Risk factors associated with unsatisfactory hip function in children with late-diagnosed developmental dislocation of the hip treated by open reduction

Background: Open reduction with or without pelvic and femoral osteotomy is the accepted treatment option for children older than 18 months with developmental dislocation of the hip (DDH). However, few studies have investigated hip function in children with late DDH treated by open reduction. Therefore, we performed a retrospective study investigating the risk factors potentially associated with unsatisfactory hip function. Hypothesis: We hypothesized that some risk factors can be associated with unsatisfactory hip function in patients with late DDH treated by open reduction. Patients and methods: We retrospectively reviewed the clinical and radiographic data of 79 children (98 hips, mean age 39.7 ± 18.6 months; range, 19–95.3) with late-detected DDH treated by open reduction. Acetabular index (AI), Tönnis grade, Center Edge Angle (CEA), avascular necrosis of the femoral epiphysis (AVN), and Severin radiographic grade were evaluated on radiographs. Hip function was rated according to modified Outcome Evaluation Standard for Congenital Dislocation of the Hip with a maximum score of 15. According to type of surgery, patients were divided into four groups: open reduction alone (Group A), open reduction in conjunction with pelvic osteotomy (Group B), and open reduction in conjunction with femoral osteotomy and Pemberton/Salter (Group C) or Bernese-type triple pelvic osteotomy (Group D). Analysis of variance (ANOVA), t-test, chi-square test, and multivariate regression analysis were used to evaluate the independent risk factors of unsatisfactory hip function. Results: The mean hip function score was 10.8 ± 2.8 (4.5–15); 61 hips (62.2%) had satisfactory function (23 [23.5%] excellent and 38 [38.8%] good), while 37 hips (37.8%) had unsatisfactory function (16 [16.3%] fair and 21 [21.4%] poor). Spearman correlation analysis indicated that age at surgery was negatively correlated with function score (r = −0.326, p = 0.001). The age of patients with satisfactory hip function (34.5 ± 14.2 months; range, 19.4−74.8) was significantly lower than those with unsatisfactory function (43.7 ± 21 months; range, 20.6–95.3) (p = 0.011). The hip function score in Group A (14.2 ± 0.8; range, 12.8–15) was significantly higher than in the other three groups (p < 0.001). Hip function score in patients with type III or IV AVN was significantly lower than those without AVN, or with type II AVN (p = 0.001). Multivariate regression analysis confirmed age at surgery, type of surgery and AVN were negatively correlated with hip function score. Logistic regression analysis and chi-square test confirmed age and type of surgery, and AVN were independent risk factors of unsatisfactory hip function. Multivariate regression analysis found ability to squat and amount of hip flexion and abduction, significantly decreased with age at surgery; while presence of limping, amount of hip flexion, abduction, adduction and external rotation significantly decreased with type of surgery. Discussion: Age at surgery, type of surgery and severe AVN are independent risk factors for unsatisfactory hip function in patients with late-detected DDH treated by open reduction. The ability to squat, the amount of hip flexion and abduction are the main functional parameters affected by age and surgery. Level of evidence: IV, case series.