper (i.e., in front of the side member) of each tested vehicle. The measured injury criteria were normalized by injury assessment reference values of each legform impactor. The test results for center and side-member impacts indicated that there were no significant differences in ligament injury assessments derived from the normalized knee ligament injury measures between the TRL legform impactor and the FLEX legform impactor. Evaluations made using the TRL legform impactor and the FLEX legform impactor are thus similar in the vehicle safety investigation for knee ligament injury. Vehicle-center impact test results revealed that the tibia fracture assessments derived from the normalized tibia fracture measures did not significantly differ between the TRL legform impactor and the FLEX legform impactor. However, for an impact against an extremely stiff structure, there was a difference in the tibia fracture assessment between the FLEX legform impactor and the TRL legform impactor owing to their different sensor types.