| 1. Background and PurposePosterolateral corner (PLC) is one of the most complex structure in the knee. With traffic accidents and competitive sports increasing, there's an ascensus tendency of the incidence of injury to the PLC. In recent years, people have realized that the PLC play an important role in maintaining the stability of the knee. It provides indemnification to ACL and PCL reconstruction by preventing varus and external rotation of the knee. To recruit the mechanical function of original PLC and improve the therapeutic effects, PLC should be reconstructed according to its original anatomic structure and mechanical characters. The surgical techniques of PLC reconstruction having changed from non-anatomical reconstruction, partial-anatomical reconstruction to anatomic reconstruction, and there hasn't a uniform standard and the clinical results have always been controversial, so reconstruction of PLC need an in-depth study.Recently, LaPrade and Bicos respectively recommend the technique of anatomical reconstruction, they both used free tendons to reconstruct the PLC, these techniques did not destroyed other structures of posterolateral knee, but could restore the biomechanical function of PLC and restore the stability of the knee. The number of reconstructed tendons and the attachments of the tendons are different in the two techniques. As we know, there were no reports about biomechanics comparative study of them. In this biomechanical study, we compared these two anatomical reconstruction techniques for the PLC with cadaveric specimens to evaluate their effects for restoring stability of the knee and provide a theoretical basis for clinical treatment.2. MethodsEight fresh cadaveric knees of normal adult body were used. (There were 20cm femur and tibia in length from the knee joint and all soft tissue remained). Then the end of femoral and the end of tibia were fixed in biomechanical testing machine using jig. Biomechanical testing was applied to these specimens in multiple flexion angles(0°, 30°, 60°, 90°), for both tibial varus-valgus rotation and internal-external rotation, a 5-N ? m(torque 2cm, torque 250N) torque was applied to the tibial cylinder, the varus and external rotation of the tibial were measured. The flowing tests were performed after transection of the lateral collateral ligament (LCL), popliteal tendon (PLT), popliteofibular ligament(PFL) to established of gradeⅢPLC injury models .We used autogenous semitendinosus tendon, gracilis tendon to reconstruct PLC flowing LaPrade technique, and autologous semitendinosus tendon to reconstruct PLC the flowing Bicos technique. Using the same method to measure the tibial varus and external rotation angle. At last all the data were analysed through statistical analysis, then produced the chart and table.3. results(1) The varus of tibial in intact knees were least at 0°of flextion and greatest at 30°of flextion, its were 3.26±0.61°and 4.73±0.94°. From30°to 90°of flextion, the varus was decreased with the flextion angle increased. The external rotation of tibial in intact knees was greatest at 30°of flextion, it was 12.64±0.94°. From30°to 90°of flextion, the external rotation was decreased with the flextion angle increased. The varus of tibial in gradeⅢPLC injury models increased significantly at all flexion angle(sP<0.05), it reached greatest at 30°of flextion(8.68±1.22°). The external rotation of tibial in gradeⅢPLC injury models increased significantly at all flexion angles(P<0.05), it reached greastest at 30°of flextion(20.58±2.11°).(2) After PLC reconstruction by using the two techniques, the varus was significantly improved , comparing with the intact knees there were no significant difference(P>0.05). After PLC reconstruction using the two techniques, the external rotation was significantly improved, comparing with the intact knees there were no significant difference (P>0.05). There are no significant difference between the two techniques (P>0.05). Although there were no significantly different with the intact knees, the varus and external rotation were still greater than the intact knees. For LaPrade technique, the varus increased 0.77±0.42°,0.75±0.65°,0.68±0.39°, 0.48±0.52°at 0°, 30°, 60°, 90°of flextion, for Bicos technique, it increased 0.85±0.84°,0.74±0.57°,0.55±0.67°%,0.40±0.23°; For LaPrade technique, the external rotation increased1.04±0.92°,1.57±1.30°,0.87±0.99°,0.78±0.97°at 0°, 30°, 60°, 90°of flextion, for Bicos technique, it increased 0.14±0.84°,0.27±1.25°,0.23±0.97°,0.68±0.84°.4. Conclusion1. Through sectioning LCL, PLT, PFL we established the gradeⅢPLC injury models. Biomechanical testing results showned: the tibial varus and external rotation had significantly increased in gradeⅢPLC injury models. The major structures of the posterolateral corner include LCL, PLT, PFL, they played an important role to resist excessive varus and external rotation forces.2. Because the soft tissue had been remained, such as the skin, subcutaneous tissue, the gradeⅢPLC injury models were more accurate and reliable than the used models, its provided a good platform for PLC reconstructions and biomechanical testing in the next step.3. The number of reconstructed tendons and the attachments of the tendons were different in two surgical techniques (LaPrade technique and Bicos technique), both reconstruction techniques could restore the stability of the posterolateral knee, and there were no significantly difference to the intact knees.4.There were no significant difference between the two techniques for restoring stability of the knee. But LaPrade technique needed to expose the posterolateral lateral tibia plateau, and builded the tibial tunnel, and needed more graft, PLC reconstruction needed more time, the operation was more complicated, surgical trauma was also relatively greater. Therefore, compared with LaPrade technique, Bicos technique had the advantages of less trauma, short operation time.5.Under corresponding torque, for both surgical techniques, although there were no significantly difference to the intact knees, the varus and external rotation were still greater than the intact knees, which indicated that there still existed potential instability. |
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