Acetabular growth and influencing factors after closed reduction in development dysplasia of the hip

Abstract

Objective To explore the progress of acetabular index (AI) in patients with developmental dysplasia of the hip (DDH) within 4 years after closed reduction and determine the association between final acetabular index (AI) and various factors.Methods From 2005 to 2008,62 (74 hips) patients diagnosed with DDH underwent closed reduction and were followed up for at least 4 years.Radiological examination was performed during each outpatient visit.They were divided into 3 groups according to age:A (0-12 months,18 hips),B (13-18 months,24 hips) and C (＞18 months,32 hips).Two-way ANOVA for repeated measures was used to evaluate the growth of acetabular over time.And multiple linear regression was employed for analyzing the association between final AI and various factors,including initial treatment age,gender,initial center-stage angle,initial acetabular index,initial CHDD,bilateral involvement or not and avascular necrosis of femoral head.Results No difference existed in AI among 3 groups prior to reduction (P＞0.05).AI decreased in all groups after reduction.At 4 years post-reduction,the values of AI of group A (21.9 ± 4.4)° were significantly smaller than group B (24.2 ± 3.4)°and group C (26.8 ± 3.8)°(P＜0.05)and group B was significantly lower than group C(P＜0.05).The total AI improvement rate was 28.6％.And the AI improvement rate of group A (0.35 ± 0.11) was significantly higher than that of group C (0.25 ± 0.10) (P =0.005).Linear regression suggested that age and initial AI were significantly correlated with final AI (R2 =0.617,F=15.031,P＜0.000 1).Other factors,such as gender,center-edge angle of Wiberg (CE),CHDD,bilateral involvement and AVN of the femoral head had no correlations with final AI (P ＞0.05).According to the coefficients,initial AI (β1 =0.432,P＜0.000 1) had greater effect than age on final AI (β2 =0.197,P =0.023).Conclusions AI decreases in all patients after reduction and achieves a steady angle at 3 years post-reduction.Age and initial AI are early predictors of the progress of AI after closed reduction in DDH patients.And AI improvement rate is negatively correlated. Key words: Hip dislocation, congenital; Age groups; Comparative stugy