Risk factors for avascular necorosis after closed reduction of developmental dysplasia of the hips / 中华骨科杂志

ABSTRACT

Objective:To analyze the risk factors of avascular necrosis (AVN) after closed reduction and spcia casting in treating developmental dysplaisa of the hip (DDH).Methods:The patients with DDH who received closed reduction in our department from January 2016 to December 2017 were retrospectively reviewed. The inclusion criteria included aged at reduction ≥6 months, achieving successful reduction, having complete data with more than 2 years follow-up. A total of 48 cases with 54 hips were included in the present study. Among them, there were 2 males and 46 females, 41 unilateral hips and 13 bilateral hips. The mean age at closed reduction was 16.4±3.8 months (range 6-24 months). The mean follow-up duration was 2.9±1.8 years (range 2.3-4.1 years). Closed reduction was conducted under general anesthesia followed with a spcia cast immobilization. The abduction angle of the cast was recorded. The stability of reduction was evaluated by Ramsey safety zone. The maximum abduction and re-dislocation abduction were recorded. The quality of reduction was evaluated by the medial gap and femoral head coverage on intraoperative arthrography and post-reduction MRI. AVN was diagnosed according to Salter criteria. The risk factors of AVN were analyzed by univariate and binary logistic regression analysis.Results:AVN occurred in 12 hips (22.2%) of 54 hips. International Hip Dysplasia Institute (IHDI) grade and the difference between maximum abduction and cast abduction (Max-Cast abduction) were related to the occurrence of AVN in univariate analysis. The incidence of AVN in hips of IHDI grade 4 (42.9%, 9/21) was significantly higher than that in hips of IHDI grade 3 (9.7%, 3/31) (χ 2=6.007, P=0.018). However, the hips of IHDI grade 3 and 2 (0%, 0/2) presented a similar incidence of AVN (χ 2=0.000, P=1.000). The Max-Cast abduction was -0.7°±5.9° in the AVN group and 6.1°±7.6° in the AVN group ( t=2.125, P=0.038). Finally, IHDI grade ( OR=8.256, P=0.015) and Max-Cast abduction ( OR=0.832, P=0.047) were both independent factors of AVN in multivariate analysis. Conclusion:Most of the hips with AVN are IHDI grade 4 after closed reduction for DDH. The abduction angle in a spica cast could not be significantly related to the occurrence of AVN. However, the risk of AVN might be increased when the cast abduction is close to or beyond the maximum abduction. Safe abduction in the cast should be 5 to 10 degrees less than maximum abduction at least.