This study aimed to investigate the effects of preliminary traction on the rate of failure of reduction and the incidence of femoral head avascular necrosis (AVN) in patients with late-detected developmental dysplasia of the hip treated by closed reduction. A total of 385 patients (440 hips) treated by closed reduction satisfied the inclusion criteria. Patients were divided in two groups according to treatment modality: a traction group (276 patients) and a no-traction group (109 patients). Tönnis grade, rate of failure reduction, AVN rate, acetabular index, center-edge angle of Wiberg, and Severin’s radiographic grade were assessed on plain radiographs, and the results were compared between the two groups of patients. In addition, a meta-analysis was performed based on the existing comparative studies to further evaluate the effect of traction on the incidence of AVN. Tönnis grade in the traction group was significantly higher than in the no-traction group (P = 0.021). The overall rate of failure reduction was 8.2%; no significant difference was found between the traction (9.2%) and no-traction groups (5.6%) (P = 0.203). The rates of failure reduction were similar in all Tönnis grades, regardless of treatment modality (P > 0.05). The rate of AVN in the traction group (14%) was similar to that of the no-traction group (14.5%; P = 0.881). Moreover, the rates of AVN were similar in all Tönnis grades, regardless of treatment modality (P > 0.05). The meta-analysis did not identify any significant difference in the AVN rate whether preliminary traction was used or not (odds ratio = 0.76, P = 0.32). At the last follow-up visit, the two groups of patients had comparable acetabular indices, center-edge angles, and Severin’s radiographic grades (P > 0.05). In conclusion, preliminary traction does not decrease the failure of reduction and the incidence of AVN in developmental dysplasia of the hip treated by closed reduction between 6 and 24 months of age.

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Background:The correlation between the number, size, and location of cannulated screws and the incidence of avascular necrosis (AVN) in children with femoral neck fractures treated surgically is uncertain. Methods: We retrospectively reviewed 153 children (mean age: 10.6 ± 3.7 y) with femoral neck fractures treated by internal fixation with 2 (n = 112) or 3 (n = 41) cannulated screws. The severity of initial displacement was divided into incomplete (type I) and complete (type II, angulation <50 degrees; type III, angulation > 50 degrees) fractures. The diameter of the screw was measured and recorded as a percentage of the femoral neck width. The distance (D) between the mid-point of each screw at the base (B) of the femoral neck and at the tip (T) of each screw and the superior and anterior cortices of the femoral neck, respectively, were measured on anteroposterior (AP) and lateral (L) radiographs. Values were expressed as the ratio between the measured distance and the width of the femoral neck (BD AP %, TD AP %, BD L %, and TD L %). The correlation between the number, size, and location of the screws and AVN was analyzed. Results: Patients with type II of initial displacement treated with 2 cannulated screws had a lower AVN rate (21.4%) than those treated with 3 screws (44.8%) (P = 0.027). Screw diameter (19%) in patients with AVN was larger than (17%) in patients without AVN (P < 0.001); patients with AVN had a lower BD AP % (48.6%) than those without AVN (56.4%) (P < 0.001). Screw size and BD AP % were risk factors for AVN (P < 0.05). Further, screw diameter > 16.5% and BD AP % <51.6% of the femoral neck width were the cutoff values for an increased AVN rate (P < 0.05). Conclusions: Patients treated with 2 cannulated screws showed a lower rate of AVN than patients treated with 3 screws. Screws of larger size and screws closer to the piriformis fossa on AP radiographs increased the risk of AVN in children with femoral neck fractures treated surgically. Level of Evidence: Level III.