Digital Anatomy And Finite Element Biomechanics Study Of The Posterolateral Complex Of The Knee Joint

Background:The posterolateral complex(PLC)is a complicated anatomical and biomechanical complex located in the posterolateral region of the knee.The PLC consists of multiple tendons and ligaments that maintain the static and dynamic stability of the posterolateral structure of the knee,preventing the knee joint from varus,external rotation and tibia posterior movement.Knee joint injuries are often accompanied by injuries to the PLC.Early diagnosis and treatment of PLC injury is critical to the recovery of knee function;therefore,many anatomists and orthopedists have focused on the anatomy,biomechanics and surgical reconstruction of the PLC.Most of the existing findings regarding the PLC are based on dissection or magnetic resonance imaging(MRI).Due to the complexity of the PLC structure and the diversity of research methods,the study of its specific composition,three-dimensional(3D)shape,adjacent relationships and biomechanics is still inadequate.Previous studies have found differences in the shape and size of the distal femur and proximal tibia joints between different races.In clinical operations,the surgical plan should be designed specifically in Total Knee Arthroplasty(TKA)surgery with consideration of the anatomical differences of the joints between different races.However,there are few studies on the anatomical structure differences of knee joint PLC among different races which can provide more anatomical reference data for clinical surgical planning.In addition,extensive research on the knee’s biomechanics by establishing a 3D finite element model of the knee joint has been conducted.But further studies are needed of the 3D finite element model of the knee joint when combined with PLC and the finite element biomechanical factor on PLC.Therefore,the anatomy of PLC,the optimization of the surgical tunnel plan,and the biomechanics need to be further studied and discussed.Purpose:1.This study is based on the thin-layer,high-precision Chinese Visible Human(CVH)dataset images to conduct digital anatomical research on PLC of knee joint,including the study of the PLC component structure,3D shape and adjacent relationship.2.Compare the component structure,3D shape and adjacent relationship of PLC of CVH dataset and American Visible Human Project(VHP)dataset.To study the anatomical differences in PLC structure between Asian and Caucasian races.3.To conduct a digital anatomical study of the knee joint PLC at the femoral and fibular tendon-bone junctions based on CVH and VHP datasets,and to determine their morphology,contact area,center points and mutual distances with the aim of providing assistance for surgical tunneling scheme.4.Based on 3D reconstruction model of the CVH dataset,construct a finite element biomechanical model of the knee joint combined with PLC structure,which lays the foundation for the finite element biomechanics experiment of PLC structure.Materials and Methods:This research selected 7 knee CVH datasets,including six sets of transverse section images of the bilateral knee joint from the CVH Datasets CVH-1,CVH-2,and CVH-5 and 1set of coronal section images.The study also selected 4 sets of transverse section images of bilateral knee joints from the Visible Human Project-male(VHP-male)and Visible Human Project-female(VHP-female)datasets.Histological section staining(HE,Masson,Mallory-Cason)images of adult and embryonic knee joints are obtained in the study.The recognition of the PLC structure is based on the stained image of the histological section of the knee joint and on the natural color of the structure in the digital human true color sectional images.Through the Amira software,data segmentation and 3D reconstruction of the knee joint bone,PLC and its adjacent structures are carried out.In addition,this study compared CVH images with MRI images of the same knee joint position.It measured the PLC structure of the knee joint 3D reconstruction image,and calculated the average and standard deviation of each structure of PLC in the CVH and VHP datasets.Then the research selected the bilateral knee joint from the datasets of CVH-1,CVH-2,CVH-5,VHP-male and VHP-female.It calculated,identified and 3D reconstructed the PLC femoral and fibular tendon-bone junctions of FCL,PT,BT,and PFL,and measured and studied their morphology,contact area,center points and mutual distances of the tendon-bone junctions.After optimizing the 3D reconstruction model of the right knee joint of CVH-5,the 3D finite element model of the knee joint combined with PLC structure was constructed through Altair Hyper Works software,and the validity of the model was verified.Results and discussion:1.Successfully reconstructed the 3D reconstruction models of PLC and its adjacent structures,including 7 sets of CVH datasets(bilateral knee joints from CVH-1,CVH-2,and CVH-5 and 1 set of digital knee joint)and 4 sets of VHP datasets(bilateral knee joints from VHP-male and VHP-female).An interactive visualization 3D-PDF file was successfully created based on the CVH-5 right knee joint model,by which can be observed and studied the anatomy of PLC’s component structures,3D shape and adjacent relationships from any angle and any orientation.2.This study found that PLC is mainly composed of Fibular Collateral Ligament(FCL),Popliteofibular Ligament(PFL),Arcuate Popliteal Ligament(APL),Popliteus Tendon(PT),Fabellofibular Ligament(FFL)and Biceps Femoris Tendon(BT),and included proximal and distal structures.The proximal parts of the posterolateral regions,from anterior to posterior,were the origins of the PT,FCL and lateral head of the APL;they were co-located in the lateral condyle of the femur.The distal parts of the posterolateral regions,from anterior to