Crowe Ⅳ Hip Dysplasia Treated By THA To Balance Functional Leg Length Discrepancy

Objective:In this paper,we measured the factors that affect functional leg length of CROWE Ⅳ DDH patients and reviewed our own methods to balance LLD of CROWE Ⅳ DDH patients.We also measured hip rotation center after surgery to determine how post surgery hip rotation center affects functional leg length.Methods:During June 2017 to June 2018,14 consecutive CROWE Ⅳ patients(17 hips)and 18 consecutive CROWEⅠpatients(20 hips)were included in this study.Prior to surgery,subluxation height of the femoral head on the affected side,functional LLD,bony length of lower limbs,and distance from teardrops to the lowest point line of the sacroiliac joint were recorded.All patients received THA,and several of them also received subtrochanter ostoetomy.After surgery,cup sizes,functional LLD,and hip rotational centers were measured.Results:Functional LLD of the CROWE Ⅳ patients group was significantly improved from 4.00(3.00-5.00)before surgery to 0(0-0.08)post surgery,P=0.003.Compared to hip center height of CROWEⅠpatients,that was significantly lower of CROWE Ⅳpatients(P<0.001).Conclusion:1.After careful preoperative measurement,intraoperative comparing of leg length and osteotomy when necessary,CROWE type Ⅳ DDH patients functional LLD improved significantly compared with that before surgery.However,compared with functional LLD of CROWE typeⅠDDH patients,not all that of CROWE typeⅣ DDH patients can be completely eliminated.2.Compared with hip center of CROWE typeⅠDDH patients,that of CROWE type Ⅳ DDH patients is significantly at more inferior position.