Objective To evaluate clinical efficacy of four-claw Ti-planes for internal fixation of multiple rib fractures and flail chest. Methods Clinical data of 93 patients with multiple rib fractures and flail chest who were admittedto Shanghai Pudong Hospital from December 2011 to November 2012 were retrospectively analyzed. There were 78 male and 15 female patients with their age of 20-80 years. All the patients received internal fixation of rib fractures using four-clawTi-planes. Finite element modeling and analysis were performed to investigate biomechanical behaviors of rib fractures after internal fixation with four-claw Ti-planes. Results The average number of rib fractures of the 93 patients was 5.9±2.1，and each patient received 3.8±1.3 four-claw Ti-planes for internal fixation. The operations were performed 6.3±3.2 days after admission. After the rib fractures were fixed with four-claw Ti-planes，rib dislocations and chest-wall collapse of flail chest were restored，and patients’ pain was relieved. Postoperative CT image reconstruction of the chest showed no dislocationor displacement at the fixation areas of the four-claw Ti-planes. Rib fractures were stabilized well，and normal contours of the chest were restored. Finite element analysis showed that the maximum bearable stress of the rib fractures after internal fixation with four-claw Ti-planes was twice as large as normal ribs. Conclusion Clinical outcomes of four-claw Ti-planesfor internal fixation of rib fractures are satisfactory with small incisions and less muscle injury of the chest wall，so this technique deserves wide clinical use.
Objective To establ ish sophisticated three-dimensional finite element model of reconstructing the whole pelvis and defects in pelvis caused by the resection of periacetabular tumor, and to research the stress distribution regularity ofthe pelvis reconstructed by the fibular transplantation through three different internal fixation techniques. Methods The CTdatasets including L3 to middle-femur, unilateral fibular and internal fixation system from 1 healthy 35-year-old male volunteer were collected to establ ish finite element models of reconstructing the pelvis after the resection of periacetabular tumors through 3 different internal fixation means, namely fibular with plates, pedicle-rods and sacral-il iac rods. Bilateral leg standing position was simulated, then vertical load of 500 N was imposed on the surface of L3, the stress distribution regularity of reconstructed pelvis, transplanted fibular and internal fixation system were evaluated. Results The finite element models of the pelvis reconstruction after resection of periacetabular tumors were establ ished. The stress concentration of transplanted fibular was extremely high in the vicinity of the host junction sites. For the three internal fixation systems, the connection between steel plate and screw or between titanium bar and screw inclined to have stress concentration; and when the titanium bar was adopted to reconstruct, the transplanted fibular and the healthy side of femoral neck had less stress concentration, while sacral-il iac rods had the most obvious stress concentration. Conclusion For the reconstruction pelvis, the three fibula transplantation and steel plate internal fixation are consistent with intact state of pelvis in terms of the stress distribution, which is a relatively good method for the treatment of bone defect after periacetabular tumor. The finite element model can be used as a tool for the pelvis biomechanics research.
Objective To establ ish sophisticated three-dimensional finite element model of the lower cervical spine and reconstruct lower cervical model by different fixation systems after three-column injury, and to research the stress distribution of the internal fixation reconstructed by different techniques. Methods The CT scan deta were obtained from a 27-year-old normal male volunteer. Mimics 10.01, Geomagic Studio10.0, HyperMesh10.0, and Abaqus 6.9.1 softwares were usedto obtain the intact model (C3-7), the model after three-column injury, and the models of reconstructing the lower cervical spine after three-column injury through different fixation systems, namely lateral mass screw fixation (LSF) and transarticular screw fixation (TSF). The skull load of 75 N and torsion preload of 1.0 N•m were simulated on the surface of C3. Under conditions of flexion, extension, lateral bending, and rotation, the Von Mises stress distribution regularity of internal fixation system was evaluated. Results The intact model of C3-7 was successfully establ ished, which consisted of 177 944 elements and 35 668 nodes. The results of the biomechanic study agreed well with the available cadaveric experimental data, suggesting that they were accord with normal human body parameters and could be used in the experimental research. The finite element models of the lower cervical spine reconstruction after three-column injury were establ ished. The stress concentrated on the connection between rod and screw in LSF and on the middle part of screw in TSF. The peak values of Von Mises stress in TSF were higher than those in LSF under all conditions. Conclusion For the reconstruction of lower cervical spine, TSF has higher risk of screw breakage than LSF.