CROWE IV hip dysplasia treated by THA combined with transverse sub-trochanter osteotomy to balance functional leg length discrepancy: a prospective observational study

Abstract Background There are various malformations in the pelvises and femurs of hip dysplasia patients, consequently leg length discrepancy(LLD) can often become one of the most common post-surgical complications in CROWE IV hip dysplasia patients. To our knowledge, there are few researched focus on relationship between acetabular prothesis position and postoperative LLD while optimal leg length balance strategy for CROWE IV hip dysplasia patients remains unclear. 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.Methods During June 2017 to June 2018, 14 consecutive CROWE IV patients (17 hips) and 18 consecutive CROWE I patients (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) to 0 (0-0.08), P=0.003. Only three of 14 CROWE IV patients remained under 1 cm functional LLD.Conclusion After elaborate pre-operative planning and leg length balancing during operation, THA combined with transverse sub-trochanter osteotomy is an effective method to achieve equal function in leg length.