| BackgroundIn traditional Chinese medicine,the anterior cruciate ligament(ACL)injury belongs to the category of "Tendon Injury" or "Jin Injury".The common reasions are sports injuries.There are a lot of description about the method to cure knee jiont "Jin Injury" in classical medical literature.All of these methods emphasize the combination of dynamic and static treatment strategies,and combinatio of internal and external treatment.There are generally conservative treatment methods recorded in classical medicine books,lack of comprehension of the ACL anatomy and surgical treatment of ACL damage.ACL injury is a common sports injury of knee joint.In the general population in the United States,every 3000 people have suffered the anterior cruciate ligament injury.The incidence of ACL injury was about 3.0%at the end of the sport's season and 40 million patients undergwent ACL reconstruction surgery each year.In China,the incidence of ACL fracture in athletes is about 0.47%.The internal risk factors of ACL injury includes:female,menstrual period,narrow intercondylar fossa,genetic and so on.In recent years,the research focused on the role of posterior tibial slope(PTS)in ACL injury,but the conclusion of the study was not consistent with each other.The reasons were various,differentias in geography and population may be two of them.At present,there are few research on PTS in the yong population of Guangdong area and few study about the relationship between PTS and ACL injury in yong adults of Guangdong area.Most previous research about PTS and ACL injury were retrospective clinical observations and studies of corpse specimens.The cadaver anatomicstructure include many changeling parameters,which were difficult to control to give an objective conclusion about a single factor in the mechanism of injury.Therefore,whether single PTS is a factor of ACL injury need further research.ACL injury will cause the stability loss of knee joint and joint dysfunction,lead to the degeneration of cartilage and meniscus,thus the osteoarthritis will be inevitable in the long term.Therefore,arthroscopic ACL reconstruction has became the first choice for the treatment of ACL rupture.At present,there are two main reconstruction methods:over-the-top single bundle reconstruction(OSBR)and anatomical single-bundle reconstruction(ASBR),and anatomical double-bundle reconstruction(ADBR).The clinical reports of the knee joint function after different reconstruction methods were not consistent.What' s the deference of the tension of reconstructed ACL and the knee stability in patients underwent defferent reconstruction methods and between patients with different PTS?This question need a clear answer in order to guide the selection of operation methods and the post operative rehabilitation.Objective1.To preliminary evaluate the PTS in non-contact ACL injury group and ACL non injury group,investigate the correlation between non-contact ACL injury and PTS in young adults in Guangdong area.2.To explore biomechanical effects of PTS on ACL sress and knee stability in three-dimensional models with defferent flexion using computer three-dimensional finite element analysis.3.To explore the biomechanical characteristics of reconstructed ACL and knee stability after reconstruction with different methods(OTBR and ASBR)in different flexion condition in order to give a reasonable reconstruction choice accordiong to PTS angle.Method1.Preliminary study of single center on correlation between ACL injury and PTS in Young adults of Guangdong areaWe retrospectively analysised clinical data of all patients from January 2012 to December 2015,all these patients underwent medical treatment due to disease of the knee or around the knee in the second people's Hospital of Guangdong Province.We divided these patients into two group:ACL injury group and ACL non injury group.Each group was carefully inspected according to the inclusion criteria and exclusion criteria.50 patients were inclouded in the ACL injury group.We choosed 100 patients consecutively in the ACL non injury group.The medial posterior tibial slope(MPTS),lateral posterior tibial slope(LPTS)were measured through MRI.The data of age,body mass index,LPTS and PTS of two groups were analysed through SPSS20.0 software.2.Three dimensional finite element analysis of the influence of posterior tibial slope on the anterior cruciate ligament