| BackgroundThe knee joint is among the most complicated joints and consists of the femoral condyle,tibial condyle and patella.The patellofemoral joint comprises the patella and femoral trochlea.Patellofemoral instability is a common orthopedic condition.Patella altaand femoral trochlear dysplasia(FTD)are major risk factors for patellofemoral instability.Patella alta and trochlear dysplasia usually occur simultaneously.However,it is still unclear whether there is a correlation between them.Among patients with-acetabular dysplasia,the acetabulum and femoral head lose normal contact when the hip becomes dislocated.In this case,normalgrowtharoundthe acetabulum and proximal femur does not occur leading to jointincongruity.Children with acetabular dysplasia who haveanatomical restoration through closed reduction or surgical’treatment can achieves normal acetabular structure.In addition,similar findings have’beenobserved in patients with shoulder dislocation.Similar to the hip and shoulder joint,the patellofemoral joint also requiresstimulation bymechanical stress for correct development.According to previous studies,patella alta can lead to,or aggravate,trochlear dysplasia.Conversely,early patellar relocation may be beneficial for trochlear development.By measuring the height of the patella and the morphological parameters of the femoral trochlea using MRI,the aim is to explore whether a correlation between patella alta and trochlear dysplasia exists and to provide some direction for the treatment of patellofemoral instability and the selection of surgical methods.PurposeThe purpose of this study was to investigate the correlation between patella alta and trochlear dysplasia by Magnetic Resonance Imaging(MRI).Patients and MethodThis was an MRI study of 108 patients(mean age 23.2±4.7 years,51.9%female).Thirty-two patients were hospitalized for surgery because of recurrent patellar dislocation(patellar dislocation group).Thirty-six cases were diagnosed with patella alta by virtue of the values of the Caton-Deschamps Index(CDI)or Install-Salvati Index(ISI)(patella alta group).An additional forty patients suffered neither recurrent patellar dislocation nor patella alta(control group).The height of the patella was measured and CDI and ISI recorded for each patient,plus morphological parameters of the femoral trochlear cartilage including the ventral trochlear prominence,trochlear angle,facet asymmetry,lateral trochlear inclination,trochlear depth,central and medial height,and patellar lateralization.ResultsComparison of morphological parameters of the trochlea of the patella alta and control groups revealed a significant difference(ventral trochlear prominence and trochlear depth,p=0.01;trochlear angle and facet asymmetry,p<0.001;lateral trochlear inclination,p=0.004;central height,p=0.014;patellar lateralization,p=0.011).There were also significant differences between the patellar dislocation and control groups(ISI,p=0.001;CDI,p<0.001;medial height,p=0.012;ventral trochlear prominence,trochlea angle,facet asymmetry,lateral trochlear inclination,trochlea depth,central height and patellar lateralization,p<0.001).Correlation analysis was performed for all comparisons,with a significant correlation found between the ISI/CDI and almost all morphological parameters of the femoral trochlea:ventral trochlear discrimination(ISI:r=0.326,p=0.001,CDI:r=0.352,p<0.001),trochlear angle(ISI:r=0.224,p=0.02;CDI:r=0.403,p<0.001),central height(ISI:r=0.319,p:0.001;CDI:r=0.308,p=0.001),medial height(ISI:r=0.217,p=0.024),patellar lateralization(ISI:r=0.256,p=0.008;CDI:r=0.445,p<0.001),trochlear depth(ISI:r=-0.258,p=0.005;CDI:r=0.35,p<0.001),lateral trochlear inclination(ISI:r=0.267,p=0.005;CDI:r=-0.271,p=0.005)and facet asymmetry(ISI:r=-0.381,p<0.001;CDI:r=-0.442,p<0.001).ConclusionAccording to our findings,significant correlation exists between patella alta and femoral trochlear dysplasia.Patients with patella alta exhibit poorer trochlear development than control subjects.Patients with recurrent patella dislocation have both poorer trochlear development and a higher patella.This study confirms that the higher the patella,the worse the development of the femoral trochlea,among which CDI was most significantly correlated with patellar lateralization(r=0.445,p<0.001)and facet asymmetry(r=-0.442,p<0.001).ISI was most significantly correlated with facet asymmetry(r=-0.381,p<0.001). |
