Résumé
Objective To analyze biomechanical properties of cervical spine after anterior cervical discectomy and fusion (ACDF) and total disc replacement (TDR) surgery. Methods Twelve cadaveric cervical spines (C2-T1) were adopted, and the motion and load distributions of the cervical segments under intact state and after ACDF and TDR surgery were tested using a three-dimensional (3D) optoelectronics measurement system. All the tests were carried out with displacement control in directions of flexion (Flex), extension (Ext), left bending (LB), right bending (RB), left rotation (LR) and right rotation (RR). Motion characteristics of the normal cervical spine and the implant were also discussed. Results In TDR-treated specimens, range of motion (ROM) was well preserved and could restore to the normal ROM distributions, especially in Flex/Ext and LR/RR direction. While in ACDF-treated specimens, ROM presented a large decrease as much as to 73.41% under the same condition compared with TDR, and ROM distributions were also changed obviously in other motions for the segments. Significant changes of ROM in LB/RB direction occurred in both TDR and ACDF group, which were up to 45.92% and 108.06%, respectively. The experimental data indicated that the normal motion of cervical spines was a 3D coupled motion, especially in LB/RB direction, where a 35% rotation around X-axis existed. The cervical spine could recover close to normal coupled motion after TDR surgery. Conclusions TDR surgery can restore the physiological motion of cervical spines more close to the normal state, especially in Flex/Ext and LR/RR direction. The study provides a theoretical basis and quantitative reference for TDR and ACDF surgery in clinic.
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This article reviews the application of finite element method in spine biomechanics during the last three years. Major progress in both finite element model improvement of detailed microstructure, personalized vertebrae parameter weights, new accurate calibration method, automated modeling approach and spine biomechanics-related applications including implant design assessment, inter-vertebral disc biomechanics, biomechanics of abnormal spinal structure, dynamic simulation are classified and summarized. Future development of finite element method being applied in trauma mechanism, surgery simulation and drug evaluation is also discussed.
Résumé
<p><b>OBJECTIVE</b>To evaluate the effectiveness and safty of tranexamic acid in patients receiving on-pump coronary artery bypass grafting (CABG) without clopidogrel and aspirin cessation.</p><p><b>METHODS</b>The current study is a prospective, randomized and placebo-control trial. A total of 116 patients receiving selective on-pump CABG with their last ingestion of clopidogrle and aspirin within 7 days preoperatively were recruited. Despite 6 patients withdrawal their consent, the rest 110 were randomized to receive tranexamic acid or placebo. The tranexamic acid regimen was a bolus of 10 mg/kg followed by a maintenance of 10 mg·kg(-1)·h(-1) throughout the surgery. The primary outcome was the volume of allogeneic erythrocyte transfused perioperatively.</p><p><b>RESULTS</b>Baseline characteristics were comparable between the groups. In patients receiving tranexamic acid and placebo respectively, the volume of allogeneic erythrocyte transfused was 4.0 (7.5) units and 6.0(6.0) units (W = 1021, P < 0.01). In these 2 groups respectively, blood loss was 930 (750) ml and 1210 (910) ml (W = 1042, P < 0.01), the incidence of major bleeding was 50.9% and 76.4% (χ(2) = 7.70, P < 0.01), the incidence of reoperation was 0 and 9.1% (χ(2) = 5.24, P = 0.02); the volume of plasma transfused was 400 (600) ml and 600 (650) ml (W = 1072, P = 0.01), the exposure of plasma was 60.0% and 85.5% (χ(2) = 8.98, P < 0.01) and the exposure to any allogeneic blood products was 85.5% and 98.2% (χ(2) = 5.93, P = 0.01). Perioperative mortality, morbidity and the incidence of adverse events were balanced between the groups without statistical significance.</p><p><b>CONCLUSION</b>Tranexamic acid reduced significantly postoperative bleeding and transfusion in patients receiving on-pump CABG without clopidogrel and aspirin cessation.</p>