ABSTRACT
Objective To compare and analyze MRI characteristics of medical patellofemoral ligament(MPFL) injury patterns in adolescents and adults after acute lateral patellar dislocation.Methods MR images of 42 adolescents and 45 adults after acute lateral patellar dislocation were retrospectively reviewed.Routine MR scanning was performed in axial,sagittal and coronal planes,including T1 WI,T2 WI and fat saturation sequence.The x2-tests were performed to analyze the MPFL injury patterns between adolescent group and adult group.Results The prevalence rate of MPFL injury was 97.6％ (41/42) in adolescent group after acute lateral patellar dislocation,including 57.1％ (24/42) of complete tear and 40.5％ (17/42) of partial tear.The prevalence rate of MPFL injury was 100.0％ (45/45) in adult group,including 64.4％ (29/45) of complete tear and 35.6％ (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 (x2 =1.084,0.486,0.223 ; P ＞ 0.05).The prevalence rate of MPFL injury at femoral attachment,patellar attachment and midsubstance were 31.0％ (13/42),78.6％ (33/42) and 26.2％ (11/42) respectively in adolescent group,whereas they were 64.4％ (29/45),40.0％ (18/45) and 15.6％ (7/45) respectively in adult group.It occurred at multiple sites in 33.3％ (14/42) of adolescents,and in 15.6％ (7/45) of adults.There were significant differences between adolescents and adults in the prevalence rate of MPFL tear at femoral attachments and patellar attachments (x2 =9.759,13.324 ; P ＜ 0.05),but there was no statistical difference at its midsubstance (x2 =1.497,P ＞ 0.05).Although not statistically significant (x2 =3.749,P ＞ 0.05),MPFL tear at multiple locations were seen more in adolescents than in adults (33.3％ vs.15.6％).Conclusion The injury degree and distribution of MPFL are similar in adolescents and adults after acute lateral patellar dislocation,but there is significant difference in the site of MPFL injury distribution between adolescents and adults.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.