The Outcome Of A Novel Simple Open Reduction In Developmental Dysplasia Of The Hip In Young Children And Analysis Of The Abduction Angle And The Ischial Thickness As Two Risk Factors

Objective:Avascular necrosis(AVN)of the femoral head and acetabular morphological deformity happens in DDH.This study evaluated the clinical outcomes of a simple novel mini-bikini incision approach of open reduction for hip dysplasia in young children and compared four measures of abduction angles during operation.Also,to investigate the regularity of ischial thickness change in young children after surgical treatment as one of the acetabular morphology deformities,and to evaluate the natural evolution of ischial thickness on magnetic resonance imaging in untreated unilateral DDH aged 0-14 years.Methods:A total of 43 patients with 49 hips were retrospectively analyzed from June2013 to December 2018 in children with DDH treated with mini-bikini incision approach of open reduction.Avascular necrosis of femoral head and development of acetabular cartilage was assessed.The data was collected and analyzed from January 2019 to November 2021 in this treatment group of children with DDH who met the criteria for intra-operative measurement of abduction angle with closed or mini-bikini incision open reduction.A total of 27 cases with 54 hips were selected and defined for the study.The intersection of the anus center O’,the inguinal fold vertical line and the intersection of the anus to the fold vertical line R’was the body surface reference.Four abduction angles were measured and recorded intra-operatively based on body surface reference points,and the abduction angles were measured on postoperative magnetic resonance imaging as the gold standard and to compare the five methods with each other.In the imaging study,134 untreated unilateral dislocations of 0-14 years old and 53 young DDH children treated with closed reduction or novel mini-bikini approach were divided into groups according to age and degree of dislocation,and zoned on MRI,the acetabular rim was zone 1 and the center was zone 2.Bilateral ischial bone thickness,epiphyseal plate thickness,iliac bone thickness,acetabular cartilage index,acetabular index,femoral head epiphyseal quotient,femoral head diameter and pubic width in axial plane were measured and compared.Correlation analysis and repeated measures ANOVA were used.The degree of hip dislocation in all studies was graded according to the International Hip Dysplasia Institute(IHDI)standard,and the serial MRI examination time was preoperative,6 months post-operation,12 months post-operation,24 months post-operation,48 months post-operation,and 72 months post-operation.The t-test,correlation coefficient,linear regression,Bland-Altman test,Pearson,Spearman correlation factor analysis,two-way repeated measures ANOVA and other test methods were sued for statistical analysis.Results:The mean follow-up was 43 months and the mean AA was 58 degree,the children treated with mini-bikini incision approach had no complications such as limited hip joint mobility and limb length deformity.The average UNC4P score was 0.92,and no children had symptoms such as scar pruritus and pain.A total of 4 hips(8%)developed AVN,3 of which were male,and 4 of which were IHDI type IV.According to the coronal acetabular cartilage index assessment,residual dysplasia occurred in 32 hips in this study;according to the coronal CCAHI,residual dysplasia occurred in 28 hips;according to the sagittal CSAHI results,the average coverage rate of 92.81%indicated the presence of sagittal mild dysplasia of the acetabulum.The results of five methods of measuring abduction angles in children with DDH:directly visualization of junior doctor[AA-JV(42.69±4.13)°]<directly visualization of senior doctor[AA-SV(44.80±4.08)°]<R’reference point[AA-AGCP(46.25±5.15)°]<gold standard of magnetic resonance image[AA-MRI(47.68±4.21)°]<anal reference point[AA-AP(51.77±5.30)°].AA-JV and AA-SV,AA-AP and AA-AGCP were statistically different(P<0.05).There was no statistical difference between AA-AGCP and AA-MRI(P>0.05).All ICC results were greater than 0.75 with good agreement.Linear regression results showed that the four methods had good or moderate linear relationship with AA-MRI,AA-AGCP(R~2=0.499)>AA-AP(R~2=0.318)>AA-SV(R~2=0.253)>AA-JV(R~2=0.217),AA-AGCP was the best measurement method.The results of AA-AGCP and AA-MRI Bland-Altman scatterplots were in good agreement,with a mean and standard deviation of bias of-0.796±3.247(95%limit of agreement:-7.160-5.568).In MRI measurement of ischial thickness in untreated children with unilateral DDH aged 0-14 years,the axial thickness of the ischial bone,the distance from the regional center to the epiphyseal plate,the diameter of the femoral head,and the width of the epiphyseal plate increased with age;The ischial thickness and axial pubic thickness increased with age in different regions and planes at age 0-9 years,and decreased slightly at age 10-14 years.The correlation coefficients between ischial thickness and iliac thickness,acetabular cartilage index,acetabular index,femoral head diameter,axial pubic thickness,epiphyseal plate width,distance from regional center to epiphyseal plate,etc.ranged from 0.01 to 0.763,it was positively correlated.The correlation coefficient with the femoral head epiphyseal quotient ranged from-0.359 to-0.026,which was negatively correlated.In the study of serial MRI ischial bone thickness after closed or mini-bikini incision approach in young children,the ipsilateral ischial bone thickness was always greater than that of the contralateral side,and the coronal ipsilateral and contralateral zone 1 and 2 ischial bone thickness increased with follow-up time.The thickness gradually increased,and there was a significantly difference between the two groups at each time node(P<0.001),and there was a significantly difference between the different groups on the ipsilateral and contralateral sides(P=0.033).There was no significantly difference in bilateral axial zone 1,but there was a significantly difference in zone 2.In the different treatment groups,the ischial thickness in the open reduction group was greater than that in the closed reduction group.There was no significantly difference between the two groups in coronal and axial area 2,but there was a significantly difference in axial area 1.Conclusion:Clinically,the minimally invasive mini-bikini incision approach open reduction was optional for children with DDH who fail closed reduction.The method was novel with short operation time,less blood loss,and prevention of muscle strength lost.The incision was more beautiful,and the scarring was cosmetic.Without adding AVN and abnormal acetabular morphology,this operation was an effective and reliable choice for open reduction after closed reduction failure.When children with DDH were immobilized in a plaster cast in the pedestrian position,the commonly used visualization method for AA was smaller,and the AA-AGCP method was recommended for estimation.The AA-AGCP method was easy to operate,had high reliability,strong consistency,objective and accurate measurement,prevented excessive hip abduction,and reduced the occurrence of AVN and deformity.On MRI,in children with unilateral DDH in the age of0-14 years,the ischial thickness of coronal zones 1 and 2 increased with age at the age of0-9 years,and gradually decreased in the age of 10-14 years.Axial ischial thickness in zones 1 and 2 from 0 to 14 years old increased with age.The ischial thickness was positively correlated with acetabular cartilage index,epiphyseal plate width,femoral head diameter,axial pubic thickness,coronal iliac thickness,and the distance from regional center to epiphyseal plate,and was negatively correlated with epiphyseal quotient.The development of ischial thickness in children with DDH was synchronous with the development of pubic,ilium,and femoral head evaluation.After closed or novel mini-bikini incision approach in young children,the ischial thickness on the ipsilateral and contralateral serial MRI gradually increased with the follow-up time.The coronal and axial ischial thicknesses in the two groups increased gradually with the follow-up after surgical intervention by closed or novel mini-bikini incision approach,and there was no significantly difference between the different surgical interventions except for the axial zone 1.