LAUSR

Dear Editor, We write this letter in response to the article titled “Total Hip Arthroplasty for Crowe Type IV Hip Dysplasia: Surgical Techniques and Postoperative Complications” by Shi et al. published in the latest issue of Orthopaedic Surgery (2019;11:966–973). This is a valuable review article focusing on the current concerns and controversies in treating Crowe type IV developmental dysplasia of the hip (DDH). Through distinctive hypotheses, comprehensive viewpoints, and a variety of documented evidences, the article’s logic and views are presented clearly. First, the authors realized the inadequacy of traditional approaches and techniques in managing Crowe type IV DDH, and assumptively introduced the direct anterior approach (DAA) to total hip arthroplasty as a surgical strategy. They also underlined the theoretical advantage of DAA in Crowe type IV DDH, and further predicted how DAA could produce satisfactory treatment outcomes for this type of population. In particular, an extraordinary work by Oinuma et al. was referenced in the article to further validate the authors’ point of view. Unfortunately, the authors have not fully revealed the technical challenges in treating Crowe type IV DDH via DAA, or the deficiency of the surgical technique proposed by Oinuma et al. Further, we did not find any insights or advice for optimizing the technique or the procedure, nor did we find a clinical result from the authors’ practice. That is the reason behind writing this Letter to the Editor, and we would like to systemically discuss these questions in the latter part of this letter. Second, the authors introduced some current debates about traditional approaches to total hip arthroplasty: it is still highly controversial whether the rotation center should be reconstructed in the true acetabulum or placed at the dislocated position. Through their analysis, the authors conveyed an important message; that high hip center technique, as much as 30–35 mm in height, resulted in relatively satisfactory outcomes in Crowe type III DDH, as the studies referenced in the article showed. This finding sheds light on a precise compromise between anatomical reconstruction in the hip center and coverage-induced stability of the acetabular component, which might be very crucial in the clinical decision-making of Crowe type III to IV DDH. The authors then switched to the decision-making process of femoral osteotomy scheme in Crow type IV DDH. Five types of femoral osteotomy techniques – including the transverse, the oblique, the step-cut, the double chevron, and the sigmoid osteotomies – were illustrated in schematic diagrams and elaborately discussed in terms of their rationality, feasibility, and reproducibility; however, the value and advantage of greater trochanter osteotomy was neglected in the article. Actually, the greater trochanter osteotomy was widely employed as an effective method in the early stage of hip arthroplasty, which also contributed to the advancement of total hip arthroplasty to this modern attitude. We have to admit that both the classical sliding osteotomy, and proximal femoral reconstruction technique proposed by Shang et al., provide efficient and reliable solutions for femoral reconstruction procedure in patients with Crowe type III-IV DDH, as well as minimal risks of bone non-union and dislocation. Third, common complications including leg length discrepancy, intraoperative fracture, bone non-healing, nerve palsy, and the pathological mechanism were generally described. In fact, the occurrence of these complications is considered to be closely related to the surgical approach. To this point, the authors should have allowed more space to propagate the benefit of direct anterior approach for highdislocated DDH. As to our best knowledge, there are very few reports to describe the technical issues and summarize the outcomes in treating high-dislocated DDH by DAA. The extreme challenges in this procedure might include multiple planar deformities in both acetabulum and proximal