Series Of Research On MRI In Diagnosis Of Acute Lateral Patellar Dislocations In Adolescents

PART ONEComparative study of medial patellofemoral ligament injurypatterns in MRI between adolescents and adults after acute lateral patellar dislocationObjectiveTo compare and analyze MRI characteristics of MPFL injury patterns between adolescents and adults after acute lateral patellar dislocation.MethodsMR images of42adolescents and45adults after acute lateral patellar dislocation were retrospectively reviewed. Routine MR Scanning was performed in axial,sagittal and coronal planes, including T1WI, T2WI and fat saturation sequence. The x2-tests were performed to analyze the MPFL injury patterns between adolescent group and adult group.ResultsThe prevalence rate of MPFL injury was97.6%(41/42) in adolescent group after acute lateral patellar dislocation, including57.1%(24/42) of complete tear and40.5%(17/42) of partial tear. The prevalence rate of MPFL injury was100%(45/45) in adult group, including64.4%(29/45) of complete tear and35.6%(16/45) of partial tear. There were no statistical difference between adolescents and adults in prevalence rate of MPFL injury, complete MPFL tear, partial MPFL tear(P>0.05).The prevalence rate of MPFL injury at femoral attachment, patellar attachment and midsubstance were31%(13/42),78.6%(33/42) and26.2%(11/42) respectively in adolescent group, whereas64.4%(29/45),40%(18/45) and15.6%(7/45) respectively in adult group. In33.3%(14/42), it occurred in more than1localization in adolescent group, compared with15.6%(7/45) in adult group. There were significant differences between adolescents and adults in the prevalence rate of MPFL tear at femoral attachments and patellar attachments (P=0.002, P=0.001),and no statistical difference at its midsubstance(P>0.05).Although not statistically significant, MPFL tear at multiple locations were seen more in adolescents than in adults (33.3%vs.15.6%,P=0.053).Conclusion1. The injury degree distribution of MPFL in adolescents is similar to adult after acute lateral patellar dislocation.2. There is significant difference between adolescents and adults in the site of MPFL injury distribution. MPFL is most easily injured at femoral attachment, secondly at patellar attachment in adults, while MPFL is most easily injured at patellar attachment, secondly at femoral attachment in adolescents. Adolescents are more likely to have multiple-site MPFL injury than adults. PART TWOMRI characteristics of acute lateral patellar dislocation in adolescentsObjectiveTo evaluate MRI characteristics of injuries after acute lateral patellar dislocation in adolescents.MethodsMR images with clinical confirmation of acute lateral patellar dislocation in adolescents were retrospectively studied. Medial patellofemoral ligament (MPFL),vastus medialis obliquus(VMO),bone contusion, articular cartilage lesions and joint effusion of the patellofemoral joint were assessed.ResultsA total of42patients (age range9-16years, average14years) were identified. The prevalence rate of MPFL injury was97.6%(41/42),including57.1%(24/42) of complete MPFL rupture and40.5%(17/42) of partial MPFL rupture. MPFL injury was present at femoral attachment in31%patients(13/42),78.6%at patellar attachment(33/42),26.2%at midsubstance(11/42). MPFL injury at more than one location was present in33.3%of patients(14/42). The prevalence rate of VMO injury was52.4%(22/42),including38.1%(16/42) of Ⅰ°injury and14.3%(6/42) of Ⅱ°injury. The prevalence rate of bone contusion in medial patella and lateral femoral condyle was95.2%(40/42). The prevalence rate of articular cartilage lesion of medial patella was90.5%(38/42),including38.1%(16/42) of chondral lesion and52.4%(22/42) of osteochondral lesion. The prevalence rate of articular cartilage lesion of lateral femoral condyle was45.2%(19/42),including26.2%(11/42) of chondral lesion and19%(8/42) of osteochondral lesion. The prevalence rate of joint effusion was100%.Conclusions 1. MPFL injury,VMO injury, bone contusion and articualr cartilage lesion of medial patella and lateral femoral condyle, joint effusion are the characteristic MRI findings after acute lateral patellar dislocation, which are similar to those in adults.2. VMO injury are all Ⅰ°or Ⅱ°injury.3. MPFL is most easily injured at patellar attachment, secondly at femoral attachment, and multiple-site MPFL injury is a common injury type in adolescents.4. Articular cartilage lesion of medial patella and lateral femoral condyle are more common in adolescents, especially osteochondral lesion.