Analysis of preoperative predictive factors of MRI for closed reduction of developmental dislocation of the hip

Objective To explore the influence of preoperative magnetic resonance imaging (MRI) on the choice of operative methods in children aged under 2 years with developmental dislocation of hip. Methods Retrospective analysis was performed for children with developmental dislocation of hip from July 2013 to February 2017. According to the Bowen's radiographic standards, they were divided into 3 groups of closed reduction (A, n=26), failure of closed reduction (B, n=24) and impossibility of reduction (C, n=7). On standard MRI, the preoperative measurement of MRI in joint sacs were anterior access angle, inferior access angle, maximal coronal entrance diameter, maximal axial entrance diameter, axial diameter of femoral head, coronal diameter of femoral head, coronal diameter ratio (CMAD/AFHD) and axial diameter ratio (AMAD/CFHD). And the significant differences of data were compared among three groups. Logistic regression analysis was performed for the correlations of gender, age, degree of dislocation, weight bearing time and final treatment. And receiver operating characteristic (ROC) curve was used for assessing the sensitivity and specificity of closed reduction group and determine the cutoff point. Results No significant difference existed in AAA/CFHD/AFHD among 3 groups (P>0.05). IAA angle (108.2±9.8)° was significantly higher in group A than that in group B (98.8±11.2)° and group C (91.7±6.9)°(P 0.05). Logistic regression analysis revealed that, except for age, no correlation existed in gender, measurement, degree of dislocation, weight bearing time or final treatment (P>0.05). The maximal area of ROC curve was 0.515 (AMAD/CFHD), its specificity (92.3%) and inflection point (0.515). Conclusions Preoperative measurements of MRI of IAA, CMAD, AMAD, CMAD/AFHD, AMAD/CFHD offer certain guiding values for treatment. When AMAD/CFHD ratio is >0.515, closed reduction is recommended. Key words: Magnetic resonance imaging; Developmental dislocation of the hip; Closed reduction; Articular sacs