and knee joint stabilityThe left knee joint of a healthy volunteer was scanned by CT and MRI.The medial posterior tibial slope(MPTS)is 7 degree measured on MRI scans.The data were imported into Mimics software to obtain 3D model of bone,cartilage,meniscus and ligament structures,and then Geomagic software was used to modify of the image.When the 3D models of these tissues were imported into the SolidWorks software,a 3D model of whole knee joint in extension with 7?PTS was established.The 3D models with 2° PTS and 12° PTS were established in Solidworks software through high tibial osteotomy.After establishment of three groups of knee extension model,30° and 90 ° flexion models were reconstructed through Solidworks software.Each 3D finite element knee models was imported into ANSYS software,then given the load and analysed by computer.ON the extension models,the tibia was fixed,1150N vertical tension applied on the femoral side;On 30° flexion models,the tibia was fixed,750N vertical tension and lateral rotary torque of 10N.m applied on the femoral side;On 90° flexion models,femur was fixed,tibial was applied 134N forward tension.The shift distence between tibia and femur and the tension of ACL were recorded.3.Biomechanical analsis of the reconstructed ACL and knee stability after reconstruction by two methods on different PTS modelsThe ACLs were removed in three different PTS angle models established in part II through Solidworks software.Then new ACLs were reconstructed respectively according to the technical requirements of OSB reconstruction and ASB reconstruction in Solidworks software(the tibial site was consistent and the femoral site was different in OSB group and ASB grooup).18 models of different PTS angles and of different reconstruction methods in defferent flexion were established,and 9 ACL deficient models were also established.Each 3D finite element knee models was imported into ANSYS software,then given the load and analysed by computer.ON the extension models,the tibia was fixed,1150N vertical tension applied on the femoral side;On 30° flexion models,the tibia was fixed,750N vertical tension and lateral rotary torque of 10N.m applied on the femoral side;On 90° flexion models,femur was fixed,tibial was applied 134N forward tension.The shift distence between tibia and femur and the tension of ACL were recorded.Results1.Preliminary study of single center on correlation between ACL injury and PTS in Young adults of Guangdong area?There is no difference in age,body mass index(BMI)between two groups.The average angle of MPTS was 10.03 ± 3.18°,the average angle of LPTS was 11.01±4.140 in ACL injury group.The average angle of MPTS was 8.53±3.06°,LPTS 8.66±3.650 in ACL non injury tibia group.Both MPTS and LPTS of ACL injury group were greater than that of non injury group,and the difference is statistical significance(P<0.05);?The average angle of MPTS of male in ACL injury group was 9.88±2.85°,that of LPTS was 11.12±4.120.The average angle of MPTS of male in ACL non injury group was 8.00±3.11°,that of LPTS was 8.39±3.26°.Both male' s MPTS and LPTS of ACL injury group were greater than that of non injury group,and the difference is statistical significance(P<0.05).?In ACL non injury group,the LPTS of male was 8.39±3.26°,the LPTS of female was 9.04±4.16°.The LPTS of male was slightly lower than that of female,but the difference was not statistically significant(P>0.05).The MPTS of male was 8.00±3.11°,and that of female was 9.29±2.85°.The MPTS of female was higher than thatof male,and the difference was statistically significant(P<0.05).2.Three dimensional finite element analysis of the influence of posterior tibial slope on the anterior cruciate ligament and knee joint stabilityThrough 3D finite element analysis,we found that the ACL tension and shift distence between tibia and femur increases with the increase of PTS on the 0 degree flexion models of the knee:ACL tension was 12.195MPa in model with 2° PTS,12.639NMPa in model with 70 PTS,18.658MPa in model with 12° PTS;the shift distence between the tibia and femur was 2.735mm in model with 2?PTS,3.086mm in model with 70 PTS,3.881mm in model with 12°PTS.The results in the 30° flexion models were:ACL tension was 24.585MPa in model with 2°PTS,25.612MPa in model with 7° PTS,31.481MPa in model with 12° PTS;the shift distence of the tibia and femur was 5.590mm in model with 2° PTS,6.721mm