The High Resolution Magnetic Resonance Imaging Appearance Of The Anterolateral Ligament Of The Knee In Association With Anterior Cruciate Rupture

Background and purposeRecent studies have characterized the anterolateral ligament(ALL)of the knee in detail.This structure is regarded as having a complementary function to the anterior cruciate ligament(ACL)which keeps anterolateral rotational knee stability.The association of ALL injuries with ACL ruptures has been postulated as a possible cause for anterolateral rotatory instability,which would result in a positive pivot-shift test after ACL reconstruction of the knee.Recently studies have evaluated the structure of ALL by using routine MRI techniques(such as 2D coronal fat suppressed PD-weighted imaging).However,the ALL is a relatively thin ligament.The routine MRI imaging can only showed a part of the ALL without the power to display the whole ligament anatomy and its adjacent relations.This study attempts to optimize the high resolution 3D MR imaging to show a better contrast which would help to better understand the structural characteristics In China,there was no great importance has been placed on this ligament.Once the ACL ruptured,the orthopedist tends to focus on the reconstruction of ACL ignoring the condition of the ALL.The purpose of the present study was to assess the incidence of injured of ALL following ACL rupture and observe the characteristics of thus injury based on MRI.Materials and methodsHealthy volunteer group:Forty-five volunteers(25 males,20 females,aged 31.2±5.6 years old)who have no history of knee injury and surgery and no knee pains were included in this study.Height was 158-192 cm.By Height divided into 3 groups(158-167 cm,168-177 cm,>177cm).All MRI scans were performed on a 3.0T MR scanner.The high resolution 3D TSE-based sequences including the T1W-VISTA,and T1W-VISTA-SPAIR were optimized for the scanning.Totally 90 knees were imaged and the ALL was divided into three portions for analyses: femoral portion,meniscal portion,and tibial portion.Two musculoskeletal radiologists with more than 5 years experience were blinded to evaluate the image of ALL separately.We make a reconstruction of the anterolateral ligament with Mimics 15.0 software.Then we measure MR image date of the anterolateral ligament including the length of the ALL three portion,and the distance from femoral origin/ Tibial origin to the joint line.Analysis and make a correlation analysis about MR measurement date divided by sex and height.ACL ruptured group: Forty-six patients(29 males,17 females,aged 27.1±7.4 years old)who have a history of knee injury included in this study.Each patient underwent clinical Lachmann test and a pivot-shift test and all have positive results which indicated the rupture of anterior cruciate ligament.Exclusions criterion were as follows: multi-ligament injuries(any full-thickness injury to posterior cruciate,either collateral ligament),fracture or other inflammation of knees,but findings of meniscus injuries was included in this study.All MRI scans were performed on the high resolution 3D TSE-based sequences including the T1W-VISTA and T1W-VISTA-SPAIR were optimized for the scanning.Chi-square test was performed to analyze the categorical variables.Binary logistic regression was performed to investigate the main cause of ALL damages.ResultsHealthy volunteer group:1.T1W-VISTA imaging technique has a high superiority in the imaging of the ALL.The ALL is described as a distinct ligamentous structure,originating from the prominence of lateral femoral epicondyle anterior to the attachment of the lateral collateral ligament and,with an oblique course,inserting on the antero-lateral side of tibial plateau and in some case can into the middle third of the lateral meniscus.2.T1-VISTA-SPAIR sequence is helpful to show the relationship between ALL and ACL injured.The tibial portion was mostly visualized(84,4 % of radiologists A,83.3 % of radiologists B),followed by the femoral portion(67.8 % of radiologists A and B)and the meniscal portions(20 % of radiologists A,21.1 % of radiologists B).3.Length of the ALL three portion,and the distance from femoral origin/ Tibial origin to the joint line was significantly associated with height,but was no significantly associated with sex.ACL ruptured group:1.Chi-square test showed that there are significant difference between the ALL injuried with the mode of injured and the time of injured.2.When the ACL and LM both injured,the ALL was the usually injured with a percentage of about 51.2%.When Only the ACL injured,the injured ALL was accounting for43.6%.When only the LM injured,the injured ALL was only accounting for about 5.13%.3.Logistic regression analysis showed that ACL injury has closer association with ACL injuries but no association with LM injuries and mode of injured and the time of injured.4.In all the ALL-injured subjects,the femoral portions of ALL were easily ruptured,tibial portions rupture was seldom.Conclusions1.3D T1W-VISTA imaging technique has a high superiority in the imaging of the ALL,which may provide more information for clinical diagnosis.2.The tibial portion being the most clearly visualized and the meniscal portion the least clearly visualized.3.There might be association of ACL ruptures with ALL injuries.And T1-VISTA-SPAIR imaging technique would provide the information for clinician to pay attention to the ALL when focus on the ACL reconstructions.