posterior,were the insertions of the FCL,BT,APL,PFL,and FFL,which were co-located on the posterolateral side of the fibular head.Because these structures had adjacent origins or insertions,the study concluded that they act in conjunction to maintain PLC stability.The APL was “Y” shaped and had a 100% occurrence in the CVH datasets.Its lateral and medial heads originated,respectively,from the posterolateral part and medial-inferior part of fibrous capsule close to the lateral femoral condyle.The APL structure was only found in the VHP-male right knee joint and had a 25% occurrence,with irregular shapes and no obvious medial and lateral heads.This study found that PT,PFL,and FCL are the main mechanics structures of PLC through anatomical observation.Chinese APL is also an important biomechanical structure of PLC,but American APL is not.It is recommended that PLC surgery scheme for Chinese should be designed according to their own anatomical characteristics.3.The PLC structures’ measurement values in the VHP datasets are generally greater than those in the CVH datasets,such as the length and width of the trunk of PT,the length,width and thickness of FCL,the width of PFL,the length and width of BT,and the length of APL.There are also a few PLC structures’ measurement values in the VHP datasets which are almost the same or slightly smaller than those in the CVH datasets,such as the length of medial bundle and lateral bundle of PT,and the length of PFL.The measurement data in this study show that the ratio of PT trunk and FCL length in the CVH and VHP dataset is about0.71,and the ratio of PT trunk,FCL and PFL width in the CVH and VHP dataset is about 0.77.This shows that the anatomical size of PLC in Americans is larger than that of Chinese,and it is speculated that there were different structure sizes and mechanical function of PLC,which match different races.In addition,the measured value of knee joint bone in the VHP data set is larger than that in the CVH data set.It is speculated that the shape and size of bone development determine the shape and size of soft tissues such as muscles,tendons and ligaments attached to it.4.Based on the observation and measurement of the 3D reconstruction of the PCL tendon-bone junction,the tendon-bone junctions of each PLC structure did not have a uniform morphology or the same contact area,but the location of the central point of the tendon-bone junction was similar and regularly attached.All measurements of the PLC structure tendon-bone junctions were smaller in the CVH dataset than the VHP dataset,which proves that the PLC anatomy of the Chinese is smaller than that of the Americans.This is consistent with previous research results.The distance between the center point of the femoral tendon-bone junction of the FCL and that of the PT was 7.73 ± 1.44 mm in the CVH dataset.Based on this study’s findings,a femoral single-tunnel reconstruction surgical tunneling scheme for Chinese is suggested.Specifically,a reconstruction scheme that uses the center point of the FCL and PT tendon-bone junctions as the femoral single tunnel point in the Chinese PLC reconstruction plan is recommended.5.In this study,a 3D finite element model of the knee joint with PLC structures was successfully constructed.The model consists of 18 parts,including femur,tibia,fibula and its cartilage,patella,patellar ligament,medial meniscus,lateral meniscus,ACL,PCL,MCL,FCL,PT,PFL,APL and BT.The model has a total of 559,800 units with high accuracy and can show the complex geometric appearance and contact relationship of the knee joint combined with the PLC structure.It can effectively simulate and reflect the stress and strain of the PLC structure under various mechanical fields,and can compensate for the insufficiency of the 3D finite element model of knee joint combined with PLC and its related research,which lays a foundation for the further development of PLC finite element biomechanics research.Conclusion:1.CVH dataset has the advantages of thin layer,high precision and true color,and it better shows the precise composition,3D morphology and spatial relationships of the PLC,thus improving the identification and diagnostic accuracy for the PLC in MRI.2.By observing and studying the PLC anatomy and interactive visualization of 3D-PDF,this study found that FCL,PFL,APL,FFL and PT are located adjacent to the posterior lateral part of the knee joint,and their origins or insertions are located at the proximal or end of the PLC structure.The study speculates that APL has an important biomechanical significance in Chinese.3.The study found that the measurements of knee joint bone and PLC structures in the VHP dataset are generally greater than those in the CVH dataset,and are in a consistent proportional relationship.It speculated that there were different structure sizes and mechanical function of PLC,which match different races.The research proposed that an appropriate surgical tunnel scheme should be developed according to the characteristics of the Chinese knee bone and PLC anatomy.4.The research proposes a femoral single-tunnel reconstruction surgical tunneling scheme for Chinese;The research data provide a theoretical basis and guidance that will help clinicians design and select knee joint PLC surgical tunneling schemes.Additionally,the anatomical data supports the theory that Chinese can obtain good stability after PLC femoral single-tunnel reconstruction.5.The 3D finite element model of the knee joint combined with PLC structure has high accuracy.It lays the foundation for the development of PLC finite element biomechanics experiments.Furthermore,it makes up for the insufficient research on the mechanical properties of PLC in China,and provides theoretical basis and guidance for optimizing PLC reconstruction surgery scheme.