[The labral plicae entrapment syndrome of hip in children: an ultrasonography study].

Objective: To study the ultrasonographic (US) features of labral plicae entrapment syndrome of hip (LPEH) in children and to evaluate the value of US in diagnosing LPEH.

Methods: (1) Twenty six LPEH models and 38 sham LPEH hips were established surgically from 32 children cadavers [15 male and 17 female, age from 2 to 8 years, mean age of (6.12 +/- 2.13) years]. US was performed on these hips double-blindly. The sensitivity, specificity, positive and negative predictive values were calculated. (2) A total of 21 children (17 male and 4 female, mean age (5.95 +/- 2.67) years) with unilateral LPEH and 21 age and gender matched children with normal hips were consecutively recruited. The 21 symptomatic hips, 21 asymptomatic hips and 42 normal hips were examined by the US (ATL 5000) using the high-frequency (7.5-12 MHz) linear array transducer.

Results: (1) The sensitivity, specificity, positive and negative predictive values of the US for the LPEH model were 88%, 84%, 79%, and 91%, respectively. (2) Fluids in hip joints were detected in all of the 21 symptomatic hips. No fluid was detected in the asymptomatic and normal hips (less than 2mm); The mean width of the inferomedial recess was significantly larger than that of the anterior recess (12.50 mm vs. 4.35 mm, P < 0.05) in the 21 symptomatic hip joints; The echogenic entrapped labral plicaes were demonstrated in the inferomedial recess of the 21 symptomatic hip joints, with a length ranging from 5.3 to 25.0 mm [mean(15.63 +/- 5.57) mm) and a width ranging from 4.0 to 17.0 mm [mean (8.90 +/- 7.81) mm], respectively; No color signal of blood flow was demonstrated in 90% of the 21 entrapped labral plicaes; With regard to the mean thickness of cartilage of femora head, anterior layer and posterior layer of the anterior capsule, there were no statistical significant differences between the three groups (P > 0.05). After manual reduction and conservative treatment, all of the entrapped labral plicae and fluids disappeared in the US follow-up examinations.

Conclusion: The entrapped labral plicae in the inferomedial recess of hip joints could be visualized by the US. The US provides a useful diagnostic clue to LPEH in children.