in model with 7° PTS,6.952mm in model with 12° PTS.The results in the 90°flexion models were:ACL tension was 5.119MPa in model with 2° PTS,8.674MPa in model with 7° PTS,9.314MPa in model with 12° PTS;the shift distence of the tibia and femur was 0.276mm in model with 2° PTS,0.577mm in model with 7° PTS,0.602mm in model with 12° PTS.3.Biomechanical analsis of the reconstructed ACL and knee stability after reconstruction by two methods on different PTS modelsThe tension and the shift distence between tibia and femur were obtained by finite element analysis in 18 ACL reconstructed models and 9 ACL deficient models respectively.?Under the condition of 0 degree flexion:in groups with OSB reconstruction,ACL tension was 5.540MPa in model with 20 PTS,5.918MPa in model with 7° PTS,6.179MPa in model with 12° PTS;the shift distence between the tibia and femur was 1.291mm in model with 2° PTS,1.700mm in model with 7° PTS,1.848mm in model with 12 0 PTS;in groups with ASB reconstruction,ACL tension was 5.699MPa in model with 20 PTS,5.966MPa in model with 7°PTS,8.955MPa in model with 12° PTS;the shift distence between the tibia and femur was 1.545mm in model with 20 PTS,1.818mm in model with 7° PTS,1.876mm in model with 12° PTS;In the models of ACL deficiency,the shift distence between tibia and femur were as follows:3.066mm in model with 2° PTS,3.504mm in model with 70 PTS,4.401mm in model with 120 PTS.?Under the condition of 30° flexion:in groups with OSB reconstruction,ACL tension was 1.795MPa in model with 2° PTS,2.483MPa in model with 7° PTS,2.815MPa in model with 120 PTS;the shift distence between the tibia and femur was 1.081mm in model with 2° PTS,1.312mm in model with 7° PTS,1.339mm in model with 12° PTS;in groups with ASB reconstruction,ACL tension was 2.313MPa in model with 2° PTS,3.071MPa in model with 70 PTS,3.248MPa in model with 12° PTS;the shift distence between the tibia and femur was 1.160mm in model with 2° PTS,1.351mm in model with 7° PTS,1.383mm in model with 12° PTS;In the models of ACL deficiency,the shift distence between tibia and femur were as follows:6.050mm in model with 20 PTS.7.356mmin model with 7° PTS.8.231mm in model with 120 PTS.?Under the condition of 900° flexion:in groups with OSB reconstruction,ACL tension was 3.427MPa in model with 2°PTS,3.635MPa in model with 7° PTS,3.694MPa in model with 120 PTS;the shift distence between the tibia and femur was 0.334mm in model with 2° PTS,0.367mm in model with 7° PTS,0.377mm in model with 12° PTS;in groups with ASB reconstruction,ACL tension was 4.409MPa in model with 20 PTS,5.940MPa in model with 70 PTS,6.402MPa in model with 120 PTS;the shift distence between the tibia and femur was 0.386mm in model with 20 PTS,0.445mm in model with 70 PTS,0.446mm in model with 120 PTS;In the models of ACL deficiency,the shift distence between tibia and femur were as follows:0.946mm in model with 2° PTS.1.036mmin model with 7° PTS.1.369mm in model with 12° PTS.Conclusion?In youny adults of Guangdong area,female has greater MPTS than male.There is statistical link between the PTS and noncontact ACL injury.With increasing of PTS,the shear tension in the ACL increased during the movement.Both great MPTS and LPTS are risk factors for noncontact ACL injury?The relationship between PTS and noncontact ACL injury in feamle in Guangdong area need further study.? When the load applied on the knee joint,the tension of ACL and the shift distence between tibia and femur increase with the increase of PTS.A steeper PTS may be a risk factor in ACL injury.?Both OSB reconstruction and ASB renconstruction can restore the stability of the knee joint.The angle of PTS does not effects the choice of reconstruction methods.Regardless the angle of tibial plateau,the tession of ACL reconstructed by OSB method waereless than that reconstructed by ASB method in the three knee flexion angles,and the stability of knee joint were better.In our study,we prefer the femoral insertion of the ligament reconstructed in the top position.For patients with steeper PTS,the reconstructed ACL will bear greater tension in the postoperative rehabilitation regardless of the OSB reconsruction or ASB reconstruction.Agressive exercise should avioded before healing of the reconstructed ligment to prevent the ligment being elongated and resulting in reconstruction failure. |
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