Effect Of Total Hip Arthroplasty On Lower Limb Alignment Of Crowe Ⅳ DDH

Objectives:To explore the features of lower limb alignment in patients with unilateral Crowe type Ⅳ developmental dysplasia of the hip（DDH）and the effect of total hip arthroplasty（THA）on the lower limb alignment.Patients with Crowe type Ⅳ DDH were divided into two groups（osteotomy and non-osteotomy）to explore the effect of THA on the lower limb alignment of patients in the osteotomy and non-osteotomy groups.Methods:We performed a retrospective analysis from the clinical data of patients who came to our department for THA caused by DDH from January 2016 to January 2021.A total of 48 people with 48 hips were included in this study,including 5 males and 43 females,aged 24-71 years with an average of 53.2years.There were 20 cases in the right hip and 28 cases in the left hip.The hipknee-ankle（HKA）angle was measured both before operation and 1 week after surgery.Statistical analysis was made on the preoperative and postoperative HKA angles.According to Crowe’s classification,patients were divided into a type I group and type Ⅳ group using the preoperative frontal pelvis radiographs of the patients.Among them,there were 24 patients with 24 hips in type I group and 24 patients with 24 hips in type Ⅳ group.In addition,patients with Crowe type Ⅳ DDH were further divided into an osteotomy group and non-osteotomy group.Among them,there were 12 cases with 12 hips in osteotomy group,12 cases with 12 hips in non-osteotomy group.Statistical analysis was performed on the preoperative and postoperative HKA angles of patients in each group.Results:There were 24 cases in type I group and 24 cases in type Ⅳ group.There was no significant difference in sex,age,height and weight between the two groups（P > 0.05）.There were 12 cases in osteotomy group and 12 cases in non-osteotomy group.There was no significant difference in sex,age,height and weight between the two groups（P > 0.05）.Comparing the HKA angle in the groups,the angle before THA tended to be valgus in both type I and type Ⅳ groups,but the valgus angle was statistically significantly larger in the type Ⅳ group than in type I group（P=0.003）.After THA,the HKA angle still tended to be valgus in both type I group and type Ⅳ group,but the valgus angle was still statistically significantly larger in the type Ⅳ group than in the type I group（P=0.024）.Comparing preoperative and postoperative HKA angles,In type I group,HKA angle was partially corrected after operation,but the difference was not statistically significant（P=0.068）.However,the postoperative HKA angle was partially corrected in the type Ⅳ group,and the difference was statistically significant（P=0.023）;Comparing between preoperative and postoperative HKA angles in patients with Crowe type Ⅳ DDH,The HKA angle in non-osteotomy group was partially corrected,but there was no statistical significance（P=0.363）.However,the postoperative HKA angle was partially corrected in the osteotomy group,and the difference between preoperative and postoperative was statistically significant（P=0.029）.Conclusion:（1）Knee valgus was more obvious in the Crowe type Ⅳ DDH group than in the type I group before and after surgery.（2）After THA,the knee valgus was partially corrected in patients with type Ⅳ DDH,but was not corrected in patients with type I DDH.（3）THA combined with osteotomy can better correct the knee valgus in patients with unilateral Crowe type Ⅳ DDH.