Research progress of tibial-graft fixation methods on anterior cruciate ligament reconstruction / 中国修复重建外科杂志

OBJECTIVE@#To review the studies about the tibial-graft fixation methods on anterior cruciate ligament (ACL) reconstruction, in order to provide clinical reference.@*METHODS@#The literature about the tibial-graft fixation methods on ACL reconstruction at home and abroad was extensively reviewed, and the factors that affect the selection of fixation methods were summarized.@*RESULTS@#The knee flexion angle, graft tension, and graft fixation device are mainly considered when the tibial-graft was fixed on ACL reconstruction. At present, the graft is mainly fixed at 0°/30° of knee flexion. The study shows that the knee joint is more stable after fixed at 30°, while the incidence of knee extension limitation decrease after fixed at 0°. In terms of graft tension, a good effectiveness can be obtained when the tension level is close to 90 N or the knee flexion is 30° to recover the affected knee over-restrained 2 mm relative to the healthy knee. In terms of the graft device, the interference screw is still the most commonly used method of tibial-graft fixation, with the development of all-inside ACL reconstruction in recent years, the cortical button fixation may become the mainstream.@*CONCLUSION@#Arthroscopic reconstruction is the main treatment of ACL rupture at present. However, there is no optimal fixation method for the tibial-graft, the advantages and disadvantages of each fixation methods need to be further studied.

Construction and simulation mechanical analysis of dynamic knee joint finite element model based on CT image / 中国骨伤

OBJECTIVE@#To construct a dynamic knee joint finite element model based on CT image data and verify the validity of the model. To provide a simulation model and basic data for biomechanical research of the knee joint by further finite element analysis.@*METHODS@#The CT data of a healthy male knee joint was selected. With the help of Mimics 19.0 and Hypermesh 12.0 software, a high simulation finite element model of knee joint was established following steps, including geometric reconstruction, reverse engineering, meshing and material characterization. The dynamic knee flexion model was generated by determining the boundary conditions and torque loading, and the validity of themodel was confirmed. The biomechanical changes of the tibiofemoral and patellofemoral joints under different knee flexion angles were analyzed by applying the loads (500 N) to the finite element model during knee flexion.@*RESULTS@#A finite element model of knee joint was established based on CT images and anatomical characteristics. The model included three-dimensional elements such as bone, ligament, cartilage, meniscus and patellar retinaculum. The different finite element models of knee flexion states were produced by applying different torques after establishing boundary conditions. According to equivalent conditions (knee flexion 30 degrees, quadriceps tendon under 200 N stretch), the peak stress value of patella was 2.209 MPa and the average Mises stress was 1.132 MPa; the peak stress value of femoral trochlear was 1.405 MPa and the average Mises stress was 0.936 MPa. The validity of the model was proved by the difference between the model and previous studies of 1% to 13.5%. Dynamic model loading showed that the Mises stressof tibiofemoral joint decreased with the increase of knee flexion angle, while the Mises stress of patellofemoral joint was positively correlated with knee flexion angle. The Mises stress of cartilage stress planes at different knee flexion angles was significantly different(<0.05).@*CONCLUSION@#The finite element model established in this study is more comprehensive and can effectively simulate the biomechanical characteristics of dynamic knee joint, which provides support for further simulation mechanics researches of the knee joint.

Effect of knee flexion angles during maximum isometric hip extension / 体力科学

The purpose of this study was to examine the effects of knee flexion angles during maximum isometric hip extension. Ten healthy men performed maximum isometric hip extension in prone position at 15° and 90° knee flexion. Then, the hip extension torque was measured, and electromyographic (EMG) data were obtained from the biceps femoris long head, semitendinosus, semimembranosus, adductor magnus, and gluteus maximus muscles. The EMG data were full-wave rectified and integrated (IEMG). The IEMG values obtained during the measurement of isometric hip extension were normalized with the values collected at 90° knee flexion (normalized IEMG [NIEMG]). The hip extension torque at 15° knee flexion was significantly greater than that at 90° knee flexion. The NIEMG values from the hamstrings at 15° knee flexion significantly increased compared with those at 90° knee flexion. Meanwhile, the NIEMG values from the gluteus maximus at 90° knee flexion were significantly greater than those at 15° knee flexion. However, the NIEMG values from the adductor magnus did not significantly differ between 15° and 90° knee flexion. These results indicate that the hamstrings effectively generate contracting force during isometric hip extension and at knee extended position because its fiber length was close to the optimal length.

Divergence of Femoral interference screw versus Knee Flexion Angle during Endoscopic ACL Reconstruction

The endoscopic single-incision technique using interference fit screws to secure patellar tendon-bone plugs in the femoral and tibial tunnels has been very popular method for ACL reconstruction. However, several potential complications has been reported such as violation of the posterior wall of the femoal tunnel, laceration of graft during femoral screw insertion, protrusion of the tibial bone block distally due to a lengthy graft and more frequently divergence of the femoral interference screw. We performed 56 consecutive endoscopic ACL reconstruction. In Groi.p I, femoral tunnel drilling were performed at 70-80 degrees of knee flexion. In Group 11, they were done at $5 degrees of knee flexion. Postoperative radiographic analysis of bone-interference screw divergence angle shows 5.9 degrees in AP view, 6.21 degrees in Lateral view in Group I and 3.14 degrees, 3.35 degre.s in Group II respectevely. In conclusion, Bone-interference screw divergence can be decreased with less knee flexion about 45 degree during preparing femoral tunnel.