Susceptibility Factors For Injuries Associated With Acute Patellar Dislocation

Objective:To assess the associated ligament,osteochondral and meniscal injuries follo wing acute patellar dislocation(APD)and to further explore the relationship be tween these associated injuries and demographic characteristics and imaging par ameters.A deeper understanding of the predisposing factors for these associated injuries will allow for early latent prediction,reduce misdiagnosis and help us to develop more rational surgical plans to reduce the incidence of complication s such as patellofemoral osteoarthritis.Methods:A retrospective analysis of 74 patients with APD admitted to the China Ja pan union Hospital of Jilin University between January 2018 and June 2022.P atients with APD were assessed by knee MRI for associated medial patellofem oral ligament(MPFL),medial patellofemoral-tibial ligament(MPTL),patellar os teochondral,lateral femoral condyle osteochondral,and meniscal injuries and gr ouped.The relationship between the demographic characteristics and imaging pa rameters associated with APD was further explored by comparing and analysing the demographic characteristics and imaging parameters between the groups.Results:1.74 patients with APD were included in the study with a mean age of 19.74 ±9.41 years.Of these,38(51.4%)were male and 36(48.6%)were female.54(73.9%)had varying degrees of talipes equinovarus(Dejour A,B,C and D types)and 28(38.3%)had unclosed epiphyses.2.MPFL injuries occurred in 98.6% of patients,with 45 partial MPFL tears,28 complete MPFL tears,and one no injury seen.In terms of site of injury: patellar end tear(57.6%),femoral end tear(41.0%),body tear(4.1%),and compound tear(4.1%).The complete tear group was more likely to have a concomitant MPTL tear than the partial MPFL tear group(80% vs 100%,P=0.011).3.MPTL tears occurred in 86.4% of patients,with the lateral epicondyle of the femur being larger in the MPTL tear group compared to the unteared group(34.40mm±3.5mm vs 37.75mm±3.0mm,P=0.002);and the lateral trochlear facet was longer(21.92mm±2.7mm vs 24.68mm±3.3mm,P=0.013).Multi-factor regression analysis identified the anterolateral condyle of the femur as an independent influence on MPTL tear(P=0.026).4.Patellar osteochondral injury occurred in 62.1% of patients,with a greater sulcus angle in the group with patellar osteochondral injury compared to the group without injury(160.54°± 15.3° vs 150.61°± 14.6°,P=0.008);the medial trochlear facet was longer(12.52 mm ± 3.7mm vs 10.99 mm ± 2.8mm,P=0.049).Multi-factor regression analysis identified the sulcus angle as an independent influence on osteochondral damage to the patella(P=0.006).5.Osteochondral injury to the lateral femoral condyle occurred in 70.2% of patients,with a greater sulcus angle in the group with osteochondral injury to the lateral femoral condyle compared to the group without injury(150.30°± 12.7° vs159.53°± 16.2°,P=0.012);a greater anteromedial condyle(21.87mm±3.3mm vs24.47mm±4.3mm,P=0.013);more with closed epiphyses(40.9% vs 69.2%,P=0.023);and more with osteochondral damage to the patella(40.9% vs 70.2%,P=0.014).Multi-factor regression analysis revealed that the sulcus angle and closed epiphyses were independent influences on osteochondral injury of the lateral femoral condyle(P=0.037,P=0.040).6.For meniscal injuries: lateral anterior meniscus horn injury(16.2%),lateral posterior meniscal horn(2.7%),medial anterior meniscal horn injury(1.3%),and medial posterior meniscus horn injury(2.7%).Osteochondral injury to the lateral femoral condyle was more likely to occur in the lateral anterior meniscus horn injury group compared to the uninjured group(100% vs 64.5%,P=0.014).Conclusions:1.Patients with APD are prone to combined osteochondral injuries of the MPFL,MPTL,patella and lateral femoral condyle.2.Patients with complete tears of the MPFL are nearly always combined with tears of the MPTL,and patients with injuries to the anterior horn of the lateral meniscus are nearly always associated with osteochondral injuries of the lateral femoral condyle.3.The anterolateral condyle of the femur is an independent influence on MPTL tears,with the larger the anterolateral condyle,the more likely it is to be combined with MPTL injury;4.The sulcus angle was an independent factor in osteochondral injuries of the patella,the greater the sulcus angle,the more likely it is to be combined with patellar osteochondral injury;5.Epiphyseal closure and sulcus angle are independent factors influencing osteochondral injury of the lateral femoral condyle,with the closed epiphysis a nd the larger sulcus angle,the more likely it is to be combined with osteocho ndral injury of the lateral femoral condyle.