Quantitative Study Of Acetabular Labrum With MRI

Objective: To study the value of magnetic resonance imaging(MRI)in detecting the acetabular labrum(1)Usage of shape and signal of the labrum to assess the growth and development,and its characteristics at different ages.(2)To find the reliability and clinical significance of LA in evaluating the containment degree of acetabulum.Subjects and Methods: Four hundered and ninety six cases of healthy hip joint were retrospectively selected and analyzed(age range,0-35 years,mean 9.09 year),between October 2014 and March 2017,who were examined in Tianjin hospital,3.0 T magnet system was used.Out of 496 cases scanned,301 cases were excluded due to various reasons(scanning method 126,bilateral hip disease 62,trauma 23,infection 15,age factor 38 and bad image quality 37).And then,16 cases whose labrum was lost,179 cases were included.The patients were divided into 5 groups according to their age.Group A had 15 cases of age ?1 year.Group B had 67 cases of age >1 and? 3 years.Group C had 63 cases of age >3 and ?8 years.Group D had 40 cases of age >8 years and ?15 years old.And Group E had 53 cases of age ?25 and ?35 years old.The measuring tool in the AW4.6 workstation was used,the coronal PDWI and coronal T1 WI sequences images were chosen to analyze the feature of all cases,and then the clearest image of the acetabular labrum where we could see the maximum diameter of the femoral head was selected.This study was divided into two parts: for the first part,Different signal characteristics of the labrum were observed on conventional PDWI.The signal intensity of the labrum and obturator externus,length,width,size and the ratio of the labrum signal to obturator externus signal was calculated and recorded to find the changes of the growth of the labrum.The signal intensity,length,width,size and the ratio of the labrum signal to obturator externus signal in each group were compared using the One-way ANOVA.Each group was again divided according to gender and two sides of hip(left and right).The length,width and size in each group was again compared within the group by using t test(Student 's t test),to see the differences between the gender and side of hip.A line chart was used to describe the trend of the length and the width and size of different groups.For the 2nd part,The bone acetabulum index(BAI),cartilaginous acetabulum index(CAI)and the labrum angle were measured and recorded of each case using two different methods to find the changes of the contain of the acetabulum with magnetic resonance imaging.The BAI,CAI,and the LA1 or LA2 of group A to E was compared using the One-way ANOVA;the LA1 or LA2 of the same group with different gender and sides of hip joint was compared using t test(Student 's t test),to see the differences between the gender and sides of hip joint.A line chart was used to describe the trend of the BAI,CAI,and LA with different groups.The correlativity was analyzed between two different methods;the BAI,CAI and LA with different groups.Results:(1)The labrum was visible on conventional PDWI images and show low signal intensity at the rim of the acetabular bone,while it was not clear to recognize it on T1 WI sequence.(2)For Group A to E,the difference in signal intensity is significant only between group A and E(P<0.05).(3)For group A ~ E,the difference of the area of the acetabulum labrum is statistically significant(P<0.05)between group E and rest of the groups,group A and C;group A and D.(4)The length of acetabular labrum had significant difference between the groups : A and B,C,D,E;B and C;C and E.(5)For group A ~ E,the difference of the width value of the acetabulum labrum in group A and D;and all other groups with group E was statistically significant(P<0.05).(6)For group A to E,the difference of the BAI,CAI,LA1 and LA2 in each group was statistically significant(P<0.05).(8)With the increase of the age,the length of the labrum was first increased and then decreased,while the width increased gradually.The CAI of the labrum increased first and declined gradually,while the BAI was decreased.(9)By using the 1st and 2nd method of the measurement of LA among the Group A to E,the difference in each group was statistically significant(P<0.05).There had a linear correlation between these two methods,and had a moderate linear correlation between LA1 and BAI,whereasit had mild correlation with CAI.No linear correlation was between between LA2 and BAI/CAI.Conclusion:(1)The labrum was visible on conventional PDWI images and show low signal intensity at the rim of the acetabular bone,while they were not clear to recognize with the changes of age.The signal of the labrum would be higher than the infants.(2)There had a clear difference of the area,length,width and LA among group A to E,it seemed to find that the growth of acetabulum labrum mainly happened in early childhood and preschool.(3)There had no correlativity between gender and sides of the acetabulum labrum with the development.(4)There had a high correlativity age and the area,length,width of the acetabular.(5)There had a high correlativity between age and the contain of the acetabular,the bony structure gradually mature as the growth,and the effect of the soft tissue had been replaced.(6)since there is linear correlation between LA and AI,LA can be used as a new measurement of acetabulum labrum to see the containment of the femoral head.