Construction of platform on the three-dimensional finite element model of the dentulous mandibular body of a normal person / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To develop a method to construct a three-dimensional finite element model of the dentulous mandibular body of a normal person.</p><p><b>METHODS</b>A series of pictures with the interval of 0.1 mm were taken by CT scanning. After extracting the coordinates of key points of some pictures by the procedure, we used a C program to process the useful data, and constructed a platform of the three-dimensional finite element model of the dentulous mandibular body with the Ansys software for finite element analysis.</p><p><b>RESULTS</b>The experimental results showed that the platform of the three-dimensional finite element model of the dentulous mandibular body was more accurate and applicable. The exact three-dimensional shape of model was well constructed, and each part of this model, such as one single tooth, can be deleted, which can be used to emulate various tooth-loss clinical cases.</p><p><b>CONCLUSION</b>The three-dimensional finite element model is constructed with life-like shapes of dental cusps. Each part of this model can be easily removed. In conclusion, this experiment provides a good platform of biomechanical analysis on various tooth-loss clinical cases.</p>

A finite element analysis of the pelvic reconstruction using fibular transplantation fixed with four different rod-screw systems after type I resection / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The pelvis often needs to be reconstructed after bone tumor resection. A major challenge here for the orthopedic surgeons is to choose a method that gives the best performance which depends upon its biomechanical properties. In this study, a 3-dimensional finite element analysis (FEA) was used to analyze the biomechanical properties of reconstructed pelvis using fibula transplant fixed by four commonly used rod-screw systems.</p><p><b>METHODS</b>A total pelvic finite-element model including the lumbar-sacral spine and proximal femur was constructed based on the geometry of CT image from a healthy volunteer. Three-dimensional finite element models of different implants including fibula, rod and screw were simulated using ways of solid modeling. Then various reconstructed finite element models were assembled with different finite element implant model and type I resected pelvic finite element model. The load of 500 N was imposed vertically onto the superior surface of L3 vertebral body, and the pelvis was fixed in bilateral leg standing positions. FEA was performed to account for the stress distribution on the bones and implants. The pelvis displacement of the different rod-screw fixation methods and the maximum equivalent stress (max EQV) on all nodes and element were figured out to evaluate the advantages and disadvantages of different reconstructive methods.</p><p><b>RESULTS</b>Stress concentration in the fibula transplant was extremely high in the reconstructed pelvis, but could be substantially decreased by internal fixation, which partially transferred the stress from the fibula to the rod-screw systems. High stress concentration was also found in the implants, especially in the connection sites between screw and rod. Among the four methods of fixation, a double rod system with L5-S1 pedicle and ilium screws (L5-S1 HR) produced the best performance: least stress concentrations and least total displacement.</p><p><b>CONCLUSION</b>According to the stability and stress concentration, the method of L5-S1 HR fixation combined with fibula transplantation is better than other fixation methods in pelvic reconstruction after type I resection.</p>

Analysis of the pelvic stability after type I resection of iliac tumor / 中华外科杂志

<p><b>OBJECTIVE</b>To analyze the pelvic stability after type I resection of iliac tumor.</p><p><b>METHODS</b>Six adult cadaveric specimens were tested. The iliac subtotal resection models were established according to Ennecking's type I resection. Markers were affixed to the key region of the pelves. Axial loading from the proximal lumbar was applied by MTS load cell in the gradient of 0-500 N in the double feet standing state. Images in front view were obtained using CCD camera. Based on Image J software, displacements of the first sacral vertebrae (S1) of the resected pelves and the intact pelves were calculated using digital marker tracing method with center-of-mass algorithm.</p><p><b>RESULTS</b>Serious instabilities were found in the resected pelves. S1 rotational movements around the normal side femoral head of the resected pelvis were found. The average vertical displacement of S1 of the resected pelvis was (7 +/- 3) mm under vertical load of 500 newtons, which were 8.3 times compared to the intact pelvis. The average angle of S1 rotation around the normal side femoral head of the resected pelvis was (4.0 +/- 1.8) degrees, which were 12.5 times compared to the intact pelvis.</p><p><b>CONCLUSIONS</b>Biomechanical model of type I resection of iliac tumor are established. Essential pelvic reconstruction must be introduced because of the serious instability of the bone defection after tumor resection.</p>

Effect of calcaneocuboid arthrodesis on kinematics of foot: a cadaveric study / 中国矫形外科杂志

[Objective]To discuss the effect of the calcaneocuboid arthrodesis on kinematics of foot and its clinical signifi-cance.[Method]In 10 fresh-frozen foot specimens,limitation dorsiflexion, plantoflexion, abduction, adduction , eversion, inver-sion motion of foot were determined before and after calcaneocuboid arthrodesis under non-weight with moment of couple, bendingmoment, equilibrium dynamic loading.[Result]A significant decrease in the motion of foot was observed (P

Effect of calcaneocuboid joint arthrodesis on weight-bearing area of subtalar joint and its clinical significance:a cadaveric study / 中华创伤杂志

Objective To discuss the effect of the calcaneocuboid joint arthrodesis on the weight- bearing area of subtalar joint and its clinical significance.Methods Twelve fresh-frozen cadaver foot specimens were used for determination of weight-bearing area of the subtalar joint on foot and ankle neutral position,dorsiflexion,plantoflexion,adduction,abduction,inversion and eversion motion by means of pressure sensitive film before and after calcaneocuboid joint arthrodesis under weight loading.Results Weight-bearing area of the subtalar joint averagely increased for (32.54?7.45)% in all positions after calcaneocuboid joint arthrodesis,with statistical significance (P＜0.05).Conclusion Weight-bear- ing area of the subtalar joint increases after calcaneocuboid joint arthrodesis,which contributes to decrea- sing the pressure and increasing the stability of the subtalar joint.