Dega osteotomy assisted with three-dimensional computed tomography for re-dislocation of developmental dysplasia of the hip in children

Objective To observe the pathological changes of re-dislocation of developmental dysplasia of the hip (DDH) undergoing pelvic osteotomy in children, to predict the outcome of Dega osteotomy assisted with three-dimensional computed tomography (3DCT) simulating osteotomy and to explore the individual therapeutics for re-dislocation of DDH. Methods From July 2012 to June 2017, retrospective analysis was conducted for a total of 28 hips in 27 children with re-dislocated DDH undergoing a second Dega osteotomy. There were 9 involved hips in 8 boys and 19 involved hips in 19 girls with an average age of 51 (28-96) months during the second operation. The involved side was left (n=17), right (n=9) and bilateral (n=1). According to the Tonnis classification scheme, the clinical types were Ⅱ (17 hips), Ⅲ (8 hips) and Ⅳ (3 hips). And the procedures included Salter osteotomy (20 hips), Dega osteotomy (1 hip), Dega osteotomy with intact inner wall (3 hips) and Pemberton osteotomy (4 hips). A simulating osteotomy by 3DCT of pelvis-femurs was performed preoperatively and Dega osteotomy with open reduction plus capsuloplasty and proximal femoral osteotomy were applied simultaneously. The preoperative and postoperative changes of acetabular index and Reimer's index were compared and P<0.01 was deemed as statistically significant. Radiological findings and improvements of extremity functions were evaluated at the latest follow-up. Results 28 involved hips were followed up successfully with an average period of 33(18-38) months. Acetabular index improved from (31°±8°) to (11°±4°) and Reimer's index decreased (0.78±0.21) to (0.16±0.03) with statistically significant differences in both acetabular and Reimer's indices pre-reoperation and at the latest follow-up (P<0.01). Disrupted preoperative Shenton lines in all hips became continuous during follow-ups. No postoperative re-dislocation was seen. Based upon the modified Severin classification scheme, the outcomes were excellent (19 hips), good (7 hips) and moderate (2 hips). And the excellent-good rate was 93%(26/28); based upon the modified McKay classification scheme, the outcomes were excellent (20 hips), good (7 hips) and moderate (1 hip). And the excellent-good rate was 96%(27/28). There was no occurrence of infection, fracture or vascular/nervous injury. Conclusions With more precise designs, meticulous operations and intuitive outcomes may be achieved with an aid of 3DCT. The short-term effect of Dega osteotomy plus open reduction, capsuloplasty and proximal femoral osteotomy for re-dislocated of DDH undergoing pelvic osteotomyis is definite. And it should be further popularized clinically in children. Key words: Osteotomy; Three-Dimensional; Developmental dysplasia of the hip