| Background and purposeAnterior cruciate ligament is important in knee joint,the ACL islimited the keen kidnict and guiding its movoment.But commonly used single-Bundle,double-bundle or even three-bundle reconstruction are not fully mimic the original ACL ligament stress patterns,resulting in poor results after the reconstruction,and gradually lead to ligament injury again,degeneration in the knee.The in-depth research of the knee ligaments, cartilage,and other biomechanical structure is a best way of understand the function of the knee,because of biological tissue composition is complex and irregular in shape,traditional engineering mechanics testing device can not research accurately.Therefore biological mechanical testing device must be used on it.Currently knee specimens for human biomechanical testing system mainly be the robtics,UFS test system,there is still insufficient in Fine ligament structure test.Anterior cruciate ligament is guiding the knee to complete its important function of the structure.Usually,that ACL may be two or three beams components,but this ACL reconstruction surgery based on the sub-beam concept can not reproducibility fully functional of ACL.Recent studies show that many ACL ranging from long fiber bundles from intertwined,and through the course of knee flexion and extension of the fiber bundles for the stress dynamic changes,which completed its precision guidance function,which is inferred that ACL is make up of many functional fiber bundles.Therefore it should be use the "multi-fiber bundles" concept of the ACL biomechanical properties of in-depth study.Therefore,this study based on the "multi-fiber bundle of ACL" concept,to be developed include special fixture,mechanical testing of the test data,acquisition, conditioning parts,control and data processing systems of four parts of "a new degree of freedom knee Loading System",thus relevant biomechanical study on the establishment of technology platforms,in knee flexion,extension,inversion,eversion Campaigns state (DOF),in-depth study of the biomechanics of ACL.Methods1.The knee freedom Dynamic mechanics Loading System Development and validation(1) The design and manufacture of special fixture include:lateral femoral and tibial side fixture multi-angle fixture.(2) Design and manufacturing testing,collection and control devices,including:sensor module,data acquisition,signal amplification and conversion modules and systems supporting dynamic acquisition acquisition software.System hardware equipment needed to complete matching software - software-hardware interface between the control system software is divided into three parts by the Visual C++ language for the preparation,including software interface,the interface and the main program.(3) Friction through the system,the system of relaxation,and other aspects of Chinese knee verify the validity of freedom loading system.2.ACL quarter beam biomechanical testingUse the sagittal and coronal axle divide the ACL tibial side into four districts: posteromedial bundle(disctrict 1),posterolateral bundle(disctrict 2),anterolateral bundle (disctrict 3),anteromedial bundle(disctrict 4) four districts,District corresponding corresponding ligament fibers divided into four beam,connected to the system after the sensor to measure:(1) The process of ACL knee flexion and extension of the beam force change;(2) The process of the knee ACL internal and external turned of the sub-beam force change;(3) The force changes of Internal and external rotation of the knee ACL;(4) The force changes of simulation the ACL drawer test.Results1.New knee freedom dynamic stress loading system(1) Evaluation System relaxation in the 10 N external force,not soft tissue loading viscoelastic material system in the 0-20 seconds no obvious stress relaxation. (2) System friction evaluation,four sensor location work in the perspective of the largest and the smallest friction coefficient system in 0.023-0.054,four-channel maximum friction coefficient 0.054.(3) Multi-channel synchronous acquisition completed.(4) Dynamic data acquisition frequencies up to 2000 Hz.(5) Self-supporting software programming stability.2.Results of ACL quarter beam biomechanical testing(1) Of knee flexion and extension process,the Area 2 fiber bundles in the knees 30 largest force(22.52±8.60N);4 District fiber bundles in the buckling 90°largest force (14.68±5.29N);REGION 3 fiber bundle when tension in flexion and extension of the earlier two small changes.1 District fiber bundle tension no big change.(2) Internal and external rotation of the knee,the external rotation at Area 2 fiber bundle largest force(16.97±1.45N,knees 30°).Internal rotation four areas of the fiber bundle to the greatest change in(11.67±2.25N,knees 90°).1 and 3 District fiber bundle in the internal and external rotation at the knee joint force changes small.(3) The knee up inside and outside the course of valgus,4 District largest force fiber bundle(3.23±1.45N,knees 90°),when inverted lateral beam(2,3 district) than medial beam force(1,4 district),and previous lateral beam(3 regions) the largest force(2.93±3.33 N,knees 30°).(4) In the drawer before doing experiments,the four areas of the fiber by the knee flexion angle increases.The Rally of 150 N,the largest force of fiber bundle appeared in four areas(19.7±2.78N knees 90°).Conclusion1.Based on the "multi-fiber bundle ACL," a new design concept knee freedom loading system with the following characteristics:(1) Be completed on the structure of the knee ligament single biomechanical testing;(2) Multi-fiber bundle ACL completed the synchronization testing;(3) Campaign to be concluded knee ligament fiber bundle in the process of change by real-time dynamic testing.(4) Be completed multi-degree of freedom simulation knee state for testing.(5) Can be carried out high-frequency acquisition; (6) Low price,installation is simple.The system made up of existing testing equipment can not be more than knee ACL fiber bundle biomechanical testing inadequate for the future knee ACL biomechanical testing provides a complete software and hardware conditions.2.The sub-bundle ACL knee in the different degrees of freedom in the state of biomechanical role as follows:(1) Multi-freedom movement in the knee joint,anterior cruciate ligament four minutes beam on the beam role in the control of the knee is different and constantly changing.(2) Posterolateral bundle is control the knee stability mainly in the knees 0°to 60°.(3) The knee stability control of anteromedial bundle is mainly in the knees 60°to 90°fixatison,and have shown very good control in all aspects of the stability of the knee.(4) Anterolateral bundle in addition to the lateral tibia forward,strong control(knees 30°),the role of the remaining stability control is weaker than the first two,its biomechanical performance includes the functions of the two districts,speculation probably as a transitional fiber bundle,both in the transition of the dynamic knee flexion and extension functions in the process of conversion.(5) The knee joint stability control of anteromedial bundle is very limited in the knee physiological activities